The social-motivation hypothesis in the world of autism research says that someone with autism spectrum disorder (ASD) finds social stimuli less rewarding than someone developing typically. In other words, these individuals may pay less attention to facial expressions and gaze, which may then lead to fewer peer interactions and collaborative play and eventually, overall social deficits.
Attempts to confirm this hypothesis have been conducted using brain scans taken while people receive different types of rewards. But results to date have been mixed. Doctoral students Caitlin Clements and Lisa Yankowitz of the University of Pennsylvania and the Children’s Hospital of Philadelphia wanted to understand why, so they conducted a meta-analysis of 13 studies that comprised 259 people with ASD ranging in age from 9 to 38.
Clements and Yankowitz, part of Penn’s Psychology Department in the School of Arts and Sciences and CHOP’s Center for Autism Research, found strong support for the idea that the brain’s reward circuitry of a person with autism looks different from that of a typical individual. They confirmed that this wasn’t limited to social stimuli but happened with non-social stimuli, too.
Penn Today spoke with the researchers about these findings, which they recently published in the journal JAMA Psychiatry.
Can you explain the social motivation hypothesis?
Clements: In a nutshell, the social motivation hypothesis posits that from a very young age, infants who pay less attention to social information like faces or where people are looking miss out on opportunities to develop social skills. Over time, these deficits cascade into the cluster of social difficulties that we know as ASD, which include showing less interest in making and maintaining friendships or engaging in conversation.
Why did you do a meta-analysis of existing studies to answer some of these questions?
Clements: A meta-analysis allows you to aggregate the current evidence out there and analyze it altogether. You can see why there are differences in findings from some studies compared to other studies, and by putting them together, you can, in theory, figure out what the truth is.
In your JAMA Psychiatry paper, you write that the reward circuitry in the brain of someone with autism reacts differently to both social and non-social stimuli than someone developing typically. How can you tell?
Yankowitz: Neuroimaging techniques like functional MRI provide us insight into what areas of the brain are most active while someone is thinking or looking at something, and we can’t get that information just by watching how fast or accurate someone is at completing a task. In our case, we gained insight into how the brains of people with ASD respond to rewarding information. Clements: There are several areas that communicate and compose what we think of as the reward circuit in the brain, and all of those parts of the brain work together and show changes in activation in response to rewarding stimuli.
What does this mean in the context of social cues?
Clements: When we looked at how the brain responds to social stimuli in people with ASD, we saw less activation in the parts of the brain that we expect to be triggered by the sight of something rewarding, like someone smiling at them or giving them thumbs up or looking happy.
What about non-social cues?
Clements: A non-social stimulus could be a game the participants play that gives them the opportunity to win money, say 5 cents a few times per minute. Winning the money should activate parts of the reward circuit in the brain. But we saw the same response as to social stimuli: diminished activation in the reward circuit compared to people who don’t have ASD. So this led us to the conclusion that people with ASD show less activation in their reward circuit to social and non-social stimuli compared to people without ASD.
What stands out to you about these results?
Clements: Though we’re not the first to make the claim that people with ASD show diminished activation in the reward circuit to social and non-social stimuli, our study used the most robust methods and the largest sample to date. We had 259 people with autism in the full analysis; each study individually included only 10 to 40 participants with ASD. Yankowitz: I want to add that a major goal in our field is improving reproducibility. We’re looking for effects that stand the test of time. Meta-analysis lets you re-analyze all previous results together and see which findings are strongest and most consistent. This paper shows how consistent the previous reward-processing results were when you look at them across samples and researchers.
How might these findings actually change treatment for individuals with ASD, or for clinicians treating such patients?
Yankowitz: It won’t immediately. There are absolutely some additional studies that would need to be run before this work would translate directly to clinical practice. But what’s nice about this work is that though it’s not testing a particular intervention, it tests a hypothesis that motivation is one of the driving factors developmentally in the manifestation of ASD. Motivation is an important part of several ASD interventions, and I hope this evidence spurs clinicians to think about new ideas for treatment, and to think about what existing treatments we have and who they work for. Clements: The primary evidence-based treatment for young children with ASD is applied behavioral analysis. This comes in a number of different packages, but all have at their core rewards for desired behavior. An example is if the child is on task and doing what she’s supposed to, she receives a Cheerio or a point, and once she gets 10 points, she gets extra screen time. A lot of treatments rely heavily on positive reinforcement.
But your work has shown that some children simply may not react to such efforts?
Clements: Right. Children with ASD might respond a little differently to rewards and that could explain why our treatments don’t work for everyone. There are almost always kids in a clinical trial who the treatment doesn’t work for, even if overall, it looks effective. And we now know that child might have differences in how her brain is responding to rewards. She doesn’t want to work for a Cheerio or five minutes of screen time. That’s not how her brain works.
Caitlin Clements is a fifth-year doctoral candidate and Lisa Yankowitz is a third-year doctoral candidate in the Department of Psychology in the School of Arts and Sciences at the University of Pennsylvania and the Center for Autism Research at the Children’s Hospital of Philadelphia. Funding for the research came from the National Science Foundation Graduate Research Fellowship Program’s Grant DGE-1321851.
