This manuscript is close to the
that was published with
(Figures not included in this email version but the ms. is easy to understand
Loftus, E.F. & Pickrell, J.E. (1995) The formation of false memories. Psychiatric Annals, 25, 720-725.
(Figures not included in this email version but the ms. is easy to understand without them)
For most of this century, experimental psychologists have been interested in how and why memory fails. As Greene2 has aptly noted, memories do not exist in a vacuum. Rather, they continually disrupt each other, through a mechanism that we call "interference." Literally thousands of studies have documented how our memories can be disrupted by things that we experienced earlier (proactive interference) or things that we experienced later (retroactive interference).
Relatively modern research on interference theory has focused primarily on retroactive interference effects. After receipt of new information that is misleading in some way, people make errors when they report what they saw3. The new, post-event information often becomes incorporated into the recollection, supplementing or altering it, sometimes in dramatic ways. New information invades us, like a Trojan horse, precisely because we do not detect its influence. Understanding how we become tricked by revised data about a witnessed event is a central goal of this research.
The paradigm for this research is simple. Participants first witness a complex event, such as a simulated violent crime or an automobile accident. Subsequently, half the participants receive new misleading information about the event. The other half do not get any misinformation. Finally, all participants attempt to recall the original event. In a typical example of a study using this paradigm, participants saw a video depicting a killing in a crowded town square. They then received written information about the killing, but some people were misled about what they saw. A critical blue vehicle, for instance, was referred to as being white. When later asked about their memory for the color of the vehicle, those given the phony information tended to adopt it as their memory; they said they saw white4. In these and many other experiments, people who had not received the phony information had much more accurate memories. In some experiments the deficits in memory performance following receipt of misinformation have been dramatic, with performance differences as large as 30 or 40%.
This degree of distorted reporting has been found in scores of studies, involving a wide variety of materials. People have recalled nonexistent broken glass and tape recorders, a clean-shaven man as having a mustache, straight hair as curly, stop signs as yield signs, hammers as screwdrivers, and even something as large and conspicuous as a barn in a bucolic scene that contained no buildings at all. In short, misleading post-event information can alter a person's recollection in a powerful ways, even leading to the creation of false memories of objects that never in fact existed.
The false memory was introduced in a short paragraph. It reminded Chris that he was five at the time, that Chris was lost at the University City shopping mall in Spokane, Washington where the family often went shopping. That Chris was crying heavily when he was rescued by an elderly man and reunited with his family.
Over the first five days, Chris remembered more and more about getting lost. He remembered that the man who rescued him was "really cool." He remembered being scared that he would never see his family again. He remembered his mother scolding him.
A few weeks later Chris was reinterviewed. He rated his memories on a scale from l (not clear at all) to ll (very, very clear). For the three true memories, Chris gave ratings of 1, 10, and 5. For the false shopping mall memory, he assigned his second-highest rating: 8. When asked to describe his getting lost memory, Chris provided rich details about the toy store where he got lost and his thoughts at the time ("Uh-oh. I'm in trouble now.") He remembered the man who rescued him as wearing a blue flannel shirt, kind of old, kind of bald on top.... "and, he had glasses."
Chris was soon told that one of the memories was false. Could he guess? He selected one of the real memories. When told that the memory of being lost was the false one, he had trouble believing it.
More recently we have completed a study that utilizes a procedure similar to that used with Chris. We asked 24 individuals to recall events that were supplied by a close relative. Three of the events were true, and one was a research-crafted false event about getting lost in a shopping mall or other public place. We now describe this study in detail.
Materials. Subjects were mailed a five page booklet containing a cover letter with instructions for completing the booklet and the scheduled interviews. The booklet contained four short stories about events from the subject's childhood provided by the older relative. In actuality, three of the stories were true, and one was the false event about getting lost. The order of events in the booklet and in the subsequent interviews was always the same, with the false event about getting lost always presented in the third position. Each event was described in a single paragraph at the top of the page, with the rest of the page left blank for the subject to record the details of his or her memory.
To see an example of the false memory paragraph, here is one created for a 20 year Vietnamese-American woman who grew up in the State of Washington: "You, your mom, Tien and Tuan, all went to the Bremerton K-Mart. You must have been five years old at the time. Your Mom gave each of you some money to get a blueberry ICEE. You ran ahead to get into the line first, and somehow lost your way in the store. Tien found you crying to an elderly Chinese woman. You three then went together to get an ICEE."
Procedure. Interviews with the relative for each subject were conducted to obtain three events that happened to the subject when they were between the ages of four and six. The stories were not to be family "folklore" or traumatic events that the subject with either remember easily or find painful to remember. In addition, the relative provided information about a plausible shopping trip to a mall or large department store in order to construct a false event where the subject could conceivably have gotten lost. The relative was asked to provide the following kinds of information: l) where the family would have shopped when the subject was about five years old; 2) which members of the family usually went along on shopping trips; 3) what kinds of stores might have attracted the subject's interest; and 4) verification that the subject had not been lost in a mall around the age of five. The false event was then crafted from this information. The false events always included the following elements about the subject: l) lost for an extended period of time, 2) crying, 3) lost in a mall or large department store at about the age of five, 4) found and aided by an elderly woman, 5) reunited with the family.
Subjects were told that they were participating in a study on childhood memories, and that we were interested in how and why some people remembered some things and not others. They were asked to complete the booklets by reading what their relative had told us about each event, and then write what they remembered about each event. If they did not remember the event, they were told to write, "I do not remember this." After completing the booklet, they mailed it back to us in a stamped envelope that we had provided to them.
Upon receipt of the completed booklet, subjects were called and scheduled for two interviews. If it was convenient, the interviews took place at the University; otherwise, over the telephone. Initially we had planned to manipulate, as an independent variable, the time intervals between the receipt of the booklet and the two subsequent interviews, however scheduling difficulties created by subject unavailability prevented us from doing this. Thus, in the end, all subjects were first interviewed approximately 1-2 weeks after receipt of the booklet, and received a second interview approximately 1-2 weeks after that. Two interviewers, both female, conducted and recorded the interview sessions.
At the beginning of the first interview, subjects were reminded about each of the four events, one at a time, and asked to recall as much as they could about them. They were instructed to tell us everything they remembered about the event, whether or not they had already written the information in their booklets. We told the subjects we were interested in examining how much detail they could remember, and how their memories compared with those of their relative. The event paragraphs were not read to them verbatim, but rather bits of them were provided as retrieval cues. When the subject had recalled as much as possible, they were asked to rate the clarity of their memory for the event on a scale of one to ten, with one being not clear at all and ten being extremely clear. Next, subjects rated their confidence on a scale of one to five that given more time to think about the event they would be able to remember more details (1=not confident and 5= extremely confident that they would be able to remember more).
The interviewers maintained a pleasant and friendly manner, while pressing for details. After the first interview, the subjects were thanked for their time, and encouraged to think about the events and try to remember more details for the next interview, but not to discuss the events at all with their relative or anyone else.
The second interview session, conducted 1-2 weeks after the first, was essentially the same: subjects tried to remember the four events, they rated their clarity and confidence, but at the end of this session they were debriefed. The debriefing phase explained our attempt to create a memory for something that had not happened, and asked subjects to guess which event may have been the false one. We apologized for the deception and explained why it was necessary for the research.
Subjects used more words when describing their true memories, whether these memories were fully or only partially recalled. For purposes of analysis, we calculated the mean number of words using only the 29% who produced a full or partial false memory in their initial booklets. The mean word length of descriptions of true memories was 138.0 whereas for descriptions of false memories it was 49.9. Six of the seven subjects used more words to describe their true than false memories, and the seventh used very few words to describe any memories (a mean of 20 for the true memories, and 21 for the false one).
During the first interview session, 17 subjects continued to maintain that they had no memory what-so-ever of the false event happening to them. One additional subject who had earlier accepted the event partially, now claimed that she did not remember being lost. Thus, 75% resisted the suggestion about being lost, and they continued to resist during the second interview.
We analyzed the clarity ratings for the subjects who embraced the false event during the first interview, and compared these clarity ratings to the ones given by these particular subjects for their true events. In general, the clarity ratings for the false events tended to be lower than for the true events. For purposes of analysis, we took five individuals who falsely remembered being lost and analyzed their mean and median clarity ratings. (Unfortunately, one subject could not be included in this analysis because clarity ratings were inadvertently not collected during the first interview). The mean clarity rating for the true memories of these five individuals was 6.3 during the first interview and also 6.3 during the second interview. The mean clarity rating for the false memory was 2.8 during the first interview and 3.6 during the second interview. (See figure 2). All five subjects had mean clarity ratings for their true events that exceeded the clarity rating for the false event. Three of the five subjects increased their clarity ratings for the false event, while two gave the same rating. Medians showed a similar pattern: higher ratings for the true than false events, and a modest rise in clarity from the first to the second interview for the false event only. The subject with missing data gave a median rating of 7.0 to her true memories and a rating of 4.0 to her false memory.
One subject's performance illustrates this pattern. She was a 20 year old woman who was convinced that she had been lost at K-Mart when she was about five. In her booklet, she used 90 words to describe her false memory, and a mean of 349 words to describe her true memories. During the two interview sessions her clarity ratings were mostly higher for the true memories than the false one, and only the clarity rating for the false memory rose from the first to the second interview. More specifically, her false memory was initially rated a 3, then rose to 4. By contrast, her true memories were rated 7 then 2, 9 then 9, and 6 then 6.
Subjects also rated how confident they were they they would be able to recall additional details at a later time, using a scale from 1 to 5. We examined the confidence ratings for the subset of subjects embraced the false event during the first interview and who provided two sets of confidence ratings. In general the confidence ratings were low, but lower for the false event that the true ones. The mean confidence rating for the true memories for this set of people was 2.7 during the first interview and 2.2 during the second interview. The mean confidence rating for the false memory was 1.8, then 1.4. (See figure 2). All five subjects had mean confidence ratings for their true events that exceeded the confidence rating for the false one. Most of the subjects gave the same low confidence rating during the two interviews.
At the end of the second session, subjects were debriefed and asked to choose which event may have been the false one. Of the 24 total, 19 subjects correctly chose the getting-lost memory as the false one, while the remaining five incorrectly thought that one of the true events was the false one.
Even though subjects sometimes correctly choose the getting-lost memory as the false one, this does not mean that they were not previously misled into genuinely embracing the false event. Sometimes they correctly choose simply by a process of elimination. Here is an example from one subject who was led to believe that she had been lost at the Hillsdale Shopping Mall. She described her getting lost experience using 66 words (as opposed to a mean of 128 words for her true memories). During the second interview she said "I vaguely, vague, I mean this is very vague, remember the lady helping me and Tim and my mom doing something else, but I don't remember crying. I mean I can remember a hundred times crying..... I just remember bits and pieces of it. I remember being with the lady. I remember going shopping. I don't think I, I don't remember the sunglasses part." She went on to remember that the elderly lady who helped her was "heavy-set and older. Like my brother said, nice." She gave her false memory a clarity rating of 4. When the subject was debriefed and asked to tell which was the false memory, she said: "Well, it can't be Slasher, 'cause I know that he ran up in the...the chimney and I know that that cat got smashed and I know that we got robbed so it had to be that mall one." Despite the debriefing, she continued to mildly struggle with her persisting memory: "..I totally remember walking around in those dressing rooms and my mom not being in the section she said she'd be in. You know what I mean?".
A predictable comment about the false memories of getting lost is that people may have actually been lost in their lives, however, briefly, and they may be confusing this actual experience with the false memory description. But our subjects were not asked about any experience of being lost. They were asked to remember being lost around the age of five - in a particular location with particular people present, being frightened, and ultimately being rescued by an elderly person. This is not to say that the actual experience of being lost briefly or of hearing about someone else being lost (even Hansel and Gretel) is not important. The development of the false memory of being lost may evolve first as the mere suggestion of being lost leaves a memory trace in the brain. Even if the information is originally tagged as a suggestion rather than an historic fact, that suggestion can become linked to other knowledge about being lost (stories of others). As time passes and the tag that indicates that being lost in the mall was merely a suggestion slowly deteriorates. The memory of a real event, visiting a mall becomes confounded with the suggestion that you were once lost in a mall. Finally, when asked whether you were ever lost in a mall, your brain activates images of malls and those of being lost. The resulting memory can even be embellished with snippets from actual events, such as people once seen in a mall. Now, you "remember" being lost in a mall as a child. By this mechanism, the memory errors occur because grains of experienced events or imagined events are integrated with inferences and other elaborations that go beyond direct experience.
All events, including the false one, were first cued with an event title (family vacation, overnight hospitalization) and an age. If subjects couldn't recall the event they received brief additional cues, such as location or other people involved. After the first interview subjects were encouraged to continue thinking about the events, but not to discuss them, and to return for a second interview one to seven days after the first.
In the first interview, subjects recalled and described 62 of the 74 true events (84%), and in the second interview they provided memories for 3 of the 12 events that had not been remembered during the first interview. As for the false events, no subject recalled these during the first interview, but 4 of 20 subjects (20%) incorporated false information in an event description by the second interview. One subject "remembered" that the doctor was a male, but the nurse was female - and also a friend from church.
In a second study, Hyman et al tried to implant three new false events that were rather unusual. The first was attending a wedding reception and accidentally spilling a punch bowl on the parents of the bride. The second was having to evacuate a grocery store when the overhead sprinkler systems erroneously activated. The third was being left in the car n a parking lot and releasing the parking brake causing the car to roll into something. While the methodology was basically the same as in the first study, there were some minor variations. Instead of beginning by simply cueing subjects with an event title and an age, they were now given more cues at the start (age, event, location, actions, and others involved). In subsequent interviews, the researchers provided only the event title and age, and, only when subjects failed to recall the event were additional cues provided. Moreover, the experimental demands were intensified somewhat by, for example, pressures for more complete recall. There were three interviews spaced one day apart.
In the first interview, subjects recalled and described 182 of the 205 true events (89%). In the second interview they provided a bit more information, and by the third interview they had provided some recall for 95% of the events. During the third interview, subjects provided memories for 13 of the 23 true events that had not been remembered during the first interview. As for the false events, again no subject recalled these during the first interview, but 13 (or 25%) did so by the third interview. For example, one subject had no recall of the wedding "accident", stating "I have no clue. I have never heard that one before." By the second interview the subject said: "...It was an outdoor wedding and I think we were running around and knocked something over like the punch bowl or something and um made a big mess and of course got yelled at for it."
These results show that people will create false recalls of childhood experiences in response to misleading information and the social demands inherent in repeated interviews8. The process of false recall appeared to depend, in part, on accessing some relevant background information. The authors hypothesized that some form of schematic reconstruction may account for the creation of false memories. What people appear to do, at the time they encounter the false details, is to call up schematic knowledge that is closely related to the false event. Next they think about the new information in conjunction with the schema, possibly storing the new information with that schema. Now, when they later try to remember the false event, they recall the false information and the underlying schema. The underlying schema is helpful for supporting the false event - it adds actual background information and provides the skeletal or generic scenes.
When false memories are created in this way, they can be thought about as a form of source confusion as described by Schacter and Curran (9). The false event is assumed to be a personal memory rather than as an event presented by the researchers as ostensibly coming from the parent. Schacter and Curran's patient, B.G. came to "remember" words that were never studied, probably because these words were represented in his long term memory prior to the experiment and this preexperimental familiarity was wrongly used as evidence that the word had recently appeared. Similarly, parts of the elements of the false memories created by us, and by Hyman and colleagues, are represented in long-term memory prior to the experiment. This pre- experimental familiarity can be wrongly used as evidence that the false event actually happened.
2. Greene RL. Human Memory. Hillsdale, NJ: Erlbaum, 1992
3. Loftus EF. Eyewitness Testimony. Cambridge: Harvard University Press, 1979.; McCloskey M, Zaragoza M. Misleading postevent information and memory for events: Arguments and evidence against memory impairment hypotheses. Journal of Experimental Psychology: General, 114, 1-16, 1985.
4. Loftus EF, Levidow, B, & Duensing, S. Who remembers best?: Individual differences in memory for events that occurred in a science museum. Applied Cognitive Psychology. 1992, 6, 93-107.
5. Loftus EF, Ketcham K. The myth of repressed memory. NY: St. Martin's Press, 1994.
6. Loftus EF, Coan J., Pickrell, JE. Manufacturing false memories using bits of reality. In Reder, L., ed. Implicit Memory and Metacognition. Hillsdale, NJ: Erlbaum, in press.
7. Hyman IE, Husband TH, Billings FJ. False memories of childhood experiences. Applied Cognitive Psychology, 1995, 9, 181-195.
8. For analogous findings with children, see also Ceci SJ, Loftus EF, Leichtman MD, Bruck M. The possible role of source misattributions in the creation of false beliefs among preschoolers. International Journal of Clinical and Experimental Hypnosis, XLII, 304-320, 1994. and Ceci SJ, Huffman, MLC, Smith E, Loftus EF. Repeatedly thinking about non-events. Consciousness and Cognition, 1994,3, 388-407.
9. Schacter DL, Curran T. The cognitive neuroscience of false memories. Psychiatric Anals, 1995, 25, 727-731.