Eliminating the memory blocking effect

Eliminating the memory blocking effect

P. Andrew Leynes

The College of New Jersey, Ewing, NJ, USA

Olga Rass

Indiana University, Bloomington, IN, USA

Joshua D. Landau

York College of Pennsylvania, York, PA, USA

Six experiments investigated the memory blocking effect (MBE) in which exposure to orthographicallysimilar words (e.g., BALLOON) impairs one’s ability to complete a similar fragment (e.g., BAL_ON_,solution is BALCONY). Experiments 1 and 2 demonstrated that blocking is not observed after a 72-hourdelay; however, repetition priming was observed after the same delay. Experiments 3 and 4 showed thatpresenting unrelated semantic information during the fragment completion test eliminates blocking.Experiment 5 demonstrated that the MBE persists despite directed-forgetting instructions, andExperiments 5 and 6 demonstrated that activating both the solutions and blocking words for a particularfragment at study eliminates blocking. Collectively, the data demonstrate that reading orthographicallysimilar primes automatically triggers retrieval of the blocking word and an executive control processworks to manage this interference. A working framework that describes how an executive controlmechanism could govern memory retrieval in the memory-blocking paradigm is presented to stimulatedevelopment of more advanced theoretical models that can explain blocking.

Keywords: Blocking; Priming.

Actually, just look at what Osam � Barack

Obama � said just yesterday. Barack Obama,

calling on radicals, jihadists of all different

types, to come together in Iraq.

(Mitt Romney, 10/23/2007)

Did Mitt Romney inadvertently confuse the

names ‘‘Osama Bin Laden’’ and ‘‘Barack

Obama’’, or was this a clever campaign tactic to

connect democratic senator Barack Obama with

leader of the al Qaeda terrorist organisation? On

1 January 2007. CNN committed a similar gaffe

during a news broadcast when they displayed a

graphic comprising an image of al Qaeda mem-

bers along with the text ‘‘Where’s Obama?’’.

Because Osama and Obama are orthographically

similar, and it seems unlikely that CNN would

engage in such egregious character assassination,

we suspect that both of these instances represent

cases of memory blocking. Memory blocking

refers to situations when the retrieval process

perseverates on erroneous information, impairing

# 2008 Psychology Press, an imprint of the Taylor & Francis Group, an Informa business

Address correspondence to: P. Andrew Leynes, Department of Psychology, The College of New Jersey, P.O. Box 7718, Ewing, NJ

08628-0718, USA. E-mail: [email protected]

This research was supported by The College of New Jersey through an internal grant award (SOSA) to the first author. We thank

J. R. Acupan, Nishan Bhagat, Jaime Brown, Kayleigh Callan, Julie Coats, Jeff Creswell, Steve Dash, Stephen DeRose, Jessica

Descker, Jalissa Hardesty, Luke Makowski, Chris Medvecky, Emrah Polat, and Kelly Soto for their help with collecting the data. We

are also grateful to two anonymous reviewers for their feedback on an earlier version of this manuscript.

MEMORY, 2008, 16 (8), 852�872

http://www.psypress.com/memory DOI:10.1080/09658210802348038

access to desired memories. This paper presentsdata from six experiments examining this type ofexperience in a laboratory setting.

In the standard memory blocking effect(MBE) paradigm (Smith & Tindell, 1997) peoplestudy a list of words (e.g., ANALOGY) and arelater asked to solve similar, but slightly different,word fragments (e.g., A _ L _ _ G Y). AlthoughANALOGY appears as a viable solution for thisfragment, a correct solution for this fragment isALLERGY. The MBE occurs when fewer ofthese ‘‘blocking’’ fragments are completed rela-tive to control fragments that were paired withunrelated words at study (e.g., Smith & Tindell,1997) or when no study words were presentedduring the study session (e.g., Landau & Leynes,2006). In this case the high degree of orthographicoverlap between the blocking word and thefragment impairs people’s ability to solve thefragments.

A review of the available MBE literatureshows that this blocking effect is immune toseveral manipulations that influence explicitmemory. Landau and Leynes (2006) found thatthe MBE was unaffected by manipulations of thedepth of processing (see Smith & Tindell, 1997,Exp. 1, for a similar finding), the time to completethe fragments, and awareness of the MBE. Like-wise, instructions to forget or ignore the blockingwords also had little influence on the MBE (seealso Logan & Balota, 2003; Smith & Tindell,1997). When people attempt to complete blockingfragments they often erroneously offer the block-ing word as the solution, even when it is obviousthe word is not a proper fit for the fragment(Landau & Leynes, 2006). This particular findingsuggests that the blocking fragments activateblocking words. Because the blocking words areso similar to the fragment solution (but do notcomplete the fragment) people perseverate onthe blocking words and this impairs their memorysearch for other potential fragment solutions.

To investigate blocking, Logan and Balota(2003) displayed a probe word a few hundredmilliseconds before each fragment instead ofpresenting words in a study list. When a blockingword (e.g., VOYAGER) appeared immediatelybefore a fragment (e.g., V O _ _ A G E), youngerand older adults were less likely to solve thatfragment (thus producing the MBE). The findingthat sub-threshold presentation of the blockingword also produced the MBE (their Exp. 3)indicates that conscious awareness of the blockingword is not required to elicit the MBE. The

blocking words also elicited a different pattern oferrors between these two age groups. Older adultswere more likely to offer the incorrect, blockingword as the solution (i.e., an intrusion error),whereas younger adults were more likely towithhold a response (an omission error). Inter-estingly, younger adults’ performance mimickedthat of older adults when blocking words werepresented below threshold (i.e., they had moreintrusions).

According to Logan and Balota’s explanationof the MBE, presentation of the word fragmentactivates several possible solutions. Blockingfragments activate a pool of candidate solutionsthat includes the blocking word as well as otherpossible solutions. In order to complete theblocking fragment, a person must be able tomanage the activation level of the intruding,blocking word and to select against it. If a personis able to reduce the activation of these incorrectalternative solutions then they will be more likelyto successfully find and select a correct fragmentsolution. Conversely, if a person is unable tomanage the activation of the blocking word thenthe memory retrieval process will perseverate onthe blocking word, interfering with the samplingand selection of other potential solutions. Loganand Balota suggested that the age differencesthey found were indicative of a less efficientexecutive control mechanism that did not helppeople sample and select relevant targets (i.e.,correct fragment solutions) from interfering alter-natives (i.e., orthographically similar words).Accordingly, the ageing process impairs theefficiency of the executive control mechanismand this leads to fewer successfully completedblocking fragments and significantly more intru-sions. The weight of their argument hinged on thedifferent pattern of errors made by the age groups(i.e., older adults made more intrusions whereasyounger adults made more omissions) and thefact that younger adults made more intrusionswhen the blocking word was presented belowthreshold in their Experiment 3.

One difficulty with Logan and Balota’s (2003)account is that they did not observe any interac-tions between age group and fragment comple-tion rates, because the young-adult group alsoexperienced blocking; therefore they did notprovide any independent evidence that eithergroup could actually control the activation onthe fragment completion test and prevent block-ing. Better evidence for a difference in the abilityto control blocking between age groups should

MEMORY BLOCKING 853

come from an interaction between age andfragment completions in which the young adultsshow no evidence of blocking but the older adultsare blocked. The problem with this approach isthat blocking has not been eliminated in anycondition described in the published studies thathave used the memory block paradigm (Kozak,Sternglanz, Viswanathan, & Wegner, in press;Landau & Leynes, 2006; Logan & Balota, 2003;Lustig & Hasher, 2001; Rass & Leynes, 2007;Smith & Tindell, 1997) except when attention wasdivided at study (Kinoshita & Towgood, 2001).Although Kinoshita and Towgood provide con-vincing evidence that the MBE magnitude isreduced by divided attention, this study providesless convincing evidence that the MBE waseliminated. More specifically, the lack of asignificant difference between blocking and con-trol fragment completions in the divided attentioncondition might represent a type II error resultingfrom a lack of statistical power, because meanfragment completions were based on observationsfrom 10 fragments per condition. This argument issupported by the fact that Landau and Leynes(2006) found significant MBE effects that weresimilar in magnitude (i.e., �.05) to those inKinoshita and Towgood’s divided attention con-dition; however, the MBE estimates in Landauand Leynes’s studies were based on 15 fragmentsper condition. Regardless of whether or notdivided attention eliminates the MBE, it is clearthat experimental conditions where exposure toblocking words does not impair fragment com-pletions are severely lacking.

The six experiments described in this paperinvestigated situations in which blocking might beeliminated, because previous studies have not yetidentified situations where blocking was notpresent. Experiments 1 and 2 demonstrated thatthe MBE dissipates after a delay. Experiment 3provided evidence that specific knowledge of theinterfering information did not eliminate theMBE, but presentation of unrelated informationat test eliminated the MBE. Experiment 4 repli-cated the basic findings in Experiment 3 andfurther demonstrated that the unrelated informa-tion must be semantic in order to eliminate theMBE. Experiments 5 and 6 demonstrated thatblocking dissipates when the correct fragmentsolution is also accessible. Collectively, theseexperiments identify conditions where the MBEis not present and suggest that executive controlplays a crucial role in the MBE paradigm.

EXPERIMENT 1

Because many memory effects dissipate overtime, the purpose of this experiment was todetermine whether a 72-hour delay betweenstudy and test would eliminate the blockingeffect. One possible outcome is that the MBEwill persist over this interval, because there isample evidence that priming is detectable after a72-hour delay (e.g., Goshen-Gottstein & Kem-pinsky, 2001; Kolers, 1976; Wohldmann, Healy, &Bourne, 2007). If blocking persists over this delaythen that would be evidence that the MBE issimilar to repetition priming. A second possibleoutcome is that the MBE will dissipate after thedelay. That result would be evidence that peopleare able to manage the activation after a longdelay. Based on previous MBE results, contrastsof blocking and control fragment completionswere planned a priori to increase statisticalpower.

Method

Participants. A total of 50 undergraduates atthe College of New Jersey participated for partialcourse credit. Because 11 participants completedthe first task and did not return for the secondsession, the data from these participants were notincluded in the analyses and produced a finalsample of 39 participants.

Stimuli. A total of 120 stimuli consisting of aword fragment, the corresponding fragment solu-tion (i.e., a positive prime),1 and an orthographi-cally similar word (i.e., a blocking word) wereselected from the Rass and Leynes (2007) corpus.Stimuli were selected because they elicited simi-lar blocking and repetition priming completionrates (see Appendix). The computer softwarerandomly assigned the stimuli to the fragmenttype and to one of the test conditions for eachparticipant.

Procedure. The procedures followed Smithand Tindell’s (1997) basic paradigm. Participantscompleted two tasks: an encoding task followedby a word fragment completion task. Duringthe encoding task (see panel A of Figure 1 fora simulation of the display), participants saw aseries of 60 blocking words in the centre of a

1 The positive primes were not used in Experiments 1, 3,

and 4.

854 LEYNES, RASS, LANDAU

monitor and they then had 5 s to rate how the

word made them feel using a scale from 1 (very

bad) to 5 (very good).Next, participants completed two fragment

completion tests that took place on two different

occasions. The immediate test followed the en-

coding task after the experimenter delivered the

instructions, whereas the delay test followed after

a 72-hour delay.During both fragment completion tests each

fragment appeared in the middle of the computer

monitor with a space in between each letter to

improve legibility. Underscores indicated the

location of the missing letters in each fragment.

Half of the fragments corresponded to the block-

ing words that participants encountered in the

affect-rating task (blocking fragments hereafter).

The solutions for the other half of the fragments

were words that did not appear during the

encoding task (control fragments hereafter). The

computer software randomised the trial sequence

for encoding and both fragment completion tests.Both the immediate and delayed tests contained30 blocking and 30 control fragments where nonewas repeated.

When participants typed on the keyboard,characters appeared directly in the blank spacesof the fragment. Pressing the backspace keycleared all of the typed characters in the frag-ment. The computer automatically advanced tothe next fragment upon entry of the last missingcharacter or after 10 s elapsed.

Dependent measures. Correct completions referto trials when participants entered the solutionbefore the 10-s response time elapsed. Omissionerrors happened when the 10-s response timeelapsed without a complete response. After theexperimental session, a rater (blind to the experi-mental condition) examined all other responses.The rater determined whether the fragment wascompleted with another valid word (e.g.,STORMS for the fragment S T _ R M _ that

Task 1(all 6 experiments)

E X P L O D E

E X _ L _ _ D

VB B N G VG

EXPLODE

Task 2:Blocking Flanker(Experiments 3 & 4 only)

Task 2:Unrelated Flanker(Experiments 3 & 4 only)

W E A L T H Y

E X _ L _ _ D

A)

B)

C)

Figure 1. Simulations of the computer display during the experiment (the spacing and text proportions were not maintained in

these exemplars). Panel A depicts the display during the encoding phase used in all six experiments. Panels B and C represent the

display in Experiments 3 and 4 in which flankers were presented above the fragment. Panel B depicts fragment completion test trials

when a blocking prime was presented above the fragment. Panel C depicts test trials when an unrelated word was presented above

the fragment.

MEMORY BLOCKING 855

corresponded to the positive prime STORMY);the response was not a valid word (other error;e.g., LEBTSER for L E _ T _ E R); or theblocking word was forced into the fragment (anintrusion). Intrusions included responses thatwere phonetically similar to the blocking word(e.g., EXPLODD for the fragment E X _ L _ _ Dthat corresponded to the blocking word EX-PLODE) or solutions that contained the sameletters as the blocking word (e.g., ENDNIG forthe fragment E _ _ N I _ that corresponded to theblocking word ENDING).

Two different response times (RT) were col-lected for correct solutions as additional metricsof blocking (Logan & Balota, 2003; Rass &Leynes, 2007). We measured the time that elapsedbetween the presentation of the fragment and thefirst keystroke (First Key RT) and the total timeto solve the fragment. Entry RTs reflected thetime that elapsed between the entry of the firstand last missing letters of the fragment. Theanalyses of entry RTs did not produce anydifferences in any of the six experiments, there-fore there is no additional discussion of thisdependent measure.

Results

The left-hand column of Table 1 displays thedependent measures for Experiment 1. Eachmeasure was analysed using a 2 (fragment type:blocking, control)�2 (test: immediate, delay)repeated measures analysis of variance (AN-OVA) model. The type I error rate was set at.05 for all analyses.

Correct completions. Overall fragment comple-tions were unaffected by the 72-hour delay, F(1,38)�1.90, p�.18, and the Fragment�Test inter-action also failed to reach a significant level, F(1,38)�2.84, p�.10. However, more of the controlfragments were completed overall, F(1, 38)�7.49, p�.009, MSE�.01. Planned comparisonsrevealed a significant MBE (i.e., control fragmentcompletions versus blocking fragment comple-tions) on the immediate test, F(1, 38)�9.99, p�.003, MSE�.01, but not after the 72-hour delay(FB1).

Errors. More intrusions were observed on theimmediate test, F(1, 38)�14.19, p�.001, MSEB

.01, and following exposure to the blockingword, F(1, 38)�4.85, p�.034, MSEB.01. TheFragment�Test interaction was not significant,

F(1, 38)�2.36, p�.13. Post hoc comparisons re-vealed that more intrusions were observed for theblocking fragments relative to control on theimmediate test, F(1, 38)�5.81, p�.021, MSEB

.01, but not on the delayed test (FB1).Examination of the pattern of omissions re-

vealed a significant Fragment�Test interaction,F(1, 38)�6.39, p�.016, MSE�.01, but no sig-nificant main effects for test (FB1) or fragment,F(1, 38)�2.36, p�.13. Post hoc contrasts re-vealed that fewer omissions were observed for thecontrol fragments relative to blocking fragmentson the immediate test, F(1, 38)�11.79, p�.001,MSEB.01, whereas the number of omissions didnot differ after a delay (FB1). Analyses of theother errors did not reveal any significant differ-ences, largest F(1, 38)�1.62, p�.21.

Response times. The analyses of first key RTsdid not reveal any significant differences, largestF(1, 38)�1.05, p�.31.

Discussion

The results from Experiment 1 provide evidencethat the MBE dissipates after 72 hours. At firstblush these data suggest that people are able tomanage the activation of the blocking word aftera delay and this obscures any detectable effect onperformance. Unfortunately, additional support isrequired because we have no direct evidence thatinformation from the initial study phase has anyeffect 72 hours later. In addition this study was awithin-participants design, and there are exam-ples of memory-based effects that are relegated toone type of manipulation (within or betweenparticipants). For example, McDaniel and Ein-stein (1986) reported a bizarreness effect with awithin-participant manipulation, but not whenusing a between-participant design. Similarly,Westerman, Lloyd, and Miller (2002) found thatcertain fluency-based memory effects were pre-sent in between-participants designs but not inwithin-participants designs.

EXPERIMENT 2

The purpose of Experiment 2 was to provideevidence of learning 72 hours later and determinewhether the same pattern of effects would appearif we manipulated the retention interval betweenparticipants. There were two key procedural


differences between this experiment and Experi-

ment 1. First, a condition where fragment solu-

tions were studied (positive primes hereafter) was

added to detect memory influences on responding

after a 72-hour delay, because priming is detect-

able after a 72-hour delay (e.g., Goshen-Gottstein

& Kempinsky, 2001; Kolers, 1976; Wohldmann

et al., 2007). Including positive primes also

increases the probability that participants would

intentionally consult their memory for the study

list, because some of these words were the

solutions for some of the fragments (Landau &

Leynes, 2006). If the absence of the MBE follow-

ing a delay was because memory was not inten-

tionally consulted, then the MBE should appear

on both the immediate and delayed tests.The second procedural change was that we

manipulated delay between participants to exam-

ine the external validity of the results reported in

Experiment 1 and to eliminate the possibility that

the results in Experiment 1 were a result of some

type of carryover effect. In addition, we ad-

dressed any potential experimental power con-

cerns by testing a larger sample.

We predicted that the MBE effects woulddissipate after the delay (replicating Experiment1) but that a repetition priming effect wouldappear after the delay. Such evidence woulddemonstrate that blocking words are capable ofaffecting responses after the delay.

Method

Participants, stimuli, and procedure. A total of115 College of New Jersey undergraduates parti-cipated for partial course credit, and none ofthem had participated in Experiment 1. Thestimuli were the same as those used in theprevious experiment. People saw a random selec-tion of 40 blocking words and 40 positive primesduring the encoding task. People in the immedi-ate test condition were tested immediately afterthe experimenter delivered the instructions (n�48), whereas people in the delay test conditionreturned after 72 hours to complete the fragmenttest. Because 7 participants failed to return forthe second session their data were not included inthe analyses, and this produced a final sample of60 participants in the delay condition. Each

TABLE 1

Proportion of responses (top) and response times (bottom) for Experiments 1 and 2

Experiment 1 Experiment 2

Test

Immediate Delay Immediate Delay

Fragment type Completions

Positive � � .63 (.12) .49 (.15)

Control .37 (.14) .36 (.15) .36 (.15) .36 (.14)

Blocking .30 (.14) .35 (.15) .31 (.16) .35 (.15)

MBE �.07* �.01 �.05* �.01

PPE � � .27* .13*

Intrusion errors

Positive � � .02 (.03) .05 (.05)

Control .08 (.07) .06 (.07) .04 (.03) .06 (.06)

Blocking .10 (.08) .06 (.07) .08 (.06) .06 (.06)

Omission errors

Positive � � .26 (.11) .31 (.12)

Control .37 (.16) .41 (.18) .46 (.18) .41 (.15)

Blocking .42 (.15) .40 (.18) .48 (.17) .43 (.15)

Other errors

Positive � � .09 (.08) .15 (.12)

Control .19 (.15) .17 (.17) .14 (.11) .17 (.14)

Blocking .18 (.13) .19 (.16) .14 (.12) .17 (.13)

First key RTs

Positive � � 2930 (556) 3100 (765)

Control 3496 (920) 3454 (933) 3748 (894) 3557 (894)

Blocking 3392 (774) 3558 (936) 3700 (1003) 3523 (849)

The value in parentheses is the standard deviation. MBE (memory block effect)�block fragment completions � control fragment

completions. PPE (positive priming effect)�positive prime fragment completions � control fragment completions. An asterisk

indicates that the MBE or PPE was significant.

MEMORY BLOCKING 857

fragment completion test contained 40 blocking,40 positive, and 40 control fragments.

Results

The right-hand column of Table 1 displays thedependent measures for Experiment 2. Eachmeasure was analysed using a 3 (fragment type:blocking, control, and positive)�2 (test: immedi-ate, delay) mixed ANOVA model.

Correct completions. Overall fragment comple-tion rates were unaffected by the delay, F(1,106)�1.85, p�.18. However, the fragment ef-fect, F(2, 212)�314.75, pB.001, MSE�.01, andthe Fragment�Test interaction were significant,F(2, 212)�44.51, pB.001, MSE�.01. Plannedcomparisons revealed a significant MBE on theimmediate test, F(1, 47)�14.01, pB.001, MSE�.01, but not when people were tested after a 72-hour delay (FB1). In contrast, repetition priming(increased completions relative to control frag-ments) was found on both the immediate, F(1,47)�321.87, pB.001, MSE�.01, and delayedtests, F(1, 59)�127.70, pB.001, MSE�.01.

Errors. The analysis of intrusions revealedsignificant effects of fragment type, F(2, 212)�26.00, pB.001, MSE�.01, and Fragment�Testinteraction, F(2, 212)�9.89, pB.001, MSE�.01.Intrusions did not differ across tests, F(1, 106)�1.57, p�.21. Post-hoc comparisons revealed thaton the immediate test more intrusions wereobserved for blocking fragments, F(1, 47)�27.29, pB.001, MSEB.01, and fewer intrusionswere observed for positive fragments, F(1, 47)�10.03, p�.003, MSEB.01, relative to controlfragments. Intrusions did not differ as a functionof fragment type on the delay test, F(2, 118)�2.32, p�.10.

The analysis of omissions revealed a significanteffect of fragment type, F(2, 212)�148.35, pB.001, MSE�.01, and the Fragment�Test inter-action was also significant, F(2, 212)�17.00,MSE�.01. Omissions did not vary across tests,FB1. A post-hoc comparison of omissions forblocking and control fragments did not reveal anysignificant differences, largest, F(1, 106)�2.61,p�.11. However, fewer omissions were observedfor positive fragments relative to the controlfragments on both the immediate, F(1, 47)�139.90, pB.001, MSE�.01, and delayed tests,F(1, 59)�55.08, pB.001, MSE�.01.

Analysis of the other errors revealed a sig-nificant effect of fragment type, F(2, 212)�15.93,pB.001, MSEB.01. The test main effect, F(1,106)�2.12, p�.09, and Fragment�Test interac-tion, F(2, 212)�2.39, p�.09, were not significant.Post-hoc tests revealed that fewer other errorswere observed for positive fragments relative tocontrol on both the immediate, F(1, 47)�17.01,pB.001, MSEB.01, and delay tests, F(1, 59)�6.93, p�.011, MSEB.01.

Response times. The analyses of first key RTsrevealed a significant effect of fragment type, F(2,212)�49.91, pB.001, MSE�271697.62, and asignificant Fragment�Test interaction, F(2,212)�4.09, p�.018, MSE�271697.62. A post-hoc comparison of the blocking and controlfragment RTs did not reveal any significantdifferences, largest F(1, 106)�1.36, p�.25. How-ever, faster RTs were observed for positivefragments relative to control on both the im-mediate, F(1, 47)�76.93, pB.001, MSE�208439.73, and delay tests, F(1, 59)�23.90, pB.001, MSE�261811.40.

Discussion

The results of the present study replicated andextended the results from Experiment 1. TheMBE was observed on the immediate test butdisappeared after the 72-hour delay. Importantly,this effect cannot be due to any type of carryovereffect because these effects were assessed be-tween participants. In addition, low statisticalpower seems an unlikely explanation because ofthe sufficient sample size, the fact that the MBEwas observed on the immediate test, and the factthat repetition priming was observed after the 72-hour delay. A more likely explanation for theoutcome of Experiments 1 and 2 is that the MBEdisappears after a delay.

One explanation for this pattern of results isthat the blocking words were simply forgotten, sothat they no longer exerted any interferinginfluence over behaviour and did not requireany cognitive control. This possibility seemsunlikely because repetition priming was observedafter the delay and there is no reason to suspectthat activation of the blocking words and positiveprimes differed in any appreciable way after the72-hour delay. Another problem with a forgettingexplanation is that it is inconsistent with theevidence that the MBE persists when participants


are instructed to ignore or forget the blockingwords (Landau & Leynes, 2006; Logan & Balota,2003; Smith & Tindell, 1997). These resultssuggest that actively trying to forget the blockingwords has little impact on the MBE.2

Although the instructions to forget blockingwords appear to have little influence on blocking,it is important to acknowledge that the directionsin these studies did not provide participants withitem-specific knowledge. Most often the instruc-tions to forget blocking words were delivered justbefore the fragment completion test and werefairly ambiguous with respect to which specificwords to forget or avoid. For example, Smith andTindell (1997) told their participants to avoidsome of the studied words despite the fact thatthey were similar to the fragments. Landau andLeynes (2006) and Logan and Balota (2003) usedsimilar instructions with some additional precau-tions. However, none of these instructions wasspecific about which words to disregard. As aresult, participants might have discounted theexperimenters’ warnings because the instructionswere not sufficiently specific or because peoplemistakenly believed that the study list wordswould help them solve the fragments. Impor-tantly, Smith and Tindell provided detailed in-structions in their fourth experiment when theyprovided a warning signal prior to each of theblocking fragments. However, this warning wasalso somewhat ambiguous because there was nodirect connection between the fragment and theblocking word, so participants might have beenunsure about which words they were supposed todisregard on any particular trial.

EXPERIMENT 3

If people can intentionally forget the blockingwords, then providing item-specific informationregarding the accuracy of the blocking wordduring the fragment completion test should elim-inate the MBE. The purpose of Experiment 3 wasto test this hypothesis using a paradigm in whichwords (hereafter referred to as flanker words)appeared directly above the fragment. Some ofthe flankers were the blocking words for that

particular fragment and some of them wereunrelated to the fragment. Presenting wordsdirectly above the fragment during the testprovided the participants with unambiguous evi-dence that the word was not the correct fragmentsolution.

If people can intentionally forget or ignore theinterfering information, then the blocking flankerword should be immediately eliminated as aviable fragment solution, which should allowmore time to search memory for alternativesolutions and increase the probability of success-ful retrieval (eliminating the MBE). We expectedto observe the MBE in the unrelated flankercondition (fewer completed blocking fragmentsrelative to control) because the semantic informa-tion was unrelated to the fragment.

Method

Participants, stimuli, and procedures. A total of40 undergraduates at the College of New Jerseyparticipated for partial course credit. None ofthese people had participated in any of theprevious experiments. The stimuli were thesame as those used in the previous experiments,except the computer software selected 60 unre-lated words from a separate pool of words. Eachunrelated word was randomly assigned to afragment, with the restrictions that it was thesame length, had a different first letter, and hadlow orthographic overlap with the fragment.

The procedures were similar to the previousexperiments with the following exceptions. Dur-ing the encoding task participants saw 60 blockingwords in the centre of a monitor and then had 5 sto rate how the word made them feel using a scalefrom 1 (very bad) to 5 (very good).

Next, participants attempted to complete 120fragments during the fragment completion task.On each test trial, a flanker word was printedtwo lines above the fragment with a space inbetween each character. For half of the test trialsthe flanker word was the blocking word for thatfragment (see panel B of Figure 1), whereas theflanker word was unrelated to the fragment forthe other half of the trials (see panel C of Figure1). Participants were told that a word wouldappear above the fragment and that they shouldignore this word because it would not help themsolve the fragment. The computer softwarerandomly assigned the stimuli to the fragmenttype and flanker type conditions, and randomisedthe trial sequence for both tasks.

2 It is important to acknowledge that intentional forgetting

prompted by instructions may not necessarily involve the same

mechanism as forgetting over time. We address the issue of

changes in orthographic activation over time more fully in the

General Discussion.

MEMORY BLOCKING 859

Results

The left-hand column of Table 2 displays the

dependent measures for Experiment 3. Each

dependent measure was analysed using a 2

(fragment type: blocking, control)�2 (flanker

word: blocking, unrelated) repeated measures

analysis of variance (ANOVA).

Correct completions. The data show evidence ofblocking because, overall, the presence of the

blocking flankers resulted in fewer completed

fragments (M�.32, SD�.12) than unrelated

flankers (M�.35, SD�.12), F(1, 39)�7.16, p�.011, MSE�.01.3 The number of completions did

not vary as a function of fragment type, and theFragment Type�Flanker interaction was also notsignificant, FsB1. Because presentation of theunrelated flankers served as a type of controlcondition in this experiment, we expected toobserve the MBE in this condition. To test thisparticular prediction a planned comparison con-trasted control fragment completions (.37) withblocking fragment completions (.34) when theunrelated flanker appeared above the fragment.Unexpectedly, this contrast did not reveal asignificant MBE, F(1, 39)�1.50, p�.23.

Errors. Analyses of intrusion errors revealed agreater number of intrusions for blocking thancontrol fragments, F(1, 39)�14.65, pB.001,MSEB.01. The flanker main effect was notsignificant, F(1, 39)�3.56, p�.07. However, theFragment Type�Flanker interaction was signifi-cant, F(1, 39)�12.06, p�.001, MSEB.01. Posthoc contrasts revealed that blocking fragmentsproduced more intrusions in the unrelated flankercondition, F(1, 39)�18.78, pB.001, MSEB.01,whereas intrusions did not differ in the blockingflanker condition (FB1).

The analyses of omission errors revealed only amain effect of flanker, indicating that there weremore omissions in the blocking flanker condition(M�.44, SD�.15) as compared with the unre-lated flanker conditions (M�.38, SD�.13) F(1,39)�18.94, pB.001, MSE�.01.

3 It is important to note that memory blocking can be

evidenced in two different measures in the flanker paradigm.

First, the Smith and Tindell (1997) MBE can be seen when

fewer blocking fragments are completed relative to control

fragments. Blocking may also appear (not a traditional MBE)

when blocking flankers decrease completions relative to other

types of flankers. In this paradigm the control fragment label

has been used to identify fragments that were totally unrelated

to any words presented in the first phase of the experiment.

Therefore, the control fragment label may be somewhat

misleading in the blocking flanker condition because these

flankers might influence fragment completions (by causing

blocking). In this paper MBE refers to cases when blocking

fragment completions are less than control fragment

completions, whereas the more general term ‘‘blocking’’ will

be used when there is other evidence that memory was

blocked.

TABLE 2

Proportion of responses and response times for Experiments 3 and 4


Flanker Flanker

Blocking Unrelated Blocking Unrelated &&&&&&


Control .32 (.15) .37 (.14) .29 (.15) .34 (.17) .37 (.17)

Blocking .32 (.13) .34 (.14) .30 (.19) .34 (.17) .30 (.15)

MBE .00 �.03 .01 .00 �.07*

Intrusion errors

Control .04 (.09) .05 (.05) .07 (.09) .05 (.05) .05 (.06)

Blocking .05 (.11) .09 (.09) .06 (.08) .09 (.10) .09 (.10)

Omission errors

Control .44 (.17) .39 (.15) .49 (.17) .44 (.17) .40 (.18)

Blocking .45 (.16) .38 (.14) .50 (.19) .41 (.18) .45 (.16)

Other errors

Control .20 (.14) .20 (.15) .16 (.13) .17 (.14) .17 (.14)

Blocking .18 (.16) .19 (.14) .15 (.15) .16 (.13) .16 (.13)

First key RTs

Control 4219 (1319) 3371 (767) 4418 (1166) 3705 (1057) 3502 (800)

Blocking 4058 (884) 3725 (1082) 4316 (1116) 3968 (969) 3682 (1134)

The value in parentheses is the standard deviation. MBE (memory block effect)�block fragment completions � control fragment

completions. An asterisk indicates that the MBE was significant.


Analysis of other errors did not reveal anysignificant differences, largest F(1, 39)�3.54, p�.07.

Response times. The time to enter the firstletter did not vary as a function of fragment type(FB1); however, First Key RTs were slower withthe blocking flankers, F(1, 39)�34.70, pB.001,MSE�401433, and there was a significant Frag-ment Type�Flanker interaction, F(1, 39)�5.58,p�.023, MSE�475757. Post-hoc comparisonsrevealed that first key RTs were slower forblocking fragments in the unrelated flanker con-dition, F(1, 39)�6.28, p�.016, MSE�399843,but that RTs did not differ in the blocking flankercondition (FB1).

Discussion

Two pieces of evidence indicate that the flankerscaused blocking. First, the number of correctlycompleted fragments decreased when the block-ing words served as flankers. Second, responsetimes slowed when the blocking words appearedas the flankers.

Additional evidence suggests that people wereunable to actively ignore or forget the blockingwords and avoid blocking. First, there were fewerintrusions and more omissions in the blockingflanker condition, which suggests that the block-ing flankers produce the realisation that thosewords did not complete the fragments. However,recognition of the mismatch between the flankersand the fragment solutions did not lead to greaterfragment completion rates. These results arestrong evidence that search of memory is blockedeven when the blocking word is clearly not thecorrect solution and should be avoided. Second,the blocking flankers impaired fragment comple-tion even when the blocking word was not studied(i.e., for the control fragments with a blockingword flanker). This finding indicates that present-ing the blocking word only during fragmentcompletion test can elicit blocking. Collectivelythese findings are consistent with previous studiesthat found instructions to avoid the influence ofblocking words were largely ineffective (Landau& Leynes, 2006; Logan & Balota, 2003; Smith &Tindell, 1997) and further demonstrate that block-ing is unavoidable even when the instructions areitem specific, in which the incorrect answers arepresented during the fragment completion task.

One surprising finding was the small, non-

significant MBE in the unrelated flanker condition

(M��.03, SD�.12; only 18 of 40 participants

showed any blocking). Because distraction at

study reduces the magnitude of the MBE

(Kinoshita & Towgood, 2001), one explanation

for this result is that the unrelated flanker distracts

people’s attention away from the interfering

information (i.e., the blocking word), improving

the probability that people will retrieve the correct

fragment solutions.Interestingly, this finding is conceptually simi-

lar to one that emerged in the conformity to

experimenter-provided exemplars literature (e.g.,

Marsh, Landau, & Hicks, 1996; Smith, Ward, &

Schumacher, 1993). In those studies participants

see examples of a particular target item (e.g., a

space alien), are admonished not to copy the

examples, and are then asked to create their

own, new items. The typical result from these

studies is that people use what is active in

memory and incorporate a significant number

of features from the examples into their own

designs. Landau and Leynes (2004) found that

people incorporated fewer features from the

examples when they were asked to include

specific information (i.e., a shape) into the novel

space creatures. Having to include specific in-

formation into their creatures disrupted their

preferred generative strategies, changed the

types of features they considered, and thus

subsequently reduced the level of conformity to

the examples.Presenting an unrelated flanker in the MBE

paradigm might produce a similar result. For

example, the unrelated flanker word might divert

attention away from the blocking word, alter the

default search process, and leave time to search

for the correct fragment solution. If a similar

mechanism is operating in these two paradigms,

then it is reasonable to predict that the type of

flanker should be a critical factor because Landau

and Leynes (2004) found that only certain shapes

caused a reduction in conformity. More specifi-

cally, they observed the typical elevated level of

conformity when the shapes were easy to incor-

porate in a space alien and a reduced level of

conformity when the shapes were more difficult

to include in the creatures. This result suggests

that some information is more likely to disrupt

memory search processes than other types of

information in the MBE paradigm.

MEMORY BLOCKING 861

EXPERIMENT 4

Experiment 4 was designed to replicate theresults from Experiment 3 and to add an addi-tional control condition to help clarify the factorsresponsible for eliminating the MBE in Experi-ment 3. More specifically, a flanker devoid ofsemantic information (i.e., a series of ampersands,&&&&&&) was added to determine whethersemantic information in the flanker word wasnecessary to reduce the MBE. If the type ofinformation provided by the flanker is a criticalcomponent in reducing the MBE, then the MBEshould be observed in the ampersand flankercondition but not in the unrelated flanker condi-tion.

Method

Participants, stimuli, and procedure. A total of48 undergraduates at the College of New Jerseyparticipated for partial course credit. None ofthese people had participated in any of theprevious experiments. The stimuli and procedureswere the same as those used in Experiment 3 withthe following exceptions. A third condition con-sisting of a series of ampersands presented abovethe fragment was added. The number of amper-sand characters matched fragment length on eachtrial. An equal number (i.e., 40) of the 120fragments were presented with blocking flankers,unrelated word flankers, or ampersands flankers.Of the 40 fragments in each of the three condi-tions, 20 were blocking and 20 were controlfragments.

Results

The right-hand columns of Table 2 display thedependent measures for Experiment 4. Eachmeasure was analysed using a 2 (fragment:blocking, control)�3 (flanker: blocking, unre-lated, and ampersand) repeated measures analy-sis of variance (ANOVA) model.

Correct completions. The ANOVA revealedsignificant main effects for flanker, F(2, 94)�8.36, pB.001, MSE�.01, and fragment, F(1,47)�4.34, p�.043, MSE�.01, and aFragment�Flanker interaction, F(2, 94)�3.56,p�.032, MSE�.01. The MBE was not observedin the unrelated (FB1) or blocking flankerconditions (FB1). However a strong MBE was

observed in the ampersand condition, F(1, 47)�11.43, p�.001, MSE�.01. The overall pattern ofresponding in the blocking and unrelated flankerconditions indicates that there were differentreasons why these two conditions failed toproduce the MBE. Whereas the blocking flanker(M�.29, SD�.15) decreased completions (aform of blocking) relative to the ampersandcontrol (M�.34, SD�.16) F(1, 47)�12.07, p�.001, MSE�.01, the unrelated flanker comple-tions (M�.34, SD�.16) were greater than block-ing flanker completions, F(1, 47)�12.98, p�.001,MSE�.01, but not different from the ampersandcontrol (FB1). These results indicate that theunrelated word eliminates the MBE, becausecompletions did not differ between blocking andcontrol fragments and overall completions did notdiffer from the ampersand control.

Errors. Intrusions were unaffected by theflanker (FB1); however, exposure to the block-ing word during encoding produced more intru-sions, F(1, 47)�10.23, p�.002, MSEB.01, andthe Fragment�Flanker interaction was signifi-cant, F(2, 94)�7.00, p�.001, MSEB.01. Posthoc contrasts revealed that blocking fragmentsproduced more intrusions than control for boththe unrelated, F(1, 47)�9.57, p�.003, MSE B

.01, and ampersands flankers, F(1, 47)�10.16,p�.003, MSEB.01, but there was no differencein the number of intrusions for the blockingflanker condition, F(1, 47)�1.14, p�.29.

Omissions varied as a function of flanker, F(2,94)�15.50, pB.001, MSE�.01, but were unaf-fected by fragment type (FB1). The Fragment�Flanker interaction was marginally significant,F(2, 94)�3.09, MSE�.01, p�.05. Post hoccontrasts revealed that the blocking flanker con-dition produced more omissions than both theunrelated, F(1, 47)�19.18, pB.001, MSE�.01,and ampersands flanker conditions, F(1, 47)�21.49, pB.001, MSE�.01, whereas omissionsdid not differ between the unrelated and amper-sand flanker conditions (FB1). The 2�2 AN-OVA conducted on other errors did not revealany significant differences, largest F(1, 47)�1.67,p�.20.

Response times. The time to enter the firstletter did not vary as a function of fragment (FB1) and there was no significant Fragment�Flanker interaction, F(2, 94)�1.50, p�.2. How-ever, RTs were affected by flanker, F(2, 94)�24.40, pB.001, MSE�604713.49. Post hoc con-trasts revealed that unrelated flanker RTs were


faster than the blocking flanker RTs, F(1, 46)�15.38, pB.001, MSE�860308.89, and slower thanthe ampersands flanker RTs, F(1, 46)�10.51, p�.002, MSE�343976.85.

Discussion

The results of the unrelated flanker conditionreplicated the findings of Experiment 3. Blockingpersisted even when it was obvious that theblocking words were not viable solutions, andprovided additional evidence that attempts tointentionally ignore or forget the blocking wordshave little impact on blocking (cf. Landau &Leynes, 2006; Logan & Balota, 2003; Smith &Tindell, 1997). More importantly, these findingsalso demonstrate that unrelated semantic infor-mation active during fragment completion re-duces the MBE to the point where blockingfragment completions are similar to baselinecompletion rates. These results are evidence thatthe MBE is not impervious to all experimentalmanipulations.

Although the exact mechanism that producedthis pattern of effects is not entirely clear, thesefindings suggest that the type of informationactive in immediate or working memory deter-mines whether or not blocking occurs. Appar-ently, a blocking fragment causes the spontaneousretrieval of the orthographically similar blockingwords. These blocking words enter into workingmemory and obstruct a search for solutions to thefragment. However, the simultaneous activationof semantic alternatives displaces the blockingword from working memory clearing a path tosearch memory.

EXPERIMENT 5

The findings of Experiments 3 and 4 suggest thatactivating alternative word fragment solutions(i.e., information other than the blocking word)can influence blocking. One important goal ofExperiment 5 was to further explore this possibi-lity. To address this goal, we combined aspects ofthe directed forgetting paradigm (e.g., Bjork,1970) with the MBE paradigm.

Researchers have investigated directed forget-ting using two primary types of experimentaldesigns: the item and list methods (see MacLeod,1999). Under the item method participants areinstructed to forget (or remember) each item as it

appears during encoding. The list method differsin that participants receive the forget instructionafter studying an entire list of items. Often,memory is better for those items that were to-be-remembered versus those that were to-be-forgotten in both paradigms; however, thesetwo methods appear to create directed forgettingeffects differently. MacLeod (1999) suggestedthat the item method causes encoding to beterminated for forget items so that they are notas well encoded. Conversely, all items are equallyencoded under the list method; therefore thedirected forgetting effects are more likely a resultof restructuring the information in memory. Onesuggestion is that the forget items are inhibited(MacLeod, 1999).

Because directed forgetting effects also gen-eralise to a fragment completion test (MacLeod,1989), we hypothesised that blending directedforgetting with memory blocking could providepotentially useful information. More specifically,participants were exposed to two differentiatedlists during the encoding phase. One list con-tained all blocking words, whereas the other listcontained correct fragment solutions (i.e., posi-tive primes). After the study phase we instructedparticipants to forget the words on the blockinglist. We used the list method to ensure that bothblocking words and solutions were sufficientlyencoded and to determine whether blockingwords could be suppressed in this context. Afragment completion test followed this studyphase. Some of the fragments on the test werecontrol fragments and some were typical blockingfragments because only the blocking word wasencountered in the study phase. The solutions andblocking words were encountered (on differentlists) for the last set of fragments (blocking�positive fragments hereafter).

This hybrid paradigm has two major advan-tages. First, the ability to suppress the blockingwords can be assessed by comparing the differ-ence between blocking and control fragmentcompletions. If the deleterious effects of theblocking words can be suppressed when theblocking words are identified by the forgetinstruction, then the MBE should be eliminated.Alternatively, the MBE might persist despite thedirected-forgetting instruction if, as the previousliterature suggests, the MBE cannot be volunta-rily avoided when there are no alternativesin memory to select. Second, the effect ofactive alternatives on blocking can be assessedby examining the blocking�positive fragment

MEMORY BLOCKING 863

completions. To the extent that blocking wordsand solutions are similarly active but at lowerthresholds in the control condition, control com-pletions represent baseline levels of selecting asolution from among many competitors. If theactivated solutions and blocking words simplycancel, then the blocking�positive fragmentcompletions should not differ from control levels.Alternatively, the blocking�positive fragmentcompletions might be greater than control com-pletions. Such a result would provide evidencethat selecting and/or rejecting activated alterna-tive candidates is an important process in memoryblocking.

Method

Participants, stimuli, and procedure. A total of44 College of New Jersey undergraduates parti-cipated for partial course credit, and none ofthem had participated in any of the other experi-ments. The stimuli were drawn from the samepool as those used in the previous experiments.

The procedures were similar to the previoustwo studies because one-third of the test frag-ments corresponded to blocking words seen onthe encoding task and one-third of the fragmentsserved as control items. One key difference in theprocedures was that the blocking words andpositive primes were seen during encoding forthe remaining third of the fragments. Anotherimportant change was that participants studiedtwo separate lists of words during the encodingphase: one list contained 60 blocking words,whereas the other list contained 60 positiveprimes. The order of the lists was counterba-lanced across participants and a filler task (10math problems) separated the lists. Of thesestudied words, 30 blocking words were randomlyassigned to the blocking fragment condition (e.g.,ACCOUNT is presented for the A _ C _ N T Sfragment). The remaining 30 blocking wordscorresponded to 30 positive primes on the otherlist (blocking�positive fragments). For example,the blocking list would contain the blocking wordEXPLODE and the positive prime list wouldcontain EXALTED because both words corre-spond to the fragment E X _ L _ _ D. The other30 positive primes served as fillers to equate thelength of the two study lists; consequently, thecorresponding fragments for these filler primeswere not part of the second task. To summarise,the 120 stimuli in the pool were randomlyassigned to be control fragments (unstudied),

task 1 fillers, blocking only fragments, orblocking�positive prime fragments.

The procedures for the fragment completiontest were similar to the previous experimentsexcept that no words appeared above the frag-ment and there were only 90 total fragments (30control, 30 blocking, and 30 blocking�positive).Before the fragment completion test began parti-cipants were told to forget the list that containedthe blocking words because these words wouldnot complete the fragments and to try to remem-ber the positive prime list because these wordswould help solve the fragments.

Results

The left-hand column of Table 3 displays thedependent measures for Experiment 5. Eachdependent measure was analysed using a re-peated measures ANOVA with one variable(fragment type: control, blocking, blocking�positive).4

Correct completions. The number of correctlycompleted fragments varied as a function offragment type, F(2, 86)�53.92, pB.001, MSE�.01. A MBE was evident (blocking vs controlfragments) following the directed-forgetting in-structions, F(1, 43)�8.16, p�.007, MSEB.01.Exposure to both the blocking word and positiveprime eliminated the MBE, F(1, 43)�52.40, pB

.001, MSE�.01, because fragment completionswere actually facilitated (a 16% increase).

Errors. Intrusions were also affected by frag-ment type, F(2, 86)�14.58, pB.001, MSEB.01.More intrusions were observed for blockingfragments relative to control fragments, F(1,43)�17.88, p�.001, MSEB.01. Intrusions didnot differ between the control and blocking�positive fragments, F (1, 43)�3.56, p�.07.

The number of omissions also varied as afunction of fragment type, F(2, 86)�27.08, pB

.001, MSEB.01. Fewer omissions were observedfor the blocking�positive fragments relative tocontrol, F(1, 43)�38.19, pB.001, MSE�.01, andomissions did not differ between the control andblocking fragments (FB1).

4 The data were also analysed using a model that included a

factor for the order of the list presentation. Because list order

did produce any significant interactions with the fragment type

variable, these analyses are not described further.


A similar pattern was observed for othererrors, F(2, 86)�7.49, p�.001, MSE�.01. Theblocking�positive fragments had fewer othererrors relative to control fragments, F(1, 43)�12.60, p�.001, MSE�.01, and other errors didnot differ between the control and blockingfragments (FB1).

Response times. The time to enter the firstletter varied as a function of fragment type, F(2,86)�25.35, pB.001, MSE�380248.83. RTs didnot differ between blocking and control frag-ments (FB1); however, the blocking�positivefragments produced faster RTs relative to control,F(1, 43)�51.54, p�.001, MSE�259324.40.

Discussion

The results from this experiment demonstratethat directing people to forget the blocking wordlist did not eliminate the MBE because peoplecompleted fewer blocking fragments than controlfragments. This shows that the activation of theblocking words persists despite the instructions toforget the list of blocking words. However, havingavailable alternatives to select in memory appearsto be a critical factor for eliminating the MBE

because exposure to both the blocking word and

positive prime eliminated the MBE. More speci-

fically, studying both the blocking word and then

the positive prime resulted in increased comple-

tions, faster response times, and a distinct pattern

of errors (fewer omissions and no more intrusions

relative to control) that does not typically emerge

when memory is blocked. This result is particu-

larly intriguing because the stimuli were pre-

matched for blocking and repetition priming

effects. As a result, the positive primes and

blocking words should have had offsetting effects

that produced no net change in behaviour if the

two types of words compete as potential solutions

in a simple probabilistic formula. Finding that

fragment completion rates increased when people

studied both the blocking words and the correct

solutions suggests that people selected the correct

fragment solution and rejected the blocking word

as a solution.One unresolved issue is that these results might

be restricted to a directed-forgetting paradigm. If

this is the case, then the MBE should persist when

the study presentation of the blocking words and

correct solutions are randomly intermixed. Alter-

natively, studying both the blocking words and

solutions might create a situation where people

TABLE 3

Proportion of responses (top) and response times (bottom) for Experiments 5 and 6



Control .33 (.13) .36 (.13)

Blocking .29 (.14) .30 (.13)

MBE �.04* �.06*

Blocking�Positive .49 (.17) .54 (.16)

MBE �.16* �.18*

Intrusion errors

Control .06 (.05) .06 (.06)

Blocking .13 (.13) .11 (.11)


Omission errors

Control .23 (.19) .18 (.15)

Blocking .23 (.17) .18 (.17)


Other errors

Control .37 (.19) .39 (.19)

Blocking .36 (.15) .41 (.18)


First key RTs

Control 3574 (895) 3431 (874)

Blocking 3634 (1130) 3480 (932)

Blocking�Positive 2795 (787) 2847 (624)

The value in parentheses is standard deviation. MBE (memory block effect)�block fragment completions � control fragment

completions. An asterisk indicates that the MBE was significant.

MEMORY BLOCKING 865

can select the correct solution and/or to reject theblocking word.

EXPERIMENT 6

Method

Participants, stimuli, and procedure. A total of45 College of New Jersey undergraduates parti-cipated for partial course credit, and none ofthem had participated in any of the other experi-ments. The stimuli and general procedures werevery similar to Experiment 5 with the followingexceptions. Positive primes and blocking wordswere randomly intermixed on the first task in thisstudy. As a result there was no directed forgettinginstruction. The 120 fragments were randomlyassigned to be control, blocking, or blocking�positive (40 in each condition).

Results

The right-hand column of Table 3 displays thedependent measures for Experiment 6. Eachmeasure was analysed using a repeated measuresanalysis of variance (ANOVA) model with onevariable (fragment type: control, blocking,blocking�positive).

Correct completions. The number of correctlycompleted fragments varied as a function offragment type, F(2, 88) � 119.51, p B .001,MSE�.01. Like Experiment 5, the MBE waspresent, F(1, 44)�22.10, pB.001, MSEB.01, andexposure to both the blocking word and positiveprime eliminated the MBE, F(1, 44)�110.93, pB.001, MSE�.01, because fragment completionswere facilitated by 18%.

Errors. The numbers of intrusions were af-fected by fragment type, F(2, 88) � 8.36, pB.001, MSEB.01. More intrusions were observedfor blocking fragments relative to control frag-ments, F(1, 44)�13.11, p�.001, MSEB.01, andfor blocking�positive fragments relative to con-trol, F(1, 44)�7.80, p�.008, MSEB.01.

Omissions varied as a function of fragmenttype, F(2, 88)�23.80, pB.001, MSEB.01. Feweromissions were observed for the blocking�posi-tive fragments relative to control fragments, F(1,44)�30.55, pB.001, MSE�.01, whereas omis-sions did not differ between the control andblocking fragments (FB1).

A similar pattern was observed for othererrors, F(2, 88)�28.31, pB.001, MSE�.01. Theblocking�positive fragments had fewer othererrors relative to control fragments, F(1, 44)�33.49, pB.001, MSE�.01, whereas other errorsdid not differ between the control and blockingfragments (FB1).

Response times. The time to enter the firstletter varied as a function of fragment type, F(2,88)�31.84, pB.001, MSE�175008.57. RTs didnot differ between blocking and control frag-ments (FB1); however, blocking�positive frag-ment RTs were faster than control, F(1, 43)�50.31, pB.001, MSE�152222.74.

Discussion

The results from this experiment replicated thosereported in Experiment 5. The MBE disappearedwhen both the solution and blocking word wereactivated at study.5 These results suggest thatwhen there are alternative solutions available,people are capable of selecting fragment solutionsdespite the fact that blocking words are highlyactivated.

GENERAL DISCUSSION

The goal of the present set of experiments was toidentify situations where the MBE could beeliminated in an effort to clarify the mechanismsthat are involved in memory blocks. Table 4

5 In Experiments 5 and 6 the MBE was eliminated because

blocking�positive fragment completions were not lower than

control fragments, instead blocking�positive fragment

completions were greater than control fragments in these

conditions. As a result, one might argue that the MBE might

have been present but simply masked by the larger repetition

priming effects. However, it is important to note that both the

blocking word and solution (prime) for each target fragment

were encountered in the study phase. This procedure pits

blocking and repetition priming effects against one another for

each individual test fragment so that a particular fragment is

blocked, unaffected, or primed on each test trial. It is possible

that repetition priming or blocking may dominate for a group

of fragments, such as repetition priming appears to dominate

for blocking�positive fragments in Experiments 5 and 6. It is

also possible that blocking and repetition priming are equally

powerful for a group of fragments. In this case the two effects

would cancel and fragment completions would be similar to

control fragment completions. Either scenario points to a

complex set of fragment-level response selection processes,

which are explored in the General Discussion.


presents a summary of the MBE effects across allthe experiments and clearly demonstrates thatthe MBE is a malleable phenomenon because itwas eliminated in many of the conditions.Experiments 3 and 4 provided the surprisingfinding that unrelated semantic information pre-sented during the fragment test reduces the sizeof the MBE. Eliminating the MBE is not merelycontingent on the presentation of unrelatedsemantic information at test, because it wasalso eliminated in Experiments 5 and 6 whenboth solutions and blocking words were activatedduring study. Although these studies indicatethat having alternative information active (solu-tions or unrelated words) creates a contextwhere the fragment solutions can be selected,Experiments 1 and 2 demonstrated that solutionscan be selected after studying blocking wordsfollowing a 72-hour delay.

There were other important findings across thestudies. Experiment 2 demonstrated that repeti-tion priming persisted after a 72-hour delay whenblocking was no longer present. Blocking couldnot be actively avoided when the blocking wordwas presented above the fragment (Experiments3 & 4) or when participants were directed toforget the blocking word list (Experiment 5). Theblocking words do not need to be studied to blockfragment completions because presenting theblocking word above the fragment decreasescontrol (unstudied) fragment completions. Effectson response times were also observed acrossstudies. Exposure to the solutions resulted infaster response times immediately and after along delay (Experiment 2), whereas blockingwords did not affect response times (Experiments1 & 2). This pattern was also observed whenparticipants studied both the blocking word andthe solution for a particular fragment (Experi-ments 5 & 6). However, presenting blocking

words above the fragments slowed response times(Experiments 3 & 4), which has also beenobserved when the blocking words were pre-sented a few hundred milliseconds before thefragment (Logan & Balota, 2003) and whenshorter study lists were used (Rass & Leynes,2007).

Collectively, this evidence supports the hy-pothesis that memory retrieval in the MBEparadigm is managed by a control mechanism(Logan & Balota, 2003). The evidence alsoclarifies several important issues concerninghow such a mechanism might operate. In thetext that follows we describe some importantobservations about the MBE along with thesupporting experimental evidence.

Important characteristics of blocking

Orthographic activation decreases with time.Experiment 2 provided strong support that ortho-graphic activation is reduced when there is a 72-hour delay between exposure to the word and thefragment completion task. Specifically, repetition-priming effects were stronger in the immediatetest condition (.27) and decreased over the 72-hour delay (.13). This conclusion is also consistentwith the observation that priming decreases witha delay between study and test (Goshen-Gott-stein & Kempinksy, 2001). These results suggestthat all orthographic activation (repetition prim-ing and blocking) diminishes as a function of thetime that elapses between the first exposure andwhen the orthographic activation is retriggered.

Blocking words influence performanceautomatically. By definition, blocking wordshave a high degree of orthographic overlap withthe solutions but they do not complete thefragments. To the extent that reading is a form

TABLE 4

Summary of the memory blocking effect (MBE) across experiments

Immediate test Delay test

Experiment 1 �.07* �.01

Experiment 2 �.05* �.01

Control condition Unrelated flanker (Exp 3) Unrelated flanker (Exp 4)

Experiment 3 & 4 �.07* �.03 .00

Control condition Blocking�Positive prime

Experiment 5 �.04* .16

Experiment 6 �.06* .18

An asterisk indicates that the MBE was significant.

MEMORY BLOCKING 867

of expertise that becomes automatic (e.g., Maurer& McCandliss, 2007), reading blocking words inan experimental context automatically activatesthe blocking words above baseline levels, which inturn reduces one’s access to successful fragmentsolutions. Considerable evidence supports thisconclusion because conscious processing of theblocking word is not necessary to produce theMBE (Logan & Balota, 2003) and becauseinstructions to avoid the MBE are largely in-effective (Landau & Leynes, 2006; Logan &Balota, 2003; Smith & Tindell, 1997). The presentstudies provide additional evidence that readingthe blocking words cannot be avoided. A blockingflanker word (Experiments 3 & 4) blockedcompletion of control fragments, and participantsremained blocked even when it was obvious thatthe blocking word was not a correct solution.These findings suggest that participants read theblocking word even when it was clearly beneficialto ignore it. Collectively, these findings suggestthat reading blocking words is an automaticprocess that can impair retrieval.

A framework for an executive controlmodel of memory blocking

Logan and Balota (2003) suggested that anexecutive control mechanism plays an importantrole in discriminating between relevant andirrelevant fragment solution alternatives in theMBE paradigm because they observed age-re-lated differences in performance. They furtherspeculated that activation in the lexical networkmight be partially mediated by frontal lobestructures that control maintenance and selectionof information. The findings in the present studiessupport this argument because the MBE dissi-pated when the solutions and the blocking wordswere both active (Experiments 5 & 6) or whenunrelated words were simultaneously activated(Experiments 3 & 4). Similarly, Landau andLeynes (2006) argued that an executive controlmechanism that inhibits interfering informationmight also apply to memory blocking.

Unfortunately, exactly how an executive con-trol mechanism governs behaviour in a MBEparadigm has not been specified any further thanthis general description. In an attempt to clarifythe details of this particular mechanism, weprovide a more detailed framework for executivecontrol during blocking based on the importantconclusions described in detail earlier.

Figure 2 is a schematic representation thatillustrates several memory blocking processes inan effort to better illustrate our working frame-work. Exposure to words during encoding in-creases their activation. When the fragment isread during the test, information is automaticallyreactivated (Figure 2, panel A). Encountering afragment that is orthographically similar to aword read during study (blocking fragments)impairs fragment completion because the similarword cannot solve the fragment. Blocking wordactivation is controlled by executive functionsthat monitor responding, detect conflict, andattempt to execute goal-directed behaviour,which in the MBE paradigm is completing afragment. The dashed line in Figure 2 depictsthe reduction or control of the blocking wordreactivation. When there is a short delay betweenreading the blocking words and the fragment test,the blocking word reactivation is so strong that itexceeds what can be controlled and performanceis impaired (Figure 2, panel B). Under thisframework, the MBE represents a failure tocontrol blocking word reactivation. The reactiva-tion elicited by the fragment weakens with thepassage of time (panel C of Figure 2). After alengthy delay, the blocking word reactivationpeaks at a lower level where it can be effectivelycontrolled and performance is seemingly unaf-fected (Figure 2, panel D).

Because repetition priming effects were ob-served after a delay when no blocking effectswere observed, the executive control mechanismappears to only control competing information.As a result, a mechanism to monitor and to detectconflict must be an important part of executivefunction during blocking. This mechanism mustdetect any conflict between the automaticallyactivated but incorrect words and the correctfragment solutions. Activation elicited by positivefragments will not trigger the engagement of thecontrol mechanism for that solution becausethere is no conflict between the activation andthe solution. However, activation of the blockingword will trigger the engagement of the controlmechanism because blocking words cannot suc-cessfully complete the fragment. The efficacy ofthis conflict-detecting mechanism must also beinfluenced by the testing context. For example,the detection mechanism should be more efficientwhen it is obvious that the blocking word cannotcomplete the fragment, such as when letters in thefragment are inserted and less efficient when the


correct solution is less obvious, such as when the

entire word is retyped or spoken.

Additional challenges

Although we propose a number of conclusions

related to memory blocking in a MBE paradigm,

this framework is by no means a complete

explanation for all types of blocking that people

might encounter. It merely serves as a more

specific basis for guiding additional empirical

work. One obvious challenge is to develop a

more formal model of blocking. We pose several

important questions in an effort to stimulate the

path to this ultimate goal.

Can memory blocks be eliminated by strategies?Our findings provide evidence that activating

alternatives can eliminate blocking in some situa-

tions; however, one challenge is to help people

develop strategies that can eliminate blocking

when it happens in everyday situations. The

results from Experiments 3 and 4 hint at least

one possible strategy. These studies demonstrated

that the interference does not affect behaviour

when orthographically unrelated words are pre-

sented with the fragment. Apparently, there must

be considerable temporal overlap between the

Act

ivat

ion

Blocking Fragments Positive Fragments

Short Delay

Low

High

Low

HighA

ctiv

atio

n

Long Delay

Low

High

Effe

ct o

n B

ehav

ior

(MB

E o

r P

PE

)E

ffect

on

Beh

avio

r(M

BE

or

PP

E)

Low

High

A) B)

C) D)

Control Threshold

Figure 2. A schematic of the activation in a memory blocking paradigm. The effects of a short delay are presented at the top of the

figure. Panel A depicts the item activation, whereas Panel B depicts the net effect on fragment completion behaviour. The bottom of

the figure depicts activation (Panel C) and effect on behaviour (Panel D) after a long delay between item exposure and fragment

test.

MEMORY BLOCKING 869

presentation of the unrelated word and fragment,because blocking is not eliminated when unre-lated words are read a few hundred millisecondsbefore the presentation of the fragment (Logan &Balota, 2003), whereas presenting the unrelatedwords at the same time as the fragment eliminatesthe interference. Perhaps presenting unrelatedwords after the fragment (after blocking hasbegun) might also eliminate blocking. Such evi-dence would suggest that a simple strategy, likegenerating unrelated semantic information orturning to a different problem, might also relievethe frustrating memory blocks that people en-counter in their daily experience.

Is the blocking word activation activelyinhibited? The present studies provide strongevidence that people can actively control theretrieval process in a MBE paradigm. Onepossibility is that the blocking word activation isactively inhibited. We found some evidence thatis at least consistent with this hypothesis. First,MBE effects were not observed following a 72-hour delay (Experiments 1 & 2); however,repetition-priming effects were still present fol-lowing the same delay (Experiment 2). There isno reason to suspect that blocking words wouldbe less active than fragment solutions particularlybecause participants had no knowledge of whichitems were solutions and which were blockingwords until the fragment completion task.Although blocking words must have been just asactive as primes after the delay, they did not havethe same pervasive effect on fragment completionperformance. An active inhibition mechanismcould have suppressed some of the blockingfragment activation to assist in goal-directedbehaviour.

Inhibition processes in other domains oftenreceive support from response time measures(Anderson & Levy, 2007), and the blockingeffects also receive similar support. Slower block-ing fragment RTs emerge when the delay be-tween blocking word exposure and the fragmentis short (Logan & Balota, 2003) or there is nodelay (Experiments 3 & 4). However, these RTdifferences become marginal when short studylists are used (Rass & Leynes, 2007) and com-pletely disappear when the delay is only a fewminutes (Experiments 1, 2, 5, & 6). These resultssuggest that blocking words slow respondingwhen their activation is strong, whereas the speedof responding is unaffected when the blocking

word activation begins to weaken after a fewminutes. It is unlikely that the RT effects in thisparadigm are so transient that they dissipate in afew minutes, because RTs were faster for positivefragments after a 72-hour delay (Experiment 2).Instead, these effects can be construed as addi-tional evidence that an inhibition mechanism issuppressing the blocking word activation.

Inhibition of memory is difficult to demon-strate (see Anderson & Levy, 2007). Conse-quently, work designed to specifically addressthis hypothesis is needed to provide more con-vincing evidence. In this paper we presentseveral examples of situations where youngadults successfully avoided the MBE. Theseexperimental contexts establish baseline condi-tions which can serve as a comparison toevaluate manipulations that influence the capa-city to inhibit information.

Can the neural correlates of blocking refine ourunderstanding of blocking?. Imaging studies pro-mise to provide additional evidence for the sourceof interference in the MBE paradigm. A largenetwork of structures including prefrontal cortex,hippocampus, and posterior cingulate supportmemory processes (e.g., Aggleton & Brown,2006) and lexical activation appears to be sup-ported by left inferior occipitotemporal cortex(Maurer & McCandliss, 2007). Consequently,careful examination of the areas that are activeduring blocking should provide a better under-standing of when and how lexical activation,episodic memory, and semantic memory contri-bute to the interference in MBE paradigms.

Neuroimaging can also provide insight into thenature of executive control, conflict monitoring,and inhibition in memory blocking. Considerableevidence suggests that the prefrontal cortex per-forms many executive control functions and theanterior cingulate cortex (ACC) monitors anddetects conflict during many types of informationprocessing (for review see van Veen & Carter,2006). Therefore, the ACC might detect whenthere conflict between activated information andthe correct solution and trigger the engagementof an inhibitory mechanism, whereas prefrontalareas might work to inhibit the interference (cf.Logan & Balota, 2003).

Manuscript received 29 April 2008

Manuscript accepted 15 July 2008

First published online 27 September 2008


REFERENCES

Aggleton, J. P., & Brown, M. W. (2006). Interleavingbrain systems for episodic and recognition memory.Trends in Cognitive Sciences, 10, 455�463.

Anderson, M. C., & Levy, B. J. (2007). Theoreticalissues in inhibition: Insights from research on humanmemory. In D. Gorfein & C. MacLeod (Eds.),Inhibition in cognition. Washington, DC: AmericanPsychological Association.

Bjork, R. A. (1970). Positive forgetting: The noninter-ference of items intentionally forgotten. Journal ofVerbal Learning and Verbal Behavior, 9, 255�268.

Goshen-Gottstein, Y., & Kempinsky, H. (2001). Prob-ing memory with conceptual cues at multiple reten-tion intervals: A comparison of forgetting rates onimplicit and explicit tests. Psychonomic Bulletin &Review, 8, 139�146.

Kinoshita, S., & Towgood, K. (2001). Effects of dividingattention on the memory-block effect. Journal ofExperimental Psychology: Learning, Memory, andCognition, 27, 889�895.

Kolers, P. A. (1976). Reading a year later. Journal ofExperimental Psychology: Human Learning andMemory, 2, 554�565.

Kozak, M., Sternglanz, R. W., Viswanathan, U., &Wegner, D. M. (in press). The role of thoughtsuppression in building mental blocks. Conscious-ness and Cognition.

Landau, J. D., & Leynes, P. A. (2004). Manipulationsthat disrupt generative processes decrease confor-mity to examples: Evidence from two paradigms.Memory, 12, 90�103.

Landau, J. D., & Leynes, P. A. (2006). Do explicitmemory manipulations affect the memory blockingeffect? American Journal of Psychology, 119, 463�479.

Logan, J. M., & Balota, D. A. (2003). Conscious andunconscious lexical retrieval blocking in youngerand older adults. Psychology and Aging, 18, 537�550.

Lustig, C., & Hasher, L. (2001). Implicit memory isvulnerable to proactive interference. PsychologicalScience, 12, 408�412.

MacLeod, C. M. (1989). Directed forgetting affectsboth direct and indirect tests of memory. Journal of

Experimental Psychology: Learning, Memory, andCognition, 15, 13�21.

MacLeod, C. M. (1999). The item and list methods ofdirected forgetting: Test differences and the role ofdemand characteristics. Psychonomic Bulletin &Review, 6, 123�129.

Marsh, R. L., Landau, J. D., & Hicks, J. L. (1996). Howexamples may (and may not) constrain creativity.Memory & Cognition, 24, 669�680.

Maurer, U., & McCandliss, B. D. (2007). The develop-ment of visual expertise for words: The contributionof electrophysiology. In E. L. Grigorenko & A. J.Naples (Eds.), Single-word reading: Biological andbehavioral perspectives. Mahwah, NJ: LawrenceErlbaum Associates Inc.

McDaniel, M. A., & Einstein, G. O. (1986). Bizarreimagery as an effective memory aid: The importanceof distinctiveness. Journal of Experimental Psychol-ogy: Learning, Memory, and Cognition, 12, 54�65.

Rass, O., & Leynes, P. A. (2007). When do primes gobad? A corpus of orthographically related primesthat inhibit fragment completion. Behavior ResearchMethods, 39, 870�875.

Smith, S. M., & Tindell, D. R. (1997). Memory blocks inword fragment completion caused by involuntaryretrieval of orthographically related primes. Journalof Experimental Psychology: Learning, Memory, andCognition, 23, 355�370.

Smith, S. M., Ward, T. B., & Schumacher, J. S. (1993).Constraining effects of examples in a creativegeneration task. Memory & Cognition, 21, 837�845.

van Veen, V., & Carter, C. S. (2006). Conflict andcognitive control in the brain. Current Directions inPsychological Science, 15, 237�240.

Westerman, D. L., Lloyd, M. E., & Miller, J. K. (2002).The attribution of perceptual fluency in recognitionmemory: The role of expectation. Journal of Mem-ory and Language, 47, 607�617.

Wohldmann, E. L., Healy, A. F., & Bourne, L. E. Jr.(2007). Pushing the limits of imagination: Mentalpractice for learning sequences. Journal of Experi-mental Psychology: Learning, Memory, and Cogni-tion, 33, 254�261.

MEMORY BLOCKING 871

APPENDIX

Blocking word Positive prime Word fragment

ACCOUNT ACCENTS A _ C _ N T S

ALLIGATOR ALIENATED A L I _ _ A T _ D

ANIMAL AERIAL A _ _ I A L

BALLOON BALCONY B A L _ O N _

BARBECUE BACKBONE B A _ K B _ _ E

BEFORE BELFRY B E _ F R _

BETTER BREWER B _ E _ E R

BICYCLE BRITTLE B _ I _ _ L E

BLONDE BELONG B _ L O N _

BOTHER BOLTED B O _ T E _

BRACELET BRACKETS B _ A C _ E T S

BREAKFAST BREAKAWAY B R E A K _ _ A _

BUCKET BUCKLE B _ C K _ E

CANCER CRATER C _ A _ E R

CAREFUL CLARIFY C _ A R _ F _

CARPET CORPSE C _ R P _ E

CASTLE CRADLE C _ A _ L E

CHEESE CHIEFS C H _ E _ S

CHICKEN CHUCKLE C H _ C K _ E

CHRIST CHAINS C H _ I _ S

CIGARETTE CONGRUENT C _ _ G R _ E N T

CIRCLE CURLED C _ R L E _

CLOSING CALMING C _ L _ I N G

CLOTHES CLOTTED C L O _ T _ _

COTTON COLONY C O _ _ N _

CRAYON CANYON C A _ Y O _

CROCODILE CLOCKWISE C _ O C K _ I _ E

DAGGER DEALER D _ A _ E R

DAUGHTER DRAUGHTS D _ A _ G H T S

DECISION DEVISING D E _ I S I N _

DIFFERENT DIVERGENT D I _ E R _ _ N T

DISAGREE DISCREET D I S _ R _ E _

DISASTER DISTASTE D I S _ A S T _

DISHES DIESEL D I _ S E _

DIVIDE DERIVE D E _ I _ E

EMBARRASS ESCAPADES E S _ A _ A _ E S

EXPENSIVE EXPRESSED E X P _ E _ S _ D

EXPLODE EXALTED E X _ L _ _ D

FAILURE FATIGUE F A _ I _ U E

FINGER FIBERS F I _ _ R S

FLOWER FLAVORS F L _ _ O R S

FOOTBALL FORMALLY F O _ _ A L L _

FORTUNE FORTIES F O _ T _ E S

FREEDOM FOREARM F _ R E _ _ M

GAMBLE GIBLET G _ B L E _

GRANDMA GROANED G R _ A N _ _

GUITAR GUTTER G U T _ _ R

HAMBURGER HOMEBOUND H _ M E B _ U _ D

HEADACHE HARDSHIP H A _ D _ H I _

HEALTH HERALD H E _ A L _

HIGHWAY HAUGHTY H _ _ G H _ Y

HUNGRY HURRAY H U _ R _ Y

HURRICANE HERITAGES H _ R I _ A _ E S

HUSBAND HUSTLED H U S _ _ E D

INDIAN INFANT I N _ A N _

INNOCENT INVOICES I N _ O _ C E S

INSTRUMENT INSTITUTED I N S T _ _ U _ E D

KANGAROO KINGDOMS K _ N G _ O _ S

LANGUAGE LINEAGES L _ N _ A G E S

LAWYER LOWERS L _ W _ R S

LEAVES LEVELS L _ V E _ S

LETTERS LEATHER L E _ T _ E R

LISTEN LESSEN L _ _ S E N

LUGGAGE LAUGHED L _ U G _ E _

MAXIMUM MARXIST M A _ X I _ _

MIDDLE MILDEW M I _ D E _

MONKEY MOANED M O _ N E _

MOTORCYCLE MONOPOLIES M O _ O P _ L _ E S

MOUNTAIN MOUNTING M O U _ T _ N _

MUFFIN MUTINY M U _ I N _

MUSCLE MISLED M _ S L E _

MUSTARD MUSICAL M U S _ _ A _

MYSTERY MOISTEN M _ _ S T E _

NICKEL NIECES N I _ C _ S

OBJECTIVE OBSCENITY O B _ C E _ I T _

ORANGE ORNATE O R _ A _ E

PAINTER PARTNER P A _ _ N E R

PANCAKES PANICKED P A N _ C K E _

PARENT PARROT P A _ R _ T

PERFUME PRESUME P _ E _ U M E

PERIOD PARODY P _ R O D _

PERSON PISTON P _ S _ O N

PICKLE POCKET P _ C K E _

PICTURE PROCURE P _ _ C U R E

PIMPLE PUMPED P _ M P E _

PLEDGE PLEADS P L E _ D _

POTATO PORTAL P O _ T A _

PRECISE PREFACE P R E _ _ C E

PRESENT PERCENT P _ R _ E N T

PURPLE PROPEL P R _ P _ L

RECIPE RECOIL R E C _ I _

REPUBLICAN REBUILDING R E _ U I L _ I N _

SAUCER SPACER S _ A C _ R

SECOND SPENDS S _ E N D _

SELLER SHELLS S _ E _ L S

SHALLOW SHADOWS S _ A _ O W S

SHOVEL SHIELD S H _ E L _

SHOWER SWERVE S W _ R _ E

SIDEWALK SNOWFALL S _ O W _ A _ L

SILVER SAILOR S _ I L _ R

SMOOTH SCOTCH S _ O T _ H

SPIDER SPRITE S P _ I _ E

SQUARE SQUEAL S Q U _ A _

STANDING STUNNING S T _ _ N I N G

STOMACH STAMINA S T _ M _ _ A

STOPLIGHT STROLLING S T _ O _ L I N _

STORAGE SCOURGE S _ O _ R G E

STREAM STORMY S T _ R M _

SUBJECT STUBBLE S _ U _ B _ E

SUBTRACT SUBTLETY S U B T _ _ T _

SUNSET SANEST S _ N _ S T

THOUGHT THRUSTS T H _ U _ T S

TISSUE TINSEL T I _ S E _

TOILET TILTED T _ L _ E D

TORNADO TORMENT T O R _ _ N _

TRAILER TRIPLED T R I _ L E _

VEGETABLE VERTEBRAL V E _ T E B _ _ L

WINTER WITHER W _ T _ E R

WRITER WRISTS W _ I _ T S

YELLOW YIELDS Y _ E L _ _


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Eliminating the memory blocking effect

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