Distractor Inhibition in Attention: An investigation into the influences of stimulus location predictability and distractor intensity

The present body of research explores some of the key conditions that influence the contribution of distractor inhibition to selective attention. In particular, the present experiments addressed three questions: (1) whether distractor inhibition is facilitated by foreknowledge of the location of a distractor; (2) whether distractor inhibition strengthens to compensate for disruption in target amplification that is caused by the target having an unpredictable location; and (3) whether distractor inhibition is strengthened by stronger processing of the distractors that is caused by the distractor being presented closer to or brighter than the target. Each of the present experiments employed a variation of Machado, Wyatt, Devine and Knight’s (2007) variable flanker task. By presenting the distractor in advance of the target, distractor interference could be measured at short intervals (via the positive compatibility effect), and distractor inhibition could be measured at longer intervals (via the negative compatibility effect). The results showed that distractor inhibition does not strengthen when the location of the distractor is known in advance; instead, advance knowledge of location can be used to apply inhibition at the appropriate level. Furthermore, distractor inhibition does not strengthen to compensate when a variable target location disrupts target processing, but weak inhibitory processing can be revealed in the presence of weaker target processing. Additionally, the strength of distractor inhibition was found to be controlled reactively, such that it strengthened when the distractor stimuli were intensely processed. These results indicate that the strength of distractor inhibition is determined not only by the physical characteristics of distractor stimuli, but also by top-down factors. As such, the present data suggest that the control of distractor inhibition is more complex than currently envisioned, and more research is required in order to fully understand the effect of advance knowledge of distractor stimuli on inhibition