Experiment

Methods Participants

Forty-eight French-speaking children (27 female) participated in the experiment, divided into two age groups: 24 younger children aged 5;2 to 6;8 years (mean age 6;0 years) and 24 older children aged 7;1 to 8;3 years (mean age 7;10 years). They were recruited in three primary schools of Geneva. Thirty-two of them (67 %) also spoke at least one other language. A parental questionnaire based on the Utrecht Bilingual Language Exposure Calculator (UBiLEC;

Unsworth, 2011, 2013) assessed the amount of exposure to the language(s) in the child’s environment. We found that bilinguals had been exposed to French from birth onwards and regularly practiced this language since then, so French was their first and dominant language. We

therefore considered bilinguals and monolinguals as one group. Bilinguals were similarly distributed across age groups (17 younger and 15 older bilinguals). Data from seven additional children were excluded from the analyses since they didn’t complete all the tasks due to fussiness (n = 5) or illness on the second testing day (n = 2). Forty-eight French-speaking adults (40 female) aged 19 to 34 years (mean age 23 years) also participated in this experiment. They were recruited from the students’ community of the University of Geneva and received course credit for participation. Seven (15 %) were bilingual, but French was always their first and dominant language.

Materials and procedures

All participants were presented with four tasks: a linguistic task involving a questions-after-stories paradigm and three non-linguistic tasks: N-back, DCCS, and Corsi. The tasks were administered within a total duration of 90 minutes, split into two testing sessions (first session: wh-question and DCCS tasks; second session: N-back and Corsi tasks). Materials and procedures of each task are detailed hereafter.

WH-QUESTION task. The same questions-after-stories design as in Lassotta and colleagues (2016, Experiment 2) was used. We created eight argument wh-question sets with two conditions: ambiguous vs. filled-gap. Ambiguous questions, as in (12), contain the fronted wh-element à qui ‘to whom’ that can be attached to one out of two possible positions: the main verb (MV) dire ‘say’ or the embedded verb (EV) offrir ‘offer’ in example (10). Hence, the question is globally ambiguous: it can either be interpreted as “To whom did Marie say something?”, reflecting an attachment of the wh-element to the MV, or as “To whom did Marie offer chocolates?”, reflecting an attachment to the EV. In case of MV attachment, the answer would be “to her mom” (corresponding to the upper right picture in Figure 8), whereas in case of EV attachment, the answer would be “to her friends” (corresponding to the upper left picture in Figure 8). Filled-gap questions, as in (13), were constructed by adding an overt PP recipient to the ambiguous questions in the empty position of the MV object, i.e., filling the gap in the main clause, which syntactically blocks the attachment of the wh-element to the MV and thus serves as revision cue disambiguating the sentence. Hence, the grammatically correct interpretation of the question in (13), is “To whom did Marie offer some chocolates?” corresponding to the EV attachment of the wh-element, and the answer would be “to her friends”. The four ambiguous questions were always presented before the four filled-gap questions in order to first establish participants’ preferential interpretation of ambiguous questions. Four experimental lists were

created containing eight stories each, in randomized orders, each story being followed by two questions. The first question consisted of the test question (either ambiguous or filled-gap), followed by a filler question to ensure that participants were paying attention to the task (i.e., simple yes/no questions about an element of the story, e.g., Est-ce que Marie a offert des bonbons?

‘Did Marie offer some candies?’). In half of the filler questions, the correct answer was “yes”. All verbal stimuli (stories and questions) were prerecorded by a female native speaker of French and test questions were carefully controlled to create a natural prosody that is compatible with both main and embedded clause attachment interpretation. The stimuli were presented via two loudspeakers located in front of the participants. Participants were randomly distributed across the four lists.

Participants listened to eight short animated cartoon stories (see example in Figure 8).

Each story contained two storylines of two events each. In the example illustrated below, the sequence of events is the following: (1.A) Marie offers some chocolate to her friends, (1.B) Marie says to her mom that she offered some chocolate to her friends, (2.A) Marie offers some candies to her sisters, and (2.B) Marie says to her dad that she offered some candies to her sisters (see full example story in Appendix C). In each story, the main character, Marie, thus accomplishes four actions: two ‘saying’ actions (dire ‘say’) and two ‘doing’ actions involving different ditransitive verbs (donner ‘give’, offrir ‘offer’, montrer ‘show’, distribuer ‘distribute’, prêter ‘lend’, envoyer

‘send’, acheter ‘buy’, or servir ‘serve’). The ‘saying’ actions are always displayed on the right side of the screen and the ‘doing’ actions on the left. So, there are two storylines with two actions each that belong together: 1.A & B and 2.A & B. The aim of presenting two ‘saying’ actions and two ‘doing’ actions was to increase the pragmatic felicity of asking a question about the ‘saying’

action as well as about the ‘doing’ action. Four picture animations corresponding to each of the four actions appeared one by one together with the pre-recorded verbal description of the event.

After each story, the experimenter presented participants with a pre-recorded wh-question about storyline 1 or 2, a factor that was randomized (half of the items were about storyline 1). Prior to starting the experiment, a practice trial identical to the test trials was introduced in order to familiarize participants with the paradigm.

Figure 8

Example of story pictures in the wh-question task

Participants were asked to provide each answer out loud after the question offset and the experimenter noted the answer. Children received regular positive comments and encouragements, independently of whether their answers were correct or not. The adult version of this task was identical to the child one, but adults received no such feedback. The task lasted approximately 15 minutes.

N-BACK task. We designed a new N-back task suitable to our child population. Memory items consisted in pictures of six well-known fruits (apple, strawberry, cherry, banana, grape, and pear; see Figure 9). A train containing one fruit per wagon travelled from the left to the right of the screen, partly hidden by a fence (see Figure 10). The content of the wagons could only be seen through a hole in the fence on the left side of the screen, next to the little girl Marie. On the right side, there was a door in the fence next to a farmer who could open this door. The goal of the game was to detect when the fruit hidden behind the farmer’s door was the same as the visible

fruit situated in the wagon next to Marie. The task was a 2-back task since the critical fruit behind the door was always situated two wagons away from the one currently seen. Participants were instructed to press a key (space bar) whenever Marie’s fruit was the same as the farmer’s.

Figure 9

Example of fruit sequence in the N-back task

In the example displayed in Figure 9, participants would have to key-press when they saw the second cherries appearing in the screen (i.e., the third wagon after the locomotive), since this is a target 2-back situation. In all other cases no key-press should be provided. Each train also contained lure items, i.e., 1-back lures (like the strawberries in Figure 9), and 3-back lures (like the bananas in Figure 9). Prior to the test phase, our N-back procedure involved a complex familiarization comprising eight steps, detailed below and illustrated in Figure 10. Each step was repeated until succeeded twice before the experimenter continued with the next step. If one of the steps was not succeeded, the experimenter stopped the task.

I. Fruit naming: All fruits are presented on the screen and participants are asked to name each fruit.

II. Recall of one fruit: A train with one wagon containing a fruit travels from the left to the right through the landscape and once it disappears, participants are asked to say which fruit it was.

III. Recall of two fruits: A train with two wagons containing a fruit each travels from the left to the right and once it disappears, participants are asked to say which fruits were in the wagons (the order did not matter).

IV. Recall of two fruits and 2-back rule introduction: Same as step III, but asking the participants to recall the order of appearance as well and to tell if the last fruit seen was the same as the one before.

V. 2-back practice with three wagons and introduction of the rules of the game: A train with three wagons containing a fruit each travels from the left to the right (see Figure 10, scenes A–C), stopping automatically when the third/last wagon is visible through the hole in the

fence (scene D). Participants are asked to press the key if the fruit seen through the hole in the fence next to the girl is the same as the one behind the farmer’s door, i.e., the one seen two wagons ago/in the first wagon, to win the game. After the participants’ response (key-press or not), the experimenter lets the farmer’s door open to show the hidden fruit (scene E). At each correct response (key-press) to a 2-back situation, a magical star appears and the farmer is jumping and smiling (scene F).

VI. 2-back practice with four wagons: Same as step V, but with four wagons (the 2-back always happening when the fourth/last wagon is visible through the hole in the fence and the train automatically stopped), and a recap of the rules of the game.

VII. 2-back practice with an ongoing train: A train with 18 wagons travels from the left to the right, stopping and revealing the content of all the wagons on key-press (the whole train being lifted above the fence). Participants are instructed to stop the ongoing train by pressing the key whenever the girl’s fruit is the same as the farmer’s fruit.

VIII. 2-back practice: Same as step VII, except the train doesn’t stop on key-press, but continues to travel behind the fence. At each hit, i.e., correct key-press in a 2-back situation, a magical star appears and positive auditory feedback is provided (sound of children cheering and applauding). False alarms, i.e., inappropriate key-presses at lure or foil items, causes a negative auditory feedback (sound of children saying a sad “ooh”).

The test phase followed after familiarization phase VIII and was identical to that phase, except that it was composed of four more trains with 18 wagons. In each train, we presented three target items and three lure items intermixed with 12 foil items. During the test phase, participants were rewarded and motivated by receiving magical stars with each hit (target detection), but no auditory feedback, and thus no negative feedback to false alarms was provided anymore. In total, the N-back task lasted approximately 30 minutes for children and 20 minutes for adults. The adult version of the task was identical to the child one, but with a reduced familiarization procedure:

only the two last familiarization phases (VII & VIII) were presented prior to the test phase. Also, in order to increase task difficulty, train speed was increased and the size of the hole in the fence reduced, such that the stimulus presentation was shortened and higher processing speed was required for adults to perform the task.

Figure 10

Example of 2-back detection in the familiarization step V of the N-back task

The dependent variables of the N-back task were overall accuracy, indexed by a d’ score, accuracy of lure items and hit latency. The d’ score takes into account the number of hits (appropriate key-press when a 2-back target occurred) and the number of false alarms (inappropriate key-press when no 2-back occurred), so d’ was estimated as d’ = Zhits - Zfalse alarms

and provides a general estimation of inhibition and working memory updating mobilized in this task. The higher the d’, the better the cognitive control performance. Lure accuracy is of particular interest since the appropriate response to lures is a non-response, i.e., to inhibit the key-press strongly triggered by the previously seen fruit. This index thus represents a specific measure of inhibition capacity, higher lure accuracy meaning better inhibition. We were also interested in hit latency (i.e., reaction times of 2-back target detection) which assesses the efficiency of working memory updating, since each new arriving fruit has to be integrated in the memorized sequence

and correctly retrieved in order to provide the appropriate key-press. The lower the hit latency, the more efficient the updating.

DCCS task. We created a computerized version of the DCCS in which participants were required to sort toys (see examples in Figure 11) according to one of two dimensions: their shape (car or teddy bear) or their color (blue or red). The colors were the same as in Zelazo (2006), and we followed the same procedure as Diamond & Kirkham (2005) testing children and adults.

Stimuli were presented with E-prime 2.0. They appeared one by one in the upper middle of the screen whereas the two response icons illustrated by grey sorting boxes were displayed in the bottom left corner and the bottom right corner. Throughout the whole experiment, the box on the left contained a picture of a blue car while the box on the right contained a picture of a red teddy bear. In the congruent condition, the stimulus to be sorted was identical to the response icons (as in Figure 11, example A), while it was different in the incongruent condition (as in Figure 11, example B).

Figure 11

Example of (A) congruent and (B) incongruent trials in the DCCS task

The task involved three blocks that assess three cognitive control components. Block 1 tested for perceptual inhibition: participants were asked to sort according to one of the two sorting rules (either shape or color), which requires to inhibit the irrelevant dimension of incongruent stimuli (color in the shape game and shape in the color game). Half of the participants started with the shape game in block 1. Half of the 12 trials contained incongruent stimuli. In block 2, participants were asked to sort cards according to the second rule: now the other dimension had to be considered (color if they initially sorted by shape and conversely). Inhibition of the irrelevant

dimension was again necessary in incongruent stimuli, but in addition, participants had to switch to a new rule. Again, half of the 12 trials of this block employed incongruent stimuli. These first two blocks parallel the standard DCCS and were followed by block 3 corresponding to the advanced DCCS. In block 3, the sorting rule changed randomly all the time, a prerecorded voice announcing the relevant rule (audio word “color” or “shape”) before each stimulus appeared. So, participants had to switch between rules flexibly and multiple times. All of the 24 trials in this block contained incongruent stimuli and half of them were switch trials. The stimuli of all three blocks were presented in a pseudo-random order. Before each one of the test blocks, a short practice block familiarized the participant with the task, but used a different set of objects (orange and purple balls and Legos).

Each participant was presented with one of two lists: color-first or shape-first. In both lists and all blocks, each trial began with the presentation of a centered black fixation cross on white background during 800 ms followed by the stimulus and the response icons appearing simultaneously, until the participant responded. Participants were instructed to press one of two keys situated on the keyboard below the left and the right sorting boxes represented on the screen.

Participants were asked to keep their fingers on the keys. Once one of the keys had been pressed, the stimulus and the response icons disappeared, leaving a blank screen during 800 ms, after which the next fixation cross was presented, starting the next trial. In block 3, the audio sorting rule cue was presented at the onset of the fixation cross. Thus, in block 3, there was an 800 ms response-cue interval and an 800 ms cue-stimulus interval. Key-press responses were recorded by E-prime 2.0. In total, the task took approximately 10 minutes. The adult version of the task was identical to the child experiment, but with twice as many trials (24 trials in blocks 1 & 2 and 48 trials in block 3).

We computed three different indexes of cognitive control cost by subject (Davidson et al., 2006): perceptual inhibition cost, single-switch cost, and multiple-switch cost. The lower a cost index, the stronger are the respective cognitive control abilities. The switching costs are expected to be related to syntactic revision, but not perceptual inhibition cost. Perceptual inhibition accuracy cost was obtained by calculating the mean accuracy in congruent trials of block 1 - the mean accuracy in incongruent trials of block 1, and perceptual inhibition latency cost was obtained by calculating the mean latency of correct responses in incongruent trials of block 1 - the mean latency of correct responses in congruent trials of block 1. Lower performance in incongruent trials (requiring inhibition) than in congruent trials (not requiring inhibition) would result in a positive value of this index, indicating a high conflict cost (i.e., low inhibition abilities).

Single-switch accuracy cost was obtained by calculating the mean accuracy in the last two

incongruent trials of block 1 - the mean accuracy in the first two incongruent trials of block 2, and single-switch latency cost was obtained by calculating the mean latency of correct responses in the first two incongruent trials of block 2 - the mean latency of correct responses in the last two incongruent trials of block 1. Lower performance in block 2 (requiring rule-switching) than in block 1 (not requiring rule-switching) would result in a positive value of this index, indicating high single-switch cost (i.e., low single-switch abilities). Multiple-switch accuracy cost was obtained by calculating the mean accuracy in no-switch trials of block 3 - the mean accuracy in switch trials of block 3, and multiple-switch accuracy cost was obtained by calculating the mean latency of correct responses in switch trials of block 3 - the mean latency of correct responses in no-switch trials of block 3. Again, lower performance with switch trials (requiring rule-switching) than with no-switch trials (not requiring rule-switching) would result in a positive value of this index, indicating high multiple-switch cost (i.e., low multiple-switch abilities).

CORSI task. In this standardized task (Corsi, 1972) assessing the spatial working memory span, participants were presented with a board containing nine blocks. The experimenter tapped a sequence of blocks that the participant was requested to replicate, i.e., to tap the same blocks in the same order. The number of blocks in the sequence increased from one to nine or until performance breakdown, which is defined as failure to each of the five items of a level. Depending on participant’s performance, the duration of the task varied between 5 and 10 minutes. The adult version of this task was identical to the child one, but starting directly at level 4, automatically considering the previous levels as being succeeded. Performance was measured by the Corsi level, i.e., the maximum sequence length at which at least one sequence was correctly reproduced (called

“span” in Farrell Pagulayan et al., 2006), ranging from 0 to 9.

Results

Wh-question task

Participants’ verbal responses to target wh-questions were coded either as MV or EV responses. Other responses, i.e., non-responses and distractor responses (concerning a character from the alternative storyline), were observed at a low and similar rate in each participant group:

16 % in 5–6-year-old children, 13 % in 7–8-year-old children, and 14 % adults. These responses were removed from analyses. Since MV and EV response types are in complementary distribution, all our analyses were conducted on proportions of EV responses for simplicity (calculated over all EV + MV responses, see Figure 12). Proportions of EV responses were analyzed using a generalized linear mixed-effects model (see Output D1 in Appendix D) with

question type (ambiguous vs. filled-gap) and age group (5–6-year-old children vs. 7–8-year-old

question type (ambiguous vs. filled-gap) and age group (5–6-year-old children vs. 7–8-year-old