Lisa Hsin

Nayeli Gonzalez-Gomez

Isabelle Barrière

Thierry Nazzi

Geraldine Legendre

S V Comprehension

I N Spanish

Barrière

Goyet

Kresh

Legendre

Nazzi

; In Spanish

Hsin Gonzalez-Gomez

SV COMPREHENSION & PRODUCTION IN SPANISH

A surprising comprehension-production asymmetry in subject-verb (SV) agreement acquisition has been suggested in the literature, and recent research indicates that taskspecific as well as language-specific features may contribute to this apparent asymmetry across languages. The present study investigates when during development children acquiring Mexican Spanish gain competence with 3 rd person SV agreement, testing production as well as comprehension in the same children aged between 3.5 and 5.5 years, and whether comprehension of SV agreement is modulated by the sentential position of the verb (i.e., medial vs. final position). Accuracy and sensitivity analyses show that comprehension performance correlates with SV agreement production abilities, and that comprehension of singular and plural third-person forms is not influenced by the sentential position of the agreement morpheme. Issues of the appropriate outcome measure and the role of structural familiarity in the development of abstract representations are discussed.

Spanish-speaking monolingual preschoolers, and test their comprehension of declarative sentences displaying two word orders, both acceptable in the presented context but of differing frequency in child-directed speech.

Cross-linguistic acquisition of SV agreement: Linguistic and methodological issues

For virtually all of the languages in which the acquisition of SV agreement comprehension has been studied, comparisons with available production data have suggested that children reliably produce 3 rd person SV agreement at an earlier age than the corresponding comprehension abilities emerge. For example, in English, children reliably produce 3 rd -person SV agreement between ages 2;6 and 3;10 (Brown, 1973), but they have not been found to comprehend it reliably until age 4;0-6;0 [START_REF] Johnson | Agreement without understanding? The case of third person singular /s[END_REF][START_REF] Legendre | Is children's comprehension of subject-verb agreement universally late? Comparative evidence from French, English, and Spanish[END_REF]. Likewise, in Spanish, children tend to produce error-free 3 rd -person SV agreement around age 1;6-1;7 [START_REF] Montrul | The acquisition of Spanish. Language Acquisition and Language Disorders[END_REF], but reliable comprehension has not been found earlier than age 3;5 [START_REF] Gonzalez-Gomez | Agarra, agarran: Evidence of early comprehension of subject-verb agreement in Spanish[END_REF][START_REF] Pérez-Leroux | Number problems in children[END_REF]. German [START_REF] Brandt-Kobele | What asymmetries within comprehension reveal about asymmetries between comprehension and production: The case of verb inflection in language acquisition[END_REF] and Xhosa (de Villiers [START_REF] De Villiers | The acquisition of number agreement in English and Xhosa[END_REF][START_REF] Gxilishe | Children's insensitivity to information from the target of agreement: the case of Xhosa[END_REF] also display this asymmetry. Data from children acquiring French do disrupt this pattern somewhat [START_REF] Barrière | Uncovering Productive Morphosyntax in French-learning Toddlers: A Multidimensional Methodology Perspective[END_REF]Culbertson et al., 2016;Legendre et al., 2010;[START_REF] Legendre | Experimental and empirical evidence for the status and acquisition of subject clitics and agreement marking in adult and child Spoken French[END_REF][START_REF] Legendre | Is children's comprehension of subject-verb agreement universally late? Comparative evidence from French, English, and Spanish[END_REF][START_REF] Nazzi | Tracking irregular morphophonological dependencies in natural language: Evidence from the acquisition of subject-verb agreement in French[END_REF]. In particular, French-speaking children display successful prefixal, subject clitic-based number agreement comprehension (see below for further discussion of this agreement subsystem) in pointing and preferential looking tasks by 30 months of age [START_REF] Legendre | Is children's comprehension of subject-verb agreement universally late? Comparative evidence from French, English, and Spanish[END_REF][START_REF] Barrière | Uncovering Productive Morphosyntax in French-learning Toddlers: A Multidimensional Methodology Perspective[END_REF] while they show sensitivity to these agreement markers in head-turn preference tasks as early as 14 months (Culbertson et al., 2016), and spontaneously produce them as early as 24 months [START_REF] Thordardottir | Early lexical and syntactic development in Quebec French and English: Implications for cross-linguistic and bilingual assessment[END_REF].

However, the kind of production data with which these comprehension findings are ordinarily compared can be subjected to some criticism. Typically, those are spontaneous production data rather than elicited productions (e.g., Brown, 1973;[START_REF] Montrul | The acquisition of Spanish. Language Acquisition and Language Disorders[END_REF]. This is potentially problematic because the patterns found in children's spontaneous productions suggest that young children especially tend to be 'grammatically conservative' (that is, their most frequent utterances reflect constructions that they regularly hear in their linguistic environment-and not innovative utterances that may be the output of a grammatical pattern they are still in the process of learning; Snyder, 2011). Indeed, the few exceptions to the reliance of research in this domain on spontaneous production are found in the context of cross-dialectal studies of English (e.g. [START_REF] Barrière | The comprehension of 3 rd Person Singular -s by NYC English-speaking Preschoolers[END_REF][START_REF] Miller | Not all children agree: Acquisition of agreement when the input is variable[END_REF], and they have led to contradictory results: either disparity [START_REF] Miller | Not all children agree: Acquisition of agreement when the input is variable[END_REF] or a close relation [START_REF] Barrière | The comprehension of 3 rd Person Singular -s by NYC English-speaking Preschoolers[END_REF] between comprehension and production of 3 rd person singular and plural subject-verb agreement markers. Highlighting the importance of the methodology used to extract SV agreement production in young children, an elicited production study of preverbal subject clitics construed as agreement markers [START_REF] Jakubowicz | L'acquisition des clitiques nominatifs et des clitiques objets en français[END_REF] reveals that children age 2;0-2;7 answer in a picture-elicitation task questions like 'What is X doing?' with a subject clitic 86%-92.4% percent of the time (depending on their MLU score), compared to a lower spontaneous level of production in an open play session with an experimenter and a parent (45.5%-71%). This somewhat muddled collection of findings indicates that drawing inferences about children's underlying competence from spontaneous productions alone may misconstrue the sophistication of their grammatical representations, leading some researchers to draw conclusions of a competence-driven asymmetry that could instead reflect nothing more than differences in experimental conditions.

Another feature of the majority of existing studies on the acquisition of 3 rd person SV agreement is the restricted nature of word orders (or constructions) presented as stimuli for comprehension-a design decision that is not without consequences for the conclusions that can be drawn from experimental research. To our knowledge, most studies of SV agreement comprehension in first-language acquisition have used stimuli embodying those languages' basic word orders. In these languages, the SV agreement marker surfaces in a sentencemedial position (e.g., in English, "he sit-S here," or German, "Sie fütter-T einen Hund," she is feeding the dog). Sentence-medial positions are associated with processing disadvantages (e.g., [START_REF] Sundara | Sentence-position effects on children's perception and production of English third person singular -s[END_REF], which may be partially responsible for depressing comprehension accuracy. A contrasting familiarity-based hypothesis, however, would argue for the advantageousness of presenting SV agreement markers for comprehension in their basic word order constructions (or 'canonical positions'): familiarity with the syntactic structure of a stimulus could plausibly facilitate its accurate interpretation (see, e.g., [START_REF] Ambridge | The ubiquity of frequency effects in first language acquisition[END_REF]. Both Johnson and colleagues (2005) and Barrière and colleagues (2019) found that the sentence-medial marker was comprehended more reliably than the sentence-final one.

The only tested language not following the sentence-medial SV agreement marker pattern is colloquial spoken French, which has been argued to have sentence-initial SV agreement as a consequence of the syntactic reanalysis of preverbal subject pronouns (clitics) into number agreement markers (Legendre et al., 2010). Interestingly, French-learning children as a group have been shown to acquire subject-verb agreement earlier than their cross-linguistic peers [START_REF] Legendre | Is children's comprehension of subject-verb agreement universally late? Comparative evidence from French, English, and Spanish[END_REF]. There is also a minimal disparity between the age at which French-learning children have been found to comprehend SV agreement (and not only in this salient position, but more generally: see [START_REF] Barrière | Uncovering Productive Morphosyntax in French-learning Toddlers: A Multidimensional Methodology Perspective[END_REF]Culbertson et al., 2016;Koulagina, Legendre, Barrière, & Nazzi, 2019) and to produce it reliably [START_REF] Thordardottir | Early lexical and syntactic development in Quebec French and English: Implications for cross-linguistic and bilingual assessment[END_REF]. However, these studies and others (e.g., Bassano, 2000;Rasetti, 2003) are grounded in spontaneous production data, or else they are measured via parental questionnaire (e.g., using a French version of the CDI, as in [START_REF] Barrière | Uncovering Productive Morphosyntax in French-learning Toddlers: A Multidimensional Methodology Perspective[END_REF], potentially missing a full measure of the competence possessed by the tested children.

The acquisition of SV agreement in (Mexican) Spanish

Spanish affords a promising opportunity to explore three hypotheses relating to these observations from the literature: whether comprehension and production truly are acquired asymmetrically in young monolingual learners, whether the representations associated with comprehension performance are more general than mere reflections of children's linguistic input, and the extent to which comprehension reflects lexical knowledge (that would predict similar performance with the same verbs across different word order conditions). Spanish is typically considered to have a default subject-verb-object sentence structure (i.e., it is an SVO language) but also displays a somewhat flexible word order (Gutierrez-Bravo, 2013). It allows location-related prepositional phrases (PPs: e.g., "on the couch," "under the tree") to be placed at the beginning of a sentence regardless of the type of verb used, the status of the subject, etc. [START_REF] Kempchinsky | Locative Inversion, PP topicalization and the EPP[END_REF]; see also Ordónez & Treviño, 1999). While features concerning the relative importance of information in a sentence can drive PP-fronting in Spanish, they need not [START_REF] Kempchinsky | Locative Inversion, PP topicalization and the EPP[END_REF], which suggests an adequate degree of functional equivalence between (intransitive) V-PP (e.g., cenan en la cocina "(they) eat in the kitchen") and PP-V (e.g., en la cocina cenan "in the kitchen (they) eat") word orders.

The preverbal (i.e., left-peripheral) position that is available in Spanish-speaking adults' grammar appears to emerge early in the speech of children who are acquiring Spanish as well [START_REF] Bel | Aspectos de la adquisición del orden de palabras: la posición del sujeto en castellano y catalán[END_REF][START_REF] Villa-García | Acquisitional evidence bearing on the account of preverbal and postverbal subjects in Spanish[END_REF]). To our knowledge, no work has been published on the frequency of preverbal PPs in child-directed Spanish, although our own preliminary corpus analyses of children's language interactions with caregivers suggest they appear extremely infrequently (only 8% of child-directed utterances containing a PP have the PP preceding the verb; see Villa-García, 2011, for the suggestion of a similar pattern among other fronted constituents). However, [START_REF] Grinstead | Subjects and Interface Delay in Child Spanish and Catalan[END_REF] shows that fronting of overt subjects and of objects and, crucially, of adverbs-which function similarly to the PPs that we test in this study, both being adjuncts-emerges early in child Spanish (i.e., around age 2-2;6). This suggests that this preverbal position is available to even the youngest speakers for a variety of uses (see also [START_REF] Hsin | Integrated bilingual grammatical architecture: Insights from syntactic development[END_REF][START_REF] Villa-García | Acquisitional evidence bearing on the account of preverbal and postverbal subjects in Spanish[END_REF].

The present study

The present study investigates when during development children acquiring Mexican Spanish gain competence with 3 rd -person SV agreement-in production as well as comprehension. We assessed comprehension abilities using videos and a pointing task that varied the number reflected in the agreement marker (singular or plural) and the surface position of the agreement marker (sentence-medial or sentence-final). Complementing this comprehension data, we also elicited the production of SV agreement using visual stimuli.

Our reporting focuses on the effects of the agreement number (singular vs. plural), as only plural agreement is overtly marked; the age of participants, testing children ranging from 3.5 to 5.5 years of age given previous data showing an emergence of 3 rd person SV agreement comprehension in Spanish around 3.5 years of age; and the possibility of a position-related effect on comprehension.

Methods

Participants

There were 51 monolingual Mexican Spanish-speaking participants (M age = 4.56 years; SD=0.62; range=3.47-5.63 years; 28 girls). Each participant completed both position conditions (medial and final) and a production task during a single test administration. All participants who began the experiment completed it.

Materials

Comprehension task

Visual stimuli. Eight pairs of videos of two boys performing a variety of 'intransitive' actions were developed and used in both conditions. The two videos in each pair could only be distinguished by the number of actors engaged in the activity. Either one boy performed the action alone (singular video), or the two boys performed the action jointly together and simultaneously (plural video), both boys appeared in every video (see Fig. 1). Videos were 6seconds-long. A video of the boys dancing in a celebratory manner was created to supply implicit feedback on the side of the correct video after each trial (as previously done in [START_REF] Gonzalez-Gomez | Agarra, agarran: Evidence of early comprehension of subject-verb agreement in Spanish[END_REF]. Verbal stimuli. Auditory stimuli consisted of short null subject sentences having either an intransitive verb + prepositional phrase for the sentence-medial condition (e.g., cena en la cocina '(he) dines in the kitchen' vs. cenan en la cocina '(they) dine in the kitchen') or a prepositional phrase + intransitive verb for the sentence-final condition (e.g., en la banca salta 'on the bench (he) jumps' vs. en la banca saltan 'on the bench (they) jump': see Appendix 1). Eight familiar verbs, referring to the eight actions in the videos, were used: escribir "write", saltar "jump", correr "run", comer "eat", llorar "cry", jugar "play", dibujar "draw", and leer "read". These verbs were chosen because they are known by many children according to the Mexican Spanish adaptation (Jackson-Maldonado, Marchman, Thal, Bates, & Gutierrez-Clellen, 1993) of the MacArthur CDI "Words and phrases" [START_REF] Fenson | The MacArthur communicative development inventories: User's guide and technical manual[END_REF] and can all be used intransitively.

Production task

A subset of the visual stimuli and procedure of the Diagnostic Evaluation of the Language Variation (DELV; [START_REF] Seymour | Diagnostic Evaluation of Language Variation: Norm Referenced (DELV-NR)[END_REF] was adapted for the purpose of this study to measure children's subject-verb agreement productions. The DELV stimuli in that section consist of pairs of pictures depicting ethnically diverse children and adults. The left picture systematically depicts two individuals (i.e., animals, children, or adults) instigating an event while the right picture depicts a single individual of the same semantic category performing the same action. We elected to use an adaptation of the DELV rather than a less constrained elicitation task in order to increase our chances of obtaining reliable, analyzable responses.

In the English version, the task is a sentence completion task during which the experimenter first produces a sentence that describes the left plural version of the picture (e.g. the horses eat hay) after they have described different elements of the pictures (e.g. horses, hay, rabbit, carrots) and prompts the child to produce the singular version of the same verb (e.g. but the rabbit…) while pointing at the singular version of the picture depicting a rabbit eating carrots: the elicitation of the 3 rd person singular in English is motivated by the fact that this feature varies across different varieties of English (Barrière et al., in press).

We adapted this section to Mexican Spanish so that the 3 rd person singular items were elicited for half of the set of stimuli and the 3 rd person plural for the other half, given that our purpose was to assess children's ability to produce the singular and the plural 3 rd person agreement makers.

Procedure

Comprehension task

Each child was tested individually in a quiet space within their kindergarten. Children sat in front of a 22" LCD touchscreen monitor (Planar PX2230MW). The experimenter sat behind the child and produced each of the stimulus utterances live. Task presentation order was counterbalanced.

In the comprehension task, first, the child was told that she would see images on the screen and be asked to touch some of them. The participant saw four training trials that displayed pairs of familiar objects (e.g., an apple and a house). After 12 seconds of visual presentation, the live experimenter said: viste la casa? muéstrame con tu dedo la casa, dónde está la casa? ("Did you see the house? point where the house is, where is the house?"). When the child touched the image, the monitor's background changed color to indicate that the response had been recorded. After the training trials, the introductory video of the boys appeared, while the experimenter explained that the child would now see videos of them doing different activities and that again the child would be asked to tap one of the videos.

The test phase then began, consisting of eight trials. During each trial, each video was played twice in silence on one of the sides of the screen, followed by the other video. The experimenter then said: viste? cenan en la cocina, muéstrame con tu dedo en cuál imagen cenan en la cocina, dónde cenan en la cocina ('Did you see? Dine-3PL in the kitchen, point where dine-3PL in the kitchen, where dine-3PL in the kitchen?'). The two videos then reappeared simultaneously in their original locations, during which time the child would touch the matching video. The background changed color, and the celebratory video appeared on the side of the correct response (supplying implicit feedback). The side, order of singlevs. dual-actor, and task presentation order were counterbalanced across participants.

Production task

The procedure was similar to the standard DELV administration. At the beginning of the testing the experimenter told children: 'Ahora te voy a enseñar unas imágenes y te voy a decir algo sobre cada una. Quiero que mires las imágenes y que termines lo que voy a decir' (I am now going to show you some pictures, and I am going to tell you something about each image. I want you to look at them carefully and to finish what I am going to say). Children were then presented with 10 different items, in each trial elements of the pictures were first described by the experimenter and then participants were expected to complete sentences, for example, 'Veo unas colas cortas y veo una cola larga. El gato tiene cola corta, pero los perros…'" (I can see a short tail and I can see a long tail. The cat has a short tail, but the dogs…). The task elicited the production of 5 plural verbs (i.e., tener 'have, dormir 'sleep', lavar 'wash' in the present and two instances of estar 'be' in the past) and 5 singular verbs (i.e., tener 'have', andar 'ride', empujar 'push', nadar 'swim', jugar 'play') in the canonical position (see Appendix 2). The score considers the accurate production of 3 rd -person singular and plural agreement markers with an overt subject in the context of these sentences.

Results

Production task

In the production task participants could produce up to ten correct responses: five singular and five plural. Overall, on average, they produced 8.80 correct responses (SD=1.45): 4.43 correct singular utterances (SD=0.78) and 4.37 correct plural utterances (SD=0.94). Both of these values were significantly greater than chance, where chance was defined as 50% accuracy: for singular items, t(50)=17.67, p<.001; for plural items, t(50)=14.27, p<.001. All but three participants answered at least two singular items and two plural items correctly. Four types of errors were documented: exchanging singular for plural forms or vice versa, producing a bare present participle (without the inflected auxiliary verb), producing only the subject noun of the target phrase, and failure to supply a response. Sixteen participants produced a singular verb where a plural was needed; 2 participants produced a plural verb where a singular was needed. Nine participants produced a bare present participle.

The subject noun alone was produced as a response by 11 of the participants, while 7 participants produced an uninterpretable response. As attested by the high average accuracy on singular and plural items across the sample, however, the incidence of all of these errors was quite low (13.65% of all trials).

The sample was divided into two age groups by a median split: the younger group's mean age was 4.03 years (range=3.47-4.50), while the older group's mean age was 5.11 years (range=4.50-5.63). A two-way ANOVA was conducted with Number (singular vs. plural) as a within-subjects factor and Age Group (younger vs. older) as a between-subjects factor.

There was a significant effect of Age Group, F[1,49]=8.18, p=.006, partial η 2 = 0.26, attesting better accuracy among older participants, which was confirmed via simple correlation analysis using a continuous Age variable, r(49)=.39, p=.005. There was no significant effect of Number, F[1,49]=0.20, p=.66, partial η 2 = 0.004, confirming the lack of difference between the two conditions, nor was there a significant interaction, F[1,49]=0.20, p=.66, partial η 2 = 0.004.

Accuracy was also compared against chance separately for the older and younger groups. Despite the fact that the older group produced accurate responses significantly more often than the younger group, both groups on average performed at above-chance levels in both conditions (all ps<.001; see Figure 2). Moreover, accurate responses on singular items were significantly correlated with accurate plural responses, r(49)=0.43, p=.002. Therefore, in subsequent analyses, we collapse singular and plural production scores into a single Production Score.

Comprehension task: Accuracy

Accuracy results are presented in Figure 3. Overall, participants pointed to the video that corresponded to the verbal stimulus in 68.75% of trials (SD=20.03%), which was significantly different from the 50% chance level, t(50)=6.68, p<.001. A three-way mixeddesign ANOVA was conducted with Number (singular vs. plural) and Position (medial vs. final) as within-subjects factors and Age Group (younger vs. older) as a between-subjects factor (using the same median split as for the Production analysis). There was a significant effect of Number, F[1,49]=49.08, p<.001, partial η 2 = 0.65, attesting better accuracy for plural trials; comparisons to 50% showed that accuracy was better than chance for plural trials, M=81.86%, t(50)=12.96, p<.001, but not singular trials, M=55.64%, t(50)=1.38, p=0.17. There was a significant effect of Age Group (F[1,49]=12.76, p=.001, partial η 2 = 0.46), attesting better accuracy in older children; yet, accuracy was better than 50% chance for both the older group, M=77.75%, t(24)=8.39, p<.001, and the younger group, M=60.10%, t(25)=2.63, p<.014. There was no significant effect of Position, F[1,49]=0.15, p=.699, partial η 2 = 0.004, nor any significant interactions. We also examined the correlations between comprehension accuracy, production accuracy, and participant age. Overall comprehension accuracy was significantly correlated with production accuracy, r(49)=.32, p=.017, and with age, r(49)=.49, p<.001. For singular items, comprehension accuracy was marginally correlated with production accuracy, r(49)=.27, p=.058, and significantly correlated with participant age, r(49)=.44, p=.001. For plural items, comprehension accuracy was significantly correlated with production accuracy, r(49)=.32, p=.023, and with participant age, r(49)=.38, p=.005.

Comprehension task: Sensitivity

Sensitivity analyses were developed to reflect the proportion of a child's points to a given video type (singular or plural) that was linked to hearing that verbal stimulus type (see [START_REF] Johnson | Agreement without understanding? The case of third person singular /s[END_REF]. For each participant, we computed two proportional sensitivity scores, one for SG trials and one for PL trials, by dividing the hit rate (i.e., the points to the SG video when a SG verbal stimulus was presented) by the sum of the hits and false alarms (i.e., all points to the SG video). In multimodal preference tasks (i.e., where participants are asked to map auditory stimuli to visual ones), participants can sometimes show a preference for one type of visual stimulus regardless of the auditory stimulus that is presented with it. Sensitivity analyses are used to compensate for those preferences: they represent a contingent value based on the number of times a participant's selection of one video or the other can be attributed to the auditory stimulus. That is, whereas an accuracy measure simply computes the proportion of video-selection responses that aligned with the auditory stimulus, the sensitivity measure computes how often the selection of a singular or plural stimulus was correct in light of the overall frequency of the selection of each.

Sensitivity results are presented in Figure 4. Overall, sensitivity scores were 69.55% (SD=21.88%), which was significantly different from the 50% chance level, t(50)=6.38, p<.001. A three-way mixed-design ANOVA was conducted with Number (singular vs. plural) and Position (medial vs. final) as within-subjects factors and Age Group (younger vs. older) as a between-subjects factor (using the median split as above). There was a significant effect of Number (F[1,49]=5.83, p=.020, partial η 2 = 0.11), attesting better sensitivity for singular; yet, sensitivity was significantly above the 0.5 chance level for both SG, M=0.72, t(50)=6.29, p<.001, and PL, M=0.67, t(50)=6.30, p<.001, stimuli. There was a significant effect of Age Group, F[1,49]=13.27, p<.001, partial η 2 = 0.64, attesting better sensitivity in older children; yet, sensitivity was better than the 0.5 chance level for both the older group, M=0.80, t(24)=8.57, p<.001, and the younger group, M=0.60, t(25)=2.31, p=.030. There was no significant effect of Position, F[1,49]=0.001, p=.973, partial η 2 < 0.001, nor any significant interactions among the factors. As with the accuracy analysis, we examined the correlations between sensitivity in comprehension, production accuracy, and participant age. Overall sensitivity was significantly correlated with production accuracy, r(49)=.33, p=.018, and with participant age, r(49)=.38, p=.005. For singular items, sensitivity in comprehension was significantly correlated with production accuracy, r(49)=.33, p=.018, and with participant age, r(49)=.42, p=.002. For plural items, sensitivity in comprehension was likewise significantly correlated with production accuracy, r(49)=.29, p=.038, and with participant age, r(49)=.49, p<.001.

Discussion

Our results demonstrate that children acquiring Spanish display comprehension of 3 rd person SV agreement as early as 3.5 years of age, and that comprehension continues to increase over the 2-year period reflected in the age range of our sample. These results also show that participants' processing of this agreement paradigm is position-independent, children's comprehension being similar in the medial and final position. Furthermore, while accuracy on plural trials was higher than on singular trials, sensitivity to singular stimuli was higher than it was to plural agreement. Sensitivity analyses also revealed that older and younger children both comprehended the agreement marker at above-chance levels. The production results show performance above chance level for the older and younger children, but better accuracy was found for the older children. Critically, comprehension ability of SV agreement, as measured by both accuracy and sensitivity, was correlated with production ability and age.

The comprehension results showed a significant effect of participant age when examining both outcome measures (i.e., accuracy and sensitivity). Nevertheless, this effect was associated with above-chance sensitivity for both the younger and the older children in our sample, indicating that we may not yet have reached the lower age bound at which Spanish-acquiring children can comprehend 3 rd person SV agreement (contra Pérez-Leroux, 2005). While sensitivity was above chance in both the older and younger groups, this was not the case with the accuracy measure: younger children displayed chance-level accuracy on singular trials. The disparity is evident in results for the younger children on singular trials, which was dependent on whether accuracy or sensitivity measures were examined, and it underscores the importance of summarizing data in multiple ways in preparation for hypothesis testing. In particular, when there are a priori reasons to believe that chance-level performance could be due to design-related rather than knowledge-related factors-such as the plural bias that has been found in many intermodal comprehension tasks like this one (e.g., [START_REF] Gonzalez-Gomez | Agarra, agarran: Evidence of early comprehension of subject-verb agreement in Spanish[END_REF]-alternative summary measures like the sensitivity calculation can reveal mastery that would otherwise be obscured. In light of the full set of results we uncovered, the present findings represent a narrowing of the gap between the age of development of 3 rd person SV comprehension abilities in Spanish-speaking (age 3;5) and French-speaking children (age 2;6), and a widening between Spanish-and English-speaking (age 4;0) children, which our future research will continue to explore by testing younger children in both Spanish and English.

From a methodological standpoint, our findings highlight the question of the kind of outcome measure to use in forced-choice tasks like the ones presented here: accuracy, reflecting the proportion of points to a visual stimulus that match the verbal one, or sensitivity, reflecting the proportion of points to a visual stimulus that are motivated by the verbal one. Given the difficulty in generating equivalently appealing visual stimuli to represent different meanings, a measure like the sensitivity computation serves to minimize the potential of a preference for one of the stimulus types and to focus the analysis on genuine comprehension ability. Indeed, in contrast to the results of our accuracy analyses that suggested greater success on plural than on singular trials, sensitivity scores showed that participants were more sensitive to the singular cue than to the plural one-somewhat surprisingly given that it is the plural that is overtly marked.

The observed greater sensitivity to the singular form, however, might be explained by the relative reliability of the singular and plural markers we tested. In addition to marking the third-person plural, /-n/ also marks second-person plural in Mexican Spanish, and is a frequent final phoneme in (singular) nouns (e.g., buzón 'mailbox', opción 'option') and adjectives (e.g., marrón 'brown', holgazán 'lazy'). It is also frequently found in (singular) deverbal nouns like canción 'song' or decisión 'decision'. In many of these singular /-n/ words, the syllable for which /-n/ is the coda is stressed, lending it additional salience-as a potential cue to morphological singularity. And although the tested singular forms share a final phoneme, either /-a/ or /-e/, that occurs in myriad nouns and adjectives in Spanish, they are associated with singular number in those contexts as well, or, with default (singular) number in verbs. Hence the forms associated with the tested 3 rd person singular markers in this study are more reliable than the plural one.

The present study also extends recent findings on the generality of SV agreement acquisition by exploring the role of the position of the verb on which the agreement morpheme surfaces within the stimulus utterance. We tested comprehension of the 3 rd person agreement marker in two positions, a more canonical and frequent structure, and one that places the marker in a processing-advantageous position. The fact that we found no difference between these conditions suggests that it is not merely familiarity with the complete sentences that participants heard that facilitates comprehension of 3 rd person SV agreement; rather, children were also able to attend to the interpretation-relevant cue in the medial position (cf. [START_REF] Barrière | The comprehension of 3 rd Person Singular -s by NYC English-speaking Preschoolers[END_REF], which found that differences in position-dependent agreement interpretation in English were related to the linguistic variant of English that children were acquiring). The similarity of responses across agreement marker positions found in the current study indicates the presence of an abstract representation of SV agreement that can be used to comprehend an utterance whether its surface form reflects the canonical order or not (contrasting with Sundara et al., 2011, studying younger children).

Given that the sentence-final structure is minimally familiar to children, it is implausible that they would be able to retrieve identical utterances from their memory and apply those to comprehension here (cf. item-based theories of acquisition; [START_REF] Tomasello | Constructing a language: A usage-based approach to child language acquisition[END_REF]more specifically Blom, Paradis, & Sorenson Duncan, 2012, on English 3 rd person singular agreement). Instead, they likely developed an abstract representation of 'singularity' and 'plurality' for application whenever the relevant morpheme is encountered, which also provides evidence against a lexically-based account of grammatical development.

These results add to the growing literature on the comprehension of plural-marking morphology (e.g., nominal plurals; [START_REF] Arias-Trejo | Early comprehension of the Spanish plural[END_REF] SV agreement in Spanish first-language acquisition and narrow the developmental disparity between early comprehension and production (age 1;6; [START_REF] Montrul | The acquisition of Spanish. Language Acquisition and Language Disorders[END_REF] of SV agreement in that language (also documented for English in [START_REF] Barrière | The comprehension of 3 rd Person Singular -s by NYC English-speaking Preschoolers[END_REF]. While older than [START_REF] Montrul | The acquisition of Spanish. Language Acquisition and Language Disorders[END_REF] participants, the participants in this study performed well above chance in the production of both singular and plural items. The errors that our participants made in production tended to reflect 3 rd person SV agreement errors, and specifically the use of the singular form where the plural was needed; the second most frequent error in which a verb form was produced involved children producing the bare present participle. Although both of these errors involve a failure to produce the third-person singular agreement, they could also be instantiations of non-finite root forms [START_REF] Davidson | Defaults and competition in the acquisition of functional categories in Catalan and French[END_REF]Wexler, 1998): tense is omitted from both (although aspect is indeed represented in the present participle response). These error patterns suggest that while participants overwhelmingly responded with target forms in the production task, their mastery of SV agreement in Spanish is still incomplete, for the purposes of production just as it is for comprehension.

The link between comprehension and production found in our study attests that both manifestations of the acquisition of 3 rd person SV agreement go hand in hand, further weakening initial hypotheses that this aspect of morphosyntax represents a special case of a comprehension-production asymmetry/dissociation. The significant correlations between comprehension and production abilities suggest that comprehension and production may indeed develop in tandem in individuals. The data that we have do not allow for directional, causal claims one way or the other, but they do show that a strong asymmetry between production and comprehension abilities is absent, at least in our sample. It is a matter of collecting data in both of these modalities from the same sample of participants, in addition to developing protocols that are of roughly equivalent difficulty in each modality so that, in principle, children's grammatical resources can be equivalently called upon in both. Future research should explore the possibility of collecting multiple measures of comprehension and production in the same sample to further refine theoretical hypotheses. The inclusion of multiple measures in each modality would be especially useful for characterizing production abilities, in light of the possible influence of grammatical conservatism on spontaneous productions and of the potential for reluctance to 'perform' verbally in elicited production tasks in an unfamiliar setting with an unfamiliar experimenter, and so forth.

To conclude, the present study found clear evidence of Mexican 3;6-5;6-year-old children's ability to use both singular and plural third-person agreement morphology to map verbal stimuli to their visual counterparts, independently of the sentential position of the agreement marker. We therefore have yet to identify the lower age limit of 3 rd person SV agreement comprehension in Spanish, comprehension that appears to stem from an abstract representation of how verbal agreement relates to meaning. Furthermore, our results indicate that the comprehension and production of subject-verb agreement go hand in hand, suggesting that this aspect of morphosyntax might not represent a special case of a comprehension-production asymmetry/dissociation as previously thought.

6. Dibujan en al pizarrón. (They) draw on the chalkboard. / En el pizarrón dibujan. On the chalkboard (they) draw.

7. Leen en el sillón. (They) read on the sofa. / En el sillón leen. On the sofa (they) read. 8. Juegan en el parque. (They) play in the park. / En el parque juegan. In the park (they) play.

Figure 1 .

 1 Figure 1. Still image from one video pair (dibujar "draw": left: singular action; right: plural

Figure 2 .

 2 Figure 2. Number of correct production responses in Younger and Older groups, separated by

Figure 3 .

 3 Figure 3. Pointing accuracy separated by Number, sentential Position, and Age Group.

Figure 4 .

 4 Figure 4. Pointing sensitivity separated by Number, sentential Position, and Age Group

linguistics symposium (pp. 178-189). Somerville, Mass.: Cascadilla Press. Wexler, K. (1998). Very early parameter setting and the unique checking constraint: A new explanation of the optional infinitive stage. Lingua, 106(1), 23-79. 5. Escriben en la mesa. (They) write on the table. / En la mesa escriben. On the table (they) write.

Appendices


Ranka Bijeljac-Babic
email: ranka.bijeljac-babic@parisdescartes.fr

Chloé Lehoucq

Thierry Nazzi

Lionel Granjon

Jacques Mehler

Perception of accent in bilingual French/American-English children by native adult speakers

Keywords:

who helped us recruit monolingual and bilingual families and allowed us to carry out the experiment with monolingual adults. In addition, we would like to thank Vicky Bouche for her collaboration in testing adults

Introduction

In studies of accent and dialect processing and representation [START_REF] Floccia | Categorization of regional and foreign accent in 5-to 7-year-old British children[END_REF][START_REF] Cristia | Linguistic processing of accented speech across the lifespan[END_REF], these authors propose different definitions of what we call "accent" and more specifically what the terms regional and/or nonnative accents cover. From a listener's perspective, if a talker is a native speaker of a variety of a language that does not match his/her own variety, the talker's speech would be considered to have a regional accent.

Moreover, if a talker is a native speaker of a different language and he speaks in a language acquired later in life, his speech would be considered to have a non native accent. In both cases, accented speech differs from the "standard" variety along phonetic, phonotactic, phonological, lexical and suprasegmental levels, though evidence suggests that the cues to accentedness differ for the two types of accents. Yet, when a listener is faced with speech that differs from his/her standard, he/she can perceive the difference in accent. However, the perception of unfamiliar regional and nonnative accents is fundamentally different [START_REF] Adank | Comprehension of familiar and unfamiliar native accents under adverse listening conditions[END_REF]Clarke & Garrett, 2004;[START_REF] Goslin | An ERP investigation of regional and foreign accent processing[END_REF]. It was also found that adults process unfamiliar accent-related variations relatively quickly. For instance, listeners are able to distinguish native from nonnative speakers with input as short as a stop burst [START_REF] Flege | The detection of French accent by American listeners[END_REF] or detect a nonnative accent in speech samples played backwards, which removes the availability of segmental, grammatical, and lexical cues [START_REF] Munro | Detection of nonnative speaker status from content-masked speech[END_REF]. The ability to identify a talker as nonnative has also been observed in nonnative listeners [START_REF] Munro | The mutual intelligibility of l2 speech[END_REF] and even in listeners who are completely unfamiliar with the target language [START_REF] Major | Identifying a foreign accent in an unfamiliar language[END_REF]. Similar results were found with 7-year-old English-speaking children [START_REF] Floccia | Categorization of regional and foreign accent in 5-to 7-year-old British children[END_REF]) and 5-year-old French-speaking children [START_REF] Girard | Perception and awareness of accents in young children[END_REF], both groups being significantly better at detecting a foreign accent in adult speech samples than a regional accent in adult speech samples.

All the above-mentioned studies concern the perception of accented speech produced by adults, either bilingual adults with a nonnative accent or adults speaking in their native language with a different regional accent. What about the way children's productions are perceived by adults, when the children are producing speech in a different regional accent, or have more than one language? At present, there are no studies exploring this issue. The main aim of the present study is to investigate whether monolingual French and American English adult speakers perceive differences between monolingual French children, American English children and bilingual children speaking these two languages from birth. To start addressing this issue, the present study focuses on the word level, thus presenting the afults with productions of disyllabic words produced by these children. Therefore, this study will, first, address the issue of whether bilingual children separate their two languages very early on, speaking both languages as monolinguals, or whether the interaction between their two linguistic systems makes their productions in each language different from the productions of monolinguals.

Second, it will also investigate whether bilinguals' mastery of each of their two languages is modulated by their relative experience with each language, contrasting children raised in France, in which French is the predominant language, with those in the US, in which American English is the predominant language. Previous studies have suggested that dominance (which can be defined in different ways, and is a multidimensional construct, see [START_REF] Bir ; Birdsong | Dominance and Age in Bilingualism[END_REF]Bedore at al., 2012) influences relative mastery of bilinguals' languages, both in adulthood [START_REF] Cutler | Limits on bilingualism[END_REF][START_REF] Cutler | The monolingual nature of speech segmentation by bilinguals[END_REF][START_REF] Dupoux | Limits on bilingual-ism revisited: Stress 'deafness' in simultaneous French-Spanish bilinguals[END_REF][START_REF] Sebastián-Gallés | The influence of initial exposure on lexical representation: Comparing early and simultaneous bilinguals[END_REF]; but see [START_REF] Boll-Avetisyan | Rhythmic grouping biases in simultaneous bilinguals[END_REF], for lack of an effect), and in infancy/childhood [START_REF] Bijeljac-Babic | Effect of bililngual-ism on lexical stress pattern discrimination in French-learning infants[END_REF][START_REF] Paradis | Bilingual children with specific language impairment: How do they compare with their monolingual peers?[END_REF]Pearson, Fernandez, Lewedeg & Oller, 1993;[START_REF] Hoff | Dual language exposure and early bilingual development[END_REF][START_REF] Marchman | How vocabulary size in two languages relates to efficiency in spoken word recognition by young Spanish-English bilinguals[END_REF][START_REF] Sebastián-Gallés | Building phonotactic knowledge in bilinguals: Role of early exposure[END_REF]; but see [START_REF] Abboub | On the importance abilities in infants from bilingual environments[END_REF][START_REF] Bijeljac-Babic | Early prosodic acquisition in bilingual infants: The case of the perceptual trochaic bias[END_REF][START_REF] Polka | Segmenting words from fluent speech during infancychallenges and opportunities in a bilingual context[END_REF] lack of an effect).

Third, the present study will contribute to the issue of the link between perception and production, as perception of speech sounds is not exclusively based on acoustics. At the phonetic/phonological level, it has been shown that it is difficult for adults to discriminate and acquire vowel and consonant contrasts that do not exist in their native language (Best, Halle, Bohn, & Faber, 2003;[START_REF] Best | Nonnative and second-language speech perception: Commonalities and complementarities[END_REF][START_REF] Flege | Perceiving vowels in a second language[END_REF][START_REF] Kuhl | Innate predispositions and the effects of experience in speech perception: The native language magnet theory[END_REF]. Similarly, at the suprasegmental level, the perception of lexical stress appears modulated by the prosodic system of the native language. For example, Spanish adults, who use stress when recognizing Spanish words, outperform French adults in their sensitivity to stress information, a property that is not lexically contrastive in French, in particular at the phonological level [START_REF] Dupoux | A destressing 'deafness' in French?[END_REF][START_REF] Dupoux | A robust method to study stress 'deafness[END_REF]. Similar effects were found when comparing the perception of lexical tones by adult speakers of Mandarin, a tonal language, and speakers of French, a non tonal language [START_REF] Hallé | Categorical perception of Taiwan Mandarin Chinese tones by Chinese versus French native speakers[END_REF]. Regarding accent perception, several studies have shown that certain acoustic measurements of non-native speech correlate with listeners' ratings of accentedness, fluency, comprehensibility, and intelligibility [START_REF] Derwing | Second Language Fluency: Judgments on Different Tasks[END_REF][START_REF] Pinget | Native speakers' perceptions of fluency and accent in L2[END_REF][START_REF] Bir ; Birdsong | Dominance and Age in Bilingualism[END_REF]. However, [START_REF] Munro | Bilingual first-language development: Dominant language takeover, threatened minority language take-up[END_REF] underline that without listeners' data, acoustic measures themselves cannot predict whether listeners will notice the accent change. This question is well illustrated in [START_REF] Birdsong | Nativelike pronunciation among late learners of French as a second language[END_REF] study of Anglophone speakers' production of French voice onset times (VOT). While some speakers' VOTs were clearly more nativelike than others, the study failed to show a statistical relationship between the values of this dimension and the accent judgments from a group of native French listeners.

In the present study of the perception of bilingual children's productions, we relied on the existence of a corpus of production of disyllabic words by French/American English bilinguals for which the prosodic correlates have been measured [START_REF] Dodane | Cross-language influences in the productions of French-English bilingual children: Separation or interaction[END_REF]. This will allow us to explore the extent to which perception of a foreign, bilingual accent in these productions is related to how lexical stress is marked. This corpus was constructed with the goal of investigating how bilingual children acquire the prosodic lexical properties of their two languages. French and English differ on many dimensions (Ladefoged, 1995) but the main motivation for choosing these two languages was that at the word level, they have clearly contrastive prosodic, lexical stress properties. French does not have stress at the word level, but at the phrase level [START_REF] Féry | Correlates of phrasing in French and German from an experiment with semi-spontaneous speech[END_REF]. Primary stress in French has a fixed position on the final full syllable of the last lexical item of a stress group [START_REF] Di Cristo | Intonation in French[END_REF] and is thus completely predictable [START_REF] Delattre | Comparing the Phonetic Features of English, French, German and Spanish[END_REF]. In contrast, English words receive lexical stress, and the position of lexical stress is variable but tends to fall on the first syllable of lexical words (trochaic stress; [START_REF] Cutler | The prosodic structure of initial syllables in English[END_REF]. Concerning the acoustic correlates of stress, primary stress in French is created mainly through temporal cues, final syllables being approximately twice as long as unstressed syllables, with no increase in f0 or intensity [START_REF] Rossi | Le français, langue sans accent? [French: A non-stressed language?[END_REF][START_REF] Vaissière | Rhythm, accentuation and final lengthening in French[END_REF]. In contrast, in English, lexical stress is made salient by the use of higher f0, greater intensity and longer duration on stressed syllables, which makes it more salient than in French.

In terms of the acquisition of the production of these properties, Vihman, DePaolis and Davis (1998) showed that English and French monolingual children, between 13 and 20 months, produce disyllabic words that have the acoustic realization of stress (f0, intensity and duration) characteristic of their respective languages. For bilinguals, it is well known that while French-English bilingual adults can speak both of their languages fluently, mastering word level stress appears problematic for a long time during childhood [START_REF] Flege | The detection of French accent by American listeners[END_REF]. Indeed, [START_REF] Labelle | A longitudinal study of lexical and prosodic differentiation by simultaneous French/English bilingual child[END_REF] argued for a trochaic bias in the English and French productions of a young English-French bilingual learner (aged 1;6-2;4). Yet, on the basis of data from another English-French bilingual child (aged 2;0-4;02), [START_REF] Rose | There is no trochaic bias: Acoustic evidence in favor of the neutral start hypothesis[END_REF] argued that this child had mastered both basic metrical properties and the main acoustic correlates of stress for each of the target languages. These conflicting results point to the fact that studies on these issues should go beyond the analysis of single cases. [START_REF] Dodane | Cross-language influences in the productions of French-English bilingual children: Separation or interaction[END_REF] thus investigated the acoustic correlates of the lexical stress of disyllabic words (mean duration ratio S2/S1, mean f0 interval S1-S2, and relative S1-S2 intensity) produced by groups of French monolinguals (Mono-FR), American-English monolinguals (Mono-US), and French/American-English bilinguals living in France (Bil-FR).

Each group consisted of 8 children (mean age: 4;6, range: 3;3-6;0). To complete the experimental design and to compare bilinguals' production in both languages as a function of the ambient language, a group of 8 American-English/French bilingual children living in Baltimore, US (Bil-US), was later recorded under the same conditions as the other 3 groups (see Appendix for methodological details used in that study).

Table 1. Acoustic properties of lexical stress realization (from [START_REF] Dodane | Cross-language influences in the productions of French-English bilingual children: Separation or interaction[END_REF] in the production of disyllabic words produced by monolingual and bilingual children in French (left panels) and in English (right panels): means (and standard deviations) for duration ratio Syllable 2/ Syllable 1 (S2/S1), mean f0 (in Hz) on S1-mean f0 on S2 (in semi tones) and relative intensity.

. The most important results can be summarized as follows : First, although the age range of the participants was large (3;6 to 6;0), there was no effect of age in the multivariate (ANCOVA) analysis of variance for each acoustic parameter tested (mean S2/S1 duration ratio, mean f0 interval, and mean S1-S2 RMS) in each language (French and English).

Second, for the French productions, the final syllable lengthening characteristic of French disyllabic words in monolinguals was found in the productions of the two groups of bilingual children: the S2/S1 ratio was higher for the Bil-FR compared to both the Mono-FR and the Bil-US, with no difference between the latter groups. The analyses of f0 differences in semitones and intensity differences between S1 and S2 were not significant. These results

show that the second syllable lengthening expected for French is observed in both groups of bilinguals. Moreover, there were some differences between the two groups of bilinguals, as only the bilingual children living in France lengthened the second syllable more than the French monolinguals.

Third, for the English productions, results on duration revealed that S1 was significantly longer than S2 in Mono-US, S1 and S2 were equivalent in Bil-US, and S2 was significantly longer than S1 in Bil-FR. For pitch, f0 tended to be higher for S1 compared to S2 in all groups, but none of these differences reached significance. For intensity, the intensity of S1 was higher than that of S2 and the group factor was close to significance, with Mono-US being significantly different from Bil-US and Bil-FR, while the two groups of bilinguals did not differ from each other. These findings establish that the acoustic parameters that mark lexical stress in English, i.e. the longer duration and higher intensity of the initial syllable, are acquired by the monolingual children in our group. This lexical stress mastery is less clear for the bilinguals. Moreover, for duration, once again a difference is found between Bil-FR and Bil-US.

The present study

To obtain perceptual ratings, we used the Elo rating system, a method that rates chess and other competitive game players. In this task, each player starts with a rating of a 1000. This rating increases if she/he wins and goes down if she/he loses. Over time a player's rating becomes a true reflection of his/her ability -relative to the entire player population. In our study, each group of monolingual adults participated in a "game" in which they heard the same word produced by two "players" and had to assess which of the two was bilingual. The Elo ranking for each child reflected his/her probability of being considered bilingual by any new judge in comparison to any other child (see Procedure for more details).

Hypotheses

We first predicted that adult monolingual speakers can make differences between English should be perceived by American English-speaking participants as more bilingual (higher Elo scores) than Bil-US children. Third, we surmise that if the acoustic differences in stress pattern realizations presented above contribute to the monolingual/bilingual ratings, then the Elo scores should correlate with some of the acoustic parameters measured.

Methods

. Participants

Twenty-four French-speaking adults (17 women, age: 19-40 years, M = 27.71, SD = 6.8) participated in Experiment 1, conducted in Paris; 23 American English-speaking adults ( 15women, age: 28-60 years, M = 38.9, SD = 13.56) participated in Experiment 2 conducted in Baltimore, U.S. None of the participants had oral or written language impairment or neurological or psychiatric problems and all adults stated they did not have any hearing problems. All participants had a high level of education. Their language level was evaluated through a Linguistic Background Questionnaire. [START_REF] Marian | The Language Experience and Proficiency Questionnaire (LEAP-Q): Assessing language profiles in bilinguals and multilinguals[END_REF]. French-speaking participants started to learn foreign languages in school at the age of 10-11 years (in the 6 th grade). Two of them had spoken French and another language in early childhood, but all of them only used French in their daily life at the time of testing. All American English-speaking participants, except two, had learned another language in school, but all used English in their daily life at the time of testing.

Participants gave written informed consent and were paid around 10 euros for their participation.

2. Materials

Disyllabic words produced by 4 groups of 8 children (mean age 4;6, range: 3;3-6;0) were recorded during a word elicitation task while looking at a picture book in the presence of one experimenter and one parent (for details see [START_REF] Dodane | Cross-language influences in the productions of French-English bilingual children: Separation or interaction[END_REF]. Two groups were recorded in France: French-speaking monolinguals (Mono-FR) and French/American English bilinguals (Bil-FR) and two (groups were recorded) under similar conditions in Baltimore : American English-speaking monolinguals (Mono-US) and American English/French bilinguals (Bil-US). As described in [START_REF] Dodane | Cross-language influences in the productions of French-English bilingual children: Separation or interaction[END_REF], only well produced disyllabic words, produced spontaneously looking at the picture book (thus excluding repetitions after parent's production) were segmented. Among the disyllabic words analyzed in this study for Elo ranking, we only selected words produced by most children, which reduced the number of words to 11 in French and 15 in English (see Appendix for the list of words).

Procedure

Participants sat in front of a computer in a quiet room and listened to the audio recordings through headphones. Each trial presented a pair of identical words (e.g., carrot in English)

pronounced by two different children from the 3 groups producing words in the same language (for French: Mono-FR, Bil-FR and Bil-US; For English: Mono-US, Bil-FR and Bil-US). The participants had to determine for each pair which child was bilingual by responding to the question "Who is bilingual?" The instructions given to the French and American listeners were similar. The answers were given on a keyboard by pressing the left arrow to select the first child and the right arrow to select the second one. The trials were set up in such a way that over the entire experiment, every child was compared to every other child: each was compared to another child for one of the words they had in common.

Thus, the bilingual children were compared to the monolingual children, but also to the other bilinguals. Similarly, the monolinguals were compared to the bilinguals but also to the other monolinguals of the same language.

The available words were used to create 248 trials in English and 271 trials in French. Six additional trials were used for training, to familiarize the participants with the procedure. The list of trials can be considered a "bilingualism competition" in which each trial represents a "match" between two children. The outcome of these matches is determined by the participants (referred to as "judges").

To avoid biased judgment, participants were not informed that the trials could present two bilingual or two monolingual children. For the same reason, the second language spoken by the children was not specified.

The task consisted of a forced choice after each listening of a pair: the next trial could not be launched until the participant had given an answer. However, a break could be taken after a trial, at any time during the test.

All participants were tested with a different list of trials: the pairs of children not being introduced in the same order and the words for which they were compared not always being the same. At the end of the test for each judge, a program (coded in Rusing the package Player Ratings- [START_REF] Stephenson | PlayerRatings: Dynamic Updating Meth-ods for Player Ratings Estimation[END_REF]) assigned an Elo score to each child, following the procedure developed by the authors.

In our experiment, the Elo score was calculated based on the number of wins and losses during the competition: a win meant that the child was considered a bilingual after a "match." The Elo rating for each child reflects the probability it will be considered bilingual by a different judge when compared with any other child of the list. Every child started the competition with an Elo score of a 1000 (this score was chosen arbitrarily). When a child "won a match," he/she gained the same number of points as that withdrawn from the score of the losing child. The number of points gained/lost varied depending on the Elo score of the adversary at the time of the competition: the greater the difference of the Elo ratings, the higher the number of points at stake.

expected outcome based on both children's current Elo W = actual outcome K = multiplier coefficient.

Results

A mean value of the Elo scores attributed to each of the 24 evaluations was computed for each of the 24 judges in Experiment 1; the same was done for the 23 evaluations in Experiment 2. Then a ranking of the children was established from the one most often judged as bilingual (with the highest mean Elo scores) to the one least often judged as bilingual (with the lowest mean Elo scores). There is a direct link between the difference in the Elo ratings and the probability of success:

For example, a difference of 50 points between two adversaries indicates that the one with the higher score has a probability of 57% to win a new match.

After each competition, the Elo scores of the winner and the loser are adjusted according to a factor called "K-factor" fixed at 10 in our study. However, Elo scores presented as bilingual evaluations are the results of all competitions (all assessments of the same judge) played over and over until the scores for all children converge. The value of the K-factor does not change the value of the final scores, only the speed of convergence.

Example of Elo points exchanged from loser to winner: If REF was equal to 1000, then that child winning against an opponent with an Elo of 1200 would gain 7.6 points (and his/her opponent would lose 7.6 points accordingly). A win against an opponent with an Elo of 1010 would only reward 5.1 points. The more unlikely the outcome, the more points exchanged.

Child

Perception of French productions

The Elo rankings are presented in Figure 1, showing that 7 of the 8 Bil-US children occupy the first place in the ranking which means that in most competitions these children were considered bilinguals. The mean Elo scores for the three groups were: Bil-US = 1063

(SD = 39), Bil-FR = 966 (SD = 78), and Mono-FR = 971 (SD = 47). The participants' responses were consistent through all 3 groups according to Cronbach's alpha coefficients:

Bil-US = 0.73; Bil-FR = 0.89; and Mono-FR = 0.77. Contrast comparisons revealed a significant difference between the Bil-US group and the other two groups (Mono-FR and Bil-FR; t(18) = 4.78, p =.0001), while the comparison between the Mono-FR and Bil-FR groups failed to reach significance (t(18) = .52, p = .61).

French-speaking adults clearly differentiated bilingual children growing up in a dominant

American-English background (Bil-US) from the other 2 groups of children growing up in a dominant French background (whether Bil-FR bilinguals or Mono-FR monolinguals). Yet, they did not discriminate between the Bil-FR bilinguals and the Mono-FR monolinguals.

There was also a significant effect of Age (F (1,18) = 8.81; p = .008; ɳ² = .15), older children having lower Elo scores. Moreover, the Group*Age interaction was significant (F (2,18) = 5.06; p = .018; ɳ² = .17). This is due to the fact that the effect of Age was significant for the Mono-FR (t(6) = -2.5; p = .04) and the Bil-FR (t(6) = -2.8; p = .03) groups, but not for the Bil-US group (t(6) = 0.8; p = .48).

Perception of English productions

The Elo rankings are presented in Figure 2 Figure 2. Plots representing the median Elo scores (and SDs) by the American English judges for the three groups of children Bil-US (bilinguals American English/French), Bil-FR (bilinguals French/American English) and Mono-US (monolinguals American/English). Dots represent individual children.

An analysis of covariance (ANCOVA) with Group (Mono-US vs. Bil-Us vs. Bil-FR) as main factor and Age as covariate was conducted. None of the effects or interactions reached significance (Group: F (2,14) = 2.43; p = .12; ɳ² = .24; Age: F (1,14) = 1.79; p = .20; ɳ² = .09; Group*Age interaction: F (2,14) < .01; p = .99; ɳ² = .00).

Although there was no Group effect, we performed contrast comparisons between the groups, as done for the analyses on French productions. The contrast between the Bil-FR group and the two other groups (Mono-US and Bil-US) was significant (t(14) = 2.15; p = .05), while the difference between Mono-US and Bil-US failed to reach significance (t(14) = 0.51, p = .62). American-English adults differentiated the bilingual children with dominant French background (Bil-FR) from the other group dominant in American-English (whether Bil-US bilinguals or Mono-US monolinguals). Nonetheless, they did not discriminate between Bil-US bilinguals and Mono-US monolinguals.

Impact of language dominance

In order to explore the impact of dominant language background in both experiments, we conducted repeated ANOVA measures with bilingual Group (Bil-FR vs. Bil-US) and language of production (French vs. English) as factors. Although the effects of Group, (F(1,11) = 0.157, p = .69, and language of production, F(1,11) = 0.103, p = .75) failed to reach significance, the interaction was significant, F(1, 11) = 12.8, p = .004. This interaction reflects the fact that when speaking French, Bil-FR are considered less bilingual then Bil-US by French judges (M = 966 vs. M = 1063), and conversely that when speaking English, Bil-US are considered less bilingual then Bil-FR by English-speaking judges (M = 978 vs. M = 1066).

Perception-Production links

In order to compare the data from the acoustic analyses of stress pattern realization (ratio duration, difference f0 S1-S2 and relative amplitude) and the Elo scores in both languages for the 4 groups, Pearson correlations were conducted. Only the correlation between the Elo score in French and the duration ratio approached significance (r = 0.39, p = .065).

General discussion

The present study examined how monolingual French and American English adults perceive productions of disyllabic words by monolingual French (Mono-FR), monolingual American-English (mono-US) and bilingual French/American-English children, aged 3;6-6;0. The bilinguals were growing up in bilingual French/American-English families, either in France or in the US, so that the predominant ambient language was French for half of them (Bil-FR),

and American English for the other half (Bil-US). The productions had been recorded and acoustically analyzed for lexical stress production by [START_REF] Dodane | Cross-language influences in the productions of French-English bilingual children: Separation or interaction[END_REF], the group of French/American-English bilinguals living in the US being later recorded and analyzed for the purpose of the current study. There were 8 children in each group.

To assess perception, we used an Elo competition task in which monolingual adult speakers were asked to assess which of two words presented in their native language were pronounced by a bilingual child. Overall, results first demonstrated that in both languages, the bilingual children reached higher Elo scores and were in the upper part of the Elo rankings, compared to monolingual children whose Elo scores were lower and in the bottom part of the Elo rankings. These results thus clearly established that both the French and American-English monolingual adults succeeded in distinguishing the bilingual children from their monolingual peers. Our findings are in line with previous results suggesting that the simultaneous acquisition of two languages by children creates a competition between two different phonological systems. Our perception results further show that when bilingual children start to speak, the cross-linguistic influences that are apparent in their word productions in each language, found before 2 years [START_REF] Vihman | Prosodic structure and templates in bilingual phonological development[END_REF] but also later, up until at least 6 years of age [START_REF] Dodane | Cross-language influences in the productions of French-English bilingual children: Separation or interaction[END_REF], are salient enough to be perceived and used to determine the monolingual/bilingual status of a child. Since our children were bilingual from birth, our results somehow challenge the idea that the earlier in life a language is acquired the less accented it will be [START_REF] Piske | Factors affecting degree of foreign accent in an L2: a review[END_REF], at least for the early years of acquisition and for the word level evaluated here. Note that for the French productions, we find an effect of age for the French monolinguals and the bilinguals living in France, with lower bilingual ratings with age, suggesting that mastery of the French productions improves with age in these two groups, while it does not in the bilinguals living in the US.

Second, by presenting the raters in our study with stimuli produced by two groups of bilingual French/English children, one living in France and the other living in the US, our study allowed us to investigate whether the predominant ambient language of the society in which the children are being raised (French in Paris, American English in Baltimore) plays a role in how their productions are assessed in each of their languages. We hypothesized that the Bil-US children should be perceived as more bilingual by the French participants rating their French productions, and the Bil-FR should be perceived as more bilingual by the American English participants rating their English productions. This hypothesis was confirmed by our results. Indeed, Bil-US children speaking French were perceived by Frenchspeaking participants as more bilingual (higher Elo scores) than Bil-FR children; conversely, Bil-FR children speaking English were perceived by American English-speaking participants as more bilingual (higher Elo scores) than Bil-US children. In addition, monolingual adults did not differentiate monolingual from bilingual children growing up in their country. In French, the Elo scores for Bil-FR (966) were similar to those for Mono-FR (971), and in English, the Elo scores for Bil-US (978) were similar to those of Mono-US (965). Therefore, our results establish that the bilinguals were better differentiated from the monolinguals in the language that was not the predominant language in the country in which they grew up. These findings are compatible with studies showing that bilingual acquisition is modulated by environmental factors that affect language balance and relative proficiency or dominance (see [START_REF] Höhle | Variability and stability in early language acquisition: Comparing monolingual and bilingual infants' speech perception and word recognition[END_REF], for a discussion of these issues for early development;

Mueller Gathercole & Thomas, 2009, for later development). The factors that define dominance are under debate in the literature and may differ depending on the language domain/ability considered. For example, studies of individual variability in simultaneous bilingual adults revealed that speech segmentation is modulated by the bilinguals' preferred language (the one they would like to keep if they were to lose one; [START_REF] Cutler | Limits on bilingualism[END_REF][START_REF] Cutler | The monolingual nature of speech segmentation by bilinguals[END_REF], phonotactic acquisition by the mother's language [START_REF] Sebastián-Gallés | The influence of initial exposure on lexical representation: Comparing early and simultaneous bilinguals[END_REF], lexical stress perception by some measure of early input (Dupoux et al., 2010), whereas rhythmic grouping appeared unmodulated across bilinguals [START_REF] Boll-Avetisyan | Rhythmic grouping biases in simultaneous bilinguals[END_REF]. Here, it appears that the language of the country of residence of the bilingual children played an important role in how their productions were evaluated.

Several explanations could be offered for the fact that acoustic differences between bilinguals' and monolinguals' productions were not perceived by the monolingual adults when the bilinguals were dominant in their language. It could be that the adult listeners' perceptual system could accept some degree of deviation from native-accented speech, and/or could adapt very quickly to the accented speech, as observed for example by Clark & Garrett (2004). Another explanation might concern more general adaptation processes related to higher cognitive and/or social processes, linked to characteristics of the listeners' group.

Perception of "foreign" accent in children's productions depended on the extent to which the variations in perceived speech matched the judge's accentual representations. It remains difficult to distinguish between these two possibilities because it is impossible to isolate the effect of linguistic (segmental and suprasegmental) deviations from social and cognitive effects related to the listener's origin.

Finally, to start exploring how variability in the assessment of the two groups of bilinguals relates to specific acoustic properties of their productions, we performed correlation analyses between the Elo scores and the acoustic measures that were available to us, measures that evaluated how the prosodic properties of the words were realized by the children in the 4 groups. No correlation reached significance, failing to reveal links between the perceptual scores by the adults and prosodic correlates of the productions, even though the acoustic analyses had revealed both differences between the productions of the monolingual and bilingual children, and between the productions of the two groups of bilinguals. Additional analyses or new studies will be needed to evaluate the potential contribution of other factors, in particular factors related to the production of the phonemes making up the words.

In conclusion, previous results of the acoustic analyses of word productions by monolingual and bilingual children had suggested that French-English bilingual children produced words that had different lexical stress patterns in each language, but that were also acoustically different from the same words produced by monolinguals [START_REF] Dodane | Cross-language influences in the productions of French-English bilingual children: Separation or interaction[END_REF]. The present accent perception study shows that the bilingual children's word productions were perceived differently from those of the monolingual children by both groups of judges, both for their productions in French and those in English. Moreover, the assessment of the children's linguistic status (bilingual vs. monolingual) appeared to be influenced by the predominant ambient language in the society in which they grow up. Given that this is the first study on the perception of bilingual children's accent by adult speakers, further studies will be needed to explore the link between the acoustic characteristics of the productions, at all relevant linguistic levels (phonetic, prosodic, …), and accent perception, and to go beyond the lexical level tested here. Additional studies will be also needed to investigate these phenomena in children acquiring other pairs of languages, that differ on different linguistic dimensions, and who are more or less linguistically related (see [START_REF] Havy | Phonetic processing when learning words: The case of bilingual infants[END_REF]Nazzi, 2016, and[START_REF] Höhle | Variability and stability in early language acquisition: Comparing monolingual and bilingual infants' speech perception and word recognition[END_REF], for a discussion on linguistic distance). Lastly, it would also be important to carry out the same perception study with bilingual adult speakers, dominant in one or the other language, to determine how accent is perceived by bilinguals themselves.

The recording of the children's production occurred during the word elicitation task in which the children had to produce 40/32 disyllabic words in French/English while looking at a picture book. Out of the 40 disyllabic words in French and 32 in English, bilingual

French-American/English (Bil-FR) children produced 16 to 23 words (mean: 19.2) in French and 13 to 27 words (mean: 18.9) in English. The French monolinguals (Mono-FR) produced 24 to 39 words (mean: 29.2). The American-English-French (Bil-US) produced 6-15 words (mean: 12. 4) in French and 6-25 (mean: 18.8) in English. The American-English monolinguals (Mono-US) produced 12 to 22 words (mean: 14.3). Overall, 510 tokens of disyllabic words were analyzed.

Segmentation and acoustic measurements.

Each disyllabic word was manually segmented from 25-30 minutes of continuous recording with the Praat software [START_REF] Boersma | Praat, a system for doing phonetics by computer[END_REF], using the simultaneous display of the sound waveform and a wideband spectrogram (frequency range: 0-8000 Hz, analysis bandwidth: 260 Hz, pre-emphasis: 6dB/octave, dynamic range: 50 dB). One annotation sheet was created, which corresponded to syllabic segmentation (see Figure 1 for an example). The acoustic analyses were based upon the segmented syllables and included measures of duration (in ms), fundamental frequency (f0 in Hertz) and intensity (in dB) for a total of 510 words. The duration was extracted for all syllables. Then, we calculated the syllabic duration ratio to determine the presence of final lengthening on S2 or on the contrary, a lengthening on S1. The mean f0 was extracted for each syllable and subsequently, we computed the mean interval between S1 and S2 in semitones, using the following equation to calculate for each syllable (Semitone = 39.86 log 10 (f0 S1 or S2/100). A negative value indicated higher f0 on the second syllable, but the most important fact was the value of the interval: the higher the value, the greater the perceptual distance between syllables. The intensity values were extracted for each syllable (in dB), and the relative intensity was determined by computing the ratio of the Root-Mean Square energy (RMS in dB) of the selected syllable (S1 or S2) to the RMS energy of the loudest point in the selected word.

Measures of reliability were carried out to evaluate the segmentation made by the two authors for 10 % of the words chosen randomly (50 words in French and 50 words in English). The percentage of exact agreement between the authors was 89,5 %.

The means for the three acoustic parameters, broken down by language of production and child group, are given in Table 1 of the paper, and the main results and statistical analyses are presented in the introduction of the paper.

  monolingual and bilingual children speaking French and American English from birth on the basis of the production of disyllabic words. Bilingual children should thus have higher mean Elo scores and be in the upper part of the Elo rankings, compared to monolingual children whose Elo scores should be lower and in the bottom part of the Elo rankings. Second, we suppose if adult listeners can differentiate bilingual from monolingual children, they are presumably influenced by the bilingual child's ambient language in their assessment. If so, they would rate the productions of bilingual children living in their own country as closer to those of monolinguals than to those of bilinguals living in the other country. Accordingly, Bil-US children speaking French should be perceived by French-speaking participants as more bilingual (higher Elo scores) than Bil-FR children; conversely, Bil-FR children speaking

Figure 1 .

 1 Figure 1. Plots representing the median Elo scores (and SDs) by the French judges for the three groups of children: Mono-FR (monolinguals French), Bil-FR (bilinguals French/American English) and Bil-US (bilinguals American English/French). Dots represent Elo scores of individual children

  . Four of the 6 bilingual children dominant in French occupy the first positions in the ranking. Mean Elo scores for the three groups: Bil-FR = 1066 (SD = 117), Bil-US = 978 (SD = 83) and Mono-US = 965 (SD = 55). The participants' responses were consistent across all 3 groups according to Cronbach's alpha coefficient: Bil-FR = 0.96; Bil-US = 0.92 and Mono-US = 0.84.

  Figure 1. Waveforms (upper panels) and spectrograms (lower panels) of disyllabic words: (a) "carotte" produced by a bilingual child in French and (b) "carrot" produced by a bilingual child in English with f0 contour (in Hz, scale 100-800 Hz) indicated in the blue line and intensity contour (in dB) indicated in the yellow line.

This work was supported by the LABEX Empirical Foundations of Linguistics (ANR-10-LABX-0083), as a contribution to the IdEx Université de Paris (ANR-18-IDEX-0001). We would like to thank Géraldine Legendre, Professor of Cognitive Science at Johns Hopkins Universityin Baltimore, to Jonathan ranking test and Christelle Dodane for the acoustic analyess.

Appendix

Participants

Eight French-English bilingual children (Bil-FR) born and living in Paris or the surrounding region (4 girls and 4 boys, mean age: 4;8, range: 3;5-6;0). These children have been regularly exposed to both languages, their mothers being native American English speakers and their fathers, native French speakers; 8 French-English bilingual children (Bil-US) born and living in Baltimore, US or the surrounding region (4 girls and 4 boys, mean age: 4;8, range: 3;5-6;0). These children have been regularly exposed to both languages, their mothers being native French speakers and their fathers, native American-English speakers; 8 monolingual French children born and living in Poitiers, France (Mono-FR), all with monolingual parents (4 girls and 4 boys, mean age: 4;5, months, range: 3;3-6;0); 8 monolingual English children born and living in Baltimore, US (Mono-US), all with monolingual parents (5 girls and 3 boys, mean age: 4;6 months, range: 3;7-5;5).

To assess the vocabulary of the bilingual children, we asked parents (or teachers for the French monolingual group) to complete the CDI (Communicative Development Inventory) for English (Fenson, Dale, Reznick, Bates, Thal, Pethik & Reilly, 1993) and a version of the same questionnaire adapted to the vocabulary of French children [START_REF] Bassano | Le DLPF : un nouvel outil pour l'évaluation du développement du langage de production en français[END_REF] in order to be certain that the children know the words that we included in the picture book. A child's language exposure was measured by an adapted version of the Language Exposure Questionnaire [START_REF] Bosch | Evidence of early language discrimination Clarke[END_REF] to obtain specific estimates of the child's exposure to each language from all possible language partners (e.g., parents, grandparents). Average French exposure for the American-English/French bilingual group from Baltimore was 42%, average American-English, exposure for the French-American-English bilinguals was 52%.

Stimuli and recording procedure

The words illustrated in the picture book are presented in Table 1. The words in BOLD are the words which are used for the current Elo experiment.