Category: ADHD - Child
Shifting, or cognitive flexibility, is a core executive function (EF) involving the ability to flexibly shift back and forth between tasks or mental sets (Miyake et al., 2012). Shifting is associated with academic performance and social competence – two of the three primary areas of functional impairment exhibited by children with ADHD (Benedetto-Nasho & Tannock, 1999; Kofler et al., 2015). Meta-analysis suggests that shifting may be impaired in ADHD (d = .46-.55; Willcutt et al., 2005). However, this conclusion may be premature because 100% of studies reviewed used shifting tasks that have been criticized for poor construct validity and may better reflect general EF rather than shifting specifically (Snyder et al., 2015). The aim of the current study was to examine set shifting in children with ADHD, using an experimental design that provided robust control for non-shifting processes involved in completing shifting tasks. It was hypothesized that shift costs would be significantly higher during a criterion shifting task relative to two counterbalanced control tasks that were identical except for the primary DV (shifting). We further expected shift costs would be significantly larger in the ADHD group (i.e., ADHD-related impairments in shifting).
The current study used the global-local task (Miyake et al., 2000) and two non-shifting control variants (global-global, local-local) to provide systematic examination of shifting in a well-characterized sample of children ages 8-13 with ADHD (n=33) and without ADHD (n=32). RT shift costs were calculated separately for each task by subtracting mean reaction times (RT) on no-shift trials from mean RT on shifting trials. Performance shift costs were calculated by subtracting number of errors on no-shift trials from number of errors on shift trials.
Results of the 2x3 ANOVA for RT shift costs revealed that the experimental manipulation was successful (task main effect, p < .001, ω2 = .13), such that the global-local task elicited greater RT shift costs than did the control conditions. However, there was no evidence of shifting deficits in ADHD as demonstrated by a non-significant group main effect (p = .21) and a non-significant interaction between task and group (p = .65). In contrast, the 2x3 ANOVA for performance shift costs revealed a significant group by task interaction (p = .014; ω2 = .04) and group main effect (p = .016; ω2 = .07). Contrasts revealed that the ADHD group demonstrated significantly more errors than the Non-ADHD group, but only during the shifting task (p = .015; p = .018). Taken together, these results indicate that children with ADHD exhibit impairments in accuracy but not speed when required to flexibly shift between two competing rule sets. Implications will be discussed.
Lauren Irwin– Florida State University, Tallahassee, Florida
Erica Wells– Graduate Student, Florida State University, Tallahassee, Florida
Elia Soto– Clinical Psychology Graduate Student, Florida State University, Tallahassee, Florida
Michael Kofler– Florida State University
Clinical Psychology Graduate Student
Florida State University