Coding one's own body: an investigation of neural, cognitive and personality determinants of self-recognition

In the last decade, research on visual perception of the human body remarkably increased, especially following the discovery of the Extrastriate Body Area, an occipito-temporal region selectively involved in body-processing (Downing et al., 2001). However, an intriguing issue is to what extent a specific kind of body representation in the brain is devoted to the knowledge of the bodily self. Research on the visual recognition of the self-body, in particular, is still scarce, especially if compared to the extensive body of research devoted to the recognition of self-face. In the present thesis, a systematic investigation of unexplored aspects of self-body and self-face recognition is presented, with particular focus on the one side, on the possible neural correlates, and on the other, on the variables of personality that may play a role in these cognitive functions. Recent work in neuroscience indicates a superiority in the visual processing of one’s own than other people’s body-parts (Frassinetti et al., 2008). Specifically, subjects show higher accuracy when asked to match pictures depicting their own compared to unfamiliar body-parts, the so-called “self advantage”. It remains to be established, however, which cortical regions are involved in this phenomenon. To this aim, in experiments reported in Chapter 2 the causal role of cortical regions specifically involved in body-parts processing (i.e., the right Extrastriate Body Area) and in self-face recognition (i.e., the right Inferior Parietal Lobule) was investigated by means of Transcranial Magnetic Stimulation. The results did not allow definitive conclusions regarding the role of the cortical areas under investigation for self body-parts recognition; nonetheless, behavioural data seem to suggest that the self-recognition ability is not as universal as generally believed. In particular, the strength of the “self advantage” showed a large degree of variability across participants. Therefore, the contribution presented in Chapter 3 was aimed at finding some possible determinants that modulate the self-body advantage. Namely, it was examined whether the self-body recognition ability is modulated by implicit and explicit self-esteem, relying upon studies linking the physical self and self-esteem. Two studies were conducted using paradigms assessing covert (Experiment 3) or overt (Experiment 4) self-body recognition (i.e., the matching-to-sample used in previous studies and a new-developed paradigm of overt recognition). Results revealed that the self-body recognition ability is qualified by individual differences in self-esteem, and especially implicit self-esteem, measured with the Implicit Association Test, a widely used procedure for measuring strengths of automatic associations between concepts (Greenwald et al., 1998). Moreover, considering the two studies together, only the implicit self-esteem showed incremental validity in predicting the ability to recognize self body-parts. The results are discussed in terms of the role of individual differences such as implicit self-esteem for cognitive functions such as self-body recognition. Finally, a study (Experiment 5) was conducted to better address whether self-esteem and other personality traits with strong interpersonal value (i.e., empathy) also correlate with the strength and stability of self-representation. Self-face representation was recently found to be less stable than believed in the past (Tsakiris, 2008). Our findings reveal that higher level of implicit self-esteem correspond to lower susceptibility to the “enfacement” illusion, measured in terms of incorporation of other people’s facial features in the self-face representation following synchronous visuo-tactile stimulation in a mirror-like setting. Moreover, the Perspective Taking component of empathy was found to correlate with the introspective experience of the illusion. All in all, the present contribution bridges recent research in the cognitive neurosciences and social cognition and points toward a complex interplay among cognitive and personality factors in the domain of self-recognition.