As humans, we share a strong desire to interact with other people. This strong motivation to engage socially directs our attention to social signals, guides us to participate in behaviours that help us to establish, maintain, and enhance our relationships with others, and allows us to enjoy social interactions and to find them rewarding. However, the Social Motivation Theory posits that individuals with Autism Spectrum Disorder may have deficits in social motivation, which may lead to difficulties in social interactions and communication. This thesis employs several methods (including behavioural, psychophysiological and neurological) to investigate social motivation in the typical population, and examines how autistic traits influence the reward value assigned to social stimuli. Specifically, this thesis investigates social motivation in relation to an important type of social stimulus, namely biological motion, which has not been the topic of research investigating social motivation.
The first empirical chapter (Chapter 3) presents a behavioural experiment that investigates the reward value of biological motion, and how this value changes as a function of autistic traits among the participant sample. The following chapter (Chapter 4) comprises two eye-tracking experiments aiming to address how viewing biological motion affects attention and arousal. The final empirical chapter (Chapter 5) employs functional magnetic resonance imaging (fMRI) to examine brain regions involved in the anticipation of social reward or social punishment in a task where participants work to either receive positive feedback or avoid negative feedback. As a whole, this thesis sheds valuable new light on questions surrounding social motivation, such as whether individuals find a broad conceptualisation of social stimuli rewarding and whether the perceived reward value of social stimuli is influenced by autistic traits. The findings from this work have important implications for developing a greater understanding of social motivation and human social behaviour more broadly.