Participants
The participants were 36 preschoolers with autism spectrum disorder (ASD; mean age = 45.5 months, SD = 11.2 months, range = 29.2–74.1) and 21 peers with William syndrome (WS; mean age = 52.5 months, SD = 17.2 months, range = 26.7–78.8) who participated in four experiments. Participants with ASD were recruited through the Victorian Autism Specific Early Learning and Care Center, an autism intervention program located at the La Trobe University Community Children’s Centre. Participants in the WS group were recruited through the Williams Syndrome Family Support Group (Victoria) and the Williams Syndrome Association Australia.
The diagnoses of ASD were previously made by community-based healthcare professionals and confirmed for the study using the Autism Diagnostic Observation Schedule (ADOS 2, [
39]) administered by a clinician with demonstrated research reliability in the use of this measure. Exclusion criteria for the ASD group included the presence of uncorrected hearing or vision impairment, and the presence of a major medical problem. All participants with WS had their diagnosis confirmed with the positive fluorescent in situ hybridization (FISH) test and displayed the typical ~1.6-Mb heterozygous microdeletion at 7q11.23 [
40].
Participants’ cognitive level was measured with the Mullen Scales of Early Learning (MSEL). Following [
41] and [
42], developmental quotient (DQ) scores were calculated for each MSEL subscale according to the formula: DQ = age equivalent scores/chronological age × 100 and averaged to create an overall developmental quotient. Additionally, participants’ adaptive behavior was assessed using the Vineland Adaptive Behavior Scales (VABS; [
43]). The ASD and WS groups did not differ on chronological age, overall cognitive level, and overall adaptive behavior (see Table
1). However, as expected, children with WS had superior scores in the socialization subscale of the VABS.
Table 1
Participant characteristics
Gender, M, F | 34, 2 | 11,10 | – |
Chron. age (months): M (SD) | 45.53 (11.21) | 52.55 (17.22) | .10 |
MSEL visual reception AE: M (SD) | 26.74 (11.37) | 29.17 (16.29) | .57 |
MSEL fine motor AE: M (SD) | 25.35 (8.63) | 24.83 (10.10) | .85 |
MSEL receptive lang. AE: M (SD) | 20.38 (10.30) | 27.67 (14.60) | .07 |
MSEL expressive lang. AE: M (SD) | 23.38 (10.65) | 26.61 (13.69) | .39 |
MSEL visual reception T: M (SD) | 30.12 (10.10) | 24.13 (7.15) | .22 |
MSEL fine motor T: M (SD) | 28.18 (13.42) | 21.86 (3.68) | .08 |
MSEL receptive lang. T: M (SD) | 28.03 (14.41) | 25.47 (9.53) | .53 |
MSEL expressive lang. T: M (SD) | 30.27 (15.77) | 24.00 (7.24) | .15 |
MSEL total DQ: M (SD) | 62.93 (27.99) | 56.44 (16.88) | .34 |
VABS communication: M (SD) | 71.81 (18.98) | 70.57 (11.65) | .79 |
VABS daily living skills: M (SD) | 72.59 (27.20) | 70.43 (11.43) | .73 |
VABS socialization: M (SD) | 72.50 (14.69) | 80.81 (12.53) | .03 |
VABS motor skills: M (SD) | 75.09 (19.32) | 68.86 (11.00) | .14 |
VABS composite: M (SD) | 69.81 (19.14) | 69.86 (10.08) | .99 |
ADOS severity score: M (SD) | 7.45 (1.88) | | |
Procedure
The study was approved by the La Trobe University Human Ethics Committee and informed consent was obtained from the children’s parents.
The children were tested in a quiet room in one of three University or early intervention settings, depending on where the child was recruited. Three children with WS were administered the standardized tests and the experimental battery in their home due to traveling difficulties on the part of their families. The length of experimental testing was approximately 25 min. The experiments presented here were part of a larger study examining social and non-social learning in young children with ASD and WS.
Preliminary validation
The validation procedure for the tasks used in the battery involved a piloting stage where 20 typically developing (TD) preschoolers were administered preliminary and current versions of each of the experimental tasks. As these were not matched for mental age, motor skills and other variables relevant to performance in the experimental tasks, they were not included as a control group, but their performance was examined to test the validity of the experimental paradigm. It was found that tasks intended to measure spontaneous imitation did indeed elicit spontaneous imitation in 85 to 100 % of the TD group. Similarly, 95 % of children showed evidence of trial-and-error learning in the task intended to measure trial-and-error learning. Additionally, we found that spontaneous imitation in the whole sample was highly correlated (r = .74, p < .001) to scores on the VABS items addressing imitation (items 9, 12, 16, and 21 in the socialization - interpersonal relationships subscale).
Experiment 1
The aim in experiment 1 was to investigate social learning in preschoolers with ASD and WS in a task in which imitation served a social affiliation function. To this end, we measured participants’ spontaneous imitation in response to a playful, socially engaging model and to a “neutral” model performing arbitrary (non-instrumental) actions on objects. This paradigm, based on behavioral research with typically developing children by Nielsen and colleagues [
10,
11] was developed to capture children’s propensity to imitate for the purpose of establishing social connectedness with the model. We hypothesized that spontaneous imitation would be modulated by the socially engaging behavior of the model in children with WS, but not in those with ASD.
In the ASD group, we found no associations between imitative performance and age, cognitive, adaptive, language, and motor functioning level (as assessed through the MSEL and VABS). Imitation of the playful model was negatively associated with the ADOS social affect calibrated social scores (r = −.43, p < .01), suggesting that children with more severe ASD symptoms in the social domain were less likely to imitate in response to the playful model. Conversely, there was no association between social symptoms and imitation of the neutral model. In the WS group, the only significant correlation was between imitation performance across conditions and chronological age (r = .55, p = .01 for imitation of the playful model and r = .73, p < .001 for the imitation of the neutral model), suggesting that older children in this group were more likely to engage in imitative behavior across conditions.
Experiment 2
In experiment 2, we used a novel eye-tracking paradigm to measure how participants’ visual attention to the model was affected by the presence/absence of socially engaging behavior. A similar procedure as in experiment 1 was used, expect that the “socially engaging” and the neutral model were presented through pre-recorded videos displayed on an eye-tracking computer to allow for analyses of visual attention. We hypothesized that visual attention and imitative response to the model would be modulated by the socially engaging behavior displayed by the model in the WS group, but not in the ASD group.
Secondly, with regard to participants’ visual attention to the model’s actions (quantified in terms of average duration of fixations to the action region), there was no effect of the group (F (1, 48) = 2.94, p = .09, η
p2 = .05), condition (F (1, 48) = 1.82, p = .18, η
p2 = .03) or group × condition interaction (F (1, 48) = .12, p = .56. η
p2 = .00), suggesting that both groups attended to the actions for similar durations across conditions.
Finally, we tested participants’ imitation performance. The main effects of the group (
F (1, 52) = .37,
p = .05,
η
p2 = .07) and condition (
F (1, 52) = 6.38,
p = .01,
η
p2 = .10) were significant, but there was no group × condition interaction, (
F (1, 52) = .26,
p = .61.
η
p2 = .00), suggesting that both groups imitated more often in response to the playful compared to the neutral model presented on the video screen, although the children with WS were more likely to imitate both models. As shown in Table
3, imitation performance in the WS group was 52.63 (SD = 40.73) in the neutral condition, and 64.37 (SD = 34.67) in the playful condition. In the ASD, it was 35.00 (SD = 40.31) in the neutral condition, and 42.85 (SD = 35.62) in the playful condition. While the majority of children across groups spontaneously imitated at least one action, a small percentage of children in the ASD group (13 %) did not engage in any imitative behavior.
For both groups, attention to the model across conditions was unrelated to age, cognitive, adaptive and language functioning. In ASD, imitation in response to the playful model was negatively correlated with the ADOS social affect scores (r = −.61, p < .001) and positively correlated with the VABS socialization scores (r = .46, p < .01), MSEL developmental quotient (r = .36, p < .05), and VABS adaptive behavior composite score (r = .36, p < .05), suggesting that children in this group with more advanced social, cognitive, and adaptive skills were more likely to imitate the playful model. Similarly, imitation in response to the neutral model was negatively correlated to the ADOS social affect scores in the ASD group (r = −.48, p < .005). As in experiment 1, the only significant correlation in the WS group was between imitation performance across conditions and chronological age (r = .81, p < .001 for imitation of the playful model and r = .83, p < .001 for the imitation of the neutral model).
Experiment 3
The aim in experiment 3 was to investigate participants’ visual attention and spontaneous imitation in the context of an instrumental imitation task, i.e., a task where imitation served a purely instrumental function (retrieving a desired object from a container). As the social affiliation components were minimized, we expected imitation performance and visual attention to the model to be unaffected by the differences in social engagement across the ASD and WS groups.
Each trial involved a different container, and after the demonstration of each video, the same container shown in the video was given to the child. Inside the container was a toy that the child was motivated by during a brief warm-up free play episode prior to the experiment. Examples of toys used for the task were Thomas the Tank Engine and a Peppa Pig puppet. No instruction was given, and participants’ spontaneous behavior with the container in response to the demonstration was video-recorded for later coding. The only way to open the container in order to retrieve the toy was to follow the procedures demonstrated in the videos. The model did not display any social or emotional behavior. We therefore reasoned that performance in this task would reflect the instrumental function of imitation (i.e., imitating in order to achieve an instrumental goal, rather than to connect with the model).
The coding procedure involved simple yes/no (1/0) for imitating each action involved in the trial. A total imitation score was obtained for each participant by calculating the proportion of imitated actions out of the total imitation opportunities (i.e., the demonstrated actions presented in each of the videos). Coding was conducted by two research assistants blind to group membership and study hypotheses. Interrater reliability (intraclass correlation) between the two research assistants, calculated on 20 % of the entire data set, was .96.
During observation of the video stimuli, participants’ eye-movements were recorded using the eye-tracker system and analyzed using frame-by-frame defined areas of interest using Tobii Studio analysis software. Fixation criteria were set to Tobii Studio defaults of a 30-pixel dispersion threshold for 100 ms. The two regions of interest included in the analyses were the model’s face and her action. Two participants in the ASD group were excluded due to equipment failure during the experiment.
Across groups, attention to the model was unrelated to age, cognitive, adaptive, and social functioning. In both ASD and WS groups, imitative performance was positively correlated with the VABS socialization scores (r = .45, p = .01 in ASD and r = .56, p < .01 in WS), MSEL developmental quotient (r = .53, p = .001 in ASD and r = .51, p < .05 in WS), and VABS adaptive behavior composite scores (r = .44, p = .01 in ASD and r = .66, p = .001 in WS). Additionally, in the ASD group, imitative performance was negatively associated with the ADOS social affect (r = -.32, p = .05) and positively associated with language as assessed through the MSEL (r = .40, p < .05 across receptive and expressive subscales). Additionally, in the WS group, there was a correlation between imitation performance and chronological age (r = .71, p < .001). As in the previous experiments, performance was unrelated to motor skills across groups.
Experiment 4
The rationale for experiment 4 was to investigate participants’ ability to learn from the consequences of their own actions via trial and error (non-social learning). As this task did not involve any social-processing demand, we expected performance to be unaffected by the differences in social engagement that distinguish ASD from WS.