Negative priming effects have been offered as evidence that distractor stimuli are identified. We conducted two experiments to determine if such effects occur even when it is easy to discriminate target from distractor stimuli. In Experiment 1, we found the usual negative priming effect when target and distractor positions varied from trial to trial, but not when these positions remained fixed. Experiment 2 extended these results to a situation where the ease of selection varied only in the prime display. These findings argue that irrelevant inputs can be filtered out prior to stimulus identification under certain circumstances and therefore pose problems for strict late selection theories.
715A central and as yet unresolved issue in the field of selective attention concerns the point at which relevant stimuli begin to be processed more extensively than irrelevant ones. According to strict late selection theories (e.g., Deutsch & Deutsch, 1963), all stimuli are identified regardless of their relevance to the task at hand, but only a subset of these are selected for input to later processes (e.g., response selection). Early selection theories, on the other hand, assert that unselected stimuli are "filtered out" at an early stage of processing, prior to complete stimulus identification. The strongest early selection theories (e.g., Broadbent, 1958) propose that unselected stimuli are discarded prior to identification; however, in weaker versions of such theories, unselected stimuli are attenuated rather than discarded (e.g., Treisman, 1960). In either case, early selection theories predict that relevant stimuli are more likely to be identified than are irrelevant stimuli (which we will call selective identification), whereas strict late selection theories predict unselective identification.To determine whether selective identification is possible in selective attention tasks, many researchers have examined the fate of irrelevant stimuli. The results indicate that such stimuli are processed semantically (i.e., are identified) in many experimental settings (e