Temporal dynamics of saccadic distraction

Abstract

The saccadic distractor effect, in which irrelevant stimuli delay saccades to target stimuli, is a popular tool for investigating saccadic competition. Here, we outline the main components of a competition framework to account for the temporal dynamics of the distractor effect, inspired by race models of saccade generation. We first test a key prediction of this framework: the degree of interference should depend upon the degree of temporal overlap of target and distractor signals in the competition stage, which will vary systematically with the relative processing speeds of the competing visual signals. In agreement with this, we found that, when varying the contrast of distractor stimuli, the presentation delay between target and distractor that maximizes interference varies systematically for different target-distractor pairs, correlated with the difference in saccadic latency for the pair. Second, our data illustrate a crucial methodological point: when comparing the effect of different distractors, measuring at only one time-point (e.g. simultaneity, as most studies have done) can produce misleading and contradictory results. Thus, it is essential to take the temporal dynamics of the system into account. Lastly, the framework predicts that the optimal delay for the latency distractor effect is different from that maximizing error rate, and our data confirms this.