Researchers from Japan and New Zealand have found that children with attention-deficit hyperactivity disorder (ADHD) adjust their behavior to changing positive reinforcements less than children without ADHD. This may help to explain the difficulty children with ADHD have in adapting their behavior to new situations with different reinforcement patterns in daily life.
“One of the most consistent findings has been that children with ADHD are more likely to choose smaller immediate rewards over larger delayed rewards in choice delay and temporal discounting,” wrote Brent Alsop, PhD, from the Department of Psychology at the University of Otago in Dunedin, New Zealand and colleagues. “[However], fewer studies have evaluated the effects of reward availability on behavior allocation in children with ADHD; that is, the extent to which children’s responses on a task are distributed according to reinforcer availability. In these studies, the contingencies are not made explicit and children learn about them through their actions.”
The researchers recruited 167 children for the study; 97 of them met DSM-IV diagnostic criteria for ADHD (72% boys), and 70 of them were typically developing children (59% boys). Within the ADHD group, 47 children were diagnosed with inattentive type, and 50 with combined type ADHD.
The researchers had the children sit in front of a computer screen upon which a grid of 10 x 10 red and blue cartoon faces would appear. The children were instructed to press the appropriate button to indicate whether there were more red or blue faces on the screen, and that sometimes, but not every time, the correct answer would earn them the reward of a token. The goal was to collect as many tokens as possible to win a prize at the end of the session. (All children were given prizes at the end of the session regardless of their performance.)
The experiment had several alternating phases in which blue, then red, then blue produced 4 times the number of rewards compared with the other. The children were not told of these changing reward patterns.
The researchers found that in cases where it was difficult to tell whether there were more red or blue faces on the screen, the children with ADHD were less likely to adapt their behavior to changing reward patterns (ie, to select the color more likely to give a reward) compared with children without ADHD.
“This is not because of an overall lack of sensitivity to positive reinforcement,” the authors wrote. “Like the children in the control group, those with ADHD developed an initial bias toward the more frequently reinforced alternative. When the ratio of available reinforcement for correct discriminations was switched, children in the ADHD group initially showed some shift in their bias away from the previously more reinforced alternative; however, this shift was significantly smaller than seen in the control group. This indicates poorer behavioral adaptation to changing reinforcement contingencies in children with ADHD.”
In addition, the children with ADHD had bias scores that remained low for the remainder of the task, suggesting that they had a more random response allocation when uncertain of the correct response, instead of choosing the alternative that provided the higher frequency of rewards. “These results may reflect reduced motivation for seeking reinforcement; that is, a reduction in the effect of the reinforcers on response allocation over time,” the researchers wrote. “Or [it may indicate] difficulty tracking reinforcement availability following unannounced contingency changes.”
Summary & Clinical Applicability
Researchers found that children with ADHD changed their behavior in response to positive reinforcement patterns less than children without ADHD, which may indicate either that children with ADHD have reduced motivation to seek positive reinforcement, or that they have more difficulty in recognizing unannounced changes in positive reinforcement patterns.
“Explicitly informing and reminding children of the reinforcement contingencies operating, and when [they] change, may help them better match their behavior to situational demands,” the researchers concluded.
“Continued efforts to understand the nature and complexity of altered reward sensitivity in ADHD remain a research priority to inform best practices.”
Limitations & Disclosures
The researchers noted that children in the ADHD group were recruited through 2 university research clinics in 2 different countries, while those in the control group were recruited from only one of these countries. This may introduce a confound to the data.
However, the same diagnostic and inclusion criteria were applied at both sites, and all assessments were supervised by the same senior author.
The researchers also noted that when the analyses were repeated to include only participants recruited in New Zealand, the study findings remained unchanged.
Alsop B, Furukawa E, Sowerby P, Jensen S, Moffat C, Tripp G. Behavioral sensitivity to changing reinforcement contingencies in attention-deficit hyperactivity disorder. J Child Psychol Psychiatry. 2016. doi:10.1111/jcpp.12561. [Epub ahead of print]