Itchy and Scratchy: Contagious Scratching and Yawning in Adults with Autism Spectrum Disorder

Background: Contagious yawning may act as a marker of traits like empathy and mimicry. Children with Autism Spectrum Disorders (ASD) seem to be less susceptible to contagious yawning than typically developing (TD) children. This could be explained by reduced attention to eyes, which are a more potent trigger of contagious yawning than the mouth. Contagious scratching is phenomenally similar but does not rely on attention to eyes.

Objectives: To compare susceptibility to contagious yawning and scratching in adults with and without ASD; To ask if contagious effects were associated with autistic symptoms/traits, empathy and alexithymia, and theory of mind. 

Methods: Participants were 21 adults with a childhood diagnosis of ASD (M=24 years) and 24 TD adults (M=28 years) matched on Full Scale IQ.  Participants were unaware of the purpose of the experiment. They watched two naturalistic videos of a person who yawned or scratched and were questioned afterwards about what they noticed about the person’s behavior and how they felt while watching. Participants were discretely filmed and videos were coded for frequency and duration of yawning and scratching (30% tapes were blind double-coded).  Other measures included: Autism Diagnostic Observation Schedule; Autism Spectrum Quotient; Interpersonal Reactivity Index; Toronto Alexithymia Scale; theory of mind battery.

Results: Contagious Yawning: A similar proportion of ASD (29%) and TD (38%) individuals showed an increase in yawning in response to the yawn video (χ²(1)=0.40, p=.53).  TD adults increased their yawning while viewing the yawn video compared to a control (scratch) video more than adults with ASD (t(43)=1.62, p=.05, d=0.49). Contagious Scratching: A similar proportion of ASD (57%) and TD (63%) individuals showed an increase in scratching in response to the scratch video (χ²(1)=0.13, p=.71).  There was no difference between groups in the amount of scratching during the scratch video when compared to the control (yawn) video (t(27.72)=1.26, p=.22, d=0.38). Participants noted the yawning and scratching, confirming that they attended to the task. About half of each group reported feeling like yawning or scratching. In the TD group feelings closely matched behavior, but in the ASD group these were dissociated. Susceptibility to contagious effects was related to lower levels of autistic traits, lower alexithymia, and higher theory of mind task performance.

Conclusions: Adults with ASD were less susceptible than TD adults to contagious yawning and there was some association between contagious effects and autistic traits, understanding others’ minds, and understanding emotions. The variation in contagious effects in both groups means that it is unlikely to have value in terms of diagnostic protocols. Subjective reports of being affected by contagious yawning did not match behavior shown by adults with ASD. Behavior could have been masked by factors such as anxiety, or there could be a general dissociation between feelings and behavior. Other people rely on our expressive behavior during interactions and a lack of matching behavior by adults with ASD could evoke discomfort in others, further contributing to difficulties in social communication. If this is true it would support the targeting of socially embedded imitative behavior in interventions.