Bridging the Gap Between Social Motivation and Empathy: Autistic Traits Modulate Spontaneous Facial Mimicry of Social Rewards in Individuals with ASD

Background: Individuals with Autism Spectrum Disorders (ASD) typically show deficits in measures related to empathy, including spontaneous facial mimicry.  Atypical responsivity to social rewards has been suggested to underlie such deficits (Chevallier et al., 2012). In a previous study we found that typically developing individuals show enhanced spontaneous facial mimicry towards faces associated with high reward value compared to those associate with low reward value (Sims et al., 2012). Importantly, the difference in mimicry for high compared to low reward faces was negatively correlated with autistic traits, suggesting a weakened link between reward and mimicry in individuals high in autistic traits. However, it is unknown how autistic traits modulate this link in individuals with a clinical diagnosis of ASD.

Objectives: We tested the modulation of the reward-mimicry link by autistic traits (as measured by the Autism Spectrum Quotient, AQ) in individuals with a clinical diagnosis of ASD, using a paradigm identical to the one used previously in neurotypicals (Sims et al. 2012).

Methods: 25 adult participants with a DSM-IV/ ICD-10 based diagnosis of Autism/ ASD/ Asperger Syndrome (13 female; age range 19-50 years [M = 30.63, SD = 11.73]) took part in an implicit reward conditioning the experiment. Briefly, it involved watching a set of faces in the context of a card game, where different identities were conditioned with different levels of reward (win/lose outcomes: POS faces were associated with wins, NEG faces with losses). Consequently, participants watched short videos of the same faces (as in the conditioning phase) making happy expressions, while facial EMG was recorded. Zygomaticus Major response to happy faces was used as a measure of spontaneous facial mimicry and compared between POS and NEG faces.

Results: In contrast to the finding reported by Sims et al. (2012) in neurotypicals, no increased mimicry for the POS vs NEG faces were noted in the whole sample (t=1.227, p=0.223). However, greater autistic symptoms (as measured by higher AQ scores) were associated with smaller difference in the extent of spontaneous mimicry for POS vs NEG faces (r= -0.457, p=0.016).

Conclusions: We conclude that autistic traits modulate the link between reward and spontaneous facial mimicry, in individuals with ASD. While there was no difference in the spontaneous facial mimicry of POS vs NEG faces in the whole sample, individual scores on autistic traits were strongly associated with the extent to which POS faces were mimicked greater than NEG faces. This further supports the idea that while there may not be a fundamental deficit in the mimicry mechanisms in ASD, an atypical modulation of these mechanisms due to reduced reward responsivity to social stimuli might underlie the previously observed deficits in spontaneous facial mimicry. This observation thus provides a potential bridge between theoretical models of autism that suggest reduced social motivation and those that suggest reduced empathy. The results further underline the importance of studying individual differences within people with a clinical diagnosis of ASD.