1072In order to achieve successful target selection, attention should be paid to the object that matches the target template, and the distractor should be ignored. However, the distractor is not simply kept unprocessed. The effect of negative priming (NP) refers to the observation that, when a distractor is repeated as the target, the response to the target is slower than that in the control condition (Tipper, 1985;Tipper & Cranston, 1985; for reviews, see Fox, 1995;May, Kane, & Hasher, 1995;Neill, Valdes, & Terry, 1995). The NP paradigm is used widely to investigate the underlying processes and aftereffects of selective attention.However, one question pertaining to NP has not yet been completely resolved: If this phenomenon merely reflects the aftereffect of attentional selection, why are probe distractors required to observe the NP effect? A typical NP task comprises couplets of prime and probe displays. In the ignored repetition (IR) condition, the prime distractor is repeated as a probe target; in the control condition, the prime stimuli are not repeated in the following probe trial. NP is measured as the difference in reaction times (RTs)-and sometimes in error rates (ERs)-between the control and IR conditions. It has been demonstrated that, when the distractor was absent during all the probe displays, the NP effect was eliminated (Lowe, 1979;Milliken, Joordens, Merikle, & Seiffert, 1998;Tipper, Brehaut, & Driver, 1990;Tipper & Cranston, 1985). With a Stroop color-naming task, Lowe's Experiment 4 demonstrated that identity NP was eliminated when there was no probe distractor word. In fact, an effect of positive priming was found when the probe distractor word was replaced by the color patch (23 vs. 21 msec). In a letter-naming task, Tipper and Cranston observed significant NP when the probe distractor was present ( 17 msec). However, response in the IR condition was faster than that in the control condition (14 msec) when the probe distractor was consistently absent. In a word-naming task, Milliken et al. (1998) also found significant NP when the probe distractor was present ( 8 msec), but they observed significant positive priming (5 msec) when the probe distractor was consistently absent. These findings are theoretically important and provide interesting insights into the NP phenomenon.
Distractor Competition HypothesisAccording to a computational model of the inhibition account of NP (Houghton & Tipper, 1994), the effect of distractor inhibition is manifested during a competition between a probe target and a probe distractor. If there is no such competition (i.e., when the probe distractor is absent), it should be easy to respond to the target. As a result, the NP effect should not surface.The study of probe distractor competition can support this hypothesis. According to the distractor competition hypothesis, NP is manifested only when the probe distractor is competitive. In other words, even when the probe distractor is present, if it is not competitive, NP should not be observed. To test this predict...