The Effect of Colour on Response Execution and Inhibition in the Stop Signal Paradigm

Recent investigations have shown that smooth pursuit target selection is biased according to a hierarchy of red, green, yellow, and blue (e.g. red is always selected over green). This implies that colours higher on the hierarchy have greater attentional salience. Using the stop signal task, we conducted experiments in which go signal colour was manipulated (exps. 1 and 2) and in which stop signal colour was manipulated (exp. 3) to determine whether the hierarchy also applied to response execution and inhibition. When colour was either irrelevant (exp. 1) or relevant (exp. 2) to response execution there was no effect on reaction times or individual RT variance. When colour was relevant to response inhibition (exp. 3) estimated stop signal reaction times were significantly faster for red (~225ms) relative to green (~250ms) stop signals. This suggests that response inhibition, but not execution, networks are sensitive to differences in colour salience.