The locus and modulation of the location negative priming effect

While Tipper et al. (1990) have shown that the prime-trial distractor object itself would be inhibited, it is clear that object inhibition cannot be the locus or cause of the location NP effect, simply because the prime distractor object does not participate in ignored-repetition trials. Rather, on these occasions, the prime distractor object is replaced by the target stimulus object. Thus, any slowing seen on ignored-repetition trials cannot be the result of the re-appearance of the prime distractor object from one trial to the next.

While the predictable removal of the probe distractor eliminates the location NP effect when the prime trial contains both a target and a distractor (Buckolz et al., 2002a), it does not do so when distractor-only primes are used (not tested for identity tasks) [Guy et al., 2004; Milliken et al., 2000]. Hence, we were able to study the influence of valid response cues when the probe trial knowingly lacked a distractor event. We want to emphasize that probe distractor manipulations do not always influence location and identity NP effects in the same way (e.g., Buckolz et al., 2004a; Guy et al., 2004; Moore, 1994; Neill et al., 1994; Tipper et al., 1990) and so the findings here in this regard are intended to be applied only to the location NP process.

An anonymous reviewer raised the possibility that the need to process cue information between prime and probe trial deliveries, irrespective of its information content (i.e., uninformative vs. informative cues), might have had some unexpected impact on the normal operation of the NP process. Accordingly, we ran a location NP task where the cue event was removed but where the time delay between prime onset and probe offset approximated that used in the cue conditions (i.e., 2,000 ms). A significant location NP effect of 30 ms was obtained [RT(IR)= 504 ms (SD= 98) vs. RT(CO)= 474 ms (SD=85)], t(15)= 3.06, SDD= 39.00, P< 0.01, which compared favourably in size to the NP effect produced with the uninformative cue condition (36 ms, Table 2). These findings indicate that requiring cue processing that intervenes between prime and probe trials does not appear to influence the normal functioning of the location NP process, and also show that the NP process continues to function for at least 2000 ms. These findings are predictable from results reported by Tipper, Weaver, Cameron, Brehaut, and Bastedo (1991). They showed that processing that intervened between prime and probe trial presentations, which is unrelated to the NP task and which might include an overt response, does not influence the location NP process, and that this process continued to operate for about 6 seconds.