Common alterations in sensitivity to type but not amount of reward in ADHD and autism spectrum disorders

Background: Children with attention deficit/hyperactivity disorder (ADHD) display abnormalities in reward processing. Most reward studies have focused on the effects of material or monetary rewards. Studies with autism spectrum disorder (ASD) have focused on social rewards. In this study we compared the effects of amount and type of reward in children with ADHD and those with ASD. Methods: Two adapted versions of the Monetary Incentive Delay Task were used to study the effects of monetary and social reward anticipation on performance in 40 typically developing (TD) children and adolescents (8-16y), 35 children and adolescents with ADHD and 31 children and adolescents with ASD. Results: Monetary and social reward improved accuracy and response time (RT) in all groups. The higher the anticipated reward, the more accurate and faster were responses. Independent of these effects, there was a differential effect of reward type. Both clinical groups, but not TD, responded faster for monetary than social rewards. Conclusions: The results, while not supporting hyposensitivity to changes in reward amount in ADHD and ASD, do suggest that both groups are generally less motivated in settings where social as opposed to monetary rewards can be earned.