Notes and Comment. Negative priming and multiple repetition: A reply to Grison and Strayer (2001)

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1 Perception & Psychophysics 2002, 64 (5), Notes and Comment Negative priming and multiple repetition: A reply to Grison and Strayer (2001) W. TRAMMELL NEILL State University of New York, Albany, New York and STEVE JOORDENS University of Toronto, Scarborough, Ontario, Canada Strayer and colleagues (Grison & Strayer, 2001; Malley & Strayer, 1995; Strayer& Grison, 1999) havereported experiments in which negative priming by ignored stimuli occurredonly for stimuli that were repeatedlysampled from small sets. These results were arguedto be inconsistentwith episodic/mismatch accounts of negative priming. We show here that a dependenceof negative priming on multiple repetition is wholly consistent with such theories. Furthermore, we argue that the inhibitory theory proposed by Strayer and colleagues cannot account for major findings regardingnegative priming and that anomalies in the data reported by Grison and Strayer are more parsimoniously explained by episodic/mismatch accounts. If one has recently attended or responded to an object, responses to a similar object are usually faster than responses to an unrepeated object ( positive priming). On the other hand, if one has recently ignored an object, responses to a similar object are often slower than responses to an unrepeated object (negative priming). The latter effect has emerged as one of the more controversial topics in the study of attention and repetition effects (see reviews by Fox, 1995; May, Kane, & Hasher, 1995; Neill & Mathis, 1998; Neill & Valdes, 1996; Neill, Valdes, & Terry, 1995). Although a variety of theoretical explanations have been proposed for the effect, they generally fall into two classes, described here as inhibitory and mismatch theories. Strayer and colleagues (Grison & Strayer, 2001; Malley & Strayer, 1995; Strayer & Grison, 1999) have reported a series of experiments in which positive priming by target target repetition occurred only if the stimuli were sampled infrequently from a large set. In contrast, negative priming by ignored distractors occurred only if the stimuli were sampled repeatedly from a small set throughoutthe experiment. Strayer and colleaguesargued Correspondence regarding this article should be addressed to either W. T. Neill, Department of Psychology,State University of New York, Albany, NY 12222( neill@csc.albany.edu), or S. Joordens, Division of Life Sciences, University of Toronto, 1265 Military Trail, Scarborough, ON, M1C 1A4 Canada ( joordens@psych. utoronto.ca). that the latter result is incompatible with mismatch theories of negative priming and proposed a specific inhibitory theory to account for their data. Here, we provide a brief historical review of this debate and a critique of the theoretical conclusions drawn by Strayer and colleagues and conclude that their results are more parsimoniously explained by mismatch theories. Inhibitory Theories In the first publisheddemonstration of negative priming, Dalrymple-Alford and Budayr (1966)compared total color-naming time for a list of unrelated Stroop (1935) color words with that for a list in which each distractor word named the color of the next color word in the list (e.g., blue written in red ink, followed by yellow in blue ink). Color naming was slower in the latter condition. (Lowe, 1979, and Neill, 1977, replicated this effect in a randomized, discrete-trials version of the Stroop task.) Dalrymple-Alford and Budayr concluded that responding to each color necessitated suppression of the competing response elicited by the distractor word; if the suppressed response was then appropriate to the next color, naming was slowed. Subsequent research cast doubt on the overt response as the locus of suppression. Negative priming is obtained even if the trial in which the distractor is ignored (prime trial) requires a different response mode (vocal or manual) from the trial in which the ignored stimulus reappears as a target (probe trial; Tipper, MacQueen, & Brehaut, 1988). Negative priming also occurs even if ignored and unrelated stimuli require the same responses (e.g., DeSchepper & Treisman, 1996; Neill, Lissner, & Beck, 1990). A purely perceptual locus is unlikely as well, because negative priming occurs between perceptually dissimilar stimuli for example, between the word and the color in the Stroop task and between pictures and associatedwords (Tipper & Driver, 1988). Inhibitorytheories have therefore emphasized a central, cognitiverepresentation of the ignored stimulus. It is commonly assumed that interference by distracting stimuli is caused by activationof their cognitive representations.it is tempting, therefore, to suppose that inhibition reduces such activation.however, the deactivation hypothesis has been disconfirmed by the finding that negative priming often depends on whether the probe trial target is accompanied by a distractor. In some studies, prime trial distractors caused significant facilitation (positive priming) on nonconflict probe trials, even though they were randomly intermixed with conflict probe trials that yielded negative priming (Lowe, 1979; Milliken, Joordens, Merikle, & Seiffert, 1998; Neill & 855 Copyright 2002 Psychonomic Society, Inc.

2 856 NEILL AND JOORDENS Kahan, 1999; Tipper & Cranston, 1985). Therefore, the distractor representation must remain activated, but its manifestation in positive priming depends on probe target conditions. Tipper and Cranston concluded that the activated distractor representation is actively blocked from accessing response mechanisms as long as the subject maintains a selection set. If the probe target is not accompanied by a distractor, the selection set is relinquished, and facilitationemerges owing to the persisting activation. Ironically, more recent inhibitory theories have resurrected the notion that the distractor representation is directly deactivated(grison &Strayer, 2001;Houghton& Tipper, 1994; Malley & Strayer, 1995; Strayer & Grison, 1999). Houghton and Tipper proposed a connectionist model of negative priming in which stimuli present on a trial are compared with an internal template of the critical selection criteria. A mismatch between the distractor object and the template results in a spread of inhibition to represented features of the distractor, resulting in negative priming when that object reappears as a target. Strayer and colleagues proposed that selective attention can either increase activation of the target representation or inhibit activation of the distractor representation. The mode of selection depends on the overall activation levels. When stimuli are presented infrequently, overall activation is low, and selection can be effected through increasing activation of the target representation. However, when stimuli are presented frequently, both target and distractor activations will be near maximum, and so selection can be effected only through deactivationof the distractor representation.consequently, negative priming occurs only if a small set of stimuli are frequently repeated, whereas positive priming by repeated targets occurs only for large sets with infrequent repetition. Mismatch Theories Mismatch theories attribute negative priming to the comparison of the current target stimulus to a remembered recent encounter with a similar stimulus (hence, they are also episodic retrieval theories). Neill and Valdes (1992) suggested that negative priming could be caused by an instance retrieval process similar to that proposed by Logan (1988, 1990) to account for the acquisition of automaticity.as elaborated by Neill, Valdes, Terry, and Gorfein (1992), the episodic retrieval theory assumes that a target stimulus cues the retrieval from memory of recent encounters with similar stimuli. Following Logan (1988, 1990), they argued that if a retrieved instance includes appropriate response information, the subject can bypass slower algorithmic computation of the response. However, if the retrieved instance is one in which the stimulus was ignored, the absence of useful response information (or perhaps an explicit ignore this tag) delays selection of an appropriate response. Critical support for an episodic retrieval process can be found in the dependence of negative priming on contextual similarity between prime and probe trials (Fox & de Fockert, 1998; Neill, 1997). Whereas Neill et al. (1992) emphasized a mismatch of response information, other theories of negative priming have emphasized a mismatch of selection criteria. Park and Kanwisher (1994) proposed such a mismatch theory to account for location-specific negative priming. Tipper, Brehaut, and Driver (1990) had previously demonstrated negative priming for ignored locations in a task requiring subjects to press a key corresponding to the location of a while ignoring a distractor + in another location. Slowed responding to a probe target occurred if it appeared in the same location as the prime trial distractor (see also Neill et al., 1992). In a crucial experiment by Park and Kanwisher, subjects were instructed to locate a target O, ignoring X, on the prime trial. However, on the subsequent probe trial, the subjects had to locate X, ignoring O. Relative to a neutral-location target, responding was faster if the target appeared in the previous distractor location (object match) but was slower if it appeared in the previous target location (object mismatch) MacDonald and Joordens (2000; MacDonald, Joordens, & Seergobin, 1999) demonstrated that the effects of match or mismatch of selection criteria occur in identification tasks as well and that such criteria can be conceptual, rather than strictly perceptual. In one experiment, MacDonald et al. presented subjects with the names of two animals (e.g., mouse dog), requiring them to read aloud the name of the larger animal. Very large ( msec) negative priming was found if the name of the smaller animal reappeared as that of the larger animal on the next trial. Most important for the present discussion, MacDonald and Joordens (2000) found negative priming by the nontarget prime if the same selection criterion (e.g., name the larger animal) was required on both prime and probe trials, but not if selection criteria were switched (e.g., name the larger animal on the prime trial, but name the smaller animal on the probe trial). In the latter case, the selection attribute of the probe target was consistent with the prime trial (e.g., both smaller). And similar to Park and Kanwisher (1994), negative priming was caused by target target repetitionswhen the selection criteria were switched (e.g., if the larger animal named on the prime trial was the smaller animal named on the probe trial). Neither inhibitory theories of negative priming nor the episodic retrieval theory proposed by Neill et al. (1992) can account for negative priming by directly attended stimuli, as in target target repetitions (see also Wood & Milliken, 1998). In view of such results, Neill and Mathis (1998) proposed a modified episodic retrieval theory in which instance retrieval tends to reinstate similar processing (cf. Kolers, 1976; Kolers & Ostry, 1974). Negative priming occurs if the reinstated processing is transfer inappropriate to current task demands. A different but related approach is taken by the temporal discriminability theory proposed by Milliken

3 NOTES AND COMMENT 857 et al. (1998). According to this theory, recently ignored stimuli are often intermediate in familiarity, relative to recently attended stimuli (highly familiar) or less recently encountered stimuli (unfamiliar). This creates an ambiguity as to how to process the stimuli for example, whether or not to rely on episodic retrieval. Under some conditions (such as delay or change in task context), attended stimuli may similarly result in intermediate familiarity and may also cause negative priming. As was noted above, negative priming often depends on the presence of a distractor stimuluson the probe trial and may reverse to positive priming in the absence of interference. Similar to Tipper and Cranston (1985), mismatch theories can account for this result because they attribute negative priming to a later stage of processing than that at which cognitive activation is assumed to occur. Hence, if the processes necessary for mismatch effects fail to occur, performance should benefit from persisting activation. Neill (1997) demonstrated that the presence of a distractor on a prime trial, but not on the probe trial, can cause a contextualmismatch that reduces the likelihood of retrieving the prime-trial episode. In addition, algorithmic computation is likely to be faster for probe targets without distractors, reducing the opportunity for episodic retrieval to affect performance (cf. Logan, 1988, 1990). The temporal discriminability theory (Milliken et al., 1998) supposes that presence or absence of a distractor affects whether the temporal discrimination process is engaged; in the absence of interference, performance improves monotonically with the familiarity (activation) of the target. Effects of Multiple Repetition Over a set of experiments in which subjects named target words flanked by distractor words, Malley and Strayer (1995) found significantnegativeprimingby ignored distractors only when words were repeatedly sampled from a set of 16 words. In contrast, they found significant positive priming for target target repetitions only when new words were sampled for each prime probe trial pair. They argued that these results were incompatiblewith the episodic retrieval theory of negative priming, reasoning as follows. Over the course of the experiment, a multiply repeated stimulus would appear as an attended target or an ignored distractor with roughly equal frequency. To the extent that the current target cues the retrieval of past episodes involving that word, the retrieval of episodes in which the word was attended should counteract episodes in which that word was ignored. In contrast, if that word had appeared only once before, as an ignored distractor, that episode should exclusively affect performance. In accordance with this logic, the results of Strayer and Grison (1999) would appear even more damaging to the episodic retrieval theory: Their Experiment 3 showed an increase in negative priming with an increase in the number of prior repetitions as a target, but not with an increase in the number of repetitions as a distractor. In addition, Strayer and Grison were unable to replicate negative priming in a task requiring matching of completely novel nonsense shapes (DeSchepper & Treisman, 1996; Treisman & DeSchepper, 1996). DeSchepper and Treisman argued that negative priming for such figures had to reflect retrieval of specific perceptual instances, because there could be no preexisting cognitive representation to inhibit (see the further discussion by Neill, 1997; Neill & Mathis, 1998). Grison and Strayer (2001) expanded on these results in word-naming experiments in which either the prime trial target or the distractor was perceptually degraded. As in previous studies (Malley & Strayer, 1995;Strayer & Grison, 1999), they also varied whether the stimuli were sampled repeatedly or were unique to each prime probe trial pair. Again, positive priming for target target repetitions occurred only for novel words, whereas negative priming occurred only for multiply repeated words. Furthermore, positive priming was reduced if the target was degraded, whereas negative priming was reduced if the distractor was degraded. In addition to reiterating their arguments against the episodic retrieval theory, they argued that their results were also inconsistent with the connectionist model proposed by Houghtonand Tipper (1994). This model assumes that inhibition is proportional to distractor activation;on the assumption that an undegraded distractor should produce greater activation, it should also cause greater negative priming. Although this did occur for multiply repeated words, there was no effect for novelwords (at least in the reaction time measure). Critique Strayer and colleagues ignored critical evidence that cognitive activation and the mechanism underlying negative priming affect different stages of processing. As was discussed above, negative priming is often dependent on the presence or absence of a distractor on the probe trial, and a prime trial distractor may cause facilitation if it reappears as a probe target without a distractor (Lowe, 1979; Milliken et al., 1998; Neill & Kahan, 1999; Tipper & Cranston, 1985). Because the theory proposed by Strayer and colleagues attributes negative priming entirely to deactivationon the prime trial, it cannot account for a reversal of negative priming to positive priming when the probe trial does not include a distractor. Furthermore, any theory that does attribute activation and negative priming to different stages of processing as do mismatch theories, as well as the blocking theory proposed by Tipper and Cranston easily accounts for the effects of multiple repetition, as will be shown in the following. Let us subdivide processing of a probe trial target into those processes leading to categorization of the stimulus and postcategorical processes ultimately leading to a response. (We refer to these sets of processes as stages, but by no means do we imply that these stages cannot be decomposed into multiple distinguishable stages.) Let

4 858 NEILL AND JOORDENS C = total time for the categorization stage and P 5 total time for the postcategorical stage. Reaction time (RT), therefore, is C 1 P. Let us also define subscripts IR and UR to represent the conditions ignored repetition (distractor-to-target repetition) and unrelated (no repetition between prime and probe trials), respectively. Negative priming (NP) is defined as RT IR 2 RT UR. Therefore. NP 5 (C IR 1 P IR ) 2 (C UR 1 P UR ) 5 (C IR 2 C UR ) 1 (P IR 2 P UR ). We agree completely with Strayer and colleaguesthat multiple repetition probably pushes the activation levels of both IR and UR conditions to some maximum. Thus, on the assumption that identification time depends on activation,c IR is approximatelyequal to C UR. Therefore, approximately,np 5 P IR 2 P UR. With the exceptions of Houghton and Tipper (1994) and Strayer and colleagues, most theories of negative priming assume that the mechanism of negative priming operates at a stage after the probe trial target has been categorized that is, P IR is slowed relative to P UR. Therefore, negative priming is expected to occur. What if stimuli are not multiply repeated? The recent presentation of a stimulus is likely to substantially increase activation, and so C IR, C UR. The magnitude of negative priming will depend on the relative size of this effect. Increased facilitation of the categorization stage will necessarily attenuate negative priming. Indeed, if the facilitation of categorization is greater than the impediment of postcategorical processing, an ignored distractor should cause positive priming that is, NP 5 (C IR 2 C UR ) 1 (P IR 2 P UR ), 0. More generally, activation by the ignored distractor will tend to counteract the mechanism of negative priming, and the effect of activation should vary inversely with presentation frequency. It should be emphasized that this analysis follows regardless of what causes negative priming. That is, the postcategorical processes (P) might be slowed by inhibition, episodic retrieval, mismatching, temporal discriminability, or anythingelse. All that is assumed is that ignored distractors can have opposite effects on processes leading to categorization (C) and postcategorical processes (P). Although it may seem gratuitous to postulate opposing processes, this assumption is mandated empirically by the fact that a prime trial distractor can cause either positive priming or negative priming, depending on whether the probe trial target is also accompanied by a distractor (Lowe, 1979; Milliken et al., 1998; Neill & Kahan, 1999; Tipper & Cranston, 1985). This analysis also accounts for the finding by Strayer and Grison (1999, Experiment 3) that negative priming was greater for stimuli multiply repeated as targets than for stimuli multiply repeated as distractors. On the assumption that activation levels for stimuli repeated as targets should be higher than those for stimuli repeated as distractors, the former would be closer to asymptotic. Therefore, C IR 2 C UR should more closely approximate zero, allowing the postcategorical component P to predominate. As was acknowledged by Grison and Strayer (2001), episodic retrieval accounts easily for the finding that negative priming is reduced if the prime trial distractor is degraded:if the distractoridentityis less well encoded, it is less likely to be retrieved on the probe trial. However, Grison and Strayer argue that episodic retrieval cannot account for the effect of degradation on negative priming only for multiply repeated words; they expect that a similar effect should occur for novel words. But this prediction follows only if it is assumed that the probability of episodic retrieval is the same for the multiple-repetition and novel conditions. Although the formal analysis above emphasized the effect of multiple repetitionon categorization, it seems likely that multiple repetition should also affect postcategorical processes. It is not implausible, for example, that a novel (less familiar) word would be a less effective retrieval cue than a multiply repeated (more familiar) word. It is inherent in the instance retrieval theory put forth by Logan (1988, 1990) that the effect of episodic retrieval will also depend on the time taken for algorithmic computation. If algorithmic computation is speeded for novel targets, because they cause a greater increase in activation relative to baseline, episodic retrieval is less likely to occur. Consequently, degradation of the prime trial distractor would be less likely to have any effect on performance. Furthermore, in the design used by Strayer and colleagues, the prime-distractor/probe-target frequency is inherently confounded with probe distractor frequency (and prime target frequency) that is, all the words in a prime2probe pair are selected from the same size pool. Does an unfamiliar probe trial distractor cause less interference than a familiar probe trial distractor? If so, algorithmicprocessing might again be more efficient. We realize that in describing how mismatch theories can account for the results of Grison and Strayer (2001), the reader might be left with the inaccurate impression that the increased flexibility provided by our notions of positive versus negative priming would allow mismatch theories to account for any pattern and, therefore, to predict none. Why would such an impression be inaccurate? Our argument is simply that if positive-priming effects have not been saturated, the positive-priming effect occurring at the identification stage will mask the negative-priming effect that occurs at later stages. This is a clear and concrete claim, and we currently know a great deal about positivepriming effects. For example, we know that priming effects are larger for degraded targets (Meyer, Schvaneveldt, & Ruddy, 1975) and for low-frequency targets (e.g., Becker, 1979; Becker & Killion, 1977). Thus, in a context in which positive priming has not yet been saturated, we would predict less negative priming for targets that are more sensitive to positive priming (i.e., degraded, lowfrequency, or degraded low-frequency targets). Clearly, this is a testable prediction of our account.

5 NOTES AND COMMENT 859 Finally, we note two anomalies in the data reported by Grison and Strayer (2001) thatare more easilyaccounted for by mismatch theories than by their inhibitory theory. First, in their Experiment 1, error rates yielded a significant negative-priming effect for ignored novel words in the degraded-target (undegraded-distractor) condition; this reversed to significant positive priming in the degraded-distractor (undegraded-target) condition.this effect actually belies two conclusions by Grison and Strayer. First, it is untrue that negative priming did not occur for novel words. Second, it is untrue that degradation did not have similar qualitative effects on negative priming for novel and repeated words. The effects were manifested in error rates, rather than in reaction times. Although negative priming is most often demonstrated in reaction time, there is no a priori justification for ignoring similar effects on accuracy. A second anomaly in Experiment 1 of Grison and Strayer (2001) is thatreactiontime in the attendedrepetition condition yielded significant negative priming for multiplyrepeated words in the degraded-targetcondition. Although the inhibitory theory proposed by Strayer and colleagues predicts little or no positive priming for multiply repeated words, it cannotaccount for negative priming in target2target repetitions. However, this effect is easily accommodated by mismatch theories, insofar as a mismatch between a degraded prime target and a undegraded probe target may cause interference. The same condition did not produce negative priming in their Experiment 2, although the degree of degradation was increased. However, the latter experiment generally showed larger positive priming and smaller negative priming than did the first experiment. In terms of the formal analysis above, Experiment 2 appears to have a greater contribution of the C component,consistent with the reduced number of repetitions in that experiment. Conclusions To summarize, the experiments reported by Strayer and colleagues (Grison & Strayer, 2001; Malley & Strayer, 1995;Strayer & Grison, 1999) do not adequately resolve whether negative priming is caused by inhibition, episodic retrieval, or some other mechanism. For the most part, all that is required to account for the dependence of negative priming on multiple repetition is the assumption that an ignored distractor can facilitate one stage of processing for a subsequent target but can impede another stage. Hence, the magnitude of overt negative or positive priming necessarily depends on the balance of facilitatory and dilatory effects. Although this assumption may seem theoretically cumbersome, it is mandated by the dependenceof priming effects on probe trial conditions,as well as on prime trial conditions.and it is this frequently replicated effect that ultimately undermines the theory proposed by Strayer and colleagues. The theories proposed by Strayer and colleagues and by Houghton and Tipper (1994) are arguably the most fully articulated inhibitory theories of negative priming. Grison and Strayer (2001) assert that the latter theory cannot account for their data. Yet the theory proposed by Strayer and colleagues cannot account for a major attribute of negative priming that it can be reversed to positive by nonconflict probes. Their theory also cannot account for anomalies in their own reported data. Given that mismatch theories can account for the data of Strayer and colleagues, as well as for the dependence of negative priming on probe trial conditions, we can only conclude that the data of Strayer and colleagues contribute further support to mismatch theories. To readers not immersed in the negative priming literature, this debate may seem akin to that concerning how many angels can dance on the head of a pin. However, the issue has important consequences beyond abstract theory: Many studies have found that negative priming is diminished in various groups characterized by cognitive impairments for example, the elderly, children, schizophrenics, poor readers, and error-prone individuals(see reviews by May et al., 1995; Neill et al., 1995). Proponents of the inhibitory view have leapt to the conclusion that such groups are deficient in the ability to inhibit distracting information and that this, in turn, accounts for their impairments. 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