Attentional capture by color without any relevant attentional set.

The aim of the present study was to investigate mechanisms underlying attentional capture by color. Previous work has shown that a color singleton is able to summon attention only in the presence of a relevant attentional set, whereas when a color singleton is not useful for a task, evidence for purely stimulus-driven attentional capture is controversial. Three visual search experiments (T-L task) were conducted using a method different from that based on set sizes, consisting of monitoring target-singleton distance in a unique display size. In Experiment 1, we demonstrated that attention can be summoned in a real stimulus-driven manner by an irrelevant color singleton. Experiment 2A extended this observation, showing that the color singleton attracted attention even when capture was detrimental. However, Experiment 2B showed that such capture can be strategically prevented. Finally, in Experiment 3, we examined whether such a capture was due to a spatial shift or to a filtering cost, providing evidence supporting the shift hypothesis. Stimulus-driven capture was observed when color was neither the defining nor the reported target attribute (Yantis, 1993) and when subjects naive of visual search tasks were used. The present results give experimental support to many contemporary models of visual attention.