Autism spectrum disorder (ASD) and 22q11.2 deletion syndrome (22q11DS) are respectively a neurodevelopmental disorder and a rare genetic syndrome, both characterized by social difficulties. However, the phenomenology of these social impairments remains poorly studied, especially with regard to everyday social interactions. The aim of the present work is thus to better characterize the social phenotypes of these two populations in order to disentangle the similarities and differences presented by each.

To achieve this goal, we propose a theoretical model of social functioning integrating the social components classically described in the literature, i.e. social skills and social motivation (which would be underpinned by social cognition according to our model), but also the component of social interactions, which we distinguish into objective aspects (named social behaviors) and subjective aspects (named social experiences). Based on this theoretical model, we propose to use ecological methods to get as close as possible to everyday social interactions, which are still too rarely studied in the current literature, especially in clinical populations such as ours. The first objective of this thesis is therefore to study social interactions, using ecological methods (i.e. momentary ecological assessment on a smartphone and role-plays), in order to plunge into the heart of the daily lives of youths with ASD and 22q11DS. The second objective is to focus on two mechanisms underlying social motivation and social cognition respectively, i.e. future projection and pleasure anticipation on the one hand, and intention discrimination based on movement observation on the other. Finally, methodological reflection forms the backdrop to this work, with questions raised about the choice of methodology in relation to the problem under study, the feasibility of ecological methods and, finally, the links between classical and ecological methods.