Autism’s Chicken – or –Egg Dilemma: Social Difficulties or Restricted Interests


When it comes to two of the core symptoms of autism spectrum disorder (ASD), diminished social interest and restricted and repetitive interests, researchers have long puzzled over which comes first – are children with diminished social interest more likely to engage in restricted and repetitive interests? Or, are restricted and repetitive interests more enjoyable than social interaction, leading to a diminished interest in social interactions?

The answer to this chicken-or-egg dilemma may lie in what scientists call the social motivation hypothesis. This hypothesis proposes that social difficulties in ASD are partially due to reduced activity in the brain’s reward system when responding to social information. According to this model, beginning early in life, a child with ASD pays less attention to people and faces and therefore has fewer chances for social interaction. As this cycle continues, the child does not build the same set of social skills and abilities as a typically developing peer. The child does not find social interactions rewarding, and so is unmotivated to seek them out, according to this hypothesis.

While this hypothesis originated several years ago, brain imaging science has had a difficult time delivering scientific proof, with multiple studies yielding contradictory results. A new study published this month in JAMA Psychiatry by researchers at Children’s Hospital of Philadelphia (CHOP) and the University of Pennsylvania (UPenn) is the first to make sense of the conflicting findings of previous research.

The research team, led by CAR’s Caitlin Clements, applied a new method of data analysis to synthesize the findings from more than a dozen previous fMRI studies. The results lent conclusive support for the social motivation hypothesis. Using 13 studies, with 259 individuals with ASD and 246 individuals without ASD, the analysis found differences in how the brains of individuals with and without ASD respond to social stimuli ( eye contact, a smile), non-social stimuli (winning money or points), and restricted interests (seeing a favorite object or video). Specifically, individuals with autism show less activity in the brain’s reward center in response to both social and non-social stimuli. In addition, people with autism had greater activity in the brain’s reward center in response to images or movies of restricted interests (trains, computers, etc.)

Clements, a UPenn doctoral candidate and researcher at the Center for Autism Research at CHOP, commented on the findings, “Where social stimuli would typically elicit an increase in the reward center of a person’s brain, our study showed the opposite in individuals with autism. However, we did see an increase in reward activation in response to restricted interest stimuli, providing a basis of support for the social motivation hypothesis”. Building off the work of her CAR colleague, Dr. Benjamin Yerys, Clements’ research would in fact be the strongest empirical evidence to date demonstrating the social motivation hypothesis using brain imaging science. Clements’ says clinically, “The findings of this study point to the importance of interventions where children develop the motivation, rather than solely the skills, for social interaction”.