Mercedes Bueno

Colette Fabrigoule

Alexandra Fort

Effectiveness of Forward Collision Warning Systems: a contribution from the cognitive analysis combining behavioural and electrophysiological measurements

This chapter discusses Forward Collision Warning Systems (FCWS), describing the characteristics and the functions of some of the systems currently on the market and presents an overview of behavioural studies evaluating the effectiveness of these systems on road and in simulators. Results are presented from recent studies using electroencephalography and the associated Event Related Potentials allowing, through the analysis of brain activity, a more indepth understanding of the nature of the cognitive processes in the context of FCWS. These studies address three important questions:

1. Are FCWS as effective as they are expected to be when drivers are distracted? 2. What are the consequences of driving with a system that is not completely reliable? 3. Is there any behavioural adaptation to the FCWS over their use in time? Are the consequences of this adaptation positive or negative?

The chapter shows that FCWS provides potential benefits for road safety, but certain factors such as the attentional state of drivers but the reliability level of the system can mitigate its effectiveness.

Introduction

Advanced driver assistance systems (ADAS) have experienced a rapid development in recent years to optimise their potential benefits on road safety. It has been estimated that these systems contribute to reducing the number of casualties on the roads. Because of this, the European Commission has recently proposed the mandatory installation of some ADAS such as the lane departure warning system and the collision warning system in heavy vehicles from 1st November 2013 [1]. Nevertheless, light vehicles will be exempted at present because of the lower benefit-to-cost ratio compared to heavy vehicles.

Since ADAS have appeared on the market, research in the field of human factor has been promoted to investigate the impact of both the benefits of these systems on drivers' behaviour and their potential failures or limitations. Some of these systems warn drivers by an audible, visual or/and haptic signal when inappropriate behaviour is detected, either because an action is required but is not carried out or because the action carried out is not the right one. This chapter presents a review of the literature focused on a particular ADAS, the Forward Collision Warning System (FCWS). Nevertheless, some of the questions and discussions considered here could be applied to other warning systems.

FCWS are designed to reduce the number and/or to avoid rear-end collisions by providing warning to drivers. Traditional behavioural measures obtained in driving simulators and field operational tests are useful tools for evaluating the effectiveness of such systems, but they are not the only ones. Physiological data obtained through the event related potential technique can complement behavioural data. Reporting on data from these different methodological approaches, we discuss whether the system reaches one of its main objectives, i.e. to assist distracted drivers, and then how the system reliability affects the efficiency of the system and driver's acceptance. Finally, in the last section of this chapter certain studies examining the behavioural adaptation to the system are presented. Specifically, the effects on behaviour due to driving with the system over the time (from the introduction of the system to long term effects of ADAS use) and the consequences of driving without the system after a period of habituation to the system are discussed.

The utility of FCWS

As mentioned above, FCWS have been developed to warn drivers of potential rear-end collisions. Although the percentage of these collisions resulting in fatalities is relatively low compared to the percentage of injuries [START_REF]Statistics of road traffic accidents in Europe and North America[END_REF], these accidents are one of the most prevalent types of collision, disturbing traffic flow and representing an important economic cost for society.

The environment (e.g. poor visibility, road type) and the vehicle (e.g. defective brakes) are some of the contributing factors to the rear-end collisions, in 5 -11% and 12 -20% of these accidents, respectively. However, the factor that most frequently contributes to rear-end collisions is the driver, accounting for between 75 -93% of the cases. More precisely, inside the driver category, distraction has been involved in about 60% of the rear-end collisions [START_REF] Knipling | Rear-end Crashes: Problem size assessment and statistical description[END_REF][START_REF] Vogel | A relationship between accident types and causes[END_REF]. FCWS are based on sensors which continuously monitor certain parameters such as the relative speed, lateral position and distance between two vehicles. Although a wide variety of algorithms have been designed to calculate the moment for triggering the warning, most of them are based either on the time to collision between the obstacle and the following vehicle or on the minimum distance required to stop the vehicle safely [START_REF] Bella | A Collision Warning System for rear-end collision: a driving simulator study[END_REF]. When a certain threshold value is reached, predicting a potential risk of collision, the system provides a warning signal (e.g. visual, auditory, and/or tactile) to alert the driver.

The system, as well as providing assistance by warning the driver (Forward Collision Warning Systems), can also take an active part in the braking process by preparing and/or by applying partial or full braking automatically (Forward Collision Avoidance Systems). This active avoidance module could prevent or reduce the severity of the collision should the driver not react in time or not react at all. Moreover, the active avoidance system has become more relevant in preventing collisions since it has been demonstrated that most drivers do not apply enough force on the brake pedal [START_REF] Breuer | Real world safety benefits of brake assistance systems[END_REF] and that a high percentage of drivers only release the accelerator pedal or even do not react at all [START_REF] Najm | Evaluation of an automotive rear end collision avoidance system[END_REF].

Driving simulators have been one of the most frequent tools used in the evaluation of FCWS and most research has shown positive effects of the system when drivers are undistracted. This benefit has been demonstrated, for example, by a reduction of the number of collisions [START_REF] Lee | Collision Warning Timing, Driver Distraction, and Driver Response to Imminent Rear-End Collisions in a High-Fidelity Driving Simulator[END_REF], by faster braking reaction times following the detection of critical situations [START_REF] Abe | Alarm timing, trust and driver expectation for forward collision warning systems[END_REF], and by the adoption of longer and safer headways [START_REF] Ben-Yaacov | Effects of an In-Vehicle Collision Avoidance Warning System on Short-and Long-Term Driving Performance[END_REF]. Other studies such as Georgi et al. [START_REF] Georgi | New approach of accident benefit analysis for rear end collision avoidance and mitigation systems[END_REF], have estimated the benefits of the system by developing models which apply the algorithm used by the system in real-life accidents. They categorized three different types of driver: lethargic drivers with the longest reaction times and lowest decelerations, realistic drivers as an intermediate level, and best drivers with the fastest reaction times and highest decelerations.

According to their predictions, FCWS prevented 74% of collisions for best drivers, 38% for realistic drivers and 1% for lethargic drivers. In a more ecological context, using a field operational test, Najm et al. [START_REF] Najm | Evaluation of an automotive rear end collision avoidance system[END_REF] assessed the impact of FCWS and advance cruise control (ACC) systems for four weeks. 66 drivers drove without the system during the first week to obtain the baseline and with the system during the remaining three weeks. The results indicated that the exposure to conflicts (brake or steer at the last-second at a comfortable deceleration), near-crashes (brake or steer at the last-second at a hard deceleration), and severe near-crashes (minimum time to collision less or equal to 3s and maximum deceleration greater than 0.3g) in the last period of the test were reduced in about 20% compared to the first period. Based on different rear-end collision databases, these authors estimated that the system could prevent about 10% of these accidents. These studies show a range of benefit from these systems which fluctuates from 10% to 70% approximately [START_REF] Anderson | Potential benefits of forward collision avoidance technology[END_REF]. This wide range could be explained by the different variables considered in these studies such as the type of system used and its limitations, the methodological approach chosen, the characteristics of drivers or the weather conditions. Moreover, it is necessary to consider other factors which can have a direct impact on the effectiveness of the system. In this chapter, the impact of the system according to the attentional state of drivers as well as the impact of the system as a function of its reliability level will be analysed. Furthermore, in order to shed light on this aspect, we are going to consider an alternative research method to the classical behavioural data such as the electroencephalography and the associated event related potentials.

A new approach for evaluating the effectiveness of FCWS

Different tools are available for investigating the effect of this kind of assistance system, from the most fundamental techniques such as simplified simulator experiments conducted in a laboratory, to more realistic contexts using driving simulators and to almost or real driving conditions such as field operational tests and naturalistic driving experiments. Among these studies we can highlight the classical trade-off between experimental control and ecological validity.

Given the difficulty in simulating rear-end collisions in real-life situations, most studies are employing driving simulators where different scenarios as well as the severity of collisions can easily be manipulated. Behavioural measures (e.g. reaction time, steering wheel angle, speed) are used most frequently by researchers in these studies. Not only behavioural data can be recorded in driving simulators. Often, these measures can be enhanced by other complementary techniques such as the analysis of information given by drivers (i.e. questionnaires, in-depth interviews) or the analysis of physiological measures (i.e. electrooculography, galvanic skin response, heart rate, electroencephalography). Although physiological measures are still not very frequent in driving simulators, they provide complementary and additional information that in some cases is not observable in drivers' behavioural performance. In this part, we therefore will focus on the electroencephalography (EEG) and the associated Event Related Potential (ERP) techniques.

Electroencephalography is the study of the spontaneous electrical activity of the brain that can be recorded by electrodes placed on the scalp. Event Related Potentials are obtained from the electroencephalogram by filtering and averaging the activity time-locked to the stimulus of interest. The stimulus of interest is repeated a great number of time. The averaging allows reducing the random noise (i.e. movement artefacts), and so extracting the specific response to the target stimulus. As a result, a different succession of waves or components appears, depending on the type of stimulus presented and the nature of the task carried out. These enables the identification of the different stages of information processing. The first stage of the neural processing chain can be identified even before the stimulus appears, reflecting the anticipation of a stimulus. For example, the contingent negative variation (CNV) is a slow negative wave appearing typically when two stimuli have been presented associated (Figure 12.2). Thus, when the first stimulus or warning always precedes the second or target stimulus, participants can expect the target stimulus and prepare their responses due to the appearance of the warning stimulus [START_REF] Loveless | The contingent negative variation related to preparatory set in a reaction time situation with variable foreperiod[END_REF]. been linked to sensory processes as well as to the discriminative processing and are mainly modulated by physical attributes of the stimuli [START_REF] Vogel | The visual N1 component as an index of a discrimination process[END_REF]. After about 200 ms, the later ERP components such as N2/P3 are thought to reflect higher cognitive processes. The N2 component is elicited by tasks involving cognitive control, novelty stimuli, perceptual matching and response conflict, and the attention required for the processing [START_REF] Folstein | Influence of cognitive control and mismatch on the N2 component of the ERP: A review[END_REF]. The P3 component can be used as an indicator of the attentional resources allocation and working memory updating [START_REF] Polich | Updating P300: an integrative theory of P3a and P3b[END_REF][START_REF] Kok | On the utility of P3 amplitude as a measure of processing capacity[END_REF]. In general, it is possible to identify differences between experimental conditions by analysing the differences in ERP in terms of peak amplitude and/or peak latency of the ERP components of interest. In a broader sense, differences in peak amplitude of the wave could indicate the different degree of attentional resources engaged in the processing of the stimulus, and differences in peak latency of the wave (earlier or later occurrence in time) could be related to the speed of stimulus information processing.

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The implementation of the ERP technique in driving studies is not widespread due to some constraints, such as the high saccadic and motor movement sensitivity and the high number of trial repetitions required in order to reach an acceptable signal-to-noise ratio. Despite these constraints, there are a few ERP simulator studies which mainly investigate the negative effect of performing a concurrent cognitive task while driving [START_REF] Strayer | Multi-tasking in the automobile[END_REF][START_REF] Rakauskas | Psychophysiological measures of driver distraction and workload while intoxicated[END_REF]. Nevertheless this technique has been implemented only recently in the study of advanced driver assistance systems and, specifically, in the study of FCWS [START_REF] Bueno | An electrophysiological study of the impact of a Forward Collision Warning System in a simulator driving task[END_REF].

Are FCWS effective for distracted drivers?

The major contributing factor to rear-end collisions is driver distraction or inattention.

Therefore, if FCWS are expected to help distracted drivers in particular, the effectiveness of these systems should be evaluated according to the attentional state of the drivers, distracted or not.

Regan et al. [START_REF] Regan | Driver distraction and driver inattention: Definition, relationship and taxonomy[END_REF] define driver inattention as 'insufficient or no attention to activities critical for safe driving (p.5)'. Driver distraction, or driver-diverted attention, is a type of driver inattention where the attention to activities critical for safe driving is threatened by the diversion towards another competing activity. These competing activities can require cognitive, perceptual (i.e. visual, auditory), and/or motor resources, identifying the different distraction categories. Secondary visuo-motor tasks seem to produce the higher degree of interference with the driving task, although this could be mitigated by compensatory strategies. For example, visual concurrent tasks tend to impair lane keeping performance and increase the number of off-road glances but also induce speed reductions, whereas cognitive tasks generally provoke the opposite effect of visual concurrent tasks [START_REF] Engström | Effects of visual and cognitive load in real and simulated motorway driving[END_REF][START_REF] Kaber | Driver performance effects of simultaneous visual and cognitive distraction and adaptation behavior[END_REF].

Several reports have focused on the impact of FCWS on distracted drivers, but few studies have compared the distraction condition with the control situation (without any distraction); that is, assessing the impact of FCWS on distracted and also undistracted drivers. Data obtained in simulators show that distracted drivers also benefit from the warning systems by the reduction of the number of collisions [START_REF] Lee | Collision Warning Timing, Driver Distraction, and Driver Response to Imminent Rear-End Collisions in a High-Fidelity Driving Simulator[END_REF], by faster braking reaction times in detecting critical situations [START_REF] Kramer | Influence of Age and Proximity Warning Devices on Collision Avoidance in Simulated Driving[END_REF], and/or by longer and safer headways [START_REF] Abe | Visual distraction when driving and its influence on driver response to a forward collision warning system[END_REF]. Moreover, in some cases, the system even completely dissipates the negative effect of the secondary task [START_REF] Lee | Collision Warning Timing, Driver Distraction, and Driver Response to Imminent Rear-End Collisions in a High-Fidelity Driving Simulator[END_REF][START_REF] Ho | Using peripersonal warning signals to orient a driver's gaze[END_REF].

Electrophysiological studies have been recently conducted in driving contexts in order to assess the impact of secondary tasks. For example, Strayer and Drews [START_REF] Strayer | Multi-tasking in the automobile[END_REF] found that in a task where participants had to react to intermittent lead vehicle decelerations, the P3 amplitude was reduced and the P3 latency was delayed when they were engaged in phone conversations, suggesting a negative impact on the driving task when the memory load increased. Similarly, Rakauskas et al. [START_REF] Rakauskas | Psychophysiological measures of driver distraction and workload while intoxicated[END_REF] studied the impact of secondary tasks while driving and detecting unexpected sounds (oddball paradigm). They found that the P3 amplitude to novel sounds was especially reduced by a cognitive secondary task presented by cell-phone, showing that the processing of novel information is deteriorated by the dual task. In the context of FCWS, the ERP technique was introduced only recently by Bueno et al. [START_REF] Bueno | An electrophysiological study of the impact of a Forward Collision Warning System in a simulator driving task[END_REF].

These authors conducted an ERP study in a simplified driving simulator to evaluate the impact of a surrogate FCWS according to the attentional state of the participants, distracted or not by a secondary cognitive task. Participants were instructed to follow a lead motorcycle and they had to react by decelerating when the brake light (target) of the lead motorcycle was lit up. An auditory warning could forewarn participants that the motorcycle was going to brake soon. The results showed that the warning system reduced the reaction time when participants were undistracted but not when they were distracted. ERP data showed a benefit from the warning system at higher cognitive level (N2) suggesting that the warning could enhance the temporal expectancy regarding the target. However, and in parallel to behavioural data, this effect was only observed in simple task condition and not when participants were distracted. A possible explanation for this unexpected result could come from the experimental design. Indeed, an initial deceleration of the motorcycle occurred systematically before braking in all trials, whether or not the braking was preceded by the warning signal.

Thus, participants may have used this motorcycle deceleration as an additional and better predictor of the brake light occurrence instead of the warning signal which was not always reliable. Therefore, in a recent study, Bueno et al [START_REF] Bueno | Effectiveness of a Forward Collision Warning System in simple and in dual task from an electrophysiological perspective[END_REF] eliminated the predictive value of this motorcycle deceleration for the forthcoming brake light in order to increase the effectiveness of the FCWS under dual task conditions. The results indicated that participants were faster when they had available the warning signal compared to when no warning signal was given.

At the electrophysiological level, this warning effect occurred at preparatory (increase of the amplitude of the CNV) and higher cognitive level (reduction of the peak latency of the P3). In addition, a strong negative impact of the secondary task was observed at behavioural and electrophysiological level with or without the system. This result suggests that the presence of the warning was not enough to compensate the negative effect of the dual task.

These last two studies have contributed to an increase in the knowledge about the processing of warning signals in driving. According to these results, it seems that the warning signal intervenes in motor preparation process (CNV) and higher cognitive processing (P3). These findings are also consistent with the findings of earlier non-driving studies showing warning signal operates in the stage of response selection [START_REF] Hackley | Which stages of processing are speeded by a warning signal?[END_REF] and that it could reduce the peak latency of the P3 [START_REF] Rudell | Does a warning signal accelerate the processing of sensory information? Evidence from recognition potential responses to high and low frequency words[END_REF].

Contrary to the positive effects on distracted drivers presented at the beginning of this section, the last two studies analysed here [START_REF] Bueno | An electrophysiological study of the impact of a Forward Collision Warning System in a simulator driving task[END_REF][START_REF] Bueno | Effectiveness of a Forward Collision Warning System in simple and in dual task from an electrophysiological perspective[END_REF] showed that the warning system was not always effective when drivers were distracted. Therefore, at present it is not clear whether these systems achieve their main purpose of mitigating the negative effects of the distraction.

Although conclusions could not be drawn due to the limited number of studies evaluating the impact of the FCWS in distracted and undistracted drivers and their diverse methodology employed, there are some relevant questions to be considered. Firstly, given that secondary tasks can differ in modality (visual, auditory, cognitive, etc.) and complexity level, the effectiveness of the system could vary depending on the type and difficulty of the secondary task. It could be possible that the dual task interferes with the warning signal when both warning and secondary task share the same modality. It is known that in dual task paradigms, the likelihood of interference produced when performing two tasks from the same modality (e.g. both tasks are auditory) is higher than when these tasks belong to different modalities (e.g. visual and auditory) [START_REF] Wickens | The structure of attentional resources[END_REF]. As a result, the effectiveness of an auditory warning could see reduced if, for example, drivers are distracted by a secondary auditory task. Thus, auditory and visual-auditory warnings seem to be effective in helping drivers to detect potential collisions when they are distracted by a visual secondary task [START_REF] Lee | Collision Warning Timing, Driver Distraction, and Driver Response to Imminent Rear-End Collisions in a High-Fidelity Driving Simulator[END_REF][START_REF] Kramer | Influence of Age and Proximity Warning Devices on Collision Avoidance in Simulated Driving[END_REF][START_REF] Ho | Using peripersonal warning signals to orient a driver's gaze[END_REF]. However, when the nature of the secondary task is auditory (i.e. phone conversations) and also when the complexity of the task increases (i.e. mental mathematics and categorisation questions), an auditory warning seems less effective than a tactile warning [START_REF] Mohebbi | Driver Reaction Time to Tactile and Auditory Rear-End Collision Warnings While Talking on a Cell Phone[END_REF].

Secondly, from research using driving simulators [START_REF] Ho | Multisensory In-Car Warning Signals for Collision Avoidance[END_REF] or ERP approach (but in non-driving related contexts [START_REF] Santangelo | Multisensory integration affects ERP components elicited by exogenous cues[END_REF]), multimodal warnings seem to be more effective that unimodal warnings. Indeed, receiving redundant warnings from two different modalities could be advantageous in the case of distraction or in the case of warning failures.

Finally, the difficulty level of the secondary task could also undermine the effectiveness of the warning system. It is known that the amount of attentional resources available is considerably reduced by the presence of another competitive task [START_REF] Wickens | The structure of attentional resources[END_REF][START_REF] Baddeley | Exploring the central executive[END_REF]. When secondary tasks are highly demanding on a cognitive level, it might be possible that participants need to invest a lot of attentional resources to dealing with both tasks at the same time. Consequently, it is possible that the warning signal cannot be completely processed given the lack of attentional resources available, as could have occurred in the study of Bueno et al. [START_REF] Bueno | An electrophysiological study of the impact of a Forward Collision Warning System in a simulator driving task[END_REF]. In another study conducted in our laboratory, we investigated the impact of the difficulty of the secondary task on the effectiveness of the warning system. In this study in a driving simulator, only behavioural measures were recorded. The results showed an increase in the reaction time (RT) when participants were distracted by a high difficulty cognitive secondary task, but also when they were distracted by a low difficulty secondary task. However, when the warning system was available, RTs were shorter than the baseline (no warning, no distraction) only in the condition of low difficulty distraction, suggesting that the benefit from the system, at least partly, depends on the drivers' attentional resources available (manuscript in preparation). This result could support the hypothesis that warning signals are not treated automatically and need attentional resources to be processed.

Does the reliability of the system affect its effectiveness?

Besides drivers' attentional state, the effectiveness and acceptance of the system and driver behaviour may also be affected by the reliability level of the system. Indeed, depending on the type of algorithm and scan sensor, the system may malfunction, producing false alerts and/or misses of critical events. False alerts refer to the situations in which an alert is issued in the absence of any potential collision, for example, when there are highly reflective objects.

Nuisance alerts can be defined as alerts triggered in an appropriate situation but perceived by drivers as inappropriate because of their frequency, timing, intensity or modality [START_REF] Campbell | Crash Warning System Interfaces: Human Factors Insights and Lessons Learned Washington[END_REF].

Nuisance alerts can also be considered as alerts triggered in an inappropriate situation but whose origin could be justified by the presence of a potential threat (i.e. an alert triggered by a stationary vehicle placed out of or near the driver's line) [START_REF] Lees | Context conditions drivers' disposition towards alarms[END_REF]. Misses occur when an alert is not triggered despite the situation requiring it. Such failures are due to the fact that the capacity to detect obstacles could be limited in situations such as bad weather, detecting twowheeled vehicles, pedestrians, stationary obstacles or very slow-moving vehicles, swerving vehicles or vehicles in bends, abrupt accelerating or decelerating. Because of these limitations, no FCWS currently works perfectly.

Real data about the false alert and miss rates are not frequent in the literature, but the existing data suggests that this rate is still far from acceptable. As already mentioned, Najm et al. [START_REF] Najm | Evaluation of an automotive rear end collision avoidance system[END_REF] collated data from drivers who drove with a vehicle fitted with Advance Cruise Control and FCWS during one month. Their results showed that 44% of the alerts were false alerts and only 56% of all warnings were triggered by in-path targets (whether all of these alerts were necessary or not is unknown). McLaughlin et al. [START_REF] Mclaughlin | Analytic Assessment of Collision Avoidance Systems and Driver Dynamic Performance in Rear-End Crashes and Near-Crashes Virginia Virginia[END_REF] evaluated the algorithm used in the previous study using real-crash data and compared it with two other algorithms. Their results showed a benefit from the first system of about 60%. However, this algorithm also accounted with the higher warning frequency, 87 alerts per 161 km driven, compared to the two other algorithms, 83 and 8 alerts per 161 km driven, respectively. Taking into account the recommendation that no more than one nuisance alert per 322 km would be an acceptable rate [START_REF] Kiefer | Forward Collision Warning Systems: Development and Validation of Functional Definitions and Evaluation Procedures for Collision Warning/Avoidance Systems[END_REF], the data presented above is not very encouraging. Drivers' trust in the warning system could be considerably undermined if the number of nuisance or false alerts is too high, because these alerts are irritating and distractive [START_REF] Maltz | Imperfect in-vehicle collision avoidance warning systems can aid drivers[END_REF]. As a result, the acceptance of the warning could be reduced and, therefore, it is likely that users ignore or react inadequately to further warnings, whether or not they are valid [START_REF] Lerner | Inappropriate Alarm Rates and Driver Annoyance[END_REF]. Moreover, concerning behavioural changes in drivers' performance, false alerts seem to lengthen the braking reaction time [START_REF] Abe | Dynamics of drivers' trust in warning systems[END_REF] and to induce unnecessary deceleration responses [START_REF] Maltz | Imperfect in-vehicle collision avoidance warning systems can aid drivers[END_REF]; however, a higher false alerts rate could be associated with increases in the speed since drivers would tend to ignore the warning [START_REF] Cotté | Older and Younger Drivers' Reliance on Collision Warning Systems[END_REF]. Misses are also critical for the acceptance and trust in the system and drivers' performance could be affected by longer reaction times, even longer than driving with no system at all [START_REF] Abe | Dynamics of drivers' trust in warning systems[END_REF]. In addition, the speed could decrease with the increase of the misses which has been interpreted as a reduction of drivers' trust on the system [START_REF] Yamada | Preliminary study of behavioral and safety effects of driver dependence on a warning system in a driving simulator[END_REF].

Besides the rate of false alerts and misses, hit alerts (alerts delivered when a potential collision is imminent) could also be considered as ineffective depending on the timing in which the alert is triggered. In general, early alerts are more effective and account with a higher acceptance level by drivers than late alerts, but if they are prompted too early, they can be considered as nuisance or false alerts [START_REF] Abe | The effect of alarm timing on driver behaviour: an investigation of differences in driver trust and response to alarms according to alarm timing[END_REF].

However not all false alerts and misses have negative effects. For example, nuisance alerts can improve the knowledge that drivers have about the way the system functions [START_REF] Lees | Context conditions drivers' disposition towards alarms[END_REF]. In addition, if a system never triggers a false alert, drivers could fail to react adequately when the first hit alert occurs [START_REF] Parasuraman | Alarm effectiveness in driver-centred collision-warning systems[END_REF]. On the other hand, if a system almost never fails to detect a potential collision, drivers may over-rely on it and become vulnerable or not react adequately, when, for example, driving another unequipped vehicle [START_REF] Parasuraman | Alarm effectiveness in driver-centred collision-warning systems[END_REF]. It is complicated to assess which level of false alerts/misses is acceptable, given that the probability of experiencing a rear-end collision is quite low, and the efforts for finding out the cut-off point have not been very

conclusive as yet [START_REF] Kiefer | Forward Collision Warning Systems: Development and Validation of Functional Definitions and Evaluation Procedures for Collision Warning/Avoidance Systems[END_REF][START_REF] Lerner | Inappropriate Alarm Rates and Driver Annoyance[END_REF].

Other studies have investigated the reliability of the system focusing on the percentage of true alerts without specifying the rate of false alerts or misses. In general, higher levels of reliability result in better performance, but the point where the system becomes useless remains uncertain. Bliss and Acton [START_REF] Bliss | Alarm mistrust in automobiles: how collision alarm reliability affects driving[END_REF] noted that participants responded more frequently to the warning and manoeuvred more appropriately in avoiding collisions when the warning was 100% reliable. Nevertheless, Maltz and Shinar [START_REF] Maltz | Imperfect in-vehicle collision avoidance warning systems can aid drivers[END_REF] and Ben-Yaacov et al. [START_REF] Ben-Yaacov | Effects of an In-Vehicle Collision Avoidance Warning System on Short-and Long-Term Driving Performance[END_REF] did not find any differences between systems reliable at 60, 80-85, and 90-95%. Subsequently, Wickens and Dixon [START_REF] Wickens | The benefits of imperfect diagnostic automation: a synthesis of the literature[END_REF] carried out a meta-analysis of twenty two studies and concluded that a reliability level of 70% could be the criterion from which a system can be considered as an aid in avoiding rear-end collisions.

Finally, it should be noted that failures of the system could have different effects depending on certain driver characteristics such as age, driving experience [START_REF] Lees | Context conditions drivers' disposition towards alarms[END_REF], or attentional state. For example, an alert triggered too early could be considered as a nuisance alert for an undistracted driver but it could be a hit alert for a distracted driver. Abe et al. [START_REF] Abe | Visual distraction when driving and its influence on driver response to a forward collision warning system[END_REF] discovered that drivers rated alerts as less unnecessary when they were distracted by a secondary visual task than when they were undistracted. Thus, it seems that distracted drivers try to compensate their lack of attentional resources by the aid of the system. Maltz and Shinar [START_REF] Maltz | Imperfect in-vehicle collision avoidance warning systems can aid distracted drivers[END_REF] did not find any differences in distracted groups with regard the percentage of the time spent in a danger or safe zone according to the reliability of the system (high, medium, and low reliability or 1, 4, and 8 errors per minute, respectively). Nevertheless, the analysis of drivers' performance in case the system failed to deliver an alert showed a higher rate of deceleration responses in the danger zone by the low reliability group compared to the medium and high reliability groups and control group. This result could suggest that even when distracted, drivers can adopt a safe behaviour when the system frequently fails in detecting the hazard; however, when the system is highly reliable, drivers did not compensate the error of the system. As in the Malt and Shinar study [START_REF] Maltz | Imperfect in-vehicle collision avoidance warning systems can aid distracted drivers[END_REF], Bueno et al. [START_REF] Bueno | An electrophysiological study of the impact of a Forward Collision Warning System in a simulator driving task[END_REF] analysed the reliability level of an FCWS (100% or 70% reliable) in drivers distracted by a secondary cognitive task but they also analysed this in undistracted drivers. Behavioural data showed that reliable and unreliable systems only reduced RT when drivers were undistracted but not when they were distracted.

However, the analysis of the electrical activity of the brain revealed a slightly different pattern of results. ERP data showed a reduction in the amplitude and the latency of the N2 by the reliable system in simple task condition; whereas the unreliable system reduced the latency of the P3 in dual task condition. These results could be interpreted as an increase of the expectancy of the target in the first case and a diminution of the time required for processing the target at higher cognitive level, in the second case. In parallel to Maltz and Shinar's study [START_REF] Maltz | Imperfect in-vehicle collision avoidance warning systems can aid distracted drivers[END_REF] but with all due caution, it could be speculated that less reliable systems are more effective than more reliable systems in dual task situations. Nevertheless, further research is needed to shed light on these phenomena.

As it has been discussed here, the cut-off between a reliable and an unreliable system does not seem to be determined exclusively by the characteristics of the system (level of reliability, type of warning signal, etc.) but also by some driver characteristics such as the attentional state.

Behavioural adaptation to the system

The last factor addressed in this chapter is the behavioural adaptation defined as "those behaviours which may occur following the introduction of changes to the road-vehicle-user system and which were not intended by the initiators of the change (p.23)" [49]. Given its repercussion for road safety, the behavioural adaptation to the assistance system has a market negative connotation, although a wider vision could be adopted by considering all relevant changes associated to the introduction of the assistance system [START_REF] Saad | Literature review of behavioural effects[END_REF].

To our knowledge, there are no studies evaluating the behavioural adaptation to the FCWS using ERP data; therefore, only behavioural studies will be considered in this section.

As previously discussed, the introduction of an FCWS can produce different effects on drivers' behaviour. Some of them are positive, such as faster reaction times and the reduction of collisions. However, undesirable behavioural changes can also appear, sometimes as a consequence of the interaction with other factors such as the attentional state of the driver or the reliability level of the system. For example, drivers could engage in more secondary tasks or even assume more risky behaviours by delegating the danger monitoring task to the system (compensatory effects). This could have unintended consequences such as an increase in the brake reaction time in the case of a real collision or in the case of the system failing to warn drivers. Concerning the failures of the system, false alerts could increase the driving speed and reaction times and a reduced miss rate could lead to over-relying on the system.

In general, FCWS have been analysed in short-term studies and, in most of the cases, the effect of introducing the system could not have been assessed in experimental studies because the order effects were eliminated by the counterbalancing. Therefore, at present it is not fully understood how drivers adapt their behaviour to the system in the first-time uses (learning and appropriation phase), nor after a prolonged use during a long period of time (integration phase) [START_REF] Jamson | Potential benefits of an adaptive forward collision warning system[END_REF]. Moreover, other factors could have an influence on the adaptation to the system, such as traffic conditions, driver characteristics and some attitudes and personality traits like driving style, sensation seeking, and the locus of control (internal or external responsibility attribution for the outcome of events). Jamson et al. [START_REF] Jamson | Potential benefits of an adaptive forward collision warning system[END_REF] conducted a driver simulator study to analyse the benefits of an FCWS taking into account the driver style, with higher or lower sensation seekers. Their results showed a positive effect of the system compared to the baseline; however, the driver style had little or no impact.

To our knowledge, only one study has been carried out showing the behavioural effect of an FCWS in the long term in a field operation test [START_REF] Ben-Yaacov | Effects of an In-Vehicle Collision Avoidance Warning System on Short-and Long-Term Driving Performance[END_REF]. In this study, participants had to drive in real traffic conditions with the system (2 nd trial) and without it (1 st and 3 rd trials, and 4 th trial six months later). Safer time headway was observed immediately after exposure to the system (3 rd trial). Interestingly, this effect was also observed six months later when participants were exposed again to the same drive without the warning assistance. We have also analysed the behavioural effect of an FCWS in the short term in a driving simulator study. Participants were required to drive without the system during the first session (baseline). Then, the system was introduced in the second, third, and fourth sessions in order to evaluate the immediate effect of introducing an FCWS and the behavioural adaptation to the system in the short term.

Finally, participants drove without the system during the fifth l session to analyse the consequences of switching off the system after a short period of habituation. The results showed that the introduction of the system drastically reduced the reaction time during the second session compared with the control group who drove without any assistance. During the integration phase (sessions two and three), reaction times were also faster for the system group than for the control group. Finally, results showed longer reaction times during the last session (with the system switched off), with an increase especially noticeable for the system groups. This last result may provide evidence for the disruptive effect of driving without the warning system, for example, by a system breakdown, once the driver is accustomed to driving with the system. Nevertheless, the control group showed a progressive increment of the reaction time along the five sessions which could be interpreted as a practice and/or fatigue effect. Therefore, it was not possible to conclude whether the longer reaction times for the system groups were completely explained by the absence of the system. As there are not many studies in this respect, further research would be necessary to investigate the effects of driving with or without the system after the integration phase.

Although the number of studies and the situations evaluated are not sufficient to draw final conclusions, it is interesting to observe that among these studies no negative behavioural adaptation effects were evidenced. It could be possible that compensatory effects when driving with an FCWS are more difficult to reproduce than when driving with other systems.

Rear-end collisions are relatively infrequent situations compared to, for example, monitoring excessive speed or lane departure. Moreover, given the safety risk involved in these collisions, it could be more difficult for drivers to rely completely on the system. Certainly the reliability level can have a strong impact on the behavioural adaptation to the system.

However it has been demonstrated that unreliable systems can also be useful in terms of assistance for drivers.

Psychology of learning could enable interpretation of why unreliable systems can be effective.

The association between the warning (stimulus 1) and the hazard (stimulus 2) is produced in very different contexts (i.e. high traffic flow, good or bad weather conditions, secondary tasks, etc.). Moreover, drivers learn that the causal relation between the two stimuli is not perfect. Indeed, as discussed earlier, the perfect system does not exist. Therefore, the presence of false alerts and misses produces an intermittent reinforcement of the warning and, consequently, more resistance to extinction [52]. Nevertheless, given the limited number of studies in this regard, further research would be necessary in order to determine the positive and negative effects of FCWS used in the short and long term.

Conclusions

This chapter aimed at reviewing literature assessing the effectiveness of FCWS. Although it has been shown that the system provides potential benefits for road safety, certain factors such as the attentional state of drivers and the reliability level of the system can mitigate its effectiveness. Further research seems necessary to clarify whether the system helps distracted drivers by manipulating the difficulty level of the secondary tasks and the type of warnings.

If, as it has been hypothesised here, the processing of the warning information is not an automated task and needs some attentional resources, it is possible that a training program could optimise drivers' performance when driving with the system. The reliability of the system is likely to be one of the most critical factors for the acceptance of the system by drivers. Although failures of the system can have a positive impact for road safety, it is necessary to find a good balance to avoid drivers deciding not to use it. Probably one of the most negative effects of behavioural adaptation could be over-reliance. The studies presented in this chapter did not show evidence of this phenomenon in drivers; however, currently there are only a few studies and, therefore, more research assessing behavioural adaptation after short and long-term use needs to be conducted.

Finally, ERP studies have shown to be promising in the analysis of the effectiveness of FCWS. Until now, FCWS had been mainly studied by recording measures of driver performance and, eventually, by analysing the visual behaviour of drivers. The ERP technique permits to elucidation and dissociation of the different stages of the information processing, some of which are not observable in open behaviour. Thus, the results showed in the studies presented above revealed that the warning signal could operate at preparatory (CNV) and higher cognitive stages (P3).

Throughout this chapter, it has been shown that the effectiveness of the FCWS and its acceptance by drivers depend on numerous factors. On the one hand, factors that directly affect the effectiveness of the system can come from the system itself. For instance, the moment for triggering the warning, the reliability level of the system or the modality of the warning (visual, auditory) are critical elements to take into consideration. But even the "best" of the systems in terms of technical parameters could not be appropriated for certain drivers.

It has been demonstrated that the effectiveness of the system could vary according to the attentional state of the driver. The different driving style, age, experience or health status of drivers should also be considered in order to insure that specific populations, for example, older drivers, could benefit as expected from these systems. Moreover, one of the issues evidenced in some of the studies above presented has been the large inter-individual variability observed among the same type of drivers. Therefore, we strongly recommend developing adaptive FCWS which take such characteristics into account.

Figure 12 . 1

 121 Figure 12.1 Example of a grand-average ERP showing a typical P3 component at parietal areas

Figure 12 .Figure 12 . 2

 12122 Figure 12.2 Example of a grand-average ERP showing a typical CNV component at central areas

Figure 12 . 1

 121 Figure 12.1 Example of a grand-average ERP showing a typical P3 component at parietal areas

  BUENO, Mercedes, FABRIGOULE, Colette, FORT, Alexandra, 2013, Effectiveness of Forward Collision Warning Systems: a Contribution from the Cognitive Analysis Combining Behavioral and Electrophysiological Measurements. In: Driver Adaptation to Information and Assistance Systems, IET Digital Library, 22 p, DOI: 10.1049/PBSP009E_ch12

Acknowledgements

The research leading to these results has received funding from the European Community's Seventh Framework Program (FP7/2007-2013) under grant agreement n°238833/ ADAPTATION project. www.adaptation-itn.eu


G Pepin

C Jallais

A Fort

C Gabaude

Detection of mind-wandering in driving: contributions of cardiac measurement and eye movements

Keywords: Inattention, Driving, Mind-Wandering, Eye Movements, Heart Rate

In 2014 in France, there are still over 3,300 killed on our roads (ONISR, 2015). Many studies have highlighted inattention as a contributing factor for 25 to 50% of injury accidents (Mosedaleet al, 2005;Galéraet al, 2012). Distraction can be defined as a diversion of attention away from critical activities to competitive ones while inattention can be defined as a state inducing endogenous shift of attention (LemercierandCellier, 2008).The term inattention gathers different states such as cognitive overload or Mind-Wandering (MW), defined asa shift in the contents of thought away from an ongoing task to self-generated thoughts and feelings (Smallwood and Schooler, 2015).

MW is a recurring phenomenon in driving, four drivers out of five declare being aware of MW on their last journey and feel being in this state for more than a third of the time (Berthiéet al, 2015). According to Killingsworth and Gilbert (2010), this state represents nearly 50% of our daily life thoughts. It's therefore necessary to study this phenomenon to limit its impact on driving.During mind-wandering, drivers suffer from a perceptual decoupling corresponding to the capacity for the mind to flexibly disengage attentional processes from sensory input (Smallwood and Schooler, 2015). MW has many consequences on the driving activity. Being in MW would improve the risk to be considered responsible for a road accident (Galeraet al, 2012). Conducted by Heet al. (2011), the very first study confirmed the perceptual decoupling by revealing a change in the driver's visual scanning of the road during MW episodes. MW also leads to adecrease of speed micro-regulations and larger deviations in the vehicle's lateral position (Lemercieret al, 2015). Several techniques have been used to identify MW episodes using eye gaze (Uzzaman and Joordens, 2011) and variability in lane position (Gabaudeet al, 2012).

Thus, cardiac and gaze data have been recorded during simulated driving sessions. Participants were asked to (a) self-report their wandering thoughts when they were aware of itwhile driving and (b) thinking aboutinnovation in specific driving phases. The results obtained after analysis shown an increase in the gaze fixity during MW episodes. Different time-window have been set up to explore gaze behavior during inattention phase. It appears that the fixity rates is higherin the last second before the self-report (a). These results haven't been highlighted when drivers were thinking about innovation. Indeed, participants had to think about a topic on a longer time. This can explain a higher fixity rate before participants resolve the task than after on a wider time-window. These results could foster the gaze fixity rate as a MW objective indicator.Thus, this physiological indicator could be used to improve the detection of MW through data fusion and then warn drivers about their own state. Indeed, cardiac data collected here have not been analyzed yet butseveral indicators could be highlighted from this signal to improve our capacity to detect MW, this direction will also be explored.

This work was supported by IFSTTAR and the Valeo Innovation Challenge funds.

Berthié, G., Lemercier, C., Paubel, P.-V., Cour, M., Fort, A., Galéra, C., … Maury, B. (2015). The restless mind while driving: drivers' thoughts behind the wheel. Accident; Analysis and Prevention, 76, 159-165. Gabaude, C., Baracat, B., Jallais, C., Bonniaud, M.and Fort, A. (2012). Cognitive load measurement while driving. In :

Human Factors: a view from an integrative perspective (p. 67-80). Human Factors And Ergonomic Society. Galéra, C., Orriols, L., M'Bailara, K., Laborey, M., Contrand, B., Ribéreau-Gayon, R., … others. (2012). Mind wandering and driving: responsibility case-control study. British Medical Journal BMJ 2012; 345:e8105 He, J., Becic, E., Lee, Y.-C.andMcCarley, J. S. (2011). Mind wandering behind the wheel: performance and oculomotor correlates. Human Factors, 53(1), 13-21. Killingsworth, M. A.and Gilbert, D. T. (2010). A Wandering Mind Is an Unhappy Mind. Science, 330(6006), 932-932. Lemercier, C., and Cellier, J.-M. (2008). Les défauts de l'attention en conduite automobile : inattention, distraction et interférence. Le travail humain, 71(3), 271. Mosedale, J., Purdy, A. and Clarkson, E. (2004)

  . Contributory factors to road accidents. Transport Statistics: Road Safety, Department for Transport, London, UK. ONISR. (2015). La sécurité routière en France : Bilan de l'accidentalité de l'année 2014. Observatoire National Interministériel de la Sécurité Routière. Smallwood, J.and Schooler, J. W. (2015). The science of mind wandering: empirically navigating the stream of consciousness. Annual review of psychology, 66, 487-518. Uzzaman, S.andJoordens, S. (2011). The eyes know what you are thinking: eye movements as an objective measure of mind wandering. Consciousness and Cognition, 20(4), 1882-1886. PEPIN, Guillaume, JALLAIS, Christophe, FORT, Alexandra, GABAUDE, Catherine, 2017, Detection of mind-wandering in driving: contributions of cardiac measurement and eye movements , 5th International Conference on Driver Distraction and Inattention, PARIS, FRANCE, 2017-03-20, 1 p


Franck Techer

Christophe Jallais
email: christophe.jallais@ifsttar.fr

Yves Corson

Alexandra Fort

Franck, JALLAIS, Christophe, CORSON Yves Techer

Effects of driver anger state on driving performance and attention

Keywords: Anger, Event-Related Potentials, Visual N1, Lateral variations, Car simulator, Mind-wandering

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Marc Brunelle

niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

1. Tone systems are an integral part of what defines a language family, since there are regular tone correspondences between languages of the same family, for example, between the various dialects of Thai-Tay or between the various dialects of Chinese.

2. A non-tonal language, when it borrows words from a tonal language, does not borrow tones, as exemplified by Siamese loanwords into Khmer.

3. The relation between tones and initials is the same in Vietnamese and in Thai-Tay. It sets apart a series of high initials (aspirates and fricatives), which do not have the same influence on tones as plain voiceless stops, the latter constituting the middle series (Maspero 1912: 114-116).

In 1924, J. Przyluski reaffirmed the Mon-Khmer affiliation of Vietnamese, pointing out that: "Until we understand the circumstances under which a given language loses or preserves its tone system, it is safer not to take into account the loss or preservation of tone systems when determining language genealogy." (Przyluski 1924: 395-396) Finally, G. Coedès further stated in 1948: "In my opinion, given that we can neither deny the fundamentally Mon-Khmer character of the Annamese vocabulary nor the fundamentally Tai character of its tone system, the real issue is to determine if it is more likely for a non-tonal Mon-Khmer language to have adopted the Tai tone system or for a Tai language to have incorporated a considerable amount of Mon-Khmer vocabulary." (Coedès 1948: 72) The progress of general linguistics, by bringing out the special importance of what distinguishes words, i.e. what is "distinctive" (the object of phonology), as opposed to the various aspects of the material realization of the sounds of language (the object of phonetics), allows us to revisit with profit some parts of Henri Maspero's work and to answer G. Coedès's question.

[1.2. The analysis of Middle Chinese tones] Let us first examine what Maspero wrote about tones: classification can be found in "On the reconstruction of initial consonants in monosyllabic languages: the case of Proto-Tai" (1956;this volume) and his 1967 article about Lakkia.] "Chinese tones were not simple phenomena; they were made up of two elements, height and contour. Height depended on the initial, while contour depended at least to some extent on the final. Vowel quality and duration were irrelevant. In Middle Chinese, there were two heights and four contours. Voiceless initials, with or without aspiration, were high; voiced initials were low. The four contours are what is commonly called 'the four tones' (四聲 sì shēng) of Chinese. The most salient feature of this system is thus the effect of the initial." (Maspero 1912: 88-89) Maspero adds in a note: "It is intriguing that the Chinese, who investigated these questions so thoroughly, do not have words to refer to the high and low tone series. This is probably due to the emphasis that they put on the theory of the four tones. They generally use the words 清 [qīng] and 濁 [zhuó] that, literally, apply to the initial and mean 'voiceless' and 'voiced', respectively, but they attribute very little importance to tone height: instead, they essentially focus on contours. In dictionaries ordered by rhymes, no distinction [in terms of tone height] is made and words with voiceless and voiced initials are jumbled together in the same rhymes." (Maspero 1912: 89, endnote 2) One could infer from Maspero's text that the Chinese of the 6th century had taken their analysis of the eight tones of their language so far that they had broken them down into four contours and two heights and they had words to designate the four contours (四聲 sì shēng) but no terms to designate tone heights. On the other hand, Maspero insists on the correspondence between initials and height: "Actually, the characteristic of Far Eastern languages is not so much the existence of tones (since examples have been found elsewhere, as in some African languages, for instance) as the regular system whereby tone height depends on whether the initial was originally voiceless or voiced." (Maspero 1912: 89, endnote 1) However, a few lines before, Maspero had admitted that "in almost all modern languages, phonetic evolution has introduced a degree of confusion that makes this phenomenon unrecognizable". To the modern linguist, it is precisely because there are no correspondences between initials and tones, i.e. because a syllable composed of the same consonants and vowels can take on any of the five or six tones of the language, 2 that Cantonese, Vietnamese and Siamese are languages that have five or six tones.

In Middle Chinese, following Maspero's own description, the situation was different: a word having a kas its initial could only receive one of the three "high" tones (out of six) and a word with an initial gcould only receive one of the three "low" tones (out of six). No syllable made up of the same consonants and vowels could select among more than three tones to form a word. In view of this state of affairs, all modern linguists will agree with the observation of the 6th-century Chinese authors: there were only three tones in Middle Chinese. The association of initials with a given musical height is an unconscious, purely phonetic phenomenon, which is also found in other languages (for instance in Hottentot: [START_REF] Beach | Phonetics of the Hottentot language[END_REF].

Middle Chinese had only three tones up until the 9th century. At that time, the voiced stops g, j [IPA: ɟ], d and b devoiced to k, c, t and p, aspirated or not depending on dialects and on tones. From that point on, the musical height of the tone became a contrastive phonological property used to distinguish words. Two words which used to be distinct because one had an initial kand the other had an initial gcame to have the same initial, k-, and to be distinguished solely by the higher tone of the former. The threetone system thus became a six-tone system.

[1.3. Analogy between the Chinese tone system and the tone systems of Thai-Tay and Vietnamese] Maspero was absolutely right to insist on the analogy between the Chinese tone system and the tone systems of Thai-Tay and Vietnamese. We do not have ancient descriptions of Thai-Tay, but the Siamese script shows that around the 12th century the language only had three tones and had voiced [initial] stops. Then, when these voiced stops devoiced -as in Chinese -, the three-tone system split into a six-tone system. These six tones are still distinct in the Thai-Tay dialects of southern China and northern Vietnam, but their number has been reduced to five in Siamese following the merger of two of the tones. In order to transcribe the three tones in Old Thai [i.e.

2 . To simplify the demonstration, we only consider non-checked syllables:

syllables ending with a voiced sound (a vowel, or a nasal consonant). Syllables closed by -k, -t or -p are treated as having additional tones in Cantonese and Middle Chinese; this is why Cantonese is said to have nine tones, and Middle Chinese to have had eight.

prior to the split of the tone system], only two symbols were needed; these symbols are still used in Thai orthography: mai ek (ไม เอก) and mai tho (ไม โท).

Vocabulary that is shared by Thai-Tay and Chinese 3 allows us to establish the following tone correspondences: H. Maspero showed that the six tones of Vietnamese can be divided into two series (Maspero 1912: 95-96): one series composed of the three tones ngang,5 hỏi and sắc was associated with former voiceless initials, while another composed of the three tones huyền, ngã and nặng occurred with former voiced initials. The situation in Old Vietnamese, i.e. before the 10th century, was thus the same as in Proto-Tai and in Chinese: there were only three tones, which were each split into two during the initial-consonant shift. We will designate these old tones by concatenating the names of their two modern reflexes: ngang-huyền, hỏi-ngã and sắc-nặng, respectively.

[
The correspondence between the three tones of Old Vietnamese and the three tones of Proto-Thai-Tay is given in a list provided by Maspero6 3 . This list of shared vocabulary was established by H. Maspero and K. Wulff (Maspero 1920: 62, 68, 84, 86, 94, 117;[START_REF] Maspero | Préfixes et dérivation en chinois archaïque [Prefixes and derivation in Old Chinese[END_REF]-1935: 321-322;Wulff 1934: 171-187) under the hypothesis of a genealogical relation; however, the list remains valid if one considers, following P. K. [START_REF] Benedict | Thai, Kadai and Indonesian: a new alignment in southeastern Asia[END_REF], that they are loanwords, which is also my opinion. (Maspero 1912: 97), to which we can also make a few additions (Tables 2, 3 and5

กี ่ ki ̄¹ kiʾ 機 ˓ki 26 'to ride (horse)' cỡi [kɤj˧˨˥] ขี ่ khi ̄¹ kʰiʾ 騎 ˓gie̯ 'written word' chữ [cɯ˧˨˥] ชื ่ อ ji ̣ ̄ạ ɟɯʾ 'name' 字 dziʾ 'bean' đỗ [ɗo˧˨˥] ถั ่ ว thvă¹ tʰuoʾ 荳 dəuʾ 'slap' vả [va˧˩˨] ฝ า p͟ ha1 faʾ 'palm' - 'basin' ảng, ang [aŋ˧˩˨], [aŋ˦˦˦] อ าง ˀaṅ¹ aːŋʾ 盎 ˀângʾ
'to make sth float'

lõng 27 [lɔŋ˧˨˥] ล อง lạṅ¹ lɔːŋʾ -
These correspondences indicate that at the time when the Tai language which is the ancestor of Siamese was spoken to the north-east of the Red River (the time when Old Vietnamese only had three tones), the tone hỏingã had the same phonetic realization as the Old Thai tone marked by mai ek and the tone qù of Middle Chinese. It was therefore a falling tone.

Chinese loanwords in Vietnamese show the same correspondence.

[

歲 si ̯wäiʾ 'hare' thỏ [tʰɔ˧˩˨] 兔 t'uoʾ 'belt' dải [ðaj˧˩˨ ] 帶 tẫiʾ 'lung' phổi [foj˧˩˨ ] 肺 pi ̯wɒiʾ 31 'to encourage' ủi 32 [uj˧˩˨] 慰 ˀweiʾ 'fairness' nghĩa [ŋiə˧˨˥ ] 義 ngie̯ ʾ 'to heal' chữa [cɯə˧˨˥] 助 ḍẓi ̯woʾ 'chopsticks' đũa [ɗuə˧˨˥ ] 箸 diwoʾ 'pouch' đãy [ɗaj˧˨˥] 袋 dâiʾ 'hat' mũ [mu˧˨˥] 帽 mâuʾ 'easy' dễ [ðe˧˨˥ ] 易 ie̯ ʾ 'interest' lãi [laj˧˨˥] 利 liʾ 'projecting, protruding' lõ [lɔ˧˨˥] 露 luoʾ
Given the considerable number of Chinese loanwords in Vietnamese, one might wonder whether the words of Chinese origin that are common to Vietnamese and Thai-Tay have been borrowed separately in the two languages. Under the hypothesis that Thai-Tay and Vietnamese are not close relatives, loanwords attest a shared culture contemporaneous with the peak of Chinese influence, from the 3rd to the 6th century AD.

[2.3. Tone sắc-nặng]

The correspondences given by Maspero for the tone sắc-nặng are presented in

ย าม yam¹ ʿˀjaːm - 'to dip' chấm [cɤm˨˦ ] จิ ้ ม cim² - - 'banana' chuối [cuəj˨˦ ] กล วย klvay² ʿkluoj - 'bread' bánh [ɓɛɲ˨˦ ] แป ง p ̱ eeṅ² ʿpɛng 餅 ʿpi ̯äng 'deformed' méo [mɛw˨˦ ] เบี ้ ยว 38 pi ̣ ̄eyv² ʿˀbiew - 'belly' bụng [ɓuŋ˨˨˨ ] พุ ง buṅ - - 'winding' quẹo [kwɛw˨˨˨ ] เคี ้ ยว 39 gi ̣ ̄eyv² - - 'that' nọ [nɔ˨˨˨ ] นี ้ ni ̄² ʿni - 'debt' nợ [nɤ˨˨˨ ] หนี ้ hni ̄² ʿn̥ i - 'alcohol' rượư [rɯəw˨˨˨ ] เหล า hlau² ʿl ̥aw 酒 ʿi ̯əu 'hook' ngạnh [ŋɛɲ˨˨˨ ]
เงี ่ ยง 40 ṅi ̄eyṅ¹

禮 ʿliei 'all' mọi [mɔj˨˨˨] 每 ʿmuâi 'cold' lạnh [lɛɲ˨˨˨] 冷 ʿlɒng 'similar' tợ [tɤ˨˨˨] 似 ʿzi
The tone sắc-nặng was thus, like the Chinese tone shǎng, a rising tone.

[3. Re-examining Maspero's argument that the existence of a middle series constitutes a uniquely shared feature of Vietnamese and Thai]

[3.1. Emergence of a middle series in Thai-Tay and in other language families of the area]

Before discussing whether we can distinguish a middle series from a high series of initials in Vietnamese, let us examine whether it is true that the existence of a middle series is really a distinguishing characteristic of the Thai-Tay language family. Maspero, projecting the tone system into the indefinite past, believed that the presence of a middle series was a Proto-Thai-Tay property, only preserved in Siamese [START_REF] Maspero | Contribution à l'étude phonétique des langues thai [A contribution to the phonetic study of the Thai languages[END_REF]1912: 99). In contrast, if we examine the facts from a dynamic point of view, we can see how the middle series became distinct during the initial-consonant shift, when the three-tone system turned into a six-tone system. In Proto-Thai-Tay, there were voiceless initials (p, t, k, pʰ, tʰ, kʰ... [i.e. voiceless stops] and m̥ , n̥ , l ̥ [i.e. voiceless continuants]), and voiced initials (b, d, g... and m, n, l...). In most Thai-Tay languages, b, d, g devoiced to p, t, k and the voicing contrast turned into a high/low tone contrast. The words that used to begin in b, d, g... and m, n, l... now belong to the low tone series while the words that used to begin in p, t, k... and m̥ , n̥ , l ̥... now belong to the high tone series. However, in Siamese (and in neighbouring Lao dialects), voiced stops became aspirated as they devoiced: b, d, g became pʰ, tʰ, kʰ, also acquiring a low pitch. [Syllables with] Proto-Thai-Tay unaspirated voiceless stops *p, *t, *k thus did not have to modify their original pitch because they were not at risk of merging with [syllables with] the former voiced stops: they do not belong to the high series because they do not have to contrast with a low series. They form an intermediate series, called "middle series", whose unmarked tone (= píng 平) merges with the unmarked tone of the low series, while its marked tones merged with those of the high series.

In Dioi, 43 according to Li Fang-kuei's analysis [START_REF] Li | The influence of primitive Tai glottal stops and preglottalized consonants on the tone system of Po-ai[END_REF], since voiced stops became voiceless unaspirated (there are no aspirates in the language), the only initials that could not undergo a merger with something else during the initial-consonant shift are the preglottalized initials: ˀb, ˀd, ˀy. The middle series is here limited to these preglottalized consonants: one of the tones of that series (corresponding to Proto-Thai-Tay mai tho) merged with the corresponding tone of the low series while the other tones merged with the high series.

In Proto-Thai-Tay and Proto-Dioi, there was a voiceless sonorant series (Thai spelling has them as hm, hn, hñ, hl and hw, but with *hr and *hṅ both written as h). That is why previously voiced sonorants now belong to the low series: former voiceless sonorants became voiced as they created the high series. In Tang Chinese, on the other hand, there was only one series of sonorants, voiced as expected, while there was a voicing contrast among stops and fricatives. In the Sino-Vietnamese dialect (the Vietnamese reading of Chinese characters) that derived from it, sonorants, albeit voiced, form a middle series: their píng tone merges with high series ngang while the other tones merge with ngã and nặng, the tones of the low series (Maspero 1912: 91-95).

In Proto-Yao (Miao-Yao [Hmong-Mien] family), there were three series of initials for both stops and sonorants: voiceless aspirated, voiceless glottalized and voiced. An initial-consonant shift first caused a merger between glottalized and voiced consonants: the voiced stops b, d, g devoiced to p, t, k and the glottalized sonorants ˀm, ˀn, ˀl became m, n, l. This is the current state of the Mien dialect, where the former voiced consonants form the low series and the former glottalized consonants form the high series. Aspirated pʰ, tʰ, kʰ and m̥ , n̥ , l ̥, when intact, have highseries tones. However, in the Mun dialect where aspirated sonorants m̥ , n̥ , l ̥ have become plain voiced sonorants m, n, l, former aspirates form a middle series in which the píng tone merges with the high series píng tone, the shǎng tone merges with the low series qù, the qù tone merges with the low series shǎng and the rù tone merges with the high series rù (Haudricourt 1951). 44 [3.2. There is no middle series in Vietnamese]

A middle tonal series is defined by the fact that some of its tones merge with those of the low series and others with those of the high series. It arises during the initial-consonant shift which creates the high and low series; whether it emerges or not depends on the onset system of the language.

In Vietnamese, sắc and ngang both belong to the high series. The presence of sắc in a correspondence where we expect ngang is thus not a proof of the existence of a middle series. Besides, this phenomenon seems anterior to the initial-consonant shift because it is found, as we will see, in Mon-Khmer words. Finally, it is clear that the existence of a middle series is not a specific property of Thai-Tay languages.

[4. The origin of the three tones of Old Vietnamese: comparison with Mon-Khmer toneless languages]

If we now examine the correspondences between Vietnamese and Mon-Khmer given by Maspero (Maspero 1912: 91-95), we realize that his distinction between high initials (i.e. aspirates) and middle initials (i.e. unaspirates) does not solve the problem of the distribution of sắc and ngang. He does find a few Vietnamese words with tone sắc that have an aspirated initial in some languages: 'eight' tám [tam˨˦ ], Mnong pham; 'leaf' 44 . [Haudricourt later corrected his interpretation of the Yao-Mun initialconsonant shift: rather than a two-way split with a middle series, he posited a one-time three-way split (tripartition) [START_REF] Haudricourt | Bipartition et tripartition des systèmes de tons dans quelques langues d'Extrême-Orient [Two-way and three-way splitting of tonal systems in some Far Eastern languages[END_REF] Nonetheless, Maspero clearly saw the correspondence of the tone hỏingã with Mon-Khmer words ending in a voiceless fricative -h stemming from *-s or *-ś. 45 Here are some examples: 'seven' bẩy [ɓɤj˧˩˨ ], Mon tpah; 'nose' mũi [muj˧˨˥ ], Mon muh; 'root' rễ [re˧˨˥ ], Mon rüh, Mnong ries.

Assuming that Vietnamese was originally a toneless Austroasiatic language, we can therefore outline the way in which the hỏi-ngã tone appeared. The final fricative became a laryngeal h produced by an abrupt slackening of the larynx. The slackening of the vocal folds produced a drop in the pitch of the preceding vowel, i.e. a falling tone. This falling tone, which was at first a mere phonetic consequence of the final h, became a phonologically relevant tone, characteristic of the word, when the final h disappeared in the course of evolution.

We can give a similar explanation for the origin of the tone sắc-nặng, thanks to new data. The Austroasiatic languages include not only the Mon-Khmer group in the south, but also the Palaung-Wa languages [START_REF] Shafer | Études sur l'austroasien [Studies in Austroasian[END_REF] in the north. Of the latter, we will cite (i) Riang, spoken in the Shan states and recorded by H. G. Luce (professor at Rangoon University and lecturer at the School of Oriental Studies of London University), (ii) Lamet, studied by K. G. Izikowitz (director of the Ethnographic Museum of Göteborg), and (iii) Khmu, recorded in Luang Prabang by the pastor W. A. Smalley (former student at Columbia University). 46 In these languages, we find final glottal stops in words which have the tones sắc and nặng in Vietnamese: 'leaf' lá [la˨˦ ], Riang laʔ, Khmu l ̥aʔ; 'rice' gạo [ɣaw˨˨˨ ], Riang koʔ, Khmu rənkoʔ; 'fish' cá [ka˨˦ ], Riang, Khmu kaʔ; 'dog' chó [cɔ˨˦ ], Riang, Khmu soʔ; and 'louse' chí [ci˨˦ ], Riang siʔ.

45

. [The symbol ś is used e.g. by Karlgren; it corresponds to a palatal or alveolopalatal fricative, presumably ɕ or ç.]

46

.

[The reference for the Lamet data is: [START_REF] Izikowitz | Lamet: Hill Peasants in French Indochina[END_REF]. Lamet (Rəmeet) vocabularies were later published by [START_REF] Lindell | Two dialects of the Rmeet (Lamet) language[END_REF]. Smalley's publications on Khmu include (i) an Outline of Khmuʔ structure (1961), which contains a short word list, and (ii) a short book chapter (1964). More substantial data on Khmu dialects were published in 1981, again by Lindell, Svantesson and Tayanin.]

A glottal stop following a vowel is produced by an increase in vocal fold tension (the opposite of what we have seen for final h). During the articulation of the vowel, the increase in vocal fold tension in anticipation of the coda glottal stop produces a rising tone. This tone, a phonetic consequence of the glottal stop, becomes a truly phonological tone used to distinguish the word when the glottal stop disappears. Unfortunately, in Palaung-Wa languages, the glottal stop is not found in sonorant-final words, so that nothing in the Riang word 'four' pon explains the tone of Vietnamese bốn [ɓon˨˦ ]. But this combination is not impossible [in principle], since it is attested in Lushai, a Tibeto-Burman language [START_REF] Henderson | Notes on the syllable structure of Lushai[END_REF]).

[Table 7 (Haudricourt 1953).

Comments

This fundamental article follows upon an article of the preceding year ("The place of Vietnamese in Austroasiatic", this volume) in which Haudricourt argued that basic vocabulary indicated that Vietnamese belonged to the Austroasiatic family, and that the presence or absence of tone does not constitute decisive evidence for language classification. In the present article, Haudricourt pursues his argument for the Austroasiatic origin of Vietnamese, showing, by comparison with related, toneless Austroasiatic languages, exactly which features evolved into the Old Vietnamese tones, giving rise to a system comparable to those of Middle Chinese and Old Thai. This demonstration provided the foundation for his theory of the Old Chinese origin of the Middle Chinese qù tone ("How to reconstruct Old Chinese", this volume) and indeed for the whole theory of the origin of tone in East Asia.

Haudricourt completed his general model of tone and register in East Asia with articles in 1961 concerning initial-driven tone splits and in 1965 concerning initial-driven register formation.

A clarification about stop-final syllables (D / rù tones)

Haudricourt did not discuss stop-final syllables (tonal category D; sinological label: rù), to simplify the demonstration. Thus Table 7 has only three blocks of rows, corresponding to the three tones of Old Vietnamese (6th century). The syllables which had (and still have) final stop consonants, because they remained toneless at the time (they became tonal only after the initial consonant shift), are not represented in Table 7. This has led to misunderstandings. To clear these up, we provide an expanded table (Table 8) which includes the missing CVC category. Table 8 follows the now widely-accepted format of Haudricourt's later articles, beginning with "Two-way and three-way splitting of tonal systems..." (1961, this volume) in which the old tonal categories are shown in columns and the old initial series in rows. The order of the tones is A (corresponding to Chinese pı ńg), B (shǎng), C (qù), D (rù, stop-final). Note that in the present article, in the exposition as well as in Tables 1 and7, the order of the tones is pı ńg, qù, shǎng, which is the traditional order of the Thai tones (basic, mai ek, mai tho).

A number of scholars (e.g. [START_REF] Diffloth | Proto-Austroasiatic creaky voice[END_REF]: 146, Thurgood 2002: 335, 2007: 265), purporting to summarize Haudricourt's article, present a table, similar to our Table 8, but conflating tonal categories B (shǎng) and D (rù) in a single column, 48 listing their respective etymological sources, glottal stop and oral stop final, together in the column header. From there it 48 The tones of these two categories have the same names (sắc, B1 and D1; nặng, B2 and D2) and the same symbols in Modern Vietnamese: see Table 8. Phonetically though, although close, they are not identical, as can be seen in the values given in the table, as well as in phonetic studies showing that Vietnamese D2 is not glottalized, unlike B2 [START_REF] Michaud | Final consonants and glottalization: new perspectives from Hanoi Vietnamese[END_REF][START_REF] Brunelle | A laryngographic and laryngoscopic study of Vietnamese tones[END_REF].

is only a short step to attribute to Haudricourt the opinion that stop finals are the direct ancestor of the B tone. Such a misrepresentation of Haudricourt's model tends to find its way into authoritative textbooks, such as the "Tonogenesis" chapter of The Blackwell Companion to Phonology [START_REF] Kingston | Tonogenesis[END_REF](Kingston : 2311)).

The distinction between a "consonant-based" and a "phonation-based" model of tonogenesis: a spurious dichotomy?

It has been argued "that the Haudricourt analysis should be updated, replacing its segmentally-driven model by a laryngeally-based model, incorporating the effects of voice quality distinctions" [START_REF] Thurgood | Vietnamese and tonogenesis: revising the model and the analysis[END_REF]. This description of Haudricourt's model as consonant-based, in contrast to a phonation-based alternative, is widely cited. The whole discussion rests on the mistaken idea that Haudricourt posited a "direct" influence of segments on pitch/tone, an idea itself derived from the confusion we explained earlier.

A careful perusal of Haudricourt's present article (for end-based events) coupled with "Mon-Khmer consonant shifts" (1965, this volume) (for initial-based events) should suffice to set this misrepresentation straight.

In this article, as generally, Haudricourt reminds us of the "special importance of what distinguishes words, i.e. what is "distinctive" (the object of phonology), as opposed to the various aspects of the material realization of the sounds of language (the object of phonetics)" (end of section 1.1). So the detailed mechanisms by which pitch arises from earlier non-pitch material is not his main object. He nevertheless offers some hypotheses.

Concerning final consonants, [START_REF] Haudricourt | Introduction à la phonologie historique des langues miao-yao [An introduction to the historical phonology of the Miao-Yao languages[END_REF] clearly states that final /-h/ and /-ʔ/ constitute laryngeal events. For category C (Chinese terminology: qù, Vietnamese: hỏi-ngã), "[t]he final fricative became a laryngeal h produced by an abrupt slackening of the larynx. The slackening of the vocal folds produced a drop in the pitch of the preceding vowel, i.e. a falling tone." As for category B (shǎng, sắc-nặng), the opposite change takes place: "A glottal stop following a vowel is produced by an increase in vocal fold tension (the opposite of what we have seen for final h). (...) the increase in vocal fold tension in anticipation of the coda glottal stop produces a rising tone."

André-Georges Haudricourt

As for voicing oppositions among initial consonants, the 1954 article does not go into the topic of the phonetic mechanisms, and is not a sufficient source to discuss Haudricourt's global model. For phonetic hypotheses about the possible mechanisms involved in tonal splits driven by an initial consonant shift, one has to turn to the 1965 article ("Mon-Khmer consonant...") where a unified mechanism for the development of tonal and registral contrasts, including vowel-timber modifications, is proposed, something like what other authors have called a "tense/lax laryngeal syndrome" (Matisoff 1973). Previous readers were less likely to see the complete picture, because they did not have all the material under the same book-covers.

Since the 1970s, experimental investigations into laryngeal behaviour have shown that much more physiological complexity is involved than was suggested by Haudricourt's reflections on phonetic mechanisms underlying tonogenesis: see in particular [START_REF] Edmondson | The valves of the throat and their functioning in tone, vocal register and stress: laryngoscopic case studies[END_REF] and [START_REF] Keating | Phonation contrasts across languages[END_REF]. Phonetic studies of synchronic variation are another recent approach, shedding light on tonogenetic processes in progress, e.g. [START_REF] Brunelle | Dialect experience and perceptual integrality in phonological registers: Fundamental frequency, voice quality and the first formant in Cham[END_REF] on Cham, Kirby (2014) on Khmer, [START_REF] Yang | A sociotonetic study of Lalo tone split in progress[END_REF] on Lalo, and [START_REF] Pittayaporn | Laryngeal contrasts in the Tai dialect of Cao Bằng[END_REF] on Cao Bằng Tai.

The issue of sonorant-final syllables carrying tone B (shǎng, sắc-nặng)

As predicted by Haudricourt's reconstruction, tone C (qù, hỏi-ngã) does not occur on nasal-final syllables of Austroasiatic stock, where it would imply earlier sequences of a nasal followed by /h/. Tone C on nasal-final syllables is only found in borrowings from Chinese, and in words of expressive origin (Ferlus 2004: 299, citing Maspero). On the other hand, there exist numerous nasal-final syllables carrying tone B. Haudricourt pointed out that the Palaung-Wa languages did not provide comparative evidence for the final resonants plus glottal stop which he was led to reconstruct for these words.

While emphasizing that present-day correspondences between Vietnamese tones and final -ʔ in other Austroasiatic languages are far from tidy, William Gage mentions in Chong (Pearic branch of Austroasiatic) the presence of four sonorant-final words with medial glottalization that are cognate with Vietnamese words of tone category B1: 'cooked' chiiˀn, Viet. chín; 'four' phooˀn, Viet. bốn; 'wind' kyaˀl, Viet. gió; and 'far' cŋɔˀy, Viet. ngái. He interprets them as "the most encouraging indications yet found in support of Haudricourt's hypothesis, allowing us to extend it beyond open syllables" (Gage 1985: 33). Diffloth (1989: 146-148) suggests, in line with Haudricourt's model, to reconstruct glottalization for all items carrying tone B in Vietnamese. He proposes to reconstruct this feature (labelled "creaky voice") at the stage of the common ancestor of Vietnamese and its closest relatives within Austroasiatic (Proto-Vietic, a.k.a. Proto-Viet-Muong), and possibly to Proto-Austroasiatic. [START_REF] Ferlus | The origin of tones in Viet-Muong[END_REF] hypothesizes that final glottal constriction on sonorantfinal syllables was absent in Proto-Austroasiatic, and that it developed in Early Proto-Viet-Muong (Proto-Vietic) on those sonorant-final words that had sesquisyllabic structure. The idea is that a syllabic "tenseness" evolved into a glottal constriction, resulting in the same tonogenetic effects as etymological -ʔ.

To this day, this remains an open issue, to be investigated through further research into the diachronic evolution of the Austroasiatic language family. [START_REF] Sagart | Chinese tones from Austronesian final consonants[END_REF] notes that the same issue is found in Chinese, and suggests that the source of the glottal stop in words of the nasal-ending series is to be found in an earlier series of voiced stop endings, developing to nasal plus glottal stop: *-b, *-d, *-g > -mˀ, -nˀ, -ŋˀ.

  Tone sắc is marked with an acute accent: á; tone nặng is marked with a subscript dot: ạ.] 34 . [Neither tiếng nor cứng match the Chinese and Tai tone A. The Vietnamese words both likely were words originally with final glottal stops. The meaning of Vietnamese cứng is 'hard'. The Chinese word 彊 'strong' (Pinyin: qiáng) was borrowed into Vietnamese as part of the Sino-Vietnamese layer, as cường [kɯəŋ˧˨ ], with the meaning 'strong'.] 35 . [Haudricourt omits the diacritic.] 36 . [Haudricourt writes dến.] 37 . Maspero gives the Siamese word หยาม hyam, which means 'to insult'; the word that we give is satisfactory meaning-wise, but its spelling is not etymological. It should be written หย าม hyam². [Due to the merger of the Old Thai tone mai tho of the high series with the tone mai ek of the low series, ย าม yam¹ and หย าม hyam² both came to be pronounced as [jaːm] with the falling tone, whence the possibility of a spelling replacement.] 38 . [Haudricourt uses the wrong diacritic.] 39 . [Haudricourt omits the diacritic.] 40 . [This word actually means 'The pointed part of a hooked object'. The diacritics are misplaced in the original].

43.[

  Remember that Haudricourt's Thai-Tay group excluded Dioi (Zhuang): in his view of the Tai family, Dioi was a sister group toThai-Tay.]

Table 1 .

 1 Tone correspondences between Thai-Tay and Chinese]

	Thai script	Chinese	[tone contour] [diacritic used in tables]
	no tone mark	平聲 píng shēng	[level tone]	[ ˓X ]
	mai ek (  )	去聲 qù shēng	[falling tone]	[ Xʾ ]
	mai tho (  ) 4	上聲 shǎng shēng	[rising tone]	[ ʿX ]

[2. The three tones of Old Vietnamese]

believed the Siamese word was of Thai stock: he compared it to a word found in Ahom and Shan (Maspero 1912: 64), but the tone of the Shan word indicates that it corresponds to Siamese ด วย tvay² 'with'. [This word means

  . [This Khmer word has the very specific meaning of 'to follow in order to mate' and refers to male animals.] 13 . [This archaic word refers to an alloy containing lead.] 14 . [The form is wrongly printed with an apostrophy instead of the tone mark in the original, and the mistake is copied in the SELAF reprint. We have restituted Karlgren's form A A2 32.] 15 . [Mòng means 'to long for'.]

	8 André-Georges Haudricourt
	). 2.1. Tone ngang-huyền [Table 2. Correspondences for the Old Vietnamese tone ngang-huyền (Sinological terminology: píng)] 2a. Maspero's examples meaning Vietnamese 7 Siamese 8 Proto-Thai-Tay Middle Chinese 9 'to pound' đâm [ɗɤm˦˦˦] ตํ า t ̱aṃ tam -'to divide' băn 10 [ɓan˦˦˦] ป น p ̱ an pan 分 ˓pi ̯uən 'to follow' noi [nɔj˦˦˦] โดย 11 toy (Khmer: េដា្យ [daɔj] 12 ) -'sloping' nghiêng [ŋiəŋ˦˦˦] เอี ยง ˀi ̄eyṅ (Khmer: េអ្យង [ʔiəŋ]) -'lead' chì [ci˧˨ ] ชิ น 13 jin ɟɯn 鉛 ˓i ̯wän 14 'net' dò [ðɔ˧˨ ] ยอ yạ --'raft' bè [ɓɛ˧˨ ] แพ bee be -'to explore' mòng 15 [mɔŋ˧˨ ] มอง mạṅ --'to flay' 16 đòn [ɗɔn˧˨ ] ทวน dvan (Khmer: េទាល 'to hit' [tʊːl] 17 ) -7 . [In Vietnamese orthography, tone huyền is indicated by a grave accent, and tone ngang is left unmarked.] 8 . [The translitteration of the forms in Thai script has been provided by the editors according to the system of Coedes.] 9 . [Middle Chinese reconstructions are cited from Karlgren (1940).] 10 . [In modern Vietnamese, this Chinese root is only found in băn khoăn 'to be torn between two options, indecisive'.] 2.2. Tone hỏi-ngã [Table 3. Correspondences for the Old Vietnamese tone hỏi-ngã (Sinological terminology: qù)] 3a. Maspero's examples meaning Vietnamese 19 Siamese Proto-Thai Middle Chinese 'spring' mỏ [mɔ˧˩˨] บ อ pạ¹ ˓ˀbɔʾ -'to be in' ở [ɤ˧˩˨] อยู  ˀyu1 puŋʾ -'ricefield' 23 rẫy [rɤj˧˨˥] ไร rai¹ rajʾ -'hole' lỗ [lo˧˨˥] รู rū ru 24 -3b. Additional examples 11 . Maspero 2b. Additional examples meaning Vietnamese Siamese Proto-Thai-Tay Middle Chinese 'taro' môn [mon˦˦˦] บอน 18 pạn -'lady' nàng [naŋ˧˨] นาง naṅ ˓naŋ 'dark' mù [mu˧˨] มั ว mvă ˓muo 'ivory' ngà [ŋa˧˨] งา ṅā ˓ŋa 牙 ˓nga 'tooth' 霧 mi ̯uʾ 'mist' 娘 ˓nia̯ ng ˓ˀbɔn meaning Vietnamese Siamese Proto-Thai Middle Chinese 'loom' 25 cửi [kɯj˧˩˨]

'by; as well, also, too' in Siamese.] Maspero adds one word, 'to stroke' mo, which is not found in Vietnamese dictionaries. 12 ˓ˀjuʾ -'to sow' vãi 20 [vaj˧˨˥] หว าน hwan¹ w̥ aːnʾ -'to bloom' nổ [no˧˩˨] หน อ hnạ¹ n̥ ɔʾ 'bud' -'to swell' 21 phỏng [fɔŋ˧˩˨] ป ง 22 p ̱ aṅ¹ 17 . [This word either means 'width, size' or 'single, unique, isolated'. It does not have the meaning attributed to it by Haudricourt, whose Khmer source we have not been able to identify.] 18 . [In Siamese, the meaning of the word has now shifted to refer to a plant of the Caladium genus.] 19 . [Tone hỏi is marked with a superscript question mark: ả; ngã is marked with a tilde: ã.] 20 . [Haudricourt follows Maspero in misspelling this word as vải.] 21 . [Phỏng actually means 'burnt'. 'To swell' is phồng. The error can be traced back to Maspero (1912: 97).] 22 . [Now spelt โป ง p ̱ oṅ¹.]

23

. The meaning is 'swidden, slash and burn field'.

24

. Maspero indicates an oblique tone. This is a mistake: the word has a level tone;

ru with mai ek means 'to scratch, to scrape'.

Table 4

 4 . [This archaic word refers to a type of leisure boat.]

	meaning 'to entrust'	Vietnamese gởi [ɣɤj˧˩˨]	Middle Chinese 28
	'chopped vegetables' 29	gỏi [ɣɔj˧˩˨ ]	嫁 kaʾ
	29 . [Gỏi is a kind of salad.]

. Correspondences between Old Vietnamese tone hỏi-ngã and Middle Chinese tone qù] 奇 kieʾ 'lots (divination)' quẻ [kwɛ˧˩˨ ] 卦 kwāiʾ 'mustard' cải [kaj˧˩˨ ] 芥 kaiʾ 'to marry (one's daughter)' gả [ɣa˧˩˨] 膾 kuâiʾ 25 . ['Loom' is khung cửi. Cửi is used in other expressions related to weaving but does not usually stand alone.] 26 . It is interesting to note that for 'loom' and 'to ride', Vietnamese and Thai agree in pointing to a reconstructed tone [qu] which disagrees with that indicated in the old rhyming dictionaries [ping]. 27 28 . The correspondences between Vietnamese g [ɣ] and Chinese k, and between Vietnamese d [ð] and Chinese t have already been pointed out elsewhere (Haudricourt 1950: 180-181). [Haudricourt notes Middle Vietnamese d as a delta: δ; the IPA equivalent is [ð]. The modern pronunciation in Hanoi Vietnamese is z.]

Table 5a

 5a

	10 André-Georges Haudricourt
	[Table 5. Correspondences for Old Vietnamese tone sắc-nặng (Sinological terminology: shǎng)] 5a. Maspero's examples
	meaning	Vietnamese 33	Siamese	Proto-Thai-Tay Middle
	'noise' 'strong' 'to arrive' 'to flee' 'to dare'	tiếng [tiəŋ˨˦ ] cứng [kɯŋ˨˦ ] 34 đến 36 [ɗen˨˦ ] trốn [ʈon˨˦ ] dám 37 [ðam˨˦ ]	เสี ยง si ̄eyṅ แข็ ง 35 kheȇṅ ถึ ง thịṅ ผลุ น phlun	˓sieŋ 'sound' ʿkʰɛŋ ˓tʰɯŋ -	Chinese 聲 ˓śi ̭äng 彊 ʿgi ̯ang --

, and additional examples are provided in Table

5b

. 30 . [Haudricourt writes củi.] 31 . [For typographical convenience, Haudricourt typed Karlgren's ɒ as A. The original notation is restored in the translation.]

32

. [This root is only found in an ủi, which means 'to comfort, to console

'.]

  Maspero deemed the first words of the list convincing enough to establish a correspondence between the Vietnamese tone sắc and the unmarked tone of the High series in Siamese. However, the first two words [of Table5] seem to be Chinese loanwords in Thai-Tay and the second word has two possible tones in Chinese, píng and shǎng. Chinese words with tone shǎng have given words with sắc-nặng in Vietnamese, as shown in Table6.[Table6. Vietnamese words with tone sắc-nặng corresponding to Chinese words with tone shǎng]

	5b. Additional examples meaning Vietnamese 'crossbow' ná [na˨˦] 'morning glory' muống [muəŋ˨˦] 'market' chợ [cɤ˨˨˨] 'down' đáy 41 [ɗaj˨˦] 'to go meet' đón [ɗɔn˨˦] 'incomplete' thiếu [tʰiəw˨˦] meaning Vietnamese Siamese หน า hna2 บุ  ง puṅ² ซื ้ อ j ̱ i ̣ ̄ạ ² ใต t ̱a̲ i² ต อน t ̱ạn² เสี ้ ยว si ̄ev² 'tile' ngói [ŋɔj˨˦] 'to host' chứa [cɯə˨˦] 'family' họ [hɔ˨˨˨] 'to dye' nhuộm [ɲuəm˨˨˨] 'to endure' nhịn [ɲin˨˨˨] 'astrological year -horse' ngọ [ŋɔ˨˨˨] 'astrological year -chicken' dậu [ðɤw˨˨˨] 'to bow' lạy [laj˨˨˨]	Proto-Thai-Tay ʿn̥ a ʿˀbung ʿzɯ 'to buy' 市 ʿźi Middle Chinese 弩 ʿnuo -ʿtəj 底 ʿtiei ʿtɔ:n -ʿsiew 少 ʿsi ̯äu Middle Chinese 瓦 ʿngwa 貯 ʿtʽi ̯wo 戶 ʿɣuo 染 ʿńi ̯äm 忍 ʿńi ̯ən 午 ʿnguo 酉 ʿi ̯əu
	meaning 'to feel moved' 'widow' 'stool' 'difficult' 'skilful' 'paper' 'race' 'lord' 'younger aunt' 'cursive' 'purple' 'bushel' 'to compare' 'plank' 'root' 42	Vietnamese cám [kam˨˦] goá bụa [ɣwa˨˦ ɓuə˨˨˨] ghế [ɣe˨˦] khó [kʰɔ˨˦] khéo [kʰɛw˨˦] giấy [ʒɤj˨˦] giống [ʒoŋ˨˦] chúa [cuə˨˦] thím [tʰim˨˦] tháu [tʰaw˨˦] tiá [tiə˨˦] đấu [ɗɤw˨˦] ví [vi˨˦] ván [van˨˦] vốn [von˨˦]	Middle Chinese 感 ʿkâm 寡婦 ʿkwa ʿbi ̯əu 杌 ʿki 苦 ʿk'uo 巧 ʿk'au 紙 ʿt'śie̯ 種 ʿt'śiwong 主 ʿt'śi ̯u 嬸 ʿśi ̯əm 草 ʿts'âu 紫 ʿtsie̯ 斗 ʿtəu 比 ʿpi 板 ʿpwan 本 ʿpuən
	41 . [This word means 'bottom'.] 42 . [The Vietnamese word is glossed by Haudricourt as capital 'main, essential'; this morpheme takes on the meaning 'original' in Vietnamese compounds.]

  . By this correction he undermines his argument that languages of various Asian families outside of Thai and Vietnamese share the typological characteristic of having a middle series. But in the next section Haudricourt demonstrates that there is no middle series in Vietnamese anyway. Several new examples of splits with middle series were listed in[START_REF] Haudricourt | Bipartition et tripartition des systèmes de tons dans quelques langues d'Extrême-Orient [Two-way and three-way splitting of tonal systems in some Far Eastern languages[END_REF] lá[la˨˦ ], Mon sla, Bahnar l ̥a; 'rice' lúa [luə˨˦ ], Mon sro. However, he also cites other words: 'fish' cá [ka˨˦ ], 'louse' chấy [cɤj˨˦ ], 'dog' chó [cɔ˨˦ ], 'four' bốn[ɓon˨˦ ], that have the same tone (sắc), but do not exhibit aspiration in Mon-Khmer languages. In contrast, the word 'year' (Bahnar and Mnong snam) corresponds to Vietnamese năm[nam˦˦˦ ] with the ngang tone.

  . Schematic table of the origin of Vietnamese tones]This account of the origin of Vietnamese tones does not disprove the relationship of Vietnamese with Tai, because it is likely that in the first century of our era, neither the ancestor of Tai, nor Old Chinese, nor Proto-Miao-Yao [Proto-Hmong-Mien] had tones. The development of tones caused by changes in codas and initials must have happened in parallel in all four languages, under the cultural influence of Chinese, an influence that is attested by loanwords.The genetic affiliation of Vietnamese must therefore be established by means of basic vocabulary

	[5. Concluding remarks]
				12th
	Early Christian era	6th century	century (six
	(no tone)	(three tones)	tones)	Now
	[earlier stage]	[later stage]
	pa		pa	pa	ba
	sla	l̥ a	l̥ a	la	la
	ba		ba	pà	bà
	la		la	là	là
	pas	pah	pà	pả	bả
	slas	l̥ ah	l̥ à	lả	lả
	bas	bah	bà	pã	bã
	las	lah	là	lã	lã
	paX 47	paʔ	pá	pá	bá
	slaX	l̥ aʔ	l̥ á	lá	lá
	baX	baʔ	bá	pạ	bạ
	laX	laʔ	lá	lạ	lạ

Table 8 .

 8 Vietnamese tones: etymology, modern orthographic names and notation. Phonetic values fromKirby (2011: 386). C i =initial consonant

	stage 1 (pre-	*CV	*CVʔ	*CVh	*CVC
	tonal)
	stage 2 (tonal)	A level	B rising C falling D toneless
	stage 3 (split) *voiceless C i tone orthog. a A1 (ngang) B1 (sắc) C1 (hỏi) á ả I P A a˦ [44] a˨˦ [24] a˧˩˨ [312] ap˦˥, at˦˥, ak˦˥ [45] D1 (sắc) áp, át, ák *voiced C i tone A2 (huyền) B2 (nặng) C2 (ngã) D2 (nặng) orthog. à ạ ã ạp, ạt, ạk IPA a˧˨ [32] a˨ [22ˀ] a˧˨˥ [3ˀ5] ap˨˩, at˨˩, ak˨˩ [21]

. [The symbol for mai tho given by Haudricourt is the current form; in the original Siamese script (in the 13th century), this tonal category was written with  .]

. Maspero used the label bằng for the tone left unmarked in the orthography. In fact, this word is a Vietnamese translation of Chinese píng 平 and refers to the set of the two tones ngang and huyền.

. [Proto-Thai-Tay and Middle Chinese forms were added byHaudricourt.]

. The meaning of đòn is rather 'stick, pole, rod'.

. [X stands for unknown phonological material that had become a final glottal stop by the stage represented in the second column.]