Memory Distortion

Several studies in normal subjects have shown that memory is susceptible to distortions and deletions. For instance, in one study, subjects viewed a film of an automobile accident. When researchers used the verb "smashed" as opposed to the verb "hit" in relation to the film, subjects gave higher estimates of the speed of the automobiles, and more subjects incorrectly endorsed the statement that broken glass was associated with the accident (Loftus & Palmer, 1974). When subjects were shown a series of slides that told a story involving a stop sign followed by a narrative that misleadingly described a yield sign, they were more likely to falsely recall that the slides included a yield sign than subjects not given the misleading information (Loftus, Miller, & Burns, 1978). In another example known as the "Deese/Roediger-McDermott paradigm," after its originators, words that are highly associated with a "critical lure," when presented in a list, will be associated with a "false" recall of the absent "lure." So, for example, if a subject is presented with the words thread, pin, eye, etc., the subject may include the "critical lure" needle, even though it was not part of the original list (Roediger & McDermott, 1995).

Memory can also be distorted to fit with subjects' expectations. Children told a story about the Six Million Dollar Man being unable to carry a can of paint, when tested 3 weeks later, were more likely to change their recall to fit with their pretesting knowledge (Ceci, Caves, & Howe, 1981).

In another study, the parents of college students provided surveys of their children's childhood events, and the students were asked to recall the events in a series of interviews. In addition to the true events, students were asked to recall the details of a fictitious episode, such as knocking over a punch bowl at a wedding (Hyman, Husband, & Billings, 1995). By the third interview, 25% of students falsely recalled the punch bowl; in addition, they tended to elaborate more on their own true events with each interview. Based on a series of studies, Oakes and Hyman (2001) outlined factors involved in the creation of false childhood memories. First, the event must be plausible, or something the individual thinks could have happened. The subject must then create an image with a narrative. Finally, the individual forgets the source of the image and narrative and incorrectly attributes it to the self.

Pezdek and colleagues (Pezdek, Finger, & Hodge, 1997) used a similar paradigm involving both plausible (lost in the mall as a child) and implausible (received a painful rectal enema as a child) stories. Consistent with the model of Oates and Hyman, only the "lost in the mall" anecdote was falsely recalled. No subjects falsely recalled the painful enema event.

These studies highlight the fact that amnesia for the source of the information plays a critical role in many of these experimental paradigms of "false memory." For instance, studies have shown that if subjects are cued to pay attention to the source of the information they receive, the false-recall effect associated with misleading information is lost (Lindsay, 1990; Lindsay & Johnson, 1989).

A clinically relevant question is whether memories can be forgotten and still be potentially accessible at a later time, or whether these memories no longer exist as memory traces in the brain. Adherents to the latter view hold that delayed recall of abuse memories are secondary to "implanting" of abuse memories by overzealous therapists (Loftus et al., 1978). They claim that authentic memories can be "overwritten" by memories that are implanted or introduced through suggestion or other means. One study addressed the question of whether memories could be overwritten. Subjects who saw slides that included a hammer were then given the misleading information that a screwdriver had been among the slides. The subjects were then forced to recall whether they had seen a hammer or a screwdriver. Subjects did not falsely recall the screwdriver more than expected by chance (McCloskey & Zaragoza, 1985). The authors concluded that if the misleading information could overwrite the original memory, then the subjects would have falsely recalled the screwdriver more often. The authors concluded that there was not evidence that memories could be "overwritten."

The past two decades of research on false memory have generated as much heat as light on this topic, with the evolution of two different languages to describe the topic. In response to the original study by Williams (Williams, 1994), Loftus, Garry, and Feldman (1994) argued that a loss of memory about abuse is related to normal forgetting. They dichotomized normal "forgetting" and "repression," and argued that there is no evidence for repression.

The choice of language, however, can often shape the conception of an issue. Loftus and colleagues chose to frame the debate about false memories of abuse by using a term derived from psychoanalysis that refers to memories that are banished from consciousness because of the existence of a painful conflict. For a variety of reasons, psychoanalysis has been resistant to empirically based research; in fact, only very recently has a published, controlled trial of psychoanalysis been performed (Milrod et al., 2007). The concept of repression is a difficult one to test empirically, which has contributed to the heated rhetoric surrounding this issue.

For instance, Pezdek and Lam (2007) reviewed the last decade of research on memory for abuse and concluded that only 13% of the articles claiming to study false memory actually used the word as originally intended (DePrince and colleagues similarly found that 70% did not use true false memory paradigms; DePrince, Allard, Oh, & Freyd, 2004). Pezdek and Lam found that most studies used the Deese/ Roediger-McDermott paradigm (false recall of a critical lure after being read a list of words highly associated to the critical lure) (Roediger & McDermott, 1995) or the introduction of misinformation. As the authors pointed out, however, the Deese/Roediger-McDermott paradigm is not a true false memory paradigm—that is, the implanting of previously nonexistent information. Pezdek and Lam concluded that false memories and flawed memories should not be conflated, and that the term false memory should not be indiscriminately applied to experimental studies on memory, since the public generally extrapolated the findings to abused patients.

Predictably, following publication of this article, the rhetoric erupted once again. Wade and colleagues (2007) disputed the need to apply a narrow definition of false memory to experimental paradigms in the literature. Pezdek later wrote that the main effect of the article was "[to] obfuscate rather than clarify the discussion of false memory" (Pezdek, 2007). These articles show that we are no closer to consensus regarding the topic of false memory than we were a decade ago.

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