Reward Processing in Children and Adolescents with Autism Spectrum Disorders and Children and Adolescents with ADHD

Background: Children with autism spectrum disorders (ASD) show deficits in their motivational processing, as they seem to be hyposensitive to social reinforcement (Garretson Fein, & Waterhouse, 1990). Some recent fMRI studies in adults with ASD show abnormalities in brain activation during receipt of reward. It seems that the diminished neural responses to rewards are particularly present when social rewards were used (Scott-Van Zeeland et al., 2010). However, abnormal reward processing is not a specific characteristic of ASD, as children with Attention Deficit/Hyperactivity Disorder (ADHD) also display abnormalities in reward sensitivity (Sagvolden et al., 1998). Children with ADHD show an aberrant sensitivity to reward amount (Luman et al., 2005). The abnormal reward sensitivity in ADHD can also be seen in the aversion for delay and delayed reinforcement in children with ADHD (Sonuga-Barke, 2002).

Objectives: In our research, processing of monetary versus social rewards (objective 1) and rewards with varying degrees of delay (objective 2) has been investigated in children with ASD, children with ADHD and a typically developing control group.

Methods: Objective 1: Two adapted versions of the Monetary Incentive Delay Task were used to study the effects of monetary and social reward anticipation on task performance. 40 typically developing control children and adolescents, 31 children and adolescents with ASD and 35 children and adolescents with ADHD participated. All children and adolescents were between 8 and 16 years old and had an estimated full scale IQ of 80 or more. Objective 2: 46 typically developing control participants, 34 participants with ASD and 39 participants with ADHD performed a hypothetical monetary temporal discounting task. They were instructed to make repeated choices between a small variable reward delivered immediately and a large constant reward delivered after a variable delay.

Results: Objective 1: Monetary and social reward improved accuracy and 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 controls, responded faster for monetary than social rewards. Objective 2: Monetary rewards were discounted faster in the ADHD group compared to the controls and the ASD group.

Conclusions: The results while not supporting hyposensitivity to changes in reward amount in ASD and ADHD, do suggest that both groups are generally less motivated in settings where social as opposed to monetary rewards can be earned. On the other hand, unlike participants with ADHD, children with ASD did not show steeper temporal discounting of hypothetical monetary rewards compared to typically developing controls.