A salient distractor does not disrupt conjunction search

Leading theories of attention posit that bottom-up and top-down factors sim ultaneously affect attentional priority in visual search. Recent evidence, however, suggests that subjects may rely exclusively on top-down guidance w hen searching for a target defined by a specific known feature (Bacon & Ege th, 1994). In the present experiment, we addressed this issue in a conjunct ion search task. We investigated how searching for a green O among green Ts and red Os is affected by the presence of a distractor with a unique shape (green X), color (blue O), or both (blue X). We showed that the salient di stractor does not disrupt performance on target-present trials, but produce s a large interference on target-absent trials. We conclude that salience-b ased and top-down processes are alternative modes of guidance, rather than joint contributors in the allocation of attentional priority.