Reach tracking reveals dissociable processes underlying inhibitory control in 5- to 10-year-olds and adults

Abstract

Researchers have proposed that two processes featuring distinct types of inhibition support inhibitory control: a response threshold adjustment process involving the global inhibition of motor output and a conflict resolution process involving competitive inhibition among co-active response alternatives. To target the development of these processes, we measured the reaching behavior of 5- to 10-year-olds (Experiment 1) and adults (Experiment 2) as they performed an Eriksen flanker task. This method provided two key measures: initiation time (the time elapsed between stimulus onset and movement onset) and reach curvature (the degree to which a movement deviates from a direct path to the selected target). We suggest that initiation time reflects the response threshold adjustment process by indexing the degree of motoric stopping experienced before a movement is started, while reach curvature reflects the conflict resolution process by indexing the degree of co-activation between response alternatives over the course of a movement. Our results support this claim, revealing different patterns effects in initiation time and curvature, and divergent developmental trajectories between childhood and adulthood. These findings provide behavioral evidence for the dissociation between global and competitive inhibition, and offer new insight into the development of inhibitory control.

Figure 1.

Example of an incongruent stimulus array in the flanker task.

Figure 2.

Illustration of a congruent trial in the flanker task presented in Experiment 1. Participants were instructed to respond by touching the target location cued by the centermost fish in the stimulus array.

Figure 3.

Children’s average error rate displayed as a function of current trial congruency (C, I), previous trial congruency (c, i), and response type (change, repeat). Error bars display standard errors.

Figure 4.

Children’s average error rate (A), initiation time (B), and curvature (C) as a function of current trial congruency and age group. Inaccurate trials are included in the averages (see text for details). Error bars display standard errors.

Figure 5.

Children’s average initiation time displayed as a function of current trial congruency (C, I), previous trial congruency (c, i), and response type (change or repeat). Error bars display standard errors.

Figure 6.

Children’s average reach curvature displayed as a function of current trial congruency (C, I), previous trial congruency (c, i), and response type (change, repeat). Error bars display standard errors.

Figure 7.

Adults’ average initiation time displayed as a function of current trial congruency (C, I), previous trial congruency (c, i), and response type (change or repeat) for adult participants. Error bars display standard errors.

Figure 8.

Adults’ average reach curvature displayed as a function of current trial congruency (C, I), previous trial congruency (c, i), and response type (change or repeat) for adult participants. Error bars display standard errors.