Sunday, February 27, 2005

The Evidence for Recovered Memories: A Short Critique

In my previous post on recovered memories, I focused mainly on the evidence we have from real-world (naturalistic) and laboratory studies of traumatic memory in general. I focused on this research because the false memory research is already well known, at least generally, even by non-experts, and because one of the best reasons for disbelieving the claims of the repression hypothesis (the hypothesis that traumatic memories can be repressed, and later recovered) is that it does not accord with anything we know about the nature of memories of trauma, or memory in general. With the false memory and traumatic memory research, the case against the repression hypothesis looks something like this:
  1. Because traumatic memories are actually more memorable, more easily recalled, and more difficult to forget, the burden is on the proponents of the repression hypothesis to demonstrate how some traumatic memories, in some individuals, are different, and what as of yet undiscovered mechanisms are involved in causing these memories, in these individuals, to behave differently.
  2. There is ample reason to believe that many memories can be explained as instances of false memories.
Given 1 and 2, it is reasonable to be highly skeptical about claims of recovered memories. However, there are types of evidence that can overcome 1 and 2 and provide support for the repression hypothesis. Such evidence would have to involve cases in which it is demonstrable that there exist individuals who a.) were abuse during childhood, b.) had no recollection of the abuse for an extended period of time after the abuse had occurred, and c.) now have accurate memories of the abuse that were not created by (i.e., implanted) external sources, such as therapists, family members, or friends who knew the details of the abuse. Research purporting to demonstrate the existence of individuals displaying a-c does in fact exist. The most prominent studies reporting such evidence are presented in two papers, one by Linda M. Williams, and the other by Alan W. Scheflin and Daniel Brown. Each of the studies presented in these two papers contains some serious flaws (in fact, the Scheflin and Brown paper, bolstering my claim that the proponents of recovered memories are the cognitive scientific analog to ID theorists, is downright deceptive). Detailing these will help to demonstrate further evidence against the repression hypothesis, and thus further strengthen the case against it.

Williams, L.M. (1995). Recovered memories of abuse in women with documented child sexual victimization histories. Journal of Traumatic Stress, 8(4), 649-673.

In this paper, Williams presents the results of a study in which 129 women with documented cases of abuse occurring in the early 1970s were interviewed almost 20 years later (between 1990-1992) about the particular case of abuse that was documented. They found that 67% of these women remembered the specific instance of abuse that was documented. This is not evidence that the other 33% have repressed the memory of the abuse. Most of the women were abused over an extended period of time, and not recalling a particular instance when asked open-ended questions about abuse is thus not surprising. However, of the 67% who recalled the abuse (80 total, 5 of whose data had to be discarded due to errors on the part of the researchers), 16% (12) of the women answered yes to the following question:
Was there ever remember a time when you did not remember that this happened to you?
Williams believes that this data provides evidence for the existence of repressed and recovered memories of trauma in some individuals. However, there are two major flaws in her data that cause it to fail to address criterion b. The first is reported by Williams herself. The average age at which the documented instance of abuse occurred, for the 12 women who reported a period of forgetting, was 6.5 years, while the average age for the women who did not report such a period was 9.5 years. This is important, because it hints that her data may be explained by the existence of childhood amnesia, a well-documented phenomena in which, up until about age 6, people have a great deal of difficulty in forming and retaining autobiographical memories, even traumatic ones. Some of the 12 "forgetters" were 3 years old during the time of the documented abuse! It is unreasonable to expect them to remember the events, even today, without having been given information from external sources. In other words, any memory of abuse at age 3 is likely to have been implanted, even if accurate, rather than to have been caused by the event itself. Memories of events before age 6 that were caused by the remembered events are likely to be very sketchy, a fact that explains another aspect of Williams' data (her finding that the "forgetters" were less confident in their memories, and felt that they did not remember everything about the events).

The second problem, which may be even more important, is the question that Williams asked. It is widely known that memory for memory (i.e., memory for whether we remembered something at a particular time in our past) is extremely poor1. In fact, researchers have shown that people will report that there have been periods during which they have forgotten events, even though there is evidence of them talking about those events during the "forgetting period!"2. The question is further problematic, as some have noted3, because it implies that the individual remembers not remembering. This would require that the person remember abuse that he or she does not remember! Thus, the sort of self-report data elicited by Williams' question about periods of forgetting is essentially worthless.

What we've learned from the Williams study, then, is that self-report data about periods of forgetting is insufficient to provide evidence that satisfies criterion b above, and that another potential explanation for instances of recovered memories is childhood amnesia. Williams' data, if it shows us anything, actually supports the case against the repression hypothesis, by demonstrating that those who report forgetting tended to be abused at an age for which we would not expect them to have good, if any, autobiographical memories that were not obtained indirectly through outside sources.

Scheflin, A.W., & Brown, D. (1996). Repressed memory or dissociative amnesia: what the science says. Journal of Psychiatry and Law, 24, 143-188.4

This is a deceptively titled review of the pro-recovered memory literature. It is the most thorough to date, and any anti-recovered memory position will have to address it. Four years after its publication, an article was published in the same journal by Piper, Pope, and Borowiecki, titled "Custer's last stand: Brown, Scheflin, and Whitfield's latest attempt to salvage 'dissociative amnesia.'" Here I'll present most of their criticisms, along with a few of my own.
  1. In arguing that the burden of disproof is on those who do not believe that repressed memories exist, Scheflin and Brown write:
    Opponents of repressed memory... cannot meet the Daubert standards of science. Other than a few pro-false memory reviews, they can cite no data-based scientific studies in support of their view.
    Piper et al. note that Brown and Scheflin are not following one of the basic tenets of the scientific method, in which we do not posit explanations that are not needed to explain the data. In other words, the burden of proof is on the pro-repressed memory crowd to provide data that requires the repressed memory hypothesis for explanation. Otherwise, the repressed memory hypothesis is merely a hypothesis without an empirical grounding.

    Furthermore, as I have already noted, there are data-based reasons for not believing that repressed and recovered memories exists. While these reasons do not amount to a thorough disproof of the existence of repressed memories, from a scientific standpoint, they serve to place the burden of proof squarely on the shoulders of the proponents of the repression hypothesis.
  2. Scheflin and Brown focus exclusively on a few studies (25), claiming that they are the only studies on the subject. They write in the abstract, "A total of 25 studies on amnesia for CSA [childhood sexual abuse] now exist, all of which demonstrate amnesia in a subspopulation; no study failed to find it." I can honestly say that this is one of the most deceptive statements I have ever seen in a peer-reviewed publication. The fact is, as Piper et al. note, there are many more studies than this, and the majority of them do not find any evidence for amnesia for CSA. Piper et al. cite their own meta-analysis of 63 studies, containing analyses of data from more than 10,000 individuals who had suffered some sort of trauma, in which they find not a single instance of amnesia.
  3. Scheflin and Brown blatantly misrepresent many of the studies they present. On pages 160-171 of the paper linked above, Piper et al. provide a lengthy list of mistatements," false statements," and quote mining, and "distorted quotes" in Brown, Scheflin, and Whitfield, many of which are also present in Scheflin and Brown.
  4. The bulk of the studies cited by Scheflin and Brown, as well as Brown et al., are retrospective studies like Williams'. In these studies, individuals are asked about episodes of forgetting in the past. For the reasons discussed above in regard to Williams' study, these studies are essentially worthless.
  5. The prospective studies that both the Scheflin and Brown papers cite fail to include important data, such as the age of the individuals at the time of abuse, making them impossible to evaluate. Leaving out the age, for instance, makes it impossible to rule out the childhood amnesia explanation.
  6. One of the arguments against the childhood amnesia explanation, offered by Brown et al., is that sexual abuse prior to age 6 is so traumatic that it is likely to be remembered. In other words, it is different from other traumatic events that children are likely to forget at that young age. However, this claim is contrary to the evidence. Piper et al. note that the research on sexual abuse shows that, by and large, most children, particularly young children, are not disturbed or adversely affected by most instances of sexual contact. In other words, these events are likely not that different from other autobiographical events which children regularly forget. Piper et al. argue that, since most children do not immediately experience sexual contact as negative, the repression hypothesis would require that those children have a highly sophisticated knowledge of the social conventions that make such contact wrong, and thus repress the memories based on that knowledge, rather than the qualitative character of the experience itself.
In short, the Scheflin and Brown article, along with their follow-up in Brown et al., not only fail to address the criticisms of repressed memory research, and the repression hypothesis itself, but in the process of avoiding these criticisms, they misrepresent the evidence and deceive the readers with misquotes, quote mining, and the presentation of flawed (and in one case, perhaps non-existent) studies.

To wrap up then, there is to date no evidence, nor the hope for any eivdence, that means criteria a-c, and thus counters the evidence against the repression hypothesis. Furthermore, since studies like the one by Williams actually give us more reasons to doubt the existence of repression and recovery (e.g., the potential for childhood amnesia to explain many cases of "repression"), it is difficult, as a scientist, to believe in them. Now the evidence against the repression hypothesis looks like this:
1. The nature of traumatic memory & 2. False memory research, from above.
3. The fact that, as Williams' data suggest, childhood amnesia may explain many actual instances of forgetting. Add to this the fact that for young children, it is unlikely that sexual abuse, the most commonly cited elicitor of repression, is actually traumatic enough to be remembered by young children when most autobiographical information is not.
4. The huge methodological flaws in all retrospective and prospective studies purporting to demonstrate the existence of repressed and recovered memories.
Based on this evidence, no court should ever admit recovered memory testimony as evidence, and no jury should ever give it any weight. Yet, as the case linked in the previous post demonstrates, the courts and juries aren't always interested in "what the science says."

1Arnold, M.M., & Lindsay, D.S. (2002). Rembering remembering. Journal of Experimental Psychology: Learning, Memory, & Cognition, 28(3), 521-529.
2 Schooler, J. W., Ambadar, Z., & Bendiksen, M. (1997). A cognitive corroborative case study approach for investigating discovered memories of sexual abuse. In J. D. Read & D. S. Lindsay (eds.), Recollections of trauma: Scientific evidence and clinical practice, (pp. 379-387). New York: Plenum Press.
3 Mcnally, R.J. (1999). Review of Memory, Trauma Treatment, and the Law. International Journal of Clinical and Experimental Hynosis, 47, 374-382.
4 See also Brown, D., Whitfield, C.L., & Scheflin, A.W. (1999). Recovered memories : the current weight of the evidence in science and in the courts. The Journal of Psychiatry and Law, 27, 5-156, which was the actual target of the Piper et al. paper.

18 comments:

Clark Goble said...

Chris, I posted a link to your comments in an other blog and a psychologist took exception with these comments.

"The studies of cognitive psychologists generally do not investigate the real question of whether memories of sexual abuse can be created in a person who was not abused. They study whether people are suggestible, which they are. Traumatic memory is of a completely different nature than regular memory, check out prominent Harvard psychiatrist, Bessel van der Kolk for plenty of documented evidence on this. It is also well documented that people who undergo ongoing severe abuse repress their memories of it in order to survive. Single incidents or short term abuse is emblazoned in the memory, but long term abuse is usually repressed. Cognitive psychologists and clinical psychologists who work with trauma are comparing apples and oranges when it comes to memory."

Is this apples and oranges as she asserts? I do know there are many studies on trauma arguing that our memories are different. My sense is that she's missing the forest for the trees. But I may be wrong, not being an expert in all this.

Clark Goble said...

If you are interested the link to the comment is here. She also references Alpert, J.L. Professional Practice, Psychological Science, and the Delayed Memory Debate. In Sexual Abuse Recalled: Treating Trauma in the Era of the Recovered Memory Debate.

Chris said...

Clark, the commentor is referencing Terr's distinction between Type I and Type II trauma. I referred to that briefly in the first post, noting that the evidence from the Holocaust survivors was in direct contradiction to her distinction. She built the distinction from a flawed study (retrospective).

Interestingly, most of van der Kolk's work demonstrating a difference between traumatic and ordinary memories comes from surgery patients who experienced a one-time trauma, making the commentor's assertions seem odd to me. What van der Kolk has found is that these patients' memories are fragmented and primarily sensory, with little narrative content. Of course, it's not surprising that patients who are waking up from general anaesthesia would have fragmented memories. Still, van der Kolk thinks this is evidence that traumatic memories are qualitatively different from non-traumatic memories.

As of yet, Dr. van der Kolk has presented no actual scientific evidence of repression, and only sketchy evidence (based on a scale he himself has produced, but which is, at least for now, not widely accepted) that traumatic memories are qualitatively different than ordinary memories. Since this actually contradicts what we know from dozens of studies of both single-incident and repetitive trauma, I just don't buy it.

By the way, I have a bunch of van der Kolk's work in pdf files, if you're interested in reading it.

Chris said...

By the way, it's not surprising that a clinician disagrees with me. The debate has always been between clinicians, who think that cognitive research on traumatic memory lacks ecological validity (a valid criticism), and cognitive psychologists who point out that the clinical research is so full of holes that it tells us very little if anything. There are attempts to bridge the gap, but for the most part, the pro-repressed memory people are wedded to their retrospective and occasionally prospective techniques, and the anti-repressed memory people are wedded to their cognitive psychological methods.

Clark Goble said...

Thank you for the information. I have to admit I've wasted several hours tonight reading both your stuff, some cognitive science stuff I googled, along with several of van der Kolk's papers he has up online at his site. I have to confess I was a bit dubious about his data, simply because he kept leaving out (to me) crucial information. But at the same time I know I have the hard scientist's bias against the soft sciences. So I have to watch myself. (I've offended accidentally far too many sociologists and psychologists in my time)

Admittedly my bias developed in college when my stats teacher kept bringing into class supposed peer reviewed sociology papers with egregious statistical errors in it. After a while I developed a rather bad attitude which my sociologist friends correctly critique me for. (They point out a lot of good work and have embarrassed me with pointing out my overgeneralizations and weak criticisms at times) So I have to watch my biases and always assume I'm unfairly thinking the worst. (I'm afraid psychotherapists are down lower on my rigor scale from sociologists so I'm doubly distrusting of my initial views of papers by therapists)

Tia said...

I've read that Williams paper, but now can't get access to it.
You say:

They found that 67% of these women remembered the specific instance of abuse that was documented. This is not evidence that the other 33% have repressed the memory of the abuse. Most of the women were abused over an extended period of time, and not recalling a particular instance when asked open-ended questions about abuse is thus not surprising.

Can you confirm for me that the subjects were asked only about a particular abuse episode (i.e. "The time when Uncle Johnny..."). Because I thought they were asked about abuse by a person, and remembered no abuse by that person.


Also, my recollection (perhaps flawed, memory is unreliable!) was that although the mean of the forgetters' ages might have been lower, the range extended to substantially higher than 6.5 years.

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