Proportional Slowing or Disinhibition in ADHD? A Brinley Plot Meta‐analysis of Stroop Color and Word Test Performance

Abstract

A meta‐analysis in the form of Brinley plots was conducted on the mean reaction times of Attention Deficit Hyperactivity Disorder (ADHD) and Control groups of children and adolescents on the Stroop Color and Word Test (SCWT). ADHD reaction times were regressed on Control group reaction times for 17 data sets (accessed from 13 published studies). These analyses yielded linear functions (mean r2 = 0.997), with slopes typically greater than one (mean b = 1.288). The response time thus increases systematically by an inflation factor of approximately 29% in ADHD children and adolescents relative to increases in their Control peers across the three conditions of the SCWT. In additional analyses, for each Brinley plot, the deviation from the linear regression line of the data point for the critical Color‐Word condition was also calculated. There was only modest evidence that a deficit in inhibition exerts any influence on performance in this condition over and above that of general slowing for children and adolescents with ADHD. These results support the notion that a general slowing hypothesis provides a more parsimonious account of ADHD reaction times on the SCWT than that provided by the inhibition account previously thought to underpin findings in this area.