A recent study found that the degree to which a person possesses autistic traits is linked to how their brain processes social rewards compared to nonsocial ones. The researchers discovered that lower connectivity between specific brain areas helps explain why people with more autistic traits often show less behavioral preference for social images. These findings were published in Personality Neuroscience.
Everyday life is filled with rewards that shape human behavior. Some rewards are purely physical or material, like a delicious slice of cake or finding money on the street. Other rewards are social, such as a warm smile from a friend or the collective joy of a family gathering. Research shows that people typically show a strong preference for social rewards right from infancy.
These social rewards remain important throughout life because they help people navigate relationships and build cooperative communities. However, individuals differ widely in how much they value social stimuli. Clinical observations and behavioral tests often show that autistic people possess a reduced preference for social rewards compared to those who are not autistic. Yet, the underlying brain architecture that explains these differences remains poorly understood.
Most brain imaging experiments tend to look at social or nonsocial rewards in isolation rather than comparing them directly. The few studies that do compare them often use artificial images, like cartoon faces, which do not reflect real life. Other studies use real pictures but fail to balance the visual brightness and contrast between the two categories. This makes it difficult to tell if brain differences are driven by the social content itself or just by a brighter image.
To bridge this gap, Anthony Haffey, Chun-Ting Hsu and Bhismadev Chakrabarti set out to investigate how the brain responds to these categories. Haffey and Hsu are researchers currently or formerly affiliated with the University of Reading in the United Kingdom, while Chakrabarti holds positions at the University of Reading and institutions in India. They wanted to see if the brain regions that recognize social situations and those that process reward value communicate differently depending on a person’s level of autistic traits.
To test this, the research team designed an experiment using functional magnetic resonance imaging. This technology measures brain activity by detecting changes associated with blood flow. When an area of the brain is active, it requires more oxygen, which the scanner can observe in real time. The researchers recruited 37 adults from a local university population to participate in the imaging sessions.
Instead of gathering people with formal autism diagnoses, the team measured autistic traits across the general population. Autistic traits exist on a spectrum, meaning people without a clinical diagnosis still possess varying degrees of characteristics associated with autism. These traits can include a preference for routine, intense focused interests, or differences in social communication. The participants completed a standard 50-item questionnaire designed to measure these traits.
During the brain scanning sessions, the participants looked at a series of photographs while lying still in the machine. Half of the pictures featured social rewards, such as happy adults or children at a wedding or a sporting event. The other half depicted nonsocial rewards, including appealing foods, beautiful scenery and money. The research team edited the images to ensure they matched in brightness, contrast and general visual salience.
The participants were instructed to simply press a button each time an image or a blank fixation cross appeared on the screen. This simple task ensured that they remained awake and attentive during the entire scanning session without requiring them to make complex decisions. By matching the visual properties, the researchers could be confident that any differences in brain activity were due to the content of the image.
Outside the scanner, the participants also rated how happy or rewarding they found each image on a scale from one to nine. This provided a behavioral measure of their preferences to compare against the neurological data.
On a behavioral level, the study revealed that participants with higher scores on the autistic trait questionnaire rated the social images as less rewarding. They did not show this same reduced enthusiasm when viewing the nonsocial images. This pattern aligns with previous behavioral studies noting a decreased preference for social rewards among individuals on the autism spectrum. The brain scan data offered a deeper look into why this behavioral difference exists.
The researchers focused on how different brain regions communicated with each other during the task. This concept, known as functional connectivity, looks at whether different parts of the brain activate in a synchronized way. If two brain areas light up together consistently, scientists assume they are sharing information. The team specifically examined the connection between the left fusiform gyrus and the anterior cingulate cortex.
The fusiform gyrus is an area in the lower visual system known for recognizing faces and human bodies. The anterior cingulate cortex is a deeper brain structure that helps assign value to a reward. Normally, these two regions show synchronized activity when a person looks at a positive social image. However, the researchers found that participants with higher autistic traits had weaker connectivity between these two areas.
The visual processing center and the reward valuation center were not communicating as strongly in these individuals. A similar pattern emerged in another pair of distinct brain regions. The left anterior insula is an area involved in processing internal physical sensations and social norms. The medial orbitofrontal cortex is located near the front of the brain and is heavily involved in calculating the basic reward value of an experience.
The researchers observed that connectivity between the anterior insula and the orbitofrontal cortex was also weaker in individuals with more autistic traits. A statistical evaluation called a mediation analysis showed that these weaker connections fully explained the behavioral differences in social preference. The human brain relies on a vast network of connections, and a reduction in a specific pathway can profoundly alter how a person experiences the world.
The reduced neural communication essentially mapped directly onto the lower ratings participants gave to the social images. When the visual and internal sensation areas fail to communicate fully with the reward processing areas, a smile or a happy crowd might simply not register as a highly positive experience. The brain still sees the face and understands the context, but the internal signal marking the event as rewarding is diminished.
While the study provides observational insight into the brain mechanics of social reward, the researchers noted a few limitations. The images used in the study were static photographs of strangers taken from the internet. While this setup is more realistic than using simple artificial figures, it still lacks the richness of a true social interaction. A picture of a smiling stranger is completely separated from the participant’s actual life context.
The study also relied on self-reported questionnaires to measure autistic traits in the general population. Self-reports can be influenced by cultural backgrounds or gender expectations, which might skew the data. A person’s subjective view of their own personality might not fully capture their neurological reality. The researchers advocate for using more objective behavioral tasks to measure these traits in the future.
The research team suggests that future experiments should use larger groups of participants to allow for the analysis of potential sex differences in reward processing. They also recommend including individuals with formal clinical diagnoses of autism to see if similar neural patterns appear at the higher ends of the spectrum. Additionally, future tests might benefit from using more engaging, interactive scenarios rather than passive image viewing. This could help capture the reality of how human brains process rewards in dynamic environments.
The study, “Autistic traits modulate neural and behavioral responses to social vs nonsocial rewards,” was authored by Anthony Haffey, Chun-Ting Hsu, and Bhismadev Chakrabarti.