Distraction vs. Interference: Handling fully irrelevant vs. potentially relevant distractors

In a series of studies (Manini et al., 2021), we investigated how task performance is affected by fully irrelevant distractors (i.e. sharing neither features nor space with the target) vs. potentially relevant distractors (i.e. sharing features and space with it) as a function of the search context/perceptual load. Although the effects of both kinds of distractor would fall within the notion of attentional capture, we observed a systematic dissociation between the two types of captures: whereas the effect of the potentially relevant distractor was larger for high perceptual demands (i.e., feature search), no difference was observed for the fully irrelevant distractor as a function of task demands. The present study aimed to further investigate the robustness of the double dissociation observed in Manini et al. (2021), investigating which variables could modulate it and comparing the effects of each distractor more fairly. In Experiment 1, we successfully observed a fully double dissociation between the effects of each distractor type: larger effect of the potentially relevant distractor for high perceptual demands, and larger effect of the fully irrelevant distractor for low perceptual demands. To further test the robustness of this dissociation, we conducted three additional experiments manipulating variables such as stimuli time exposure, load presentation (within vs. between blocks), and distractor predictability. Despite these variations, a consistent difference between the effects of relevant and irrelevant distractors was observed. Importantly, in the final experiment, we directly compared the two distractor effects, confirming that each type of distractor interacts differently with search context / perceptual load. Overall, our findings support the existence of qualitatively different processes: distraction (of the fully irrelevant distractors) and interference (of the potentially relevant distractors), as a result of the interaction between distinct attentional mechanisms.