The effect of visual signals on spatial decision making.

We examined the effect of an irrelevant visual transient on the decision where to look for a hidden object. Participants also performed a conventional 'inhibition of return' localization task. In Experiments 1 and 2 the two tasks were blocked and in Experiments 3 and 4 they were randomly interleaved. In every experiment there was a bias to select the cued location in the spatial decision task. This facilitory effect was greatest when the cue occurred at a strategically unfavored location and even occurred for participants who reported strategically selecting a non-cued location, indicating that the facilitory effect is automatic and independent of other strategic biases. Inhibition of return was observed only when the tasks were blocked and the localization task preceded the decision task. The findings suggests that spatial decisions engage different attentional control settings than those engaged when detecting visual transients; and that this attentional mode affects the processing of visual transients such that they do not inhibit the subsequent speeded detection of onset targets.