Self-regulation is a complex process requiring awareness of contextual demands, self-monitoring of one’s behavior to evaluate whether it is appropriate for a context, and adjusting behavior when necessary. Impairments in self-regulation may result in developmentally inappropriate inattentive, hyperactive and impulsive behaviors that define Attention-Deficit/Hyperactivity Disorder (ADHD) (Sergeant, 2000
). Regulatory deficit models better account for the variability which characterizes individuals with ADHD. However, the nature of the self-regulatory deficit in ADHD remains unclear.
Adaptive behavior is an important component of self-regulation. Within the context of a cognitive task, post-error slowing or slowing of response speed on a trial following a commission error is thought to reflect adaptive behavior at a very basic level (Rabbitt, 1966
). When an individual performs an action that is inconsistent with the demands of a situation, an awareness of this inconsistency (e.g., error) and initiation of adaptive control processes to alter behavior may contribute to slowing of a response to increase the likelihood that performance will be improved. Similarly, errors often occur when an individual does not take the time required to ensure an accurate response. Therefore, response slowing on a trial following an error is a form of adaptive behavior. Improving our understanding of post-error slowing at the cognitive level may elucidate the components of self-regulation and whether this process is disrupted in ADHD.
The literature examining post-error slowing in children with ADHD has produced somewhat mixed results with some studies reporting diminished post-error slowing in ADHD (e.g., Schachar et al., 2004
; Wiersema, van der Meere, & Roeyers, 2005
) whereas other studies found comparable post-error slowing for ADHD and control groups (e.g., Groom et al., 2009
; O'Connell, Bellgrove, Dockree, & Robertson, 2004
; van Meel, Heslenfeld, Oosterlaan, & Sergeant, 2007
). This is surprising as deficient adaptive behavior is theoretically implicated in ADHD as a component of impaired self-regulation (Sergeant, 2000
). Inconsistent results for post-error slowing in the ADHD literature may be affected by characteristics of the sample (e.g., age range, comorbid conditions, ADHD subtype), characteristics of the task (e.g., cognitive demands, event rate), or the type of error (e.g., inhibition versus discrimination errors).
Another important factor to consider is the way in which post-error slowing is quantified. The majority of studies have compared the mean reaction time (RT) for correct trials following an error versus all other trials. However, if post-error slowing is adaptive following the impulsive response that produced the error, comparing post-error RT with the pre-error RT may provide a more sensitive measure of adaptive behavior. Participants may have slowed their response on the post-error trial compared to the pre-error RT, which tends to be relatively fast. Only one study measured post-error slowing by evaluating the difference between pre-error and post-error RTs and they reported equivalent post-error slowing in ADHD and control children (O'Connell et al., 2004
). Further, it may be critical to exclude pre-error RTs from the correct RT mean since these have been shown to be faster than the mean correct RT (Epstein et al., 2010
). Thus, excluding pre-error RTs from the correct RT and examining the two separately may be important since not doing so may reduce the correct RT and inflate the post-error slowing difference. In addition, isolating these RT components may provide information about whether ADHD is associated with an impulsive response style (e.g., pre-error speeding), impairments in adaptive behavior (e.g., pre- to post-error slowing) or both.
The current study builds on previous work by examining post-error slowing on two cognitive tasks, a Choice Discrimination Task (CDT) and Stop Signal Task (SST), in a large sample of children with ADHD-Combined type (ADHD-C), ADHD-Inattentive type (ADHD-I), and typically developing controls. Furthermore, a novel analytic approach was applied to examine post-error slowing, isolating the contributions of pre-error, post-error, and correct RTs. We hypothesized that pre-error speeding and pre- to post-error slowing would be evident across both tasks and post-error slowing would be diminished in children with ADHD, regardless of subtype.