Abstract
Irrelevant peripheral visual onsets have consistently been shown to interfere with target processing, a phenomenon attributed to their ability to divert attention from the target. Here we show that in addition to their detrimental effect on performance, irrelevant visual onsets may also facilitate target discrimination. However, this beneficial effect only emerges once habituation mechanisms have fully abolished onset capture. At a 20% onset rate, onsets produced only interference, with capture habituating across blocks of trials. At 50% and 80% rates, a stronger habituation was observed, and once capture was eliminated, onsets began to facilitate performance, as evidenced by faster response times when onsets were present compared to when they were absent. A further experiment demonstrated that visual onsets facilitate performance by allowing temporal expectation about the target moment of appearance, rather than by a generic alerting effect. These findings demonstrate that irrelevant visual onsets trigger two independent processes in the nervous system, resulting in two opposite effects on performance: interference due to attentional capture and facilitation due to temporal expectation. Our results highlight the flexibility of the attentional system in utilizing the same stimulus representation for different purposes, exogenous orienting with subsequent habituation, and temporal orienting, both of which capitalize on stimulus regularities to optimize processing efficiency.