Traumatic Memories: The Case Against Memory Recovery

Every time I read or hear about the outcome of a criminal case resting on testimony from a "victim" who has recently recovered memories of the crime, of which he or she had no recollection for many years between the incident(s) and the memory recovery, I cringe. I mean I really cringe. To cognitive psychologists, such stories are worse than fingernails on a chalkboard. Recovered memory theories are our Intelligent Design theories, only instead of having only a little success in affecting textbook and curriculum decisions, our equivalent of ID proponents are actually getting people convicted of serious crimes, and sent to prison for the rest of their lives. As is the case with ID in biology, much of the general public is ignorant of the relevant research, and of the nature of the issues involved, but since members of the public serve as jurors in criminal cases, their ignorance can have dire consequences. A juror in a recent child molestation case in which the prosecution's primary witness was a man who had recovered memories of the abuse in his 20s, told reporters

We agreed after discussion that you can experience something up to a point, and then not think about it and have plenty of other things in your life that are more important.

She said this after she and the other jurors had convicted a man who was subsequently sentenced to 12 to 15 years in prison. Yet, her defense of her and her fellow jourors' acceptance of the recovered memory testimony displays a complete ignorance of memory in general, and even what recovered memory proponents believe recovered memories are. They are not memories that have simply not been reflected on for a period of time, or that have been overshadowed by more pressing concerns and other memories (perhaps even from the same time period). Recovered memories are memories that had been mysteriously repressed, and thus completely unavailable for retrieval, until some triggering event (usually psychotherapy) made them available again. The jury members couldn't distinguish between going a year or two without thinking about someone they dated a couple times in college and not being able to remember incredibly traumatic childhood sexual abuse for decades. Yet, they convicted a man anyway. I am disturbed by the fact that religious fanatics who are ignorant of biology can influence education policy, but I am terrified by the idea of people who are so blatantly ignorant of the science of memory could convict me, or anyone else, of a crime that could result in the loss of freedom for years. Almost as disturbed as I am by the fact that recovered memories, for which there is almost no non-anecdotal empirical evidence, while there is a wealth of evidence calling their existence and accuracy into a question, are even admissable in criminal cases.

Don't misinterpret that angry paragraph as implying that I do not believe that it is possible to repress and later recover memories for traumatic events. As is the case with an intelligent designer, I am agnostic about the possibility of the existence of repressed and recovered memories. Since there is no empirical evidence for the existence of such memories that does not come from either case studies or self-report surveys (and asking people if they did not remember their trauma at some point in their life invites misunderstandings like those displayed by the juror in the quote above, making this data even more worthless), and to this point no one has any viable suggestion for the mechanisms involved in repressing and recovering memories. Add to this the fact that the existence of repressed memories goes against everything we do know, from experimental investigation, about memory and its mechanisms, and it seems irresponsible to claim that they do exist, to say nothing of convicting someone of a crime based on them, but cognitive science is a young discipline, and there is much that we do not know, so it's not very responsible, scientifically, to claim that they definitely do not exist, either.

So, now you know where I stand. Since I'm an intellectual (or at least, someone who holds himself to intellectual standards), I should probably say why that's where I stand. I don't want to run through the evidence for false memories. It's easy to find and read about, and most people who have read this far have probably heard a lot about that already. False memories, and the manipulability of memory in general, are reason enough to question any accusations and beliefs based on recovered memories, without any independence evidence to back them up. Yet, our propensity for the production and belief of false memories doesn't say much about the existence of accurate recovered memories. To be able to speak to that, we have to look at what we have learned from actual studies on memory for traumatic events. Since that research is less-often discussed in public debates on recovered memories, I will talk about it instead.

The first, and perhaps most important thing to note about research on traumatic memory is that it suffers from serious methodological hurdles. It is impossible, for ethical reasons, to draw research participants randomly from the population, and then randomly select some of them to suffer from extremely traumatic events, and the other to experience emotionally stimluating or mundane events of other sorts. Short of that, experimental research into the nature of traumatic memory will be incomplete. Still, there are methods with which we can gain some knowledge of memory for traumatic events, and then compare what we've learned to the claims of recovered memory proponents. Here are some of the things that we know:

• There are some extreme psychological syndromes, most notably psychogenic amnesia, Dissociative Identity Disorder, and fugue, which may result from traumatic events. Psychogenic amnesia is notoriously difficult to diagnose, because ruling out all physical causes is next to impossible. Furthermore, psychogenic amnesia for traumatic events rarely lasts for more than a few hours, in documented cases, and begins during the traumatic event itself. Repressed memories, on the other hand, are said to be repressed for years, and the repression itself is generally said to begin at some point after the traumatic event. Disocciative Identity Disorder, if it in fact exists (a question that is also hotly debated), is extremely rare (with a prevalency of about 1%, over the last decade or so), and because of the other symptoms involved, can not be used to explain the vast majority of recovered memory cases. Fugue is even rarer (.02%), and again, involves symptoms that distinguish it from most recovered memory cases.
  
• Laboratory studies overwhelmingly show that higher arousal levels increase memory accuracy and the ease of retrieval, while at the same time decreasing suggestibility, at least for the arousal-inducing events themselves². In fact, unlike non-traumatic memories, memory for traumatic events actually improves over time. This is particularly striking in cases of Post Traumatic Stress Disorder, in which the repeated retrieval of traumatic memories makes them more difficult to forget, and in many cases, more detailed. This is likely due to the fact that traumatic memories tend to be repeatedly retrieved (and, particularly in the case of PTSD, involuntarily retrieved). Repeated recall has been shown to improve recall ability and accuracy, particularly for traumatic memories³. There are plausible neurological explanations for this. For example, it is likely that the brain regions activated and hormones released during emotionally-stimulating events are the same ones that are involved in memory storage⁴. It's not surprising, then, that increased arousal produces better memory.
  
• In PTSD, memories are almost impossible to forget, or to repress. However, the difficulty of forgetting, and increased accuracy and memorability for traumatic memory is not exclusive to people who suffer from PTSD. Two famous studies illustrate this well. In the first⁵,26 children were interviwed immediately after being abducted in their school bus, and buried for more than a day, and interviewed again four years later. During both interviews, their recall of the event was very good, and they showed no real decrease in recall over the four year period. In the second study⁶, more than 70 Holocaust survivors who had written about their experience soon after the end of World War II were asked to recall their experiences. Despite the study being conducted in the late 1980s, more than 40 years after the traumatic experiences, the survivors' memories for the events were exteremely accurate when measured against their written accounts from after the event. This second study speaks directly to one of the more concrete claims of repressed memory proponents, made by Lenore Terr⁷, the author of the school-bus kidnapping studies. She has argued that there are two types of traumatic experience, which she calls Type I traumas and Type II traumas. Type I traumas, like that experienced by the school-bus kidnapping victims, occur only once. Type II traumas, such as repeated sexual or physical abuse during childhood, occur repeatedly over extended periods of time. Terr argues that the latter can produce repressed memories, while the former produce enhanced memories. However, the Holocaust survivors suffered years of repeated traumatic events, and their memory accuracy was excellent over time. In another study, young children who had been subjected to painful and embarassing medical procedures also experienced no decrease in memory recall⁸, a result that is also at odds with Terr's theory. Since the only evidence for Terr's Type II trauma and its effects on memory comes from a study of children who experienced trauma prior to age 5, when children's memories are notoriously inaccurate and short-lived, and there is a great deal of evidence that traumatic memories are better remembered, over time, than ordinary memories, Terr's theory, the only serious attempt to explain the experimental data, is difficult to support.
  

In sum, the evidence from laboratory and real-world studies of traumatic memory doesn't provide us with much of a basis for believing in the existence of repressed memories. Combine this with the well-demonstrated suggestibility of human memory and the frequency of false memories, and, as scientists, we have to come to the conclusion that the repression and recovery of traumatic memories are both extremely unlikely. There is certainly not enough evidence to admit recovered memory testimony in court cases. Lie detectors, which aren't admissible as evidence of guilt in 49 states, have accuracy rates of around 70%. There is no reason to think that repressed memories have an accuracy rate anywhere near that, and plenty of reason to think their accuracy rate is near 0%. Yet, judged continue to allow them, and juries continue to convict solely on the basis of them.

UPDATE: After careful consideration (and a strong suggestion from a friend), I'm pretty sure that I stole the recovered memory-Intelligent Design analogy from PZ Myers, who compared the proponents of recovered memory to creationists in this post. Given the importance of source-monitoring in the debate about false memories, I find my inability to remember the source of the analogy (I thought I was clever enough to come up with it on my own, but it turns out I'm not) kind of funny.

¹ Ross, C.A. (1991). Epidemiology of multiple personality disorder and dissociation. Psychiatric Clinics of North America, 14(3), 503-517.
² Christianson, S.A. (Ed.) (1992). The Handbook of Emotion and Nemory: Research and Theory. Hillsdale, NJ: Erlbaum.
³ See for example Bornstein, B.H., Liebel, L.M., & Scarberry, N.C. (1999). Repeated testing in eyewitness memory: a means to improve recall of a negative emotional event. Applied Cognitive Psychology, 12(2), 119-131.
⁴ LeDoux, J. (1996). The Emotinoal Brain. New York: Simon & Schuster; McGaugh, J. L. (1992). Affect, neuromodulatory systems, and memory storage. In S.A. Christianson (Ed.), The Handbook of Emotion and Memory: Research and Theory, pp. 245-268. Hillsdale, NJ: Erlbaum.
⁵ Terr, L. (1981). Psychic trauma in children. Observations following the Chowchilla school-bus kidnapping. American Journal of Psychiatry, 138, 14-19; Terr, L. (1983). Chowchilla revisited: The effects of psychic trauma four years after a school-bus kidnapping. American Journal of Psychiatry, 140, 1543-1550.
⁶ Wagenaar, W.A., & Groeneweg, J. (1990). The memory of concentration camp survivors. Applied Cognitive Psychology, 4, 77-87.
⁷ Terr, L. (1994). Unchained Memories. New York: Basic Books.
⁸ Goodman, G. S., Quas, J.A., Batterman-Faunce, J.M., Riddlesberger, M.M., & Kuhn, J. (1994). Predictors of accurate and inaccurate memories of traumatic events experienced in childhood. Consciousness and Cognition, 3, 269-294.