Modulation of response activation leads to biases in perceptuomotor decision making

Humans are constantly enacting motor responses based on perceptual judgments or decisions. Recent work suggests that accumulating evidence for a decision and planning the action to enact the decision are coupled. Further, decision commitment may occur when the action reaches its motor threshold. Across several experiments, this coupled perception-action account of perceptuomotor decision making was tested by determining if increasing response activation corresponding to one decision influenced the evidence needed to make that decision. Participants were presented with stimuli that contained varying ratios of yellow-to-blue squares and made a speeded left/right-hand response to report whether the stimulus had more yellow or blue squares, respectively. Response activation was modulated by presenting stimuli laterally on the screen-spatially compatible or incompatible with the color reports. When stimuli appeared leftward (spatially compatible with a left response/"yellow" report), the threshold for a "yellow" perceptuomotor decision was reduced-consistent with the hypothesis that increasing "yellow" response activation would lead to a "yellow" reporting bias. Further, when stimuli appeared rightward (spatially compatible with a right response/"blue" report), the threshold for a "blue" perceptuomotor decision was reduced. An additional experiment revealed that directional saccades occurring during the task were unlikely to account for biases. Overall, spatially induced response activation influenced the decision outcomes, providing support for a tightly coupled perception-action system underlying perceptuomotor decisions. (PsycInfo Database Record (c) 2023 APA, all rights reserved).