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Although neuroimaging studies have consistently identified the temporoparietal junction (TPJ) as a key brain region involved in social cognition, the literature is far from consistent with respect to lateralization of function. For example, during theory-of-mind tasks bilateral TPJ activation is found in some studies but only right hemisphere activation in others. Visual perspective-taking and imitation inhibition, which have been argued to recruit the same socio-cognitive processes as theory of mind, are associated with unilateral activation of either left TPJ (perspective taking) or right TPJ (imitation inhibition). The present study investigated the functional lateralization of TPJ involvement in the above three socio-cognitive abilities using transcranial direct current stimulation. Three groups of healthy adults received anodal stimulation over right TPJ, left TPJ or the occipital cortex prior to performing three tasks (imitation inhibition, visual perspective-taking and theory of mind). In contrast to the extant neuroimaging literature, our results suggest bilateral TPJ involvement in imitation inhibition and visual perspective-taking, while no effect of anodal stimulation was observed on theory of mind. The discrepancy between these findings and those obtained using neuroimaging highlight the efficacy of neurostimulation as a complementary methodological tool in cognitive neuroscience.

This thesis aimed to investigate self-other processes in social cognition. Contrary to the traditional approach of focusing on self-other processes within the confines of a single domain, this thesis highlights the prominent role of these processes across different socio-cognitive domains. Three main empirical questions form the basis of the research reported here. The first is concerned with the extent to which self-other representations are shared across three different socio-cognitive abilities: the control of imitation, theory of mind, and visual perspective taking. The second relates to the neural underpinnings of self-other representations, in particular, the role of the temporoparietal junction (TPJ) during socio-cognitive processing. The third question examines the role of culture as a modulatory factor of self-other processes. The findings from Experiment 1, 3 and 4 showed a relationship between the control of imitation and visual perspective taking. This relationship seems to rely on the online control of co-activated self-other representations, which at the neural level are mediated by the TPJ (bilaterally). In Experiment 2 it was found that individuals with mirror-touch synaesthesia are impaired in the control of imitation but their performance on visual perspective taking and theory of mind is comparable with non-synaesthetes. It is hypothesised that atypical self-other processes in mirror-touch synaesthesia might be confined to situations in which representations of the ‘other’ should be inhibited, but not when they should be enhanced. Experiment 5 showed that acculturation strategies adopted by migrants modulate their imitative behaviour towards a member of the heritage vs. a member of the host culture. The diverse nature of the studies reported in this thesis shows the complexity of self-other processes in social cognition. Taken together, these findings demonstrate how adopting a wider approach to the investigation of self-other processes contributes towards a better understanding of the mechanisms underlying socio-cognitive abilities.

A new task ('CARER') was used to test claims of reduced empathy in autistic adults. CARER measures emotion identification (ability to identify another's affective state), affective empathy (degree to which another's affective state causes a matching state in the Empathiser) and affect sharing (degree to which the Empathiser's state matches the state they attribute to another). After controlling for alexithymia, autistic individuals showed intact affect sharing, emotion identification and affective empathy. Results suggested reduced retrospective socio-emotional processing, likely due to a failure to infer neurotypical mental states. Thus, autism may be associated with difficulties inferring another's affective state retrospectively, but not with sharing that state. Therefore, when appropriate measures are used, autistic individuals do not show a lack of empathy.

In this Commentary article we critically assess the claims made by Schurz, Kronbichler, Weissengrubler, Surtees, Samson and Perner (2015) relating to the neural processes underlying theory of mind and visual perspective taking. They attempt to integrate research findings in these two areas of social neuroscience using a perspective taking task contrasting mentalistic agents (‘avatars’), with non-mentalistic control stimuli (‘arrows’), during functional Magnetic Resonance Imaging. We support this endeavour whole-heartedly, agreeing that the integration of findings in these areas has been neglected in research on the social brain. However, we cannot find among the behavioural or neuroimaging data presented by Schurz et al. evidence supporting their claim of ‘implicit mentalizing’—the automatic ascription of mental states to another representing what they can see. Indeed, we suggest that neuroimaging methods may be ill-suited to address the existence of implicit mentalizing, and suggest that approaches utilizing neurostimulation methods are likely to be more successful.