Redundancy effects of a moving distractor generated by alerting and orienting

Redundancy effects refer to improvement of performance in response to irrelevant stimulation, or distractors. Previously described redundancy effects have mainly been associated with relatively high-level perception. The present study examines whether redundancy effects exist in basic attentional and perceptual systems, such as alerting and orienting. Participants performed speeded detection of briefly presented targets while ignoring moving distractors. The presence/absence of distractors and their spatial relationships with targets were manipulated to dissociate possible alerting and orienting redundancies. The distractor pathway (straightforward vs. chaotic) and its motion predictability (blocked vs. intermixed sequences of straightforward and chaotic trials) were also manipulated. The presence of a distractor resulted in faster responses (alerting redundancy). Furthermore, participants responded faster to targets behind distractors (orienting redundancy). Orienting redundancy was found only in the straightforward condition. This indicates that generating an orienting redundancy effect is a relatively slow process based on continuous observation of motion. Lastly, a blocked sequence of trials improved the alerting redundancy effect in comparison with an intermixed sequence.