Pierre Avanzini

Benoît Thuilot

Philippe Martinet

Obstacle Avoidance and Trajectory Replanification for a Group of Communicating Vehicles

Keywords: mobile robots, nonlinear control, platooning, automatic guided vehicles, vehicle-to-vehicle communications

Various "Urban Transportation Systems" are currently in developing, in order to put forward solutions to congestion and pollution in dense areas. Autonomous electric vehicles in free-access can be seen as an attractive approach, in view of the large flexibility that can be expected. One instrumental functionality linked to this solution is platoon motion: several autonomous vehicles accurately follow a trajectory defined on a dedicated circulation lane, with pre-specified inter-distances. A global decentralized platoon control strategy, supported by inter-vehicle communications and relying on nonlinear control techniques is here proposed. In the nominal case, each vehicle is controlled with respect to the same smooth reference trajectory modelled by cubic B-Splines. This trajectory is locally modified and relayed on-line when a vehicle detects an obstacle. The trajectory distortion naturally reflects a driver's behaviour, since it consists in approximated clothoidal trajectories and the use of B-Splines ensures consistent connections. Experimental results, carried out with several urban vehicles, demonstrate the capabilities of the proposed approach.

I. INTRODUCTION

In this paper, congestion of vehicle traffic in dense areas and correlated pollution and waste of time, are addressed. Specifically, alternative transport systems, based on autonomous electric vehicles in free-access moving on dedicated lanes, are here considered, in view of the large flexibility that can be expected. One functionality of special interest is automated platooning, i.e. several autonomous vehicles following the same trajectory with pre-specified inter-distances. Such a functionality, on the one hand allows to easily adapt the transport offer to the actual need (via platoon length), and on the other hand provides more coherent motions and an enhancement in safety. Platooning is therefore considered in this paper.

Different approaches can be proposed. They can be classified into two categories, according to the information used for vehicle control: local and global strategies. The most standard approaches rely on local strategies, i.e. each vehicle is controlled exclusively from data relative to the neighboring vehicles. The well-known leader-follower approach, considering the preceding (or following) vehicle is widely used. For instance, visual tracking has been proposed in [START_REF] Benhimane | Vision-based control for car platooning using homography decomposition[END_REF] and generic control laws have been designed in [START_REF] Wang | Unified control design for autonomous carlike vehicle tracking maneuvers, chapter 8[END_REF] and [START_REF] Consolini | Leader-follower formation control of nonholonomic mobile robots with input constraints[END_REF]. Alternatively, neighboring vehicles (and not only the preceding one) are taken into account when using virtual structure approaches: a structural analogy, characterized by a serial chain of springdamper, is for instance proposed in [START_REF] Yi | Impedance control for a vehicle platoon system[END_REF] and a control law is then derived from the combined front and rear virtual forces.

These strategies present however some drawbacks, the most concerning one being error accumulation: the servoing errors, induced by sensor noises and/or actuator delays, are inevitably growing from the first vehicle to the last one, leading to unacceptable oscillations. Such problems can be overcome by considering global strategies, i.e. each vehicle is now controlled from the data received from all vehicles, collected from appropriate communication channels. Most of the virtual structure approaches belong to this category. In [START_REF] Rafael E Caicedo | Preliminary results of one-dimensional vehicle formation control using structural analogy[END_REF], a mechanical analogy is used to design feedback controllers to achieve straight line motion. A single virtual rigid structure is also considered in [START_REF] Dong | Formation Control of Nonholonomic Mobile Robots Using Graph Theoretical Methods[END_REF], relying on graph theory. Nevertheless, since these techniques aim at imposing some prespecified geometric pattern, the vehicles cannot all reproduce the trajectory of the first one: in a curve, if vehicles are kept according to a straight line pattern, they all describe a distinct trajectory. In contrast, in previous work [START_REF] Bom | Nonlinear control for urban vehicles platooning, relying upon a unique kinematic GPS[END_REF], a trajectorybased global control strategy has been proposed: relying on nonlinear control techniques, vehicle lateral and longitudinal control have been exactly decoupled. Lateral guidance of each vehicle with respect to the same reference path can then be achieved independently from longitudinal control, designed to maintain a pre-specified curvilinear vehicle inter-distance. Data acquisition and exchange are then predominant factors. Communication issues are therefore specifically addressed in this paper. This work is also enhanced in order that the platoon reference path can be replaned on-line if an obstacle appears ahead of the automated platoon. When vehicles move in a dedicated road infrastructure, such a problem has generally been tackled by considering lane change maneuvers [START_REF] Swaroop | The design of a controller for a following vehicle in an emergency lane change maneuver[END_REF]. The simplest solution consists in generating a trajectory by concatenating lines and arc segments [START_REF] Jacobs | Planning smooth paths for mobile robots[END_REF], [START_REF] Laumond | A motion planner for nonholonomic mobile robots[END_REF]. However, the resulting path presents then discontinuities. To overcome this difficulty, it has been proposed (e.g. [START_REF] Fraichard | From Reeds and Sheeps to continuous curvature paths[END_REF], [START_REF] Scheuer | Collision-free and continuous curvature path planning for car-like robots[END_REF]) to consider clothoids, i.e. curves whose curvature is linearly related to the arc length, to ensure a C 2 continuous transition between the arc segments. In addition, clothoids allow to reflect a natural driver's behaviour and they are commonly used in highway route design. Since clothoidal trajectory generation requires complicated computations with Fresnel integrals, many approximation techniques [START_REF] Wang | An approximation approach of the clothoid curve defined in the interval [0, π/2] and its offset by free-form curves[END_REF] [14] [START_REF] Sànchez-Reyes | Polynomial approximation to clothoids via s-power series[END_REF] have been developed for road design. However, they are not fast enough for online path planning. On-line high-accurate representations have been proposed in [START_REF] Montés | Trajectory generation based on rational bezier curves as clothoids[END_REF], but the attention is only focused on the avoiding path pattern, neglecting the transition with respect to the original trajectory. The paper is organized as follows: the global decentralized control strategy for vehicle platooning is first sketched in Section II. Related communication issues are then adressed in Section III. The on-line trajectory replanification and generation process are then described and discussed in Section V. Finally, in Section VI, experiments carried out with three electric vehicles demonstrate the capabilities of the proposed approach.

II. GLOBAL DECENTRALIZED CONTROL STRATEGY

A. Modeling assumptions

Urban vehicles involved in platooning applications are supposed to move at quite low speed (less than 5m.s -1 ) on asphalted roads. Therefore dynamic effects can be neglected and a kinematic model can satisfactorily describe their behavior, as corroborated by extensive tests performed with our experimental vehicles shown in Fig. 1. In this paper, the kinematic tricycle model is considered: the two actual front wheels are replaced by a unique virtual wheel located at the mid-distance between the actual wheels. The notation is illustrated in Fig. 2.

• Γ is the common reference path for any vehicle (to be inferred from the trajectory of the first one), defined in an absolute frame [A, X A , Y A ]. • O i is the center of the i th vehicle rear axle.

• M i is the closest point on Γ to O i . • s i is the arc-length coordinate of M i along Γ. • c(s i ) is the curvature of path Γ at M i , and θ Γ (s i ) is the orientation of the tangent to Γ at M i w.r.t. [A, X A , Y A ]. • θ i is the heading of i th vehicle w.r.t. [A, X A , Y A ]. • θi = θ i -θ Γ (s i )
is the angular deviation of the i th vehicle w.r.t. Γ. • y i is the lateral deviation of the i th vehicle w.r.t. Γ. • δ i is the i th vehicle front wheel steering angle.

• L is the vehicle wheelbase. • v i is the i th vehicle linear velocity at point O i .

B. Vehicle state space model

The configuration of the i th vehicle can be described without ambiguity by the state vector (s i , y i , θi ). The current values of these variables can be inferred on-line by comparing vehicle absolute localization to the reference path. It can then be shown (see [START_REF] Samson | Control of chained systems: application to path following and time-varying point stabilization of mobile robots[END_REF]) that tricycle state space model is:

       ṡi = v i cos θi 1 -yi c(si) ẏi = v i sin θi θi = v i tan δi L -c(si) cos θi 1 -yi c(si) (1)
Platooning objectives can then be described as ensuring the convergence of y i and θi to zero, by means of δ i , and maintaining the gap between two successive vehicles to a fixed value d * , by means of v i . It is considered that y i = 1 c(si) (i.e. vehicles are never on the reference path curvature center). In practical situations, if the l vehicles are well initialized, this singularity is never encountered.

C. Control law design

In previous work [START_REF] Bom | Nonlinear control for urban vehicles platooning, relying upon a unique kinematic GPS[END_REF], it has been shown that exact linearization techniques offer a relevant framework to address platoon control: equations (1), as most of kinematic models of mobile robots, can be converted in an exact way into a socalled chained form, see [START_REF] Samson | Control of chained systems: application to path following and time-varying point stabilization of mobile robots[END_REF]. Such a conversion is attractive, since the structure of chained form equations allows to address independently lateral and longitudinal control.

Steering control laws δ i can first be designed to achieve the lateral guidance of each vehicle within the platoon. In these control laws, v i just appears as a free parameter. Since conversion of equations ( 1) into chained form is exact, all nonlinearities are explicitly taken into account. High tracking performances (accurate to within ±5cm when relying on an RTK GPS sensor) can then be ensured, whatever initial errors or reference path curvature are. Details can be found in [START_REF] Thuilot | Accurate automatic guidance of an urban electric vehicle relying on a kinematic GPS sensor[END_REF].

Control variables v i can then be designed to achieve longitudinal control. In nominal situation, the objective for the i th vehicle is to regulate e 1 i = s 1s i -(i -1) d * , i.e. the arc-length longitudinal error w.r.t. the leader. This control objective is attractive, since the location s 1 of the leader represents a common index for all the vehicles into the platoon, so that error accumulation and inherent oscillations can be avoided. In addition, since it is an arc-length error, this control objective remains consistent whatever the reference path curvature is (in contrast with euclidian inter-distances). Nevertheless, for obvious safety reasons, the location of the preceding vehicle cannot be ignored. Therefore, in previous work [START_REF] Bom | Nonlinear control for urban vehicles platooning, relying upon a unique kinematic GPS[END_REF], the longitudinal control law has been designed to control a composite error: a smooth commutation function gives the predominance either to the global error e 1 i or to the local one e i-1 i = s i-1s id * according to some security distance. Once more, exact linearization techniques have been used, so that nonlinearities in equations ( 1) are still explicitly accounted, ensuring high accurate regulation. More details, as well as experiment results carried out with Cycab and RobuCab vehicles (see Fig. 1), relying on RTK GPS sensors for vehicle localization and WiFi technology for inter-vehicle communications, can be found in [START_REF] Bom | Nonlinear control for urban vehicles platooning, relying upon a unique kinematic GPS[END_REF].

III. COMMUNICATION ISSUE

The proposed global control strategy demands for intervehicle data exchanges. The V2V communication system is first presented, and then it is discussed how the asynchronous localization data that are collected, are processed in order that the control laws can rely on temporally consistent information.

A. Device and communication procedure

Inter-vehicle communications are carried out using the ieee802.11g standard, along with IPv4 and UDP protocols. A WiFi access point is located on the leader and each vehicle is connected to the wireless network via a high-level laptop equipped with an internal adapter. According to the control strategy (see Fig. 3), leader localization data are broadcasted, while other vehicles only send information to their direct follower. Data are asynchronously transferred as soon as they are supplied by the localization devices. Raw localization data consist in 97 bytes.

B. Platoon information updating

For each vehicle to be appropriately controlled, the lateral and longitudinal control laws have to be evaluated at a constant sampling frequency. However, the data from which control laws have to be inferred, are asynchronously supplied, and therefore temporally inconsistent. This difficulty appears even at the vehicle level: the vehicle state is indeed inferred from exteroceptive and proprioceptive sensors. The vehicle absolute localization is supplied by either a RTK GPS receiver or a monocular camera, while its velocity and steering angle are obtained via odometric sensors. Each sensor possesses its own latency, acquisition frequency (10Hz with RTK GPS receivers, up to 15Hz with cameras and 60Hz with odometers), and possibly varying processing time (vehicle absolute localization can be derived from monocular vision with a mean image processing time equal to 30ms, see [START_REF] Royer | Towards an alternative GPS sensor in dense urban environment from visual memory[END_REF]). The platoon state, obtained by collecting other vehicle states via V2V communication, displays of course larger temporal inconsistencies: the data transmission delays have been measured within the range [20.6ms , 98.4ms], with a 47ms mean value. However, the standard troubles inherent to wireless technology, such as dropout, packet collisions or communication obstacles may occasionally increase the temporal inconsistencies between variables within the platoon state.

To appropriately control vehicles, the data to be reported into control laws should reflect the state of each vehicle within the platoon at the same time instant. To meet this demand, the software framework AROCCAM [START_REF] Tessier | A real-time, multi-sensor architecture for fusion of delayed observations: Application to vehicle localization[END_REF] is currently used. Driver modules, responsible for the communication with sensors, collect in separated threads the information. A datation procedure allows to correctly timestamp those data: the sensor latency and processing time are taken into account in order that the date reflects accurately the perception time. This date is then sent jointly with the sensor data to the other vehicles, in order for them to be able to properly use the data, whatever communication delays. To ensure that a common time reference is shared by all the vehicle computers, a simple NTP (Network Time Protocol) client allows the system clock to be set to match the time obtained when communicating with one server. It is run at a 1Hz frequency on each vehicle high-level laptop, after having defined the reference server. A set of consistently dated information is then available, when AROCCAM highest priority thread, associated with a 10Hz timer, demands for control law computation. The platoon state is first updated: from vehicle kinematic model (1), the value of any variable in the platoon state is predicted at the current time instant, relying on a classical Runge-Kutta fourth-order method. These predictions, that are temporally consistent, can then be reported into lateral and longitudinal control laws, and the values supplied by these algorithms can be sent to the actuators. Of course, a watchdog has been considered: if some raw data have not been acquired (due to communication troubles for instance) for a long period (the threshold depends on vehicle velocities), then predictions are no longer computed and the vehicle begins a stopping phase. The deceleration is calculated according to the last acquired localization data of both the vehicle and its preceding one. If the communication trouble disappears, the vehicle is allowed to start again.

The variables within the platoon state that are the more sensitive to temporal inconsistencies are vehicle curvilinear distances s i along the reference trajectory. Fig. 4 presents the updates on these variables calculated by the third vehicle during a full-scale experiment. More precisely, the top figure shows the updates on the current (i.e. third) vehicle curvilinear distance, and the bottom one displays the updates on the leader curvilinear distance. It can be observed in the top figure that the update is non-negligible: it varies linearly, due to the quasi-constant difference between the control timer and the localization acquisition frequencies, and can reach 10cm since the vehicle velocity and the control sampling frequency were respectively 1m.s -1 and 10Hz (greater values are present at the beginning, because the vehicle is a bit faster than 1m.s -1 to reach the desired inter-vehicle distance). This illustrates the importance of AROCCAM task scheduling. The bottom figure shows that the update on variables obtained via communication channels is, of course, more significant: due to communication delays, it is generally superior to 4.7cm (the distance, shown as a dotted line, covered by the vehicle during the mean communication delay 47ms) and can reach 30cm.

IV. OBSTACLE AVOIDANCE STRATEGY

A key element in the proposed control approach is the reference trajectory. The error variables to be regulated in lateral and longitudinal control are either a gap w.r.t. the reference trajectory (i.e. y i and θi ) or a measurement w.r.t. this trajectory (i.e. s i ). As a result, the reference trajectory representation must exhibit the following features:

• it should accept an analytic expression, in order to enable an accurate computation of the error variables, • it should be at least C 2 , since the reference path curvature c(s i ) is needed in control laws. In order to meet these requirements, B-Spline curves have been used in previous work [START_REF] Avanzini | Online reference trajectory generation for manually convoying a platoon of automatic urban vehicles[END_REF] and proved to be a relevant tool to address vehicle platooning. The B-Spline curves can be supplied a priori, in the case of a fully automated platoon, or created on-line according to the motion of a manually driven leader vehicle. Following [START_REF] Avanzini | Online reference trajectory generation for manually convoying a platoon of automatic urban vehicles[END_REF], B-Spline curves of degree 3, with a 1.5m arc-length for each polynomial curve, are here considered. Moreover, it is assumed that an accurate map of the environment, enclosing road sides, is available.

A. Avoidance steps

A lane change maneuver, combining circle and clothoids, is here proposed to carry out obstacle avoidance in a dedicated urban environment. The maneuver consists into 3 steps, shown in Fig. 5: • When an obstacle is detected, it is first decided, relying on the environment map and on the obstacle features captured by the vehicle sensors (width, position, . . .), if the obstacle can be safely avoided. If the answer is positive, then a virtual danger zone is defined around the obstacle as the smallest surrounding rectangle. At this step, this zone is only partially defined, since the obstacle depth is unknown. Nevertheless, two key locations can already be introduced: point A is the projection of the vehicle controlled point on the nominal reference trajectory (i.e. A is the current point M , defined in Fig. 2) and point B is a waypoint on the road free space, sufficiently far from the obstacle, so that the vehicle can safely avoid this latter (here assumed to be motionless) if it moves to B. Then, an Sshaped curve, consisting in 4 clothoids and 2 optional circles, is defined to join A to B, see Fig. 5. Clothoids are elementary curves characterized by a curvature k(s) linearly varying with the arc-length:

k(s) = λ s (2)
Since clothoids allow to reflect a natural driver's behaviour, they are the main element of the proposed S-shaped pattern.

Circles are only introduced if the pattern built with 4 clothoids exhibits curvature values exceeding the vehicle admissible one. • When the vehicle is tracking the S-shaped pattern, it can eventually observe the obstacle length. Then, the third key location is defined: point C is introduced in the road free space, sufficiently far from the obstacle, so that the vehicle can safely pass along this latter if it moves from B to C. A C-shaped curve, consisting in only 2 clothoids, is defined to join B and C. Such a pattern is appropriate in view of the curve profile of standard roads. If the obstacle is very long, then intermediary points can be considered to pass along it.

• Finally, the last key location is introduced: point D is chosen on the nominal reference trajectory, in such a way that points C and D can be joined by 4 clothoids, see Fig. 5.

B. Pattern construction

When building each pattern, the objective is to join two 2D locations, with the additional constraint to satisfy tangent and curvature continuity at these points. For instance, for the first pattern, the objective is to link the configuration (A, q A , k A ) to (B, q B , k B ), where q {A,B} and k {A,B} denote the tangent vector and the curvature at A or B. In order to ensure C 2 continuity with the nominal reference path Γ, q A and k A are chosen as the tangent vector and curvature of Γ at point A. In order to specify these variables at point B, let us introduce point P as the closest point to B on Γ. Then, q B is chosen identical to q P , the tangent vector to Γ at P , and k B = k P /(∆ k P + 1), with ∆ the lane width and k P the curvature of Γ at P .

The increasing curvature profile, induced by the first clothoid, allows to lead the avoidance trajectory towards the middle of the road, up to point I 1 , see Fig. 5. The curvature k I1 at that point presents a local maximum. If |k I1 | ≥ k max , with k max the vehicle admissible curvature (k max can be computed from the vehicle wheelbase L and the maximum steering angle δ max : k max = | tan(δ max )/L|), then a circle is introduced. The maximum curvature is then maintained, up to point I 2 . The avoidance trajectory is still led towards the middle of the road. Next, an inflection point I is reached (i.e. k I = 0) via the second clothoid. The same strategy is finally applied to join points I and B. It can easily be noticed that this avoidance trajectory necessarily stays on the road and does not collide with the obstacle, as desired. Exactly the same method is followed to build the other patterns B -C and C -D.

C. Optimization procedure

Let us consider the first S-shaped pattern linking A to B (once more, the same method has been applied to the other patterns). As a first step, a pattern consisting in only 4 clothoids is searched for. A clothoid starting from some given configuration is completely described when the rotation angle α (see Fig. 7) and the curvature at its extremity are both given. Consequently, since a S-shaped pattern encloses an inflexion point (k I = 0), then it is completely described by 6 parameters: (α 1 , α 2 β 1 , β 2 , k I1 and k I3 ), see Fig. 7. In order to simultaneously reduce the number of parameters and provide a "balanced" avoidance trajectory, the curvature rates of the 4 clothoids are chosen identical (i.e. the parameter λ in (2) is the same for the 4 clothoids). Then, the S-shaped pattern is completely specified by only 2 parameters: α 1 and k I1 . Parameter k I1 mainly acts on the longitudinal aspect of the S-shaped curve (i.e. in the direction of the vector --→ AB), when α 1 value impacts its lateral aspect (i.e. in the direction perpendicular to the vector --→ AB). The parameters (α 1 , k I1 ) of the S-shaped pattern linking A to B could be computed analytically via Fresnel integrals. However, calculations are quite intricate and time-consuming. Consequently, the concept of discrete clothoid, developed in [START_REF] Meek | An arc spline approximation to a clothoid[END_REF] and shown in Fig. 6, has here been used. A discrete clothoid of arc-length S is formed of n + 1 arcs, numbered 0 to n (with n ≥ 1). Arc 0 and arc n have length S/(2n), while arcs 1 to n -1 have length S/n. The curvatures of the n + 1 arcs are k j = k 0 + jh, j = 0, 1 . . . , n, where here h = (k Bk A )/n. It is proved [START_REF] Meek | An arc spline approximation to a clothoid[END_REF] that the approximation error between the exact clothoid and a discrete clothoid with n + 1 arcs is of magnitude O((1/n) 2 ). Finally, in order to be consistent with the nominal reference trajectory Γ defined with B-Spline curves, the alternative one, constituted of S/C-shaped trajectories, is also approximated thanks to B-Spline curves. The approximation is carried out via standard least square method. However, a special attention is paid to the curvature profile: first, the optimization criterion aims at minimizing both distances and tangent angle deviations between a configuration set extracted on the S/C-shaped trajectories and the approximating B-Spline curve. Then, since B-Spline curves have not been designed to present a linear relation between arc-length and curvature, the arc-length of elementary polynomial curves has to be chosen shorter than in the nominal case: 0.5m-long polynomial curves are considered, rather than 1.5m-long ones for the nominal trajectory Γ. The curvature profile of the B-Spline approximating the alternative trajectory is then very similar to the desired one (maximum curvature error equals to 0.0281), thus providing a comfortable guidance.

V. EXPERIMENTAL RESULTS

In order to investigate the capabilities of the proposed approach, preliminary experiments have been carried out with three vehicles in Clermont-Ferrand on "PAVIN Site" (see Fig. 1), an open platform devoted to urban transportation system evaluation.

1) Experimental set-up: Experimental vehicles are shown in Fig. 1. They are electric vehicles, powered by lead-acid batteries providing 2 hours autonomy. Two (resp. four) passengers can travel aboard Cycabs (resp. RobuCabs). Their small dimensions (length 1.90m, width 1.20m) and their maximum speed (5m.s -1 ) are appropriate to urban environments. On-board RTK GPS receivers provide absolute localization measurements accurate to within 2cm at a 10Hz sampling frequency. Platoon control laws are implemented in C++ language on Pentium-based computers using RTAI-Linux OS.

2) Experimental results: The behaviour of an automatic guided platoon involving two vehicles has been investigated. A motionless third vehicle (green rectangle in Fig. 8) is obstructing the 100m-long reference path at arc-length abscissa 55m (see also Fig. 1). The leader vehicle velocity is 1m.s -1 . and the obstacle is perceived during a bend (k A = -0.2589). At that time, the curvilinear distance between the leader and the obstacle is 7.0193m. The leader vehicle successfully computes an alternative admissible trajectory, whose maximum curvature is 0.2604m -1 (when k max = 0.3886m -1 ). This alternative trajectory is then sent to the follower vehicle, so that both vehicles manage to avoid the obstacle. Moreover, the accuracy of the lateral and longitudinal control laws is preserved. As illustrated in Fig. 8, the behavior is identical to what was obtained in previous work, when vehicles were guided w.r.t. a fixed and pre-specified reference trajectory (see [START_REF] Bom | Nonlinear control for urban vehicles platooning, relying upon a unique kinematic GPS[END_REF]), namely a 10cm accuracy. The on-line reference trajectory modification disturbs neither lateral nor longitudinal performances.

VI. CONCLUSION

In this paper, communication issues within a platoon of vehicles have first been addressed. A data actualization procedure has been proposed in order to ensure temporal consistence when implementing the global decentralized control strategy. Then, an on-line reference trajectory modification, consisting in reshaping the B-Spline curves used to define the nominal reference path, has been developed in order to address obstacle avoidance: the alternative trajectory approximates the shape and the curvature profile of clothoids, in order to reflect a natural driver's behaviour. Finally, full scale experiments, carried out with three vehicles, have demonstrated the efficiency of the proposed approach.

Fig. 1 .

 1 Fig. 1. Two vehicles avoiding a broken down one on PAVIN site

Fig. 2 .

 2 Fig. 2. Tricycle model description

Fig. 3 .

 3 Fig. 3. Communication scheme

Fig. 4 .

 4 Fig. 4. Updates on curvilinear distance estimation

Fig. 5 .

 5 Fig. 5. Obstacle avoidance pattern

Fig 7 .

 7 Fig. 6. Discrete clothoid representation Fig. 7. Change lane trajectory

Fig. 8 .

 8 Fig. 8. Vehicle lateral and inter-distance errors


Patrick Perret

BrunoDauvier Miliana Ayad

Bruno Dauvier

Anne Congard

Self-and parent-rated measures of personality are related to different dimensions of school adjustment

Keywords: personality, academic adjustment, child development, Big Five, subjective wellbeing Highlights

Links have often been drawn between individual personality differences among children, as captured by the Big Five personality traits, and academic achievement. Published research shows that conscientiousness is the most decisive factor, and its predictive power is greater when it is other-rather than self-assessed. In the current study (N = 161; Mage = 10.79 years), we examined the associations between both forms of personality assessment and two dimensions of school adjustment. Results confirmed that other-assessments are more statistically predictive of academic adjustment, but showed that self-assessments are more statistically predictive of subjective wellbeing at school. Complementary analyses in the form of generalized additive models indicated that the relationship between personality and wellbeing can follow either a linear or a nonlinear pattern, depending on which particular trait is considered. Such results may have practical implications for the choice of assessment method, and theoretical ones for the study of relations between personality and subjective wellbeing at school-an area that is still relatively unexplored.

Introduction

According to the Big Five theory [START_REF] Mccrae | Personality trait structure as a human universal[END_REF], variations in human personality are structured around five main traits: openness, extraversion, conscientiousness, agreeableness, and emotional stability (or neuroticism). Although this Five Factor Model (FFM) was derived from research with adults, a growing number of studies suggest that it also provides a heuristic framework for examining how children's personality is constructed and how it can influence varied facets of their developmental trajectories [START_REF] Shiner | The structure of temperament and personality traits: A developmental perspective[END_REF]. Several authors, for example, have suggested that these five personality traits constrain the way in which children adjust to different dimensions of the school experience [START_REF] De Raad | Personality in learning and education: A review[END_REF] and modulate their likelihood of encountering problems there [START_REF] Ehrler | Extending Big-Five theory into childhood: A preliminary investigation into the relationship between Big-Five personality traits and behavior problems in children[END_REF].

Accordingly, children who are highly active and gregarious, with a tendency to be assertive (i.e. high level of extraversion), may find it easier to forge relationships with their peers and thrive on the many opportunities for social interaction available at school. For their part, children who have an inquiring mind and are interested in acquiring new knowledge (i.e., high level of openness) may be driven by intrinsic motivation, which is more beneficial for learning. Children who set themselves high standards in their work, are organized and persistently pursue their objectives (i.e. high level of conscientiousness) may adopt a mode of functioning that particularly favors academic achievement. Meanwhile, prosocial children who are attentive to their interlocutors (i.e. high level of agreeableness) may be quicker at forming bonds with adults based on trust and cooperation, making it easier for them to engage in the educational relationship and grasp the rules of how to behave in a school setting. Lastly, children who manifest little predisposition to feelings of distress (i.e., high level of emotional stability) may be more willing to fit into school life.

Empirical research has confirmed that some components of children's personality are significantly predictive of their academic achievement. For example, when Laidra, Pullman, and Allik (2007) examined the links between intelligence, personality traits and academic performance in children and young people aged 7-19 years, they found that cognitive reasoning abilities were the best predictors of performance, but that conscientiousness and openness also made significant contributions. Data also highlight a growing role of conscientiousness across schooling, as teaching formats demand increasing autonomy from pupils in their work. [START_REF] Poropat | A meta-analysis of the five-factor model of personality and academic performance[END_REF]'s meta-analysis confirmed that conscientiousness is a factor for educational attainment that is independent of intelligence and just as decisive. [START_REF] Spengler | Personality is related to educational outcomes in late adolescence: Evidence from two large-scale achievement studies[END_REF] showed that even when they are assessed using a very short personality questionnaire, conscientiousness and openness clearly help to explain children's academic results. A recent study using latent variable models (Lechner, Danner, & Rammsted, 2017) even supported the conclusion that, with regard to grades, personality alone explains almost twice the variance that intelligence does. Personality traits other than consciousness and openness seem less involved in academic performances [START_REF] Poropat | Other-rated personality and academic performance: Evidence and implications[END_REF], but influence other dimensions of school adjustment.

For instance, children's neuroticism has been found to predict teachers' assessments of their internalizing behaviors a few months after starting school (Zupancic & Kavcic, 2011), agreeableness has been found to predict children's social status within peer groups at primary school [START_REF] Andrei | Social status and its link with personality dimensions, trait emotional intelligence, and scholastic achievement in children and early adolescents[END_REF], and extraversion has been found to be associated with a higher level of behavioral problems at school [START_REF] Goldner | Attachment security, personality, and adjustment of elementary school children[END_REF].

These consistent findings support Zupancic and Kavcic's (2011) view that "children differing in personality interpret and react differently to similar experiences, evoke different responses from others and actively tend to select or create different environments for themselves" (p. 500).

Consequently, school practitioners should pay close attention not only to children's intellectual development, but also to their emergent personality, through the use of suitable assessment tools.

Most of the currently available tools are questionnaires that contain statements reflecting different facets of the personality traits identified in the Big Five model. They do differ, however, in the identity of the informants. For example, the Hierarchical Personality Inventory for Children (HiPIC; Mervielde & De Fruyt, 2002) relies on parental accounts to gauge how children behave in their everyday lives. By contrast, Barbaranelli, Caprara, Rabasca, and Pastorelli (2003)'s Big Five Questionnaire-Children version (BFQ-C) is completed by the children themselves. Several studies have looked at how far the personality measures derived from these different types of assessment converge. Correlations have generally been found to be modest (e.g., Olivier & Hervé, 2015), especially for children of primary school age (Barbaranelli, Caprara, Rabasca, & Pastorelli, 2003). There are several possible explanations for these respondent-based (i.e., parent vs. child) divergences. For a start, children's perceptual acuity may depend on the maturation of their self-awareness and their ability to compare themselves with others [START_REF] Quartier | A study of personality in children aged 8-12 years: Comparing selfand parents' ratings[END_REF]. This would explain why parents and children's assessments tend to converge with age. A complementary explanation is that some personality dimensions are, by their very nature, more difficult for others to assess [START_REF] Vazire | Who knows what about a person? The self-other knowledge asymmetry (SOKA) model[END_REF]. In a recent study, Luan, Hutteman, Denissen, Asendorpf, and Aken (2017) showed that traits which manifest themselves in visible behaviors (e.g., extraversion and conscientiousness) tend to elicit higher interrater agreement than less visible traits (e.g., emotional stability and openness).

Because of these divergences, both practitioners and researchers may be in a quandary as to which of the two assessment types to choose. One useful strategy for making this choice is to examine the respective validity of each one. In 2014, Poropat carried out a fresh meta-analysis, this time looking specifically at studies (with samples of students aged 16-30 years) that had used personality ratings provided by other informants (parents, teachers or peers). As well as confirming the specific effects of conscientiousness and openness, results also and above all revealed that other-rated assessments of personality are considerably more predictive of educational attainment than self-assessments. Taking the analysis one step further, MacCann, Lipnevich, [START_REF] Maccann | Self-and parent-rated facets of Conscientiousness predict academic outcomes: Parent-reports are more predictive, particularly for approach-oriented facets[END_REF] showed, with a sample of students aged 13-16 years, that this observation is not simply due to greater internal consistency of parental assessments. Rather, the divergences in predictive power stem from the nature of the information and comparisons used by informants to respond to personality questionnaires. The authors' methodological conclusion was that other-assessments are more valuable in educational and research studies examining the impact of personality on academic achievement.

Nevertheless, the divergence between parents' and children's personality assessments does not mean that self-assessments are baseless and invalid, but rather that they rely on different information from that used by external observers to establish a judgment. In a recent longitudinal study, for instance, Luan, Hutteman, Denissen, Asendorpf, and van Aken (2017) showed that parents have more positive perceptions of changes in their children's personality during the transitional period of adolescence than the children do themselves. Another longitudinal study [START_REF] Clark | Personality in the age of industry: Structure, heritability, and correlates of personality in middle childhood from the perspective of parents, teachers, and children[END_REF] suggested not only that "the story of personality in middle childhood differs a bit based on who is telling it" (p. 140), but also that the predictive validity of these different sources varies according to which area is being explored.

As we suggested earlier, different personality traits are liable to influence different dimensions of school adjustment. While academic performances undeniably constitute a core dimension, they certainly do not represent the sum total of children's experience of school. For example, [START_REF] Zee | Student-teacher relationship quality and academic adjustment in upper elementary school: The role of student personality[END_REF] found that the pupil-teacher relationship is predicted by different personality traits from those that usually influence educational attainment.

More generally, children's subjective wellbeing at school could be a key dimension not only of their current experience but also of their school trajectory [START_REF] Samdal | Relationship between students' perceptions of school environment, their satisfaction with school and perceived academic achievement: An international study[END_REF], as long as subjective wellbeing appears to play a causal role in the achievement of many positive outcomes, including sociability, altruism, effective conflict resolution skills, and original thinking [START_REF] Lyubomirsky | The benefits of frequent positive affect: Does happiness lead to success[END_REF]. Research has therefore been undertaken to better define the concept of subjective school wellbeing (e.g., Garcia-Bacete, Marande-Perrin, Schneider, & Blanchard, 2013) which refers to children's self-perception of their school experiences as conveying positive emotions and thoughts. A themed analysis of research in this area recently led [START_REF] Renshaw | Assessing adolescents' positive psychological functioning at school: Development and validation of the Student Subjective Wellbeing Questionnaire[END_REF] to identify four dimensions of children's experiences that together contribute to such a positive perception of their school life: School connectedness, joy of learning, educational purpose, and academic efficacy. Within this framework, subjective school wellbeing is regarded as an emergent phenomenon rising from diverse converging factors.

Despite numerous studies indicating that personality is one of the major influences on adults' subjective wellbeing (e.g. Steel, Schmidt, & Schultz, 2008), its impact on pupil wellbeing continues to receive far less attention. Furthermore, personality studies have generally assumed that the variables being investigated are linearly related. More recently, researchers in the field have begun to pay more consideration to arguments in favor of curvilinear relationships (e.g., [START_REF] Carter | The downsides of extreme conscientiousness for psychological wellbeing: The role of obsessive compulsive tendencies[END_REF]Nickel, Roberts, & Chernyshenko, in press).

Nonlinear predictions frequently stem from what [START_REF] Pierce | The too-much-of-a-good-thing effect in management[END_REF] called the too-muchof-a-good-thing-effect in the management literature, that is, when a valuable and generally adaptive individual characteristic reaches a point beyond which the relationship with a desirable outcome becomes either asymptotic or negative. For instance, one could hypothesize that children who are attentive to other pupils' emotions and needs (i.e., with high agreeableness) may benefit from fulfilling social interactions at school, as this enhances their feelings of connectedness (a facet of subjective school wellbeing). However, one could equally well hypothesize that an extreme level of agreeableness also makes children excessively sensitive to the interpersonal challenges that are inherent to the school context, to the point of reducing their subjective wellbeing.

In the present study, we asked children aged 9-13 years, along with one of their parents (mother), to complete a short form of the HiPIC so that both assessments were made with the same instrument. The HiPIC is one of the few inventories specifically intended to assess children's personality according to the FFM, and it is the only French-language tool available with norms for clinical practice. Furthermore, [START_REF] Quartier | A study of personality in children aged 8-12 years: Comparing selfand parents' ratings[END_REF] developed a shortened version specifically designed for self-reports, by selecting items on their ease of understanding and readability for school-aged children. Their validation study [START_REF] Quartier | A study of personality in children aged 8-12 years: Comparing selfand parents' ratings[END_REF] indicated that the short form had good correlations with the full-scale version, and factorial analyses confirmed its structural validity. Each child also completed the Student Subjective Wellbeing Questionnaire [START_REF] Renshaw | Assessing adolescents' positive psychological functioning at school: Development and validation of the Student Subjective Wellbeing Questionnaire[END_REF]) so that we had a general indicator of their wellbeing at school. As mentioned above, school wellbeing is here envisaged as a metaconstruct encompassing four main first-order constructs, each with its own substantive validity. The validation process that the authors undertook revealed a statistically robust multidimensional latent-trait structure, with general subjective wellbeing as a second-order construct. Lastly, each child's lead teacher filled in a questionnaire about his or her level of academic adjustment, taken from the School Adjustment Scale [START_REF] Congard | Validation d'une échelle d'adaptation scolaire à destination des enseignants: SAS (School Adjustment Scale)[END_REF]. In view of the theoretical and methodological issues raised in the literature about the links between personality and school adjustment, the study was designed to tackle three main research questions (RQ):

(RQ 1) How far do children and parents' judgments of personality traits coincide? Previous studies using comparable instruments and designs (e.g., [START_REF] Bouvard | Validité convergente entre deux outils d'évaluation de la personnalité et agrément entre l'enfant et un observateur[END_REF] led us to anticipate moderate correlations between parents' and children's judgments, as well as an increase in convergence with age.

(RQ 2) Is the greater predictiveness of parental judgments of personality restricted to academic adjustment, or does it extend to children's subjective wellbeing at school? Informed by previous research [START_REF] Poropat | Other-rated personality and academic performance: Evidence and implications[END_REF], we expected other-rated measures to be better statistical predictors of academic adaptation than self-rated measures, but we could offer no such hypothesis regarding the prediction of children's subjective wellbeing. More specifically, and whatever the informant, we expected conscientiousness to be the main personality trait related to academic achievement.

Children with high level of conscientiousness tend to be orderly, planful and persistent in their activities. Transposed in a school context, these cognitive and behavioral features should favor children's adjustment to schoolwork requirements and teachers' expectancies.

(RQ 3) Which Big Five traits are most strongly associated with pupils' subjective school wellbeing? More specifically, although consciousness is regularly recognized as the most decisive dimension of personality for academic achievement, we hypothesized that personality traits that are more related to social relations (i.e., agreeableness and extraversion) would be also associated with school wellbeing, inasmuch as the latter concept incorporates not only a sense of academic efficacy but also a sense of social connectedness. Furthermore, we wanted to investigate whether the associations between personality traits and subjective wellbeing at school can best be described by linear or curvilinear relationships. In the present study, the use of generalized additive models (GAMs; [START_REF] Wood | Generalized additive models: An introduction with R[END_REF] allowed us to examine the occurrence of nonlinear relationships of this type in our dataset.

Method

Participants

Participants were 161 children (81 boys and 80 girls) with a mean age of 10.79 years (SD = 1.16, range = 9-13). They were recruited in five different elementary and middle schools in the South of France. A total of 46 children were in Grade Four (mean age = 9.56 years, SD = .50), 53 were in Grade Five (mean age = 10.47 years, SD = .50), 35 in Grade Six (mean age = 11.61 years, SD = .49), and 27 in Grade Seven (mean age = 12.44 years, SD = .57).

Measures

Personality

The children's personality was assessed both by themselves and by their mothers, via the French short version of the HiPIC [START_REF] Quartier | A study of personality in children aged 8-12 years: Comparing selfand parents' ratings[END_REF], which comprises 32 items assessing the Big Five personality traits: conscientiousness (e.g., "Leaves everything lying around"); extraversion (e.g., "Keeps feelings and thoughts to him/herself"); benevolence (related to the FFM's agreeableness domain; e.g., "Finds it hard to share with others"); imagination (related to the FFM's openness domain; e.g., "Likes to draw"); and emotional stability (or neuroticism; e.g., "Is afraid of making mistakes"). Items were framed in the first or third person, depending on the informant (child or mother). Participants indicated their degree of agreement with each statement on a five-point Likert scale ranging from Strongly disagree to Strongly agree. In the present study, internal consistencies varied considerably with trait and informant (see Table 1).

Academic adjustment

Teachers indicated children's overall academic adjustment on the corresponding subscale of the School Adjustment Scale [START_REF] Congard | Validation d'une échelle d'adaptation scolaire à destination des enseignants: SAS (School Adjustment Scale)[END_REF]. This comprises eight items rated on a 5-point Likert scale ranging from Strongly disagree to Strongly agree. The term academic adjustment refers to the grades achieved by children, but also to their attitudes toward learning in general, which are known to promote academic achievement. The subscale explores four dimensions: academic results (e.g., "The pupil achieves good results in evaluations"); attention (e.g., "The pupil shows concentration during class"); autonomy (e.g., "The pupil can work on his or her own"); and motivation (e.g. "The pupil seems to be curious and interested by what he or she learns"). In the present study, the Academic Adjustment subscale had satisfactory internal consistency (Cronbach's alpha = .95).

Subjective wellbeing at school

The Student Subjective Wellbeing Questionnaire (SSWQ) is a 16-item self-report questionnaire designed to explore four dimensions of subjective school wellbeing. School connectedness refers to the extent to which the child feels cared for at school and how well he or she gets on with others (e.g., "I feel like people at this school care about me"). Academic efficacy is related to the child's appraisal of his or her ability to meet the academic requirements (e.g., "I do well on my class assignments"). Joy of learning refers to the satisfaction experienced by the child when he or she engages in classroom activities (e.g., "I feel happy when I am working and learning at school"). Educational purpose corresponds to the child's appraisal of school as a meaningful context for learning and development (e.g., "I believe the things I learn at school will help me in my life"). A composite score representing the pupil's general subjective wellbeing is obtained by summing the subscores. In the present study, internal consistency was high (Cronbach's alpha = .91).

Procedure

After obtaining the consent of the local education authorities and school principals, parents were informed about the study. Envelopes containing a written consent form, an explanatory letter, and the child personality inventory to fill in at home were distributed in the classrooms.

Parents who gave their consent were asked to sign the form, fill in the questionnaire and return them in the envelope to the child's lead teacher. Research assistants went into the classrooms to brief small groups of children on the study, ensure that they answered all the questions on their own, and give any support that was needed. Children assessed their personality traits and wellbeing at school via the abbreviated HiPIC and Student Subjective Wellbeing Questionnaire with no time restriction. Finally, the lead teachers filled in the Academic Adjustment subscale.

Participation was voluntary and anonymity was guaranteed. The complete participation rate was 89.4%. The ethics committee of Aix-Marseille University approved the protocol of this experiment, which complied with ethical standards for the treatment of human samples.

Data analyses

We began by measuring correlations between the children's and parents' personality assessments for the whole sample in order to estimate the degree of agreement between the two.

Next, to analyze how these correlations changed with the children's age, we calculated variable coefficient models [START_REF] Hastie | Varying-coefficient models[END_REF] for each personality trait. More specifically, these multiple regression models showed how far the self-assessment values were explained by otherassessment values interacting with age. We also calculated multiple regression analyses, then GAMs, to examine links between our two dependent variables (academic adjustment and pupil wellbeing) and the children's self-and other-assessed personality traits. A GAM is a generalized linear model in which the response variable depends on a set of smooth nonlinear functions of some predictor variables. The approach is similar to a polynomial regression that automatically selects the level of nonlinearity required to describe the data. It therefore allows smooth nonlinear relationships between the predictors and the dependent variable to be identified. A model selection mechanism is integrated within the fitting procedure so as to retain only the nonlinear effects that deviate significantly from a linear relationship. GAMs were estimated with the mgcv package [START_REF] Wood | mgcv: GAMs and generalized ridge regression for R[END_REF] in R software (R Core Team, 2017).

Results

Descriptive statistics for the self-and other-assessed personality variables and their correlations are set out in Table 1. Analysis of scores on the Academic Adjustment subscale (M = 31.5, SD = 7.2) and Student Subjective Wellbeing Scale (M = 63, SD = 10.1) revealed good internal consistency. Cronbach's alphas for children's ratings on the HiPIC abbreviated version were quite low (ranging from .52 for agreeableness to .64 for emotional stability) but they were somewhat comparable to the reliability coefficients reported by previous studies using the same instrument. Internal consistency of parent's ratings on the HiPIC slightly exceeded that of children, with alphas extending from .61 for emotional stability to .77 for conscientiousness.

To detect age-related changes in the agreement between children's and adults' personality trait judgments, as well as possible differences in these changes across traits (RQ 1), we calculated variable coefficient models [START_REF] Hastie | Varying-coefficient models[END_REF] for each trait. Descriptively, the agreement between children's and mother's assessments increased with age for extraversion, and either remained stable or fell slightly for the four other traits. However, none of these interactions was statistically significant.

Personality, academic adjustment and subjective wellbeing at school: complementarity of the self-and other-assessments

Multiple regression analyses were used to answer our second research question, namely whether the greater statistically predictive value of parental versus children's judgments of personality traits pertains not only to academic adjustment but also to pupil wellbeing.

Results showed that the children's personality, as assessed by their mothers (i.e., otherassessment) accounted for 18.3% of the variance in their academic adjustment, compared with just 12.6% when it was assessed by the children themselves (i.e., self-assessment). Personality is therefore more closely associated with academic adjustment when it is assessed by the mother rather than by the child. When traits were assessed by the mothers, conscientiousness (β = .319, p < .001) and openness (β = .198, p < .05) predicted academic adjustment significantly positively, and extraversion (β = -.170, p < .05) significantly negatively. When traits were assessed by the children themselves, only conscientiousness was significantly and positively associated with children's academic adjustment (β = .354, p < .001).

We ran multiple regression analyses to identify which of the Big Five traits were most statistically predictive of subjective wellbeing at school. Personality explained only 10.7% of the variance when it was judged by mothers, but this figure rose to 31.5% when personality was assessed by the children themselves. Thus, in contrast to academic adjustment, pupil wellbeing was better predicted by assessments of overall personality when these were produced by the children themselves. In the other-assessments, only conscientiousness (β = .327, p < .001) helped to explain differences in subjective school wellbeing, whereas in the self-assessments, pupil wellbeing was associated not only with conscientiousness (β = .322, p < .001), but also with agreeableness (β = .169, p < .05) and openness (β = .248, p < .001). In contrast to findings for adults, emotional stability did not appear to correlate with children wellbeing at school. This surprising finding raised the possibility that the relations between self-assessed personality traits and subjective wellbeing might be nonlinear in children. Regarding our third and final research question, we therefore calculated a GAM to investigate this possibility. In this model, 38.6% of the children's school wellbeing was explained by their self-assessed personality traits assessments. The model's parameters are set out in Table 2. The results of the GAM revealed that, as we hypothesized (RQ3), personality traits linked to social relations were associated with subjective wellbeing at school: not only conscientiousness and openness, but also agreeableness and extraversion, helped to explain variance in the SSWQ (see Table 2). Figure 1 shows the relationship between mean pupil wellbeing (hence the negative values on the y-axis) and each of the five personality traits. The most markedly nonlinear effect was for agreeableness (edf = 3.32, p = 0.03). Children with the lowest level of agreeableness also had a low level of wellbeing, whereas children with either moderate or high levels of agreeableness differed little on wellbeing. The model also revealed a nonlinear effect of extraversion (edf = 2.92, p = 0.04). The most introverted children had a low level of wellbeing, as did the most extraverted ones. An intermediate level was therefore most favorable to school wellbeing.

Figure 1

Nonlinear effects of children's self-assessed personality traits on their subjective wellbeing at school.

Discussion

The present study explored how far self-and other-assessments of children's personality coincide and how far these two forms of assessment are associated with two dimensions of school adjustment: academic adjustment and subjective school wellbeing. Our first objective was to investigate the convergence/divergence of children's personality assessments according to the source of information (child or mother). Correlations between self-and other-assessments were significantly positive, indicating that parents and children generally coincided in their views of the latter's overall personality under construction. Nevertheless, the modest nature of these correlations also showed that these judgments could not be seamlessly superimposed. The degrees of agreement did not seem to change significantly across the developmental period we considered. We did, however, find variations when we looked at individual traits, with agreement ranging from .19 for agreeableness to .43 for extraversion. These variations could be interpreted in terms of the self-other knowledge asymmetry model [START_REF] Beer | Evaluating the predictive validity of personality trait judgments using a naturalistic behavioral criterion: A preliminary test of the self-other knowledge asymmetry model[END_REF][START_REF] Vazire | Who knows what about a person? The self-other knowledge asymmetry (SOKA) model[END_REF], whereby judgments tend to coincide or diverge as a function of two main factors. The first of these is observability: some traits have more salient behavioral manifestations that help to increase convergence between judgments, as is the case for extraversion. The second factor is evaluativeness: some traits more clearly have a socially desirable pole that can affect the accuracy of judgments and reduce convergence, as is the case for agreeableness. [START_REF] Poropat | Other-rated personality and academic performance: Evidence and implications[END_REF] further argued that other raters base their assessments on behavioral evidence rather than complex thoughts and feelings. This exclusive focus on externalized manifestations of personality could explain divergences between children and parents in the assessment of some personality traits, as well as the closer correlations of other-ratings with academic adjustment, which is behavioral in nature. This interpretive framework could extend to the closer correlations we found between children's ratings of their personality and subjective school wellbeing, given that both dimensions are grounded on inner thoughts and feelings that are not necessarily expressed in overt behaviors.

Indeed, the second result of our study was that the predictive power of self-and otherassessments seemed to depend on the dimension of adjustment. Our data are in line with the findings of [START_REF] Poropat | A meta-analysis of the five-factor model of personality and academic performance[END_REF][START_REF] Poropat | Other-rated personality and academic performance: Evidence and implications[END_REF]'s two meta-analyses, showing that parental assessments of personality are more closely associated with academic adjustment than children's selfassessments, and highlight the particular link of conscientiousness and openness to pupils' ability to adopt an attitude that favors educational attainment. By contrast, when it came to predicting subjective wellbeing at school, the children's assessments of their personality had a greater value than those of their parents. Moreover, they revealed the potential involvement of a broader range of personality traits in explaining individual variability in pupils' subjective experience of school.

Here once again, conscientiousness and openness emerged as adaptive factors, but in contrast to our results for academic adjustment, we also found that individual variations in agreeableness and extraversion were associated with wellbeing at school. Accordingly, observations of divergences between parents' and children's personality ratings may not lead to the hasty exclusion of data yielded by self-assessments. Rather, both sources of information may prove valuable in research and clinical practice, providing their respective predictive power is taken into account.

One should note, however, that we found low internal consistencies for the shortened HiPIC, particularly for the children's self-reports (Table 1), which warrants attention. The Cronbach's alphas in our study were comparable to those reported by two previous studies using the same instrument. In [START_REF] Quartier | A study of personality in children aged 8-12 years: Comparing selfand parents' ratings[END_REF]'s study, reliability for 10-year-old children's ratings ranged from .43 to .69 (M = .56). In Olivier and Hervé (2015)'s study, conducted with children in the same age range as ours, alphas ranged from .40 to .64 (M = .49). Laidra, De Fruyt, and Konstabel (2017) recently reported higher psychometric properties for a short version of the HiPIC in Estonian. Contrary to Quartier and Rossier's adaptation, this version was designed to be fulfilled by parents. Therefore, item selection did not rely on readability for children, but was merely driven by the highest alphas obtained with a preliminary longer version. This selection procedure led to stronger internal consistencies in the validation study, with final alphas exceeding .70 for all domain scales. Similar results were found for a short-form HiPIC in Norwegian that relied on an empirically driven procedure of item selection (Vollrath, Hampson, & Togersen, 2016). Thus, it may be that a proper balance between good psychometric properties and suitability for children's self-reporting remains difficult to achieve.

One consequence of these low reliabilities, however, is that the relationships between children's self-ratings of personality and dependent variables may be questioned. Interestingly, MacCann, Lipnevich, [START_REF] Maccann | Self-and parent-rated facets of Conscientiousness predict academic outcomes: Parent-reports are more predictive, particularly for approach-oriented facets[END_REF] theoretically predicted such an asymmetry in the reliabilities of self and others' personality measures. They argued that external observers' ratings are grounded on a unique source of information (i.e. the child's behavior) in a restricted range of situations, which should result in a rather consistent set of information. In contrast, when answering a personality questionnaire, children rely on multiple sources of information (i.e. not only their behaviors, but also their motivations, feelings and believes), and take into account a more diverse array of situations in which their behaviors and emotions may vary, resulting in a less consistent picture of their reactional tendencies. MacCann, Lipnevich, [START_REF] Maccann | Self-and parent-rated facets of Conscientiousness predict academic outcomes: Parent-reports are more predictive, particularly for approach-oriented facets[END_REF] then envisaged that the superiority of parents' reports in predicting outcome variables (such as academic achievement) could simply be the byproduct of more reliable measures, due to a lower proportion of measurement error in the observed score.

Using correlations corrected for attenuation, their study ruled out this possibility, and the authors concluded that the differences in predictive validity between self and others' measures of personality should not be attributed to the higher internal consistency of parents' ratings.

In light of these arguments and findings, we reasoned that the results of our study could hardly be interpreted as merely reflecting the weakness of the reliability of children's assessment. The fact that the children's ratings, despite a lack of consistency, seemingly captured facets of their personality that were significantly associated with meaningful outcomes, encourages to pursue the search for developmentally relevant tools.

GAM analyses further showed that the relationships between self-assessed personality traits and pupil wellbeing could take contrasting forms. Conscientiousness and openness both had linear relations with wellbeing, such that the more conscientious or open children were, the more likely they were to thrive at school. Agreeableness and extraversion, on the other hand, had nonlinear relations. It would therefore be inaccurate to state that the more extraverted children are, the more they flourish at school, as the GAM analyses indicated that moderate extraversion was the optimum level for this dimension. When De [START_REF] De Raad | Personality in learning and education: A review[END_REF] summarized the arguments linking extraversion to school adjustment, they provided two different predictions: extraverted students may have a high level of energy to invest in their school life, but may direct this energy toward socializing, to the detriment of their academic focus. The latter prediction may help to explain our finding that extraversion (when assessed by mothers) was negatively related to academic adjustment. A tentative interpretation could then be proposed for the emergence of the nonlinear effect. The first half of the inverted U-shaped curve may suggest that extraversion, as opposed to introversion, encourages children to invest in social relations and contributes to their feeling of wellbeing at school. The second half of the curve suggests that, beyond a certain threshold, this preoccupation with social relations could become detrimental to actual learning, to the extent that it compromises pupil wellbeing. Agreeableness had a different profile, as children with very low agreeableness ratings seemed to be at particular risk of failing to thrive at school. However, beyond a certain threshold, variations in agreeableness no longer seemed to be related to differences in wellbeing. A high level of agreeableness did not appear to compromise subjective wellbeing at school, but the relationship clearly contrasted with the linear ones observed for conscientiousness and openness.

The current study had a number of methodological limitations that could be addressed in future work. One of them is that personality traits and the dimensions of wellbeing were both measured via self-report questionnaires with comparable formats. The predictive superiority of the personality self-assessments may thus have been overestimated owing to a bias induced by common-method variance [START_REF] Podsakoff | Common method biases in behavioral research: A critical review of the literature and recommended remedies[END_REF]. Avoiding this bias classically entails using external informants. In the present case, however, gauging subjective wellbeing was ontologically linked to the children's viewpoint on their internal experience of school. Furthermore, Kammeyer-Mueller, [START_REF] Kammeyer-Mueller | The other side of method bias: The perils of distinct source research designs[END_REF] have shown that even distinct source designs are not immune to measurement caveats concerning the estimation of relationships between predictors and dependent variables. As suggested by an anonymous reviewer, one way of lending stronger support to the finding that children's and parents' ratings of personality have different predictive powers independently of source biases could be to make the pupils themselves assess their academic adjustment, and test whether parent-rated measures continue to be more strongly related. Another limitation of the study is the participants' age range, which may have been too restricted to allow us to detect developmental changes in the children's perceptions of their own personality, as well as changes in parent-child agreement. The sample size was also quite small when it came to considering interactions involving age effects.

Another limitation is the cross-sectional and correlational design of the present study, which does not allow for causal inferences about the variables under our investigation. Future research using longitudinal designs could offer additional insights into the truly predictive validity of children's and parents' FFM assessments. It might also be useful to include control variables, such as parents' socioeconomic status or their own personality traits, which may influence both their reports about their children's personality and how they support their children's academic attainment (the finding of statistical predictive validity does not end the search for the underlying mechanisms of influence).

Due to this set of methodological limitations, the present results should be interpreted with caution. In particular, the low reliability of children's ratings on the HiPIC abbreviated form suggests that alternative assessment tools should be considered in future works. The present study helps to identify the methodological hurdles that will need to be overcome and call for the pursuit of researches investigating the respective validity of children's and parents' personality ratings rather than simply giving up using self-reports. Keeping in mind the limitations of our study, a number of implications and directions for future research could be considered.

First, our results contribute to a growing body of data alerting professionals and researchers to the fact that children's burgeoning personality, like their intellectual skills, appears to be significantly associated with their school adjustment. The conceptualization and assessment of personality traits could help teachers gain a more accurate picture of their pupils' characteristics, allowing them to tailor the educational environment and their own relational strategies to the children's individual needs. [START_REF] Poropat | Other-rated personality and academic performance: Evidence and implications[END_REF] suggested, for instance, that children with low levels of conscientiousness require more structured learning contexts, where tasks are broken down into separate steps and the teacher's expectations are more clearly signposted. He also argued that as personality traits seem more malleable and sensitive to experience than intellectual skills, they offer a means of helping children to progress faster and improving their academic functioning. [START_REF] Roberts | A systematic review of personality trait change through intervention[END_REF] recently conducted a meta-analysis that sought to investigate whether personality traits were amenable to significant and lasting changes in response to clinical interventions. This meta-analysis convincingly supported a plasticity principle whereby personality is best be viewed as an open system liable to undergo substantial change. The literature reviewed by the authors only concerned adult studies, but as plasticity tends to decrease with age [START_REF] Roberts | The development of personality traits in adulthood[END_REF], it seems reasonable to assume that children could be given opportunities to develop personality traits in ways that would help them cope with school challenges.

Second, our results indicate not only that personality is associated with achievement and academic adjustment, but also that this association may extend to children's subjective wellbeing at school. This relationship has been far less extensively investigated. The present study suggests that, contrary to the academic achievement dimension, for which conscientiousness is regarded as the crucial noncognitive predictor [START_REF] Dumfart | Conscientiousness is the most powerful noncognitive predictor of school achievement in adolescents[END_REF], pupils' school wellbeing is related to more diverse facets of their personality, which also call for consideration. A recent study [START_REF] Evans | Personality, coping, and school well-being: An investigation of high school students[END_REF]) also examined this relationship, and suggested that students' personality traits may influence their subjective experience of school by favoring qualitatively different strategies for coping with school's stressful demands. Our analyses further suggest that the relationship between personality and outcome variables may take different forms, both linear and nonlinear. The fact that curvilinear links emerged in our data could encourage researchers in the field to lend more attention to the possibility of nonlinear relationships between personality and outcome variables, and calls for theoretical process models that can account for threshold effects.

Finally, the most practical implication of the present study is that school practitioners may consider children's assessments of their personality alongside those of adults. Our data point to the possibility that self-ratings have incremental validity over those of external informants. As already mentioned, this last result calls for additional research designs able to address commonmethod variance issues and to incorporate control variables, but it suggests that the process of gathering information conceivably could be enriched by multiple sources of data. As [START_REF] Bollich | In search of our true selves: Feedback as a path to self-knowledge[END_REF] argued, "the point is not to claim that one perspective is more accurate than the other overall, but to establish that each perspective has some knowledge that the other does not" (p. 3). These authors envisaged the conditions under which feedback on personality from trusted and credible sources (e.g., teachers or school psychologists in a school context) could help to refine self-knowledge and compensate for the blind spots of subjective self-perception. Feedback is only beneficial if recipients are ready to process the information. We contend that the introspective exercise of completing self-report personality questionnaires could be the first step toward refining self-knowledge, relating it to adults' perceptions and expectations, and being able to modify reactions that might otherwise hinder school adjustment.

Table 1

 1 Descriptive Statistics for the Link between Self-and Other-Assessments

		Other-assessment Self-assessment
	Variables Number	M	SD Alpha M	SD Alpha Agreement
	of items

Table 2

 2 Estimated Regressions and GAM Parameters for Studying the Effects of Self-Rated Personality

	on Subjective School Wellbeing
	Variables	β	t	p(t)	edf p(GAM)
			5.607	< .001
	Agreeableness	0.169	2.305	0.022	3.32 .03*
	Emotional stability	0.058	0.847	0.398	1.00 .33
	Extraversion	0.045	0.670	0.504	2.92 .04*
	Conscientiousness	0.320	4.413	< .001	2.11 < .01**

This presupposes the design of assessment instruments that (i) are suited to children's levels of understanding, and (ii) exhibit more satisfying psychometric qualities. For example, when Measelle, John, Ablow, Cowan, and Cowan (2005) administered the Berkeley Puppet Interview, which features contrasting statements that elicit children's self-perceptions, they found that respondents as young as 5 years could provide coherent descriptions of themselves in terms of the Big Five. More recently, Mackiewicz and Cieciuch (2016) suggested that studies among primary school children could use questionnaires featuring drawings, in order to illustrate the different social situations characterizing the Big Five dimensions in a less abstract way. An instrument that was specifically designed for children, rather than being derived from questionnaires for adults, could yield a more consistent picture of the way children view their functioning. We hope that, by further documenting the possible respective merits of children's and others' perspectives, the present study will encourage further research efforts in this direction.

Declarations of interest: none

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors


John Mullen

Singers and musicians in the union

Who are the Variety Artistes Federation ?

At the beginning of the war there are between 2600 and 2700 members of the Variety Artistes Federation, and an editorial suggests that this is out of 4 000 artistes in the country who would be eligible to be members. Like many unions, numbers increased during the war and (DEC19 1918) at the end of 1918, the VAF has 3900 members, which is 700 more than the previous year.

In 1914, members paid a £1 entrance fee on joining, in addition to weekly subs, but the fee could be paid in up to eight instalments if required: we see that care was taken to attract poorer artistes. 1 I'm interested here not in the stars but in the run-of-the-mill music hall artistes, members of the VAF. A third of them were singers, and many others instrumentalists. Many many artistes earned just enough to scrape by, and were 1 The Performer,

frequently unemployed.

What was their working life like? If they were working in London, they would often play at three or four theatres during any given day; but they were often on tour, staying in specialized lodging houses, offering 'three to a room,

[for] thirty five pence, and that included a morning cup of tea and fish and chips at night.' 2 They would be working by now in quite big theatres, 1000 to 3000 seats. The Paisley Hippodrome had 1400 seats, the Empire in Preston and the New Hippodrome in Folkestone had 3 000 each. Here is a recent photograph of the Bradford Alhambra, which opened in 1914 with 1400 seats.

Slide Alhambra

Musicians in the VAF

The photos in the union journal show that many members were musicians.

Here are a couple of examples.

Slide photo banjoists and photo cellist

Virtuosity or novelty -one or the other -would be the Unique selling point of a given turn.

In May 1917, for example, extracts from operas were on tour at the halls and at the Hippodrome in London, a famed Russian pianist was performing. 3 2 Harding, George Robey, 27. At the time there were 240 pennies, or twenty shillings, in a pound. 3 The Encore, 24 May 1917. In these photos we see that there were plenty of women members in the VAF, (though almost none on the leadership committee).

Artistes and trade unionism

What was special about the artistes' trade unionism? From an economic point of view, the artistes were in a contradictory position. On the one hand, they were independent artisans, negotiating individually with their customers (theatres or record companies), and were in direct competition with other artistes to get bookings or top billing. This helped to ensure that there was some truth in what one member said in their memoirs: that VAF members were 'Staunch individualists for whom a "red nose" was infinitely preferable to the red flag.'4 And yet, the economic power of theatre managers (and the increasingly influential chains of theatres) tended to reduce the entertainers to the status of dependent wage workers.

The revolution in variety which had started just before the warthe rise of the revueaccelerated this tendency. Instead of an evening entertainment made up of individual turns, more and more theatres were moving to a single team showrevue-an artistically centralized form, integrating music hall turns. Revue was a result of the concentration of capital, and a show which created newish groups of semi skilled workers such as chorus girls. In July 1918, the paper lists the titles of 87 revues on tour in the UK. July 4 1918 All this meant that artistes were ever more prone to use collectivist tactics to improve their situation.

Collectivism was not entirely new. Mutual aid associations had been founded in the 1870s, in particular the Music Hall Artistes Railway Association, which negotiated special tariffs for music hall entertainers on trains, and gradually took on other union roles, not without vigorous polemics between proand anti-trade union artistes.

By 1897, there were 5 000 members of the MHARA. In 1906, its leaders joined up with other organizations to found the Variety Artistes Federation, During the great music-hall strike in London in 1907, the artistes were able to force a government arbitration which introduced important improvements in standard contracts. The right of theatres to ban artistes from playing in other venues in the same town was limited, and additional shows such as matinees had from then on to be remunerated.

The strike was active and dynamic and lasted 22 days. On both sides, all the habitual union and management tactics were implemented. Some theatre managers doubled the salaries of non-strikers for the duration of the conflict, and others put pressure on artistes to sign a written promise not to join the union.

On the strikers' side, rallies and picket lines were organized in front of the theatres, and over a million leaflets were given out. Strike-breakers were expelled from the union, and alternative evenings of entertainment were held with big name stars to raise money for the strikers. Only the London theatres were on strike, but union members in the rest of the country gave five per cent of their salary every week to the strike fund. 5 Solidarity was available from other sections of the labour movement.

Southwark Trades Council, for example, held meetings with speakers from a series of manual workers unions and from the Independent Labour Party. The union also supplyied pro forma contracts, was involved in national negotiation with employers, and occasionally supported strike action. 5 Honri, Music Hall Warriors, 12.

But the union retained important aspects of a friendly society, highly necessary in these pre-welfare state days.

For example death grants. Each member paid in addition to weekly subs, a fixed sum every time a member died. The sum collected in this way was given to the family of the dead man or woman. In 1915, the death levy was sixpence that is to say the family received around three hundred pounds death grantthis represented a year's wages for the smaller artistes. In 1915 there were 19 death levies to pay, in 1916pay, in , 20. Nov 22 1917: : So the amount given to the widow or family varies, but the VAF hands over immediately 25 pounds on proof of death (enough to pay for the burial).

The VAF is also closely associated with the music hall sick fund, and with the rest homes for retired artistes set up in 1895 in Scotland and in 1911 in England.

Regular charity carnivals were held in aid of the rest homes as well as events to raise money for the Variety artistes benevolent fund, and the music hall ladies guild. This last would take children of poorer artistes on holiday in the summer We know nothing of politics, and the Variety artistes federation is not a political organization. We have been good friends with the International Artistes Lodge of Germany for many years , and they have done much to lighten the burden of the British artiste when on the Continent. If Fate places us in different camps, it is for each to do his duty to the State to whiCh he belongs, trusting, when it is « all over » to renew the friendships of the past. It is neither « ours » nor « theirs » to reason whyand neither would respect the other who did not put his duty to his country before everything. What has to be in the meantime is in the « lap of the Gods ».

December 2 1916 Conscription and the music halls is discussed "with the political aspect of the subject we are not interested. What is of more direct importance to variety artistes is… to what extent would the music hall and the music hall profession generally be affected?"

The newspaper shows itself proud of the men who join up, and it refers favorably to an attempt to put together a battalion only made up of men from the music hall industry (4.2.15) All VAF members who are called up are kept in benefit for the duration provided they were fully paid up when they joined the army "the federation is thus loyally backing up the patriotism of all its members who are with the colours". (13 April 1916) Slide cartoon war worry and cartoon war cloud So the union paper doesn't not at all go in for recruitment propaganda or arguments for or against conscription, but is in favour of music hall artistes playing a full role in the national mobilization.

-Building the union

Slide cartoon recruiting new members

The main priority throughout the war was recruiting new members.

23 july 1914 A « gold medal » is awarded to the member who recruits the largest number of new members.

A specific campaign was run to recruit workers in revue: members of the chorus in particular. Demands were put forward of particular interest to these groups : strict limits on unpaid rehearsals, no dismissal without notice etc. A new rule was introduced so that any performer earning less than four pounds a week could join the vaf for an entrance fee of one shilling rather than the usual guinea.

Jan 13 1916 The VAF decided in 1916 to resume holding monthly meetings -Manchester Liverpool Glasgow Newcastle and Birmingham as well as in London -Questions of artiste professionalism

The journal spent a good deal of space on issues of what was seen as artiste professionalism, as you can see in these two cartoons.

Slide cartoon old business and cartoon vulgarity

On the left the cartoon recommends that performers renew their turn regularly.

On the right the cartoon expresses concern about vulgarity, which is massively and regularly denounced in the paper. or claimed that it had been largely eliminated, in response to attacks from groups such as the National Vigilance Association, though vulgarity itself is often not clearly defined. (APRIL 6 1916) When in 1916, one comedian wrote to the Performer denouncing moralism and defending vulgarity, an avalanche of letters were published disagreeing with him. I have written of this elsewhere.

June 22 1916 In June 1916 the Editorial was entitled "vulgarity and the halls" and its attitude to the risqué comedian is quite clear: "where one fool would applaud his suggestive witticism, hundreds of decent people experience no feeling beyond that of disgust -Defending the music hall industry Many pages of the journal in the war years concentrate on defending the music hall industry, employers and workers together, against excessive encroachments of rationing in particular.

Slide cartoon night club and cartoon problem leaves with peace sun

So here we can see a protest at the imposition of early closing to save energy.

The music hall is hit by the curfew whereas the night clubs for the upper classes are left alone. There is a class element then to this protest -salaries and working conditions Slide cartoon tinker tailor soldier spy and cartoon dressing rooms Wages and working conditions were obviously a priority At the start of the war a "Cooperative scheme" was set up for a few months;

Everyone was sure that income from music halls would collapse, and the union negotiated a pro-rata wage reduction in the hope of enabling everyone to surviuve the few months it was thought the war would last. This caused much debate in the union, partly because of management abuse of the system, and the scheme was abandoned when it became clear that ticket sales had rapidly recovered and were even booming.

In September 1918, the (26.09.18) editorial was on health and safety issues, in particular damp and draughty dressing rooms.

But no doubt the two most important campaigns were against Sunday opening of music halls, and against the split week. After a series of mass union meetings, it was decided that members accepting contracts for less than one week's work would be disciplined. (2 July 1914) Relations with other workers in the theatres Slide other workers (tips or award payments)

Askwith made an award for the duration of the war Wages increased and certain employees such as dressers who were paid by tips only now have a minimum wage (6d a night) (The Performer, 21.09.1960) In 1918 the Chairman's page carried a discussion of tips given by artistes to stage hands, and proposed they should be replaced by a fixed system for specific services (setting up or operating turn equipment etc) The union is generally against tipping as not dignified, and would prefer a scale. An agreement seems to be in progress about fixed charges for such help. This is the subject of discussion between the vaf and the national association of theatrical employees. (The Performer, June 6 1918) In this issue then the union is playing its role of standardizing payment, and not allowing it to depend of subjective criteria which prevent workers' solidarity. Its work as a friendly society helped hundreds who were in dire circumstances in this period long before the arrival of a welfare state. Its work as negotiator backed up with the threat of industrial action, and the acceptance of union discipline by performers, helped maintain working conditions at an acceptable level. At the same time its obsession with respectability, and its routine participation in the war drive were both elements which acted more in the interests of national elites than those of the music hall performers and their largely working class audiences.

  kings or Jan Naylor violoncello virtuoso On a less traditional note, successful turns included the handcuffed violinist the Apache lady violinist The only girls bagpipe band in the world The Grainger girlsthe only singing cyclists Or Odette Myrtil, who sings a French song and plays the violin whilst dancing" (The Encore Jan 4 1917) SLIDE Three sisters singers and woman bugler Slide Two more female singing groups

  The VAF : A Trade Union of a hybrid type : with elements of the friendly society and the professional association So by the time of the first world war, the VAf was a real modern trade union , With union discipline, the giving legal advice and legal representation Feb 1 1917 (77 legal cases were supported in 1915: 52 in 1916).

(

  40 went to Bognor regis in 1913) and in the Winter would visit sick or retired artistes and give them free coal. (Jan 7 1915) Finally the VAF had aspects of a professional organization, defending the profession and the sector, as we shall see. « The Performer » and its wartime priorities Here then is the Union journal Slide two front pages it's main sections included Debate and opinion on all aspects of show business Slide editorials and letters' page As well as the down to earth necessity of finding a gig. Here are adverts for turns with vacant dates: Slide lots of adverts for turns July 3 1913 But also frequent legal notices remind us it can be a cut throat industry « notice is hereby given to all whom it may concern that the idea and title of the living piano (huge capital letters) is registered and full protected". Sole agent A Goldstein Slide adverts for hampers and agents And then there are adverts for essential accessories such as hampers, and agents. And adverts for digs in every issue, as thousands of artistes tour the country. These small ads claim « cooking and cleanliness a speciality » « electric light » for one or two of them « troupes accommodated » « patronized by leading professionals » « piano in each room » « lavatory in house » say a few of them « one minute from halls » « trains met with lorry on receipt of wire » What are the priorities of the union during the war ? -patriotism Like many milieux, the music hall milieu is patriotic and support for the war drive goes without saying. ? Nevertheless it is consensual patriotism and impossible as yet to say or even to imagine what effect this terrible tragedy of a european war will have on the music hall industry »

  Drury Lane complained to the VAF that they had been rehearsing for six to eight weeks without pay.sep 6 1917 In September1917 a girl while rehearsing unpaid was seriously injured and the theatre chain involved -Moss Empires -refused to pay compensation saying she hadn't been employed on a contract. for members working in revues.(25 Nov 1916)

  Also in the journal there were reports on strikes by other unions, esp amalgamated musicians union and their long 1914 dispute with the theatre chain owned by Oswald Stoll. They also report sympathetically on attempts to get wage rises by the national union of theatrical employees. August 3 1916 Strike in Golders green of stage hands, when all union members were sacked. Expressed support in 1917 for the vaudeville strike in the united states. Conclusions I hope then that these cartoons and these comments have shown something of the nature of the trade unionism of variety performers during the war years.Looking at this trade unionism allows us to be reminded of the situation of the average performer : a very long way from the situation of the stars who one hear much more about.

Peter Honri, Music Hall Warriors. The History of the Variety Artists Federation 1906 to 1967 (London: Greenwich Exchange, 1997), v.


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