Psychonomic Bulletin & Review1996,3 (I), 87-90

Varieties of positive and negative priming

MICHAEL A. STADLER and MARY E. HOGANUniversity ofMissouri, Columbia, Missouri

Numerous recent investigations have focused on a particular relation between the roles a stimu­lus plays in successive displays: when a stimulus ignored by a subject on one occasion is to be at­tended on a succeeding occasion, reaction time to that stimulus is slowed relative to a control con­dition. But this is but one possible case of negative priming. There are other ways in which negativepriming might occur, and there are several varieties of positive priming as well. All these possibili­ties were explored in the present experiment.

Devoting attention to an object has consequences forresponses to the object at that time and at later times, asdoes trying to ignore it. This paper explores the range ofconsequences that attending to and ignoring stimuli canhave on later processing.

Recent research shows that one consequence of ignor­ing an object is that it may be more difficult to attend toat a later time (e.g., Neill, 1977; Tipper, 1985; for recentreviews see Fox, 1995, and May, Kane, & Hasher, 1995).This phenomenon has been termed negativepriming, be­cause people respond more slowly to stimuli that theyhave recently ignored than to stimuli they have not seenat all. For example, suppose subjects are shown a row ofthree digits and asked to respond to the middle one whileignoring the two flanking digits, as in the Eriksen task(Eriksen & Eriksen, 1974). We are interested in the rela­tion between one display, usually termed the prime dis­play, and a display that follows it, usually termed theprobe. The subjects will respond more slowly to theprobe if the target is the same digit that they ignored (be­cause it was a flanker) in the prime than if the probe tar­get did not appear in the prime display. Priming is thedifference in reaction time (RT) between conditions inwhich a stimulus is repeated and a control condition inwhich no stimuli are repeated. Priming is negative whenthe repetition causes a slowing of responses relative tothe control, positive when the repetition causes a speed­ing of responses relative to the control.

The term negative priming is interesting, because itcould be applied more broadly than it generally has been.That is, it need not refer to only one relation between twodisplays; it could instead refer to any case in which pre­sentation ofa stimulus in one instance leads to a slowingof performance when that same stimulus is presented

These experiments were presented at the annual meeting ofthe Mid­western Psychological Association in 1994 in Chicago. The authorsare grateful to Nelson Cowan, Elaine Fox, Gordon Logan, Tram Neill,and Rich Schweickert for comments on previous drafts of this manu­script. Correspondence should be addressed to the first author at De­partment of Psychology, University of Missouri, 210 McAlester Hall,Columbia, MO 65211 (e-mail: psymike@mizzoul.missouri.edu),

87

again at a later time. Moreover, there are also various waysto achieve positive priming.

One current theoretical account of negative priming(but not the only one; see also Neill, Valdes, Terry, &Gorfein, 1992; Park & Kanwisher, 1994) assumes thatselective attention involves both activation and inhibitionof the representations of objects and events encounteredin a scene (e.g., Neumann & DeSchepper, 1991; Tipper,1985). Stimuli that are to be attended are activated; stim­uli that are to be ignored are inhibited. The activation orinhibition that occurs from one display is then assumedto carryover to the next display, thus affecting RT if someofthe same stimuli are presented again. That is, the rela­tive activation and inhibition of stimulus representationsare assumed to influence the selection ofa response, per­haps because the response selection process operates bysearching for the most activated representation. Thus, innegative priming, a stimulus that is ignored in the prime dis­play and then attended in the probe display is first inhib­ited and then activated. It takes longer to achieve the neces­sary level ofactivation for responding, and RT is longer,because the initial inhibition must first be overcome.

As outlined by Neumann and DeSchepper (1991), ifthis reasoning holds there should be other ways in whichRT might be speeded or slowed by repetition ofa stimu­lus on successive trials. Consider positive priming first.This might occur because the attended (target) stimulusis repeated in two successive displays. Of course, suchrepetition priming is quite common (see, e.g., Rabbitt &Vyas, 1973; Scarborough, Cortese, & Scarborough, 1977).We term this an AA trial, because the attended stimulusin the prime display (designated by the first A in AA) isalso attended in the probe display (designated by the sec­ond A). Presumably, the activation ofthe target from theprime display carries over and facilitates activation ofthetarget in the probe. Positive priming might also occur,however, if the ignored (flanker) stimuli are repeated intwo successive displays. This would be an II trial. Here,positive priming might occur because inhibition of theflankers during the prime display carries over and facil­itates their inhibition in the probe display. Ifboth the tar­get and the flanking stimuli are repeated, the attendedstimulus is the same in both the prime and the probe (an

Copyright 1996 Psychonomic Society, Inc.

88 STADLER AND HOGAN

AA trial), as is the ignored stimulus (an II trial). Thisyields an AA/II trial in which response selection shouldbe even easier and RTs even lower than in the AA or IIconditions.

Wehave already discussed one form ofnegative prim­ing, the case in which the ignored stimulus in the primemust be attended in the probe (IA trials). Again, the ideais that inhibition of the ignored stimulus in the primemakes attending to it in the probe more difficult. A dis­tractor turned target is more difficult to activate. Anadditional form of negative priming might also be con­sidered. According to the model being considered, re­sponding is influenced by the levels ofactivation and in­hibition in the relevant stimulus representations. If theattended stimulus in one display is the same as the ig­nored stimuli in the next display (an AI trial), it shouldbe more difficult to inhibit the stimuli that are to be ig­nored because they have just been activated, whichshould slow responding. And, as with the two cases ofpositive priming, the two forms of negative priming (IAand AI) can be combined, forming an lA/AI trial inwhich negative priming should be even greater.

To date, theoretical efforts have been directed almostexclusively toward explaining IA effects (but see Lowe,1979; Neill, 1978), but the other types of priming arealso theoretically important. For example, Tipper andCranston (1985) found that repetition of the same dis­tractor over many successive trials produced facilitationrelative to a control condition in which the distractorchanged on every trial. Tipper, Bourque, Anderson, andBrehaut (1989) concluded that this effect was due to ha­bituation to the repeated distractor. However, after find­ing that II trials produce positive priming relative to acontrol with no repeated stimuli and that AA/II trialsproduce more positive priming than do AA trials, Neu­mann and DeSchepper (1991) argued that Tipper et al.sresult was due to inhibition ofthe repeated distractor, nothabituation. Their reasoning was that perceptual habitu­ation would not be expected after one trial, so any bene­fit of repeating a distractor from one trial to the next mustbe due to inhibition. Thus, the IA effect is not the onlyone oftheoretical importance. The other possible stimu­lus repetition effects also have important implications.

Previous efforts to examine these various repetitioneffects have produced mixed results, so we sought to ex­amine them again. Neumann and DeSchepper (1991), onthe one hand, obtained the pattern of results that theypredicted on the basis of the activation-suppression the­ory and that we have reviewed here. Their effects werequite small, however, with a range from the fastest to theslowest RT ofonly 21 msec (Experiment 3). Lowe (1979,Experiment 1), on the other hand, obtained a differentpattern of results in which the AI condition producedpositive priming instead of negative and the lA/AI con­dition produced less negative priming than did the IAcondition (see also Neill, 1978). Lowe's effects weremuch bigger, with a range from the fastest to the slowestRT of 160 msec. Also, Neumann and DcSchepper's re-

sults for positive and negative priming were fairly sym­metric; Lowe's positive priming effects tended to be big­ger. Neumann and DeSchepper attributed the differentpatterns of results to the fact that their procedure re­quired subjects to remember the target character in theprime display for report after their response to the probe,whereas Lowe used a continuous trials procedure inwhich primes and probes were indistinct from the sub­ject's perspective (i.e., the transition from probe on onetrial to prime on the next was the same as the transitionbetween prime and probe within a trial). However, therewere other differences in the procedures that might alsoaccount for the different patterns of findings.

The main purpose of the experiments reported herewas simply to explore again all these possible relationsbetween one display and the next, this time with theEriksen flanker task (Eriksen & Eriksen, 1974). Eachtype of stimulus repetition was compared with a controlcondition in which there was no repetition ofeither an at­tended or an ignored stimulus. The activation-suppressionmodel we have discussed predicts the following orderingof conditions by RT: AA/II, AA and II, control, IA andAI, lA/AI. Note that we do not predict any particular or­dering of the AA and II trials relative to one another orof the IA and AI trials relative to one another. It is notclear from current theoretical accounts whether or notthe mechanisms that activate or inhibit stimulus repre­sentations should be expected to produce effects that arecomparable in magnitude or not.

METHOD

SubjectsThe subjects were 19 University of Missouri-Columbia undergrad­

uates who participated as part ofa requirement in an introductory psy­chology course.

ApparatusAll stimuli were presented and responses collected by IBM-compatible

computers equipped with VGA monitors. The stimuli were the digits1-4, which were approximately 4 mm high and 3 mm wide. The sub­jects sat approximately 50 em from the monitor and responded by press­ing the C, V,B, and N keys with their left middle, left index, right index,and right middle fingers, respectively. They pressed the C key if the tar­get stimulus was I, and so on. All timing was in milliseconds, and thepresentation of stimuli was synchronized with the raster scan of themonitor.

DesignKeeping in mind that a trial comprised a pair of displays (a prime

followed by a probe), suppose that the probe display was aba, where thesmall letters stand for the central and flanking digits for now. With theconstraint that the target and the flanker were never identical, the primedisplay could then be aba (yielding an AAf11 trial); aca or ada (11); cbcor dbd (AA); cdc or dcd (control); bcb or bdb (IA); cac or dad (AI); orbab (lAfAI). Thus, there were 12 possible pairs ofdisplays, or trials, thatcould then be broken down into the 7 different types of priming rela­tion. Each of the possible trials was presented once every 12 trials in arandom order with the digits 1-4 randomly assigned to the letters a-dfor each trial. The AA/11and lA/AI trials each occurred I/12th of thetime, whereas each of the other types oftrial occurred 1/6th of the time.Subjects did each of the 12 possible trials a total 000 times, so theysaw 30 AA/11 and lA/AI trials and 60 trials of each of the other typesof priming relation.

VARIETIES OF POSITIVE AND NEGATIVE PRIMING 89

ProcedureAlthough for our purposes the displays were paired as primes and

probes in a total of360 trials, from the subject's perspective there wasjust a continuous stream of 720 displays, with a break after every 120displays. For each display, three digits-the target and the two identi­cal flankers-were presented in white in the middle of the screen. Thesubjects were to press the response key that corresponded to the targetdigit. They were instructed to respond as quickly as they could with­out making errors on more than 5% of the displays. The display re­mained on the screen until the subject responded, after which thescreen was blanked. Four hundred milliseconds later, the next displaywas presented. After each break, the subjects initiated the next trialwhen they were ready.

RESULTS

Only the responses to probe displays were analyzed.For these data, the mean RT of all correct responses andthe proportion of responses that were errors were calcu­lated for each of the seven different priming relations foreach subject. The results, which are presented in Table 1,are quite straightforward. The pattern was exactly as pre­dicted by the activation-suppression hypothesis. Positivepriming was greatest in the AA/II condition and de­creased in the AA condition and again in the II condi­tion. Note that some of our effects are much larger thanthose reported by Neumann and DeSchepper (1991).There were 96 msec of positive priming in the AAlIIcondition and about 67 msec in the AA condition, butonly 12 msec in the II condition. Negative priming wasgreatest in the IAIAI (-44 msec) condition and less inthe IA (-11) and AI (- 8) conditions. Recall that the IAcondition was the form of negative priming investigatedin most previous investigations.

Because there were seven means and four orderings ofthose means that would fit the predicted pattern of re­sults (because we did not make predictions about the or­dering of the AA and II conditions or of the IA and AIconditions), the probability of observing the predictedpattern by chance was only 4/7! or approximately .0008.The observed pattern of results is one of those four pat­terns, so it is statistically significant. Moreover, a subse­quent experiment including similar conditions (Stadler

& Hogan, 1994) produced an exact replication of the re­sults reported here.

The data were also subjected to a within-subjectsanalysis of variance and to planned comparisons ofeachcondition with the control condition. The overall effectof condition was significant [F(6,108) = 52.70, MSe =847.33,p < .05]. The results of the contrasts are shownin Table 1. Only the AI condition was not significant.

The pattern of results in the error data, also presentedin Table 1, mirrored the pattern in the RT data almost ex­actly; where RT was low, errors were low, and so on.Overall, the effect of condition was significant for pro­portion errors [F(6,I08) = 5.82, MSe = 0.00099, P <.05]. The contrasts revealed that only the AAlII and AAconditions were significantly different from the control.

DISCUSSION

There are indeed varieties of positive and negative priming. The pat­tern of results predicted by the theory that selective attention relies onthe activation of attended objects and the inhibition of ignored objectswas clearly obtained. Repetition ofan attended or ignored stimulus inthe same role speeds processing. Processing is further speeded ifbothare repeated in the same role. In contrast, responses are slowed whenattended or ignored stimuli are repeated in different roles. The slowingof processing is even greater if both stimuli change roles.

The present observations replicate those of Neumann and DeSchep­per (1991). However, our effects were larger than theirs, particularlywhen positive priming was observed. Our effects were also not sym­metrical as Neumann and DeSchepper's were. This could simply be dueto the restricted range within which their results occurred, or it couldbe due to some procedural factor. Recall that Lowe's (1979, Experi­ment I) results were also not symmetrical; although not all our effectswere in the same direction, the absolute magnitudes of the effects weobserved were rougly comparable to Lowe's, with the exception of theIA and lA/AI conditions, which were reversed in magnitude. Therewere several differences between our experiment and Neumann andDeSchepper's that might explain the differences in magnitude andsymmetry, including the modality of responding (manual vs. vocal),the probabilities of the different types of trial (in our study, these prob­abilities were the same as would be found in a random sequence of dis­plays; in theirs they were not), the characteristics of the display (we hadtwo distractors, they had one; our distractors were the same color as thetarget, theirs were not). It is not clear which of these factors, alone orin combination, might account for the different magnitudes of thepriming effects that we obtained.

Table 1Reaction Time (RT), the Proportion of Trials That Were Errors,

Priming in Each Experimental Condition, and the Results ofContrasts of Each Condition With the Control

Priming Condition

AA/Ii AA Ii Control AI IA lA/AI

RTMean (msec) 565 594 649 661 669 672 705Priming (msec) 96* 67* 12* -8 -11* -44*t 11.34 7.43 2.29 -1.06 -2.06 -4.53SE 8.45 8.97 5.25 7.45 5.36 9.67

Proportion errorsMean 0.012 0.027 0.045 0.047 0.043 0.061 0.06Priming .035* .020* 0.002 0.004 -0.014 -0.013t 4.66 3.66 0.31 0.64 -1.19 -1.31SE 0.0075 0.0055 0.0084 0.0068 0.0118 0.0093

*p < .05, one-tailed.

90 STADLER AND HOGAN

In replicating the results of Neumann and DeSchepper (1991), ourresults deviate from those of Lowe (1979, Experiment I) and Neill(1978). This is somewhat surprising, because our procedure was morelike Lowe's than Neumann and DeSchepper's. This also contradictsNeumann and DeSchepper's idea that the differences between theirresults and Lowe's were due to their task's requiring subjects to hold theprime target in memory for report after their response to the probe. Ourprocedure, in which we used a continuous task like Lowe's, did notrequire this, yet we obtained the same results as did Neumann andDeSchepper.

The discrepancies between our results and Lowe's are in the AI andINAI conditions; our AI results also differ from those ofNeill (1978).It is hard to say exactly what might have caused these differences. Onepossibility is that Lowe and Neill used the Stroop (1935) task, whichmeans that AI or IA repetitions would have to involve a conceptuallevel of processing and not a physical level. That is, the AI conditioninvolves a repetition effect from an attended ink color to an ignoredword name, whereas the IA condition involves a repetition effect froman ignored word name to an attended ink color. In our experiment, therepetition effects were at a physical (and possibly conceptual) level,with a digit appearing in one role in the prime and in another role in theprobe. Perhaps activation and inhibition work differently for differentlevels of processing.

Our observation of positive priming in the II condition and fasterresponses in the ANII condition relative to the AA condition wouldseem to support Neumann and DeSchepper's (1991) rejection of Tipperet al.s (1989) conclusion that the repeated presentation of the samedistractor produces habituation. However, it is quite possible that sev­eral successive presentations of a distractor do lead to habituation afteran initial period when the distractor is actively suppressed. An experi­ment in which a distractor that is repeated in several displays thenbecomes the attended stimulus (an III1I1I1A condition, for example)would test this hypothesis. We are currently performing this and otherexperiments to further test the habituation hypothesis. This issuedemonstrates why it is important for theories to consider not only theIA negative priming effect, but all the varieties ofpositive and negativepriming.

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(Manuscript received December 20, 1994;revision accepted for publication July 14, 1995.)