Facilitation of simultaneous control? A meta-analysis of the inhibitory spillover effect

Impaired inhibitory control is a core transdiagnostic mechanism in psychopathology. Directly targeting inhibitory control in intervention studies has, however, produced only little improvement. Recently, promising improvements in inhibitory control were shown by capitalizing on the inhibitory spillover effect (ISE). The central requirement of ISE is a simultaneous execution of two tasks, allowing for improved inhibitory control in the target task when control is simultaneously recruited in an induction task. The magnitude of the ISE remains to be assessed. In this preregistered meta-analysis, we synthesized eligible data from studies across psychology with the central requirement of simultaneity; thus, we deliberately included also studies meeting this requirement without the explicit aim to investigate the ISE. Results confirmed previous evidence of the ISE and documented a statistically significant small effect size (g = 0.27). Of the different induction types, cognitive induction showed the largest effects, whereas physiological and attentional induction tasks were less effective. In contrast, motor induction did not result in a significant ISE. Due to high between-study heterogeneity, we analyzed several preregistered and exploratory moderators, out of which only duration of the experimental sequence, group affiliation, and planned investigation of the ISE were significant. Sensitivity analyses yielded no indication of a publication bias. Taken together, this meta-analysis suggests that the ISE is a small, but substantial and robust effect. Future research should investigate how the ISE is applied best to reap its practical value in new treatment approaches for individuals with inhibition impairments. (PsycInfo Database Record (c) 2023 APA, all rights reserved).