Memory Inhibition – Arizona Forensic Services, LLC

Snap Shot

The question: Can the act of remembering some things, or trying not to think about others, make memories harder to retrieve, and does that research bear on claims of repressed memory?

What the research shows: Practicing retrieval of some details can temporarily impair recall of related details that were not practiced, including in an eyewitness procedure and in conversation. In some studies, people told to keep a memory out of mind later recalled it somewhat less well (a meta-analysis found a small-to-moderate suppression effect in healthy participants), but the effect has not been found consistently and a preregistered replication found none.

What it does not show: The suppression effect is variable, has failed in several replication attempts including a preregistered one, and was weaker in anxious and depressed participants. Laboratory word-pair studies do not establish that trauma can be unconsciously repressed and later recovered, nor that it cannot, and they cannot show what happened to any one person’s memory.

The law: Expert testimony on these effects is governed by Rule 702 and, in courts-martial, Houser; in Arizona, Chapple and Nordstrom allow general memory testimony but not an opinion that a particular witness is right or wrong.

Issues for each side: Prosecutors should obtain and record a complete free account before targeted questioning and should not rest a recovered-memory case on inhibition research; defense counsel can show how selective questioning may narrow an account, but should not present the suppression literature as proof that a particular memory was lost, recovered, or false.

Remembering depends not only on bringing the right information to mind but also on keeping competing information out of the way. Memory inhibition is the name researchers give to processes that are thought to reduce the accessibility of memories that compete with, or are unwanted by, the person trying to remember. On this view some forgetting is not a passive loss but a by-product of using memory: a person who tries to recall where the car is parked today is helped if yesterday’s parking spot is harder to retrieve.

The topic reaches court in two ways. The first is practical and concerns interviewing: if retrieving some details makes related details harder to recall, then repeated questioning about selected facts, or a conversation that covered only part of an event, may shape what a witness can later report. The second is contested: deliberate memory suppression has been offered as a laboratory model of repression, and the research is cited on both sides of the debate over recovered memories of abuse.

This paper describes retrieval-induced forgetting, directed forgetting, and the think/no-think procedure; the replication record and the theoretical dispute over whether “inhibition” is the right explanation; and what the research does and does not contribute to the repression debate. It then addresses the limits of the evidence and the law governing expert testimony on these topics.

Retrieval-Induced Forgetting

In the standard procedure, participants study category-item pairs (for example, several fruits and several drinks) and then repeatedly practice retrieving half of the items from some categories. On a later test, the practiced items are recalled better, as expected. The surprise is that the unpracticed items from the practiced categories are recalled worse than items from categories that were never practiced at all (Anderson et al., 1994). The act of retrieving some memories appears to reduce access to related ones. A meta-analysis found this retrieval-induced forgetting across many procedures and materials, with results that largely, though not uniformly, supported the view that retrieval itself, and not mere re-exposure, produces the effect (Murayama et al., 2014).

The effect has been demonstrated with witnessed material. In a mock-eyewitness study, participants who were repeatedly questioned about some of the objects they had seen later recalled other, unquestioned objects of the same kind less well than comparable baseline details, even though the questioning contained no misleading information (Shaw et al., 1995). Conversation can produce the same result: when one person recounts part of a shared experience, listeners later have more difficulty recalling related details that the speaker left out (Cuc et al., 2007). Lane and Houston (2021, pp. 133–134) draw the forensic implication that conversations before an interview may suppress details no one discussed.

The effect also has limits. Retrieval-induced forgetting has faded quickly in some studies. A 2026 study with a single retrieval session found it within minutes and hours of the selective retrieval but not after a day or a week, because the unpracticed items were then forgotten more slowly than the controls (Meixensperger & Bäuml, 2026); by contrast, a 2025 study found socially shared forgetting persisted up to three weeks after repeated selective recounting spaced over time (Sozer et al., 2025). Most studies use word lists tested shortly after study, and the size of the effect in an actual case, after days or months and with emotionally significant material, is not known.

Directed Forgetting

In directed forgetting studies, participants are told after each item, or after a list, that it should be remembered or forgotten. Items marked to be forgotten are later recalled less well than items marked to be remembered, which shows that people have some ability to limit what they retain when instructed to do so. A meta-analysis of item-method studies found the effect generally smaller for emotional than for neutral material, by about four percentage points on average, with wide variation across studies (Hall et al., 2021). In other words, emotional information is usually somewhat harder to forget on instruction, although not in every study.

Directed forgetting has been used to test whether people who report abuse have an unusual capacity to forget trauma-related material. In two studies, women who reported childhood sexual abuse, including groups with posttraumatic stress disorder and groups reporting repressed or recovered memories, did not show better forgetting of trauma-related words than comparison groups (McNally et al., 1998, 2001). These studies are informative about one laboratory ability; they did not test memory for the abuse itself, and their bearing on the broader debate is read differently by the two sides described below.

Suppressing Unwanted Memories: The Think/No-Think Procedure

In the think/no-think procedure, participants learn word pairs and then see some cue words with instructions to bring the paired word to mind and others with instructions to keep the paired word out of awareness. Anderson and Green (2001) found that the suppressed words were later recalled less well than baseline words, the forgetting grew with the number of suppression attempts, and it appeared even when memory was tested with new cues. The authors proposed that executive control can suppress unwanted memories, and they linked the finding to the long-disputed idea of repression. Later imaging work associated suppression with prefrontal control and reduced hippocampal activity (Anderson & Hanslmayr, 2014).

A focused meta-analysis of 96 effects from 25 studies found significant suppression-induced forgetting in healthy participants, with a small-to-moderate effect size of 0.28, while noting that this estimate may be inflated by publication bias (Stramaccia et al., 2021). The same analysis found the effect weaker in more anxious participants (an estimate below zero) and in more depressed participants (close to zero), and stronger in people with a repressive coping style (0.42). Effects were larger when instructions told participants exactly how to suppress, for example by blocking retrieval directly or by substituting another thought, than when instructions were unspecific.

The Replication Record and the Theoretical Debate

The suppression effect has not replicated consistently. An early set of experiments found no reliable suppression with either the original or new cues (Bulevich et al., 2006). A later reanalysis of unpublished and published replication attempts from the 2000s, run across many plausible analytic choices, found suppression with the original cues in most samples but mostly non-significant results with new cues, which the authors argued posed problems for the inhibition account (Wessel et al., 2020). A preregistered replication with 150 healthy adults, conducted online with an experimenter present, found no suppression-induced forgetting with either kind of cue (d = 0.03 and 0.06); the authors cautioned that the online format should be considered in interpreting the null result (Wiechert et al., 2023). Taken together, these studies indicate that deliberately avoiding a memory can lower its later recall under some laboratory conditions, that the size and reliability of the effect remain disputed, and that procedural details appear to matter.

A separate dispute concerns explanation. Inhibitory accounts hold that retrieval and suppression actively lower the accessibility of competing memories (Anderson & Spellman, 1995). Critics have argued that the same results can often be explained by interference and changes in retrieval cues, without a distinct inhibitory process, and that “inhibition” groups several different ideas under one label (MacLeod et al., 2003). For legal purposes, the label matters less than the observation underneath it, which both sides of the theoretical debate generally accept: retrieving or rehearsing some information can, at least for a time, make related information harder to retrieve.

Memory Inhibition and the Repression Debate

Since suppression was offered as a laboratory analogue of repression, this research is cited in the debate over recovered memories of abuse, and both positions should be understood. Researchers on one side argue that the claim that traumatic experiences are commonly blocked from awareness and later recovered intact lacks convincing support, that laboratory suppression of word pairs does not demonstrate such a mechanism, and that belief in unconscious repression remains widespread among the public and some clinicians (Otgaar et al., 2019, 2021). On this reading, the weak and variable suppression effect and the directed-forgetting findings (McNally et al., 1998, 2001) give little support to repression.

Brewin (2021) responded that these critiques overlook a long-standing consensus that recovered memories may be genuine, false, or a mixture, and that they target a theory of unconscious repression that major publications do not endorse. On this reading, motivated forgetting is a normal capacity with laboratory support, and the stronger effect among people with a repressive coping style (Stramaccia et al., 2021) is consistent with individual differences in the ability to avoid unwanted memories. Lane and Houston (2021, pp. 70–71) describe the 1990s debate as having ended in general agreement that recovered memories are sometimes accurate and sometimes the product of suggestion. Neither reading permits a conclusion about a particular person’s memory. The laboratory findings show that ordinary material can be made somewhat less accessible; they neither establish nor rule out the forgetting and recovery of a particular traumatic experience. These questions are addressed more fully in Recovered and Repressed Memory.

Limits of the Evidence

Most of this research uses word pairs, category lists, or pictures, studied by university students and tested within minutes or hours. Real events are richer, more personally significant, and usually recalled after much longer delays, and retrieval-induced forgetting faded within a day after a single retrieval session in one recent study, while another found socially shared forgetting up to three weeks after repeated, spaced recounting. Effect sizes in the suppression literature are modest, may be inflated by selective publication, and vary with instructions and testing format; a preregistered replication found none. Clinical and trauma-exposed samples are few and are tested with laboratory materials rather than with memory for the trauma itself. The theoretical mechanism is disputed. Above all, group findings describe tendencies under controlled conditions; they cannot establish that a particular witness forgot a particular detail because of selective questioning, or that a particular memory was suppressed and later recovered.

Questions to Ask About This Research

When Anderson and Green (2001) is cited for the proposition that people can suppress memories, counsel should ask whether the finding has held up, since Bulevich et al. (2006) and a preregistered replication (Wiechert et al., 2023) did not find it, and how large the effect is, since the meta-analytic estimate in healthy participants was 0.28 and possibly inflated (Stramaccia et al., 2021). When the same research is cited for or against a claim of repressed memory, counsel should ask who was studied and what was tested: healthy volunteers suppressing word pairs, not memory for abuse. When Shaw et al. (1995) or Cuc et al. (2007) is offered to explain an omission, counsel should ask whether the conclusion applies at the delays in the case, since Meixensperger and Bäuml (2026) found the effect absent after a day and a week with a single retrieval session (although Sozer et al., 2025, found socially shared forgetting up to three weeks after repeated selective recounting spaced over time), and whether the questioning or conversation actually covered related details. When McNally et al. (1998, 2001) is offered to cast doubt on a recovered memory, counsel should ask whether a word-list task can bear that conclusion; and when Brewin (2021) or the repressive-coping finding is offered in support of one, counsel should ask the same question of that evidence. These questions are explained in “Reading Research Claims: A Guide for Attorneys” on this site.

Memory Inhibition and the Law

Federal and Military Standards

Expert testimony on retrieval-induced forgetting or memory suppression is governed by Federal Rule of Evidence 702, as amended December 1, 2023, under which the proponent must show that it is more likely than not that the testimony rests on sufficient facts or data and reflects a reliable application of reliable methods. Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993) made the trial judge a gatekeeper, and Kumho Tire Co. v. Carmichael (1999) extended that obligation to all expert testimony, including technical or other specialized knowledge. The mixed replication record of the suppression effect is the kind of question a court may weigh in deciding whether testimony about it reflects reliable principles, and testimony about retrieval-induced forgetting must fit the delays and questioning in the case. Military Rule of Evidence 702 tracks the federal rule, and under Military Rule of Evidence 1102 the Joint Service Committee’s 2025 compilation reflects the 2023 amendment (Joint Service Committee on Military Justice, 2025); practitioners should confirm current text. Military judges also apply the six factors of United States v. Houser (1993).

Arizona

Arizona Rule of Evidence 702 adopted the federal formulation and the Daubert standard effective January 1, 2012, and was amended effective January 1, 2024, to conform to the 2023 federal amendment (Ariz. Sup. Ct. Order R-23-0004). State v. Chapple (1983), Arizona’s leading case on eyewitness expert testimony, held that excluding such testimony was an abuse of discretion on its facts; admission is otherwise discretionary, and State v. Nordstrom (2001) upheld limiting an expert to general factors without an opinion on a particular witness’s accuracy. Experts may not opine on whether a particular witness is truthful (State v. Lindsey, 1986, 149 Ariz. at 475; State v. Moran, 1986).

Special Issues in Legal Practice

The principles described above apply with equal force to every party in a legal proceeding. The science operates the same way regardless of who is asking the questions, and the research summarized here does not by itself favor either side. What differs between the parties is not the science but the vantage point — the particular places where these issues tend to surface, and the particular errors each party is best positioned to guard against. The two summaries below identify those recurring issues. They are offered for orientation, not as litigation strategy; in every case the controlling question is what the evidence in that case will, and will not, support, and the expert’s role is to inform the trier of fact rather than to advocate for either side.

Special Issues for Prosecutors

The research supports several propositions prosecutors can legitimately use. In one 2026 single-session study, retrieval-induced forgetting was absent after a day and a week, although one 2025 study found socially shared forgetting up to three weeks after repeated selective recounting spaced over time, so an argument that questioning weeks or months earlier erased specific details goes beyond what the studies reviewed here show. People generally find emotional material harder to forget on instruction than neutral material, and the suppression effect is modest and inconsistent, so the research does not support a presumption that a witness has lost large parts of an experience through questioning or avoidance. Prosecutors are also well positioned to prevent the problem: obtaining and recording a full, open-ended account before targeted follow-up questions, and documenting who spoke with a witness before an interview, preserves breadth and answers later claims that interviewing narrowed the account.

The research also counsels caution. Selective questioning and pre-interview conversations can, at least for a time, make unasked details harder to recall, so the absence of a detail from a later, narrowly focused account is not strong evidence that it was never there. Where a case rests on a memory reported as recovered after a period of not remembering, the suppression literature cannot carry the weight of showing that the memory was repressed and accurately recovered; the scientific debate is unresolved, and corroboration and the circumstances of recovery will matter more than the laboratory paradigm.

Special Issues for Defense

The research supports several propositions defense counsel can legitimately use. Remembering some details can impair recall of related ones, even when questioning contains no misinformation, and conversations can suppress details a speaker left out; an expert can explain these findings so that the factfinder can consider how an account was elicited. The think/no-think effect is modest, sometimes fails to replicate, and has been studied with word pairs rather than trauma, so testimony presenting it as a validated mechanism of repression overstates the evidence, a point counsel may raise when the research is offered as support for a recovered memory.

The research also counsels caution. Retrieval-induced forgetting does not show that any particular missing detail was lost through questioning, or that it would have favored the accused, and the effect was absent after a day in a single-session study, although socially shared forgetting lasted up to three weeks after repeated, spaced recounting in another. That laboratory suppression is a weak model of repression is not evidence that any given recovered memory is false; the general agreement described by Lane and Houston (2021) is that they can be accurate or the product of suggestion. The same effects apply to the accused’s account, which may also have been narrowed by questioning or discussion.

This paper is for educational purposes only and is not legal advice. The author is a psychologist, not an attorney; summaries of law are general and must be verified against current authority or with a licensed attorney.

References

Anderson, M. C., Bjork, R. A., & Bjork, E. L. (1994). Remembering can cause forgetting: Retrieval dynamics in long-term memory. Journal of Experimental Psychology: Learning, Memory, and Cognition, 20(5), 1063–1087. https://doi.org/10.1037/0278-7393.20.5.1063

Anderson, M. C., & Green, C. (2001). Suppressing unwanted memories by executive control. Nature, 410(6826), 366–369. https://doi.org/10.1038/35066572

Anderson, M. C., & Hanslmayr, S. (2014). Neural mechanisms of motivated forgetting. Trends in Cognitive Sciences, 18(6), 279–292. https://doi.org/10.1016/j.tics.2014.03.002

Anderson, M. C., & Spellman, B. A. (1995). On the status of inhibitory mechanisms in cognition: Memory retrieval as a model case. Psychological Review, 102(1), 68–100. https://doi.org/10.1037/0033-295X.102.1.68

Brewin, C. R. (2021). Tilting at windmills: Why attacks on repression are misguided. Perspectives on Psychological Science, 16(2), 443–453. https://doi.org/10.1177/1745691620927674

Bulevich, J. B., Roediger, H. L., III, Balota, D. A., & Butler, A. C. (2006). Failures to find suppression of episodic memories in the think/no-think paradigm. Memory & Cognition, 34(8), 1569–1577. https://doi.org/10.3758/BF03195920

Cuc, A., Koppel, J., & Hirst, W. (2007). Silence is not golden: A case for socially shared retrieval-induced forgetting. Psychological Science, 18(8), 727–733. https://doi.org/10.1111/j.1467-9280.2007.01967.x

Hall, K. J., Fawcett, E. J., Hourihan, K. L., & Fawcett, J. M. (2021). Emotional memories are (usually) harder to forget: A meta-analysis of the item-method directed forgetting literature. Psychonomic Bulletin & Review, 28(4), 1313–1326. https://doi.org/10.3758/s13423-021-01914-z

Joint Service Committee on Military Justice. (2025). Amendments to the Military Rules of Evidence since 1984 (G. E. Maggs, Ed.; 2025 ed.). https://jsc.defense.gov/Portals/99/MRE%20Amendments%202025.pdf

Lane, S. M., & Houston, K. A. (2021). Understanding eyewitness memory: Theory and applications. New York University Press.

MacLeod, C. M., Dodd, M. D., Sheard, E. D., Wilson, D. E., & Bibi, U. (2003). In opposition to inhibition. In B. H. Ross (Ed.), The psychology of learning and motivation: Advances in research and theory (Vol. 43, pp. 163–214). Academic Press. https://doi.org/10.1016/S0079-7421(03)01014-4

McNally, R. J., Clancy, S. A., & Schacter, D. L. (2001). Directed forgetting of trauma cues in adults reporting repressed or recovered memories of childhood sexual abuse. Journal of Abnormal Psychology, 110(1), 151–156. https://doi.org/10.1037/0021-843X.110.1.151

McNally, R. J., Metzger, L. J., Lasko, N. B., Clancy, S. A., & Pitman, R. K. (1998). Directed forgetting of trauma cues in adult survivors of childhood sexual abuse with and without posttraumatic stress disorder. Journal of Abnormal Psychology, 107(4), 596–601. https://doi.org/10.1037/0021-843X.107.4.596

Meixensperger, S. R., & Bäuml, K.-H. T. (2026). Items that are subject to retrieval-induced forgetting show slowed forgetting over time. Memory, 34(3), 302–314. https://doi.org/10.1080/09658211.2026.2615993

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Otgaar, H., Howe, M. L., Dodier, O., Lilienfeld, S. O., Loftus, E. F., Lynn, S. J., Merckelbach, H., & Patihis, L. (2021). Belief in unconscious repressed memory persists. Perspectives on Psychological Science, 16(2), 454–460. https://doi.org/10.1177/1745691621990628

Otgaar, H., Howe, M. L., Patihis, L., Merckelbach, H., Lynn, S. J., Lilienfeld, S. O., & Loftus, E. F. (2019). The return of the repressed: The persistent and problematic claims of long-forgotten trauma. Perspectives on Psychological Science, 14(6), 1072–1095. https://doi.org/10.1177/1745691619862306

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Stramaccia, D. F., Meyer, A.-K., Rischer, K. M., Fawcett, J. M., & Benoit, R. G. (2021). Memory suppression and its deficiency in psychological disorders: A focused meta-analysis. Journal of Experimental Psychology: General, 150(5), 828–850. https://doi.org/10.1037/xge0000971

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Legal Authorities

Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993).

Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999).

State v. Chapple, 135 Ariz. 281, 660 P.2d 1208 (1983).

State v. Lindsey, 149 Ariz. 472, 720 P.2d 73 (1986).

State v. Moran, 151 Ariz. 378, 728 P.2d 248 (1986).

State v. Nordstrom, 200 Ariz. 229, 25 P.3d 717 (2001).

United States v. Houser, 36 M.J. 392 (C.M.A. 1993).

Fed. R. Evid. 702.

Ariz. R. Evid. 702.

Ariz. Sup. Ct. Order R-23-0004 (2023).

Mil. R. Evid. 702.

Mil. R. Evid. 1102.