Model 1 Model 2 Model 3
b SE b SE b SE FIXED PART Intercepta 5.087*** 0.117 5.735*** 0.132 5.753*** 0.133 Test: Coop 3.197*** 0.106 3.440*** 0.132 3.395*** 0.134 Test: Post 1.397*** 0.114 1.721*** 0.139 1.704*** 0.141 Group: Special -1.768*** 0.218 -1.785*** 0.219 Test: Coop * Group: Special -0.662** 0.219 -0.548* 0.23 Test: Post * Group: Special -0.895*** 0.233 -0.902*** 0.236
Entropy 0.354 0.467
Test: Coop * Entropy: Coop -2.081** 0.67 Test: Post * Entropy: Post -0.371 0.649 Group: Special * Entropy -0.376 0.759 Test: Coop * Group: Special * Entropy: Coop 1.323 1.126 Test: Post * Group: Special * Entropy: Post 1.067 1.065 RANDOM PART
Level 1: Child
Intercept variance: Individual 0.266 0.27 0.269 Slope variance: Test within individual 0.134 0.13 0.131 Intercept-slope covariance 0.189 0.187 0.188 Level 2: Dyad
Intercept variance: Dyad 2.3 1.51 1.476 Slope variance: Test within dyad 0.082 0.041 0.038 Intercept-slope covariance 0.435 0.248 0.236 Residual variance 3.093 3.094 3.09 Deviance 7598.7 7501.2*** 7482.6* Deviance difference 97.5 18.7 Degrees of freedom df = 3 df = 5 Chi2 best fit model 101.814 13.265
* p < .05, ** p < .01, *** p < .001
a The intercept represents: Test = Pre; Group = Regular.
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Model 1 consisted of the dependent variable task performance and the predictor condition. As can be seen in Table 2, there was a significant effect of Condition on Task Performance. Children performed significantly better when cooperating and on the posttest, compared to the pretest. In Model 2, the effect of Group was added, as was the interaction between Condition and Group. As shown in Table 2, children attending special primary education performed significantly worse than children attending regular primary education (effect of Group) and this was the case for all Conditions (pretest, coop, and posttest; effect of Condition x Group), meaning that the interaction was not significant.
To further examine the potential contribution of entropy to task performance, the interactions between Condition and Entropy, Group and Entropy, and Condition, Group and Entropy were added. Thus, Model 3 was the most comprehensive model. As can be seen from the significant drop in deviance, this made for a better model. Looking at the fixed effects, there was a significant additional effect of entropy when cooperating. However, this effect did not differ between groups. Thus, independent of groups, better task performance when cooperating was predicted by less disorder in the synchrony of the dyadic postural sway patterns.
Discussion
Three questions on the role of interpersonal synchrony and cooperation were raised. The first one was the issue of task performance differences between children with and without neurodevelopmental disorders. Scores on the tangram task of both groups in the cooperation condition and on the posttest were compared to those on the pretest. We hypothesized that individual children’s task performance would be better when cooperating and on the posttest than on the pretest. The results confirmed this hypothesis. This is consistent with previous research that has shown that in a cooperative task the best results are often obtained when cooperating (e.g., Fawcett & Garton, 2005; Underwood, McCaffrey, & Underwood, 1990) and that working together on a task can have a retention effect, in that individuals performed better on a task when they cooperated prior to the individual task (Johnson & Johnson, 1989, in Johnson & Johnson, 1996). Second, we hypothesized that children attending regular primary education would outperform children attending special primary education in all three conditions, since many of the children in the latter group (often) have learning difficulties as well. This hypothesis was also confirmed.
The second question concerned differences in the level of interpersonal synchrony. We used entropy, that is, the level of disorder, as a measure to assess interpersonal synchrony. No difference in level of entropy emerged between children with and without neurodevelopmental disorders in any of the three conditions. Thus, having a neurodevelopmental disorder did not affect the ability to synchronize with another
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child. This seems to the suggest that the process of cooperating, measured by means of a bodily variable, is similar in children with and without neurodevelopmental disorders.
The third and focal point of this study was the potential differential nature of the relationship between interpersonal synchrony and task performance in children with and without neurodevelopmental disorders. Results revealed a significant effect of entropy (i.e., the level of disorder of the synchrony) on task performance when cooperating that was independent of group. Thus, in the group of children with as well as in those without neurodevelopmental disorders, less disorder in synchrony (and also a less deterministic structure of the synchrony) was related to better task performance when cooperating. In other words, better task performance was accompanied by shorter periods of synchronized postural sway (as indicated by the lower level of determinism) and more order in this synchronized movement (as indicated by the lower level of entropy). The fact that this was the case for both groups suggests that, although children in special education performed worse on a cognitive task, the underlying timing mechanism acted in a similar way. This is surprising, since research has shown that children with a neurodevelopmental disorder often experience movement (i.e., postural sway) problems as well, and one would expect this to lead to changes in the level of interpersonal synchrony as well. We showed that this was not the case when cooperating.
In summary, children with a neurodevelopmental disorder and potentially comorbid postural sway disturbances did perform less than their typically developing peers, but their movement process (i.e., interpersonal synchronization) was similar. In addition, the fact that less disorder in synchrony predicted better task performance supports the view that in less restricted tasks where there is multifinality (i.e., more than one way of solving the problem) “diversification of action is likely to occur, and complementary forms of interaction will in many cases supersede synchronous kinds of interaction” (Wallot, Mitkidis, McGraw, & Roepstroff, 2016, p. 3).
As said, all children performed the task without restrictions, apart from being asked to stand on the Wii Balance Board. This is different from previous studies and to our knowledge no other study has taken this approach when analyzing postural sway. In general, participants in studies on postural sway are instructed to stand still in one place for a short amount of time (30 – 60 seconds; e.g., Riley et al., 2003; Stoffregen et al., 2007). Notwithstanding the significance of these studies, they do not shed light on how postural sway works in a real-life context. Interactions often last longer than 30-60 seconds and movement is usually unrestricted. In addition, many studies on interpersonal synchrony have used a controlled experimental setup, for example by using confederates that purposefully do or do not synchronize with the participant (e.g., Hove & Risen, 2009; Macrae et al., 2008). However, in real-life this is not the case; synchronization occurs unintentionally. In a recent meta-analysis of research
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on interpersonal synchrony and prosociality, Rennung and Göritz (2016) stated that research in more naturalistic settings and with populations other than students is required to further our understanding of this phenomenon. This is what we did in the present study. Note that, although their meta-analysis focused on prosociality and not task performance, we do believe this recommendation is valid for research in the entire domain of interpersonal synchrony. What we showed is that, indeed interpersonal synchrony is present, but that its relation to task performance is opposite to that of previous studies. Where for example Macrae et al. (2008) showed that more synchrony was related to better memory, we showed that in this more naturalistic setup less synchrony (i.e., more coordination) is better. Future research should investigate whether this is also the case in other naturalistic settings. In addition to the naturalistic setup of the present study being different from previous studies, we are unaware of any study on interpersonal synchrony of this magnitude. In total, almost 600 children (i.e., 300 dyads) participated in the present study. Thus, this study was unique in more than one way and we hope that future research will continue to examine interpersonal synchrony in different populations in naturalistic settings.
In summary, the present study provides additional support for the idea that in certain (cooperative) tasks, it is better to coordinate than synchronize. In other words, sometimes coordination is more suitable for the task at hand, especially in the presence of multifinality (Wallot et al., 2016). In addition, and perhaps most importantly, we showed that although task performance differed between children attending regular and special primary education, the performance of both groups was influenced in the same way by the level of interpersonal synchrony (i.e., the level of disorder of the synchrony). Thus, on a more fundamental level both groups showed similar dynamical behavior, although the task outcomes were different. Future studies of children’s performance in naturalistic settings should examine other modalities than postural sway to investigate similarities and differences between dynamical processes of children with and without neurodevelopmental disorders.
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