Neural sensitivity to facial signals of trustworthiness in 6-month-old infants

One of the most important aspects of social interactions concerns the ability to discern social signals conveyed by other people. We know that adults and pre-schoolers easily distinguish between fine-grained differences in the level of trustworthiness expressed by faces. Nevertheless, only a few studies investigated the sensitivity to social signals of trustworthiness in infancy (Jessen & Grossmann, 2016; Jessen & Grossmann, 2017). By using computer-generated faces of male identities, these studies found no evidence of neural discrimination between trustworthy and untrustworthy faces, although both face types were discriminated from neutral faces. In this study, we aimed at investigating whether, at the age of 6 months, infants are able to discern between trustworthy and untrustworthy faces of truthful female identities. Infants were administered with a Fast-Periodic Visual Stimulation (FPVS) task, where two face identities were presented at a rate of 6 Hz (Baseline) following an Oddball paradigm. Every 1.2 Hz (Oddball), the trustworthiness level changed (a trustworthy face every 4 untrustworthy faces, or vice versa, in a counterbalanced order). Preliminary analyses show significant Signal-to-Noise Ratios (SNRs) at 6 Hz in occipital regions. More importantly, significant SNRs at 1.2 Hz were found in right occipital and right occipito-temporal regions. These results suggest that at 6 months infants are able to discriminate between different levels of trustworthiness, and that this discrimination takes place in brain areas known to play an important role in face discrimination. Future studies should investigate how fine-grained this sensitivity is, and how brain sensitivity is related to behavioural responses.