Social Proficiency Relates to Socially-Adaptive Mirror System Functioning

Background: Individuals with a diagnosis of autism spectrum disorders (ASD) have impairments in social communication and interaction. Also in the neurotypical population, individual differences in terms of social proficiency are prevalent. Researchers have proposed the fronto-parietal action observation network or ‘mirror system’ as a basic neural mechanism for socio-cognitive (dys)functioning. In contrast to the well-known but controversial ‘Broken Mirror Hypothesis’, Wang and Hamilton’s (2012) social top-down response modulation (STORM) model proposed that people with social difficulties (such as patients with ASD) may have an intact mirror system, but unlike social proficient participants, fail to modulate mirror system functioning according to the social context.

Objectives: In this study, we explored whether inter-individual differences in social proficiency and/or attachment towards others are related to one’s ability to show socially-adaptive mirror system functioning.

Methods: A total of 56 neurotypical participants were assessed on adaptive neurophysiological mirror system functioning by means of a well-established single pulse transcranial magnetic stimulation (TMS) paradigm. While undergoing TMS, participants observed video stimuli of an actress performing simple hand movements combined with either direct or averted gaze. In general, TMS-assessed mirror-motor responses are significantly larger upon the observation of actions accompanied by direct eye contact, compared to averted eye gaze. To assess inter-individual differences in social proficiency, participants completed the self-report versions of the Social Responsiveness Scale (SRS) and the State Adult Attachment Measurement (SAAM). The data-driven k-means cluster analysis technique was used to identify subgroups based on the standardized questionnaire scores.

Results: Cluster analysis revealed two meaningful profiles of social proficiency. Cluster 1, labeled the ‘Secure’ cluster, represented participants with secure attachment styles and high levels in social proficiency (n = 26). Cluster 2, the ‘Avoidant’ cluster, represented participants that are highly socially avoidant and have mild to severe impairments in social responsiveness (n = 30). The two subgroups showed a clear differentiation in terms of socially-adaptive mirror system functioning (Gaze × Cluster interaction: F(1,49) = 7.85, p < .01). Particularly, only for the ‘Secure’ social profiles, direct gaze specifically enhanced ‘mirroring’ (p = .02). For participants belonging to the ‘Avoidant’ cluster however, direct eye contact did not facilitate mirroring (p = .18). The general level of mirroring was similar for each group (p = .51). In other words; in participants that are less socially proficient, mirroring is intact; but it is not socially modulated by relevant social cues, such as eye gaze.

Conclusions: Our results provide further support to the STORM model by showing that the process of mirroring is adaptive to relevant social cues (such as eye contact). Specifically, the observation that not mirroring per se but socially-adaptive mirroring is diminished in individuals with low social proficiency argues against a strong account of the Broken Mirror Theory. Instead our results provide evidence that the top-down response modulation of the mirror system is altered in individuals with social difficulties. Although established in the neurotypical population, these findings may also be highly relevant for people with ASD.