Low-level motor inhibition in children:Evidence from the negative compatibility effect

The masked prime task was used to investigate low-level inhibitory motor control processes in two groups of children (7-8 years and 11-12 years) and in older adolescents/young adults (16-23 years). Masked prime stimuli, presented below the level of conscious awareness, systematically affected reaction times (RTs) to subsequent supraliminal target stimuli: RTs were longer when prime and target were mapped to the same response than when they were mapped to different responses. This negative compatibility effect did not differ significantly between age groups, consistent with the hypothesis that the underlying low-level inhibition processes are already fully developed in children as young as seven years of age. In contrast, performance differences between response repetition and response alternation trials were significantly larger in children, consistent with the hypothesis that higher-level control processes are less effective in children. Results provide converging evidence that whereas the latter processes are mediated by late-maturing (prefrontal cortical) areas, the former processes are mediated by earlier-maturing (possibly subcortical) structures.