One of the most influential and highly cited studies in the history of psychology was that reported by Elizabeth Loftus and Jaqueline Pickrell in 1995: “The formation of false memories”. The study is widely referred to as the “Lost in the mall” study, because it claimed to demonstrate that it was relatively easy to implant full or partial false memories in some adults of a childhood event that never actually happened – specifically, of getting lost in a shopping mall at the age of five. The study is not only described in virtually all introductory psychology textbooks but is often cited by expert witnesses in cases involving allegations of childhood abuse that may potentially be based upon false memories.
In recent years, however, the study has been the target of criticism from commentators who believe that the ease with which false memories can be implanted may have been exaggerated. Attention has been drawn to a number of shortcomings of the original study. The major criticisms of the 1995 study are the small sample size (only 24 participants took part), the lack of clear definitions of what was meant by a “partial” or “full” false memory, the lack of clear descriptions of any coding system used to categorise memory reports, and finally the lack of direct replications by other researchers. Fortunately, the results of a recent replication attempt which address all of these criticisms have just been published, showing that the conclusions of the original study are essentially sound.
Before going any further, it is worth understanding the original study by Loftus and Pickrell. Participants were informed that they were taking part in a study of childhood memories and asked to remember as much as they could about four events that were said to have taken place in childhood. Three of the events really had taken place, according to close family members, but one of them had not. The fictitious event was getting lost in a shopping mall at the age of five, being very upset, and eventually being reunited with parents. A week or two after the initial presentation of the four events, participants were interviewed and asked if they could remember any more details. They were asked to try to remember as much as they could prior to a second interview one or two weeks after the first. It was claimed that six of the participants developed full or partial memories of the target event.
The recent replication attempt, led by Gillian Murphy, was carried out by researchers at University College Cork and University College Dublin. Apart from changes to address the methodological weaknesses of the original study described above, the same methodology was generally followed, and details of the planned data analysis were pre-registered. A much larger sample of participants took part (N = 123) and clear definitions of a “full” and “partial” memory were given. Coders were trained, and followed detailed instructions on how memories should be coded. Overall, 35% of participants reported full (8%) or partial (27%) false memories for the target event based upon the coding system used.
The replication study went further than the original study by presenting statements describing 111 false memories from participants’ interviews to over a thousand respondents in an online “mock jury” study. In general, the mock jurors were very likely to believe the false memory reports.
The original “Lost in the mall” study has been criticised on the grounds that the necessary deception involved is unethical and might upset those taking part once it is revealed. Murphy and her colleagues took the opportunity to actually ask their participants and their familial informants how they felt about the deception once they had been fully debriefed. It turned that both groups held generally positive attitudes about taking part, indicating that they had enjoyed the experience and had learned something interesting about memory.
Perhaps the results of this replication should not come as a surprise. Although no direct replications of Loftus and Pickrell’s study had been reported prior to that of Murphy and colleagues, Alan Scoboria and colleagues had previously reported the results of a “mega-analysis” of interview transcripts of eight published memory implantation studies (total N = 423) using the same approach as that pioneered by Loftus and Pickrell. Across the studies, a range of different false childhood memories had been implanted including getting into trouble with a teacher, taking a trip in a hot air balloon, and spilling a bowl of punch over the bride’s parents at a wedding. The original studies had reported a wide range of estimates of the rate of successful memory implantation reflecting the use of different coding systems to define full and partial false memories by different investigators. Scoboria and colleagues came up with their own coding system based upon memory science and applied that same standard system to the transcripts from the eight studies. On that basis, some 30.4% of cases were classified as false memories, a result pretty much in line with that of Murphy and colleagues.
The recent recognition of the value of direct replication studies is to be welcomed. In a previous article for the Skeptic, I reported that a large, multi-lab study aimed at replicating a controversial paranormal effect had in fact demonstrated pretty conclusively that the original effect was not real. In the words of the researchers, “the original experiment was likely affected by methodological flaws or it was a chance finding”. The current successful replication of a classic memory study should suffice to silence critics of the original study. The results of both unsuccessful and successful replication attempts are of great value to science.
