Thursday, 28 November 2013

People with exceptional autographical memory are still prone to false memories

It's only in the last few years that researchers have documented the existence of a select group of individuals who have memories like a diary. Give them a random date from the past and they can tell you what they were doing that day, they can name public events happening around the time, and they can say what day of the week it was. Indeed, their memory for a day a decade ago is typically better than yours or mine for a day last month. Does this mean that their memories are less prone to distortion than ours? Not according to a new study.

Lawrence Patihis and his colleagues, including the doyenne of false memory research Elizabeth Loftus, tested 20 people with highly superior autobiographical memory (HSAM; also referred to as hyperthymesia), and 38 age and sex-matched controls, on a range of established tests of susceptibility to memory distortion.

One of these tests involved the participants studying a list of words on a particular theme, and then saying afterwards which of a series of further words were present in that original list or not. When an entirely new word fits the theme from the original list, people often make the mistake of thinking it was in the list. The HSAM participants made this error for 70.3 per cent of these so-called "lure" words compared with 70.8 per cent of control participants.

Another test involved participants looking at 50 photos depicting a robbery, and then 40 minutes later reading 50 facts about that same crime, six of which contained misinformation about what happened. Tested afterwards about what had happened during the robbery, the HSAM participants actually reported more misinformation than the controls. Prompted to identify the source of this information they sometimes (just as often as the controls) misremembered that the information came from the photographs.

Yet another test found that nearly as many HSAM participants as controls were easily tricked into thinking they'd seen non-existent footage of United Airlines Flight 93 crashing into Pennsylvania on September 11 2001 (20 per cent of them thought they had after being told such footage exists, compared with 29 per cent of controls - the difference is not statistically significant).

Throughout these and other tests the researchers also split the HSAM group into two - the highest performers and lowest performers in terms of their exceptional autobiographical memory. There was no evidence that the highest performing HSAM participants were any less vulnerable to memory suggestion than the others.

Taken altogether, these results present something of a conundrum: if people with HSAM are just as prone to memory distortion and misinformation than the rest of us, how come their autobiographical memories are usually so detailed and precise? Patihis and his colleagues don't doubt the abundant and accurate recall of HSAM individuals - in fact interviews with their HSAM participants about September 11 revealed the astonishing detail in their memories. Rather, the researchers think that the HSAM participants' exceptionally strong memory traces for their life tend not to be subject to much misinformation in normal circumstances, meaning there is usually little distortion in their memories.

In terms of the science of memory, the results from these tests suggest that people with HSAM have reconstructive memories like the rest of us. They are richer and more detailed, but when tested in the right conditions they are just as vulnerable to suggestion. "Whatever the source of their exceptional autobiographical memory ability is, this does not prevent them from having memory distortions," the researchers said. "Although it is always possible that some group might be found to be immune to memory distortions, none has yet been discovered."

_________________________________ ResearchBlogging.org

Patihis L, Frenda SJ, Leport AK, Petersen N, Nichols RM, Stark CE, McGaugh JL, and Loftus EF (2013). False memories in highly superior autobiographical memory individuals. Proceedings of the National Academy of Sciences of the United States of America PMID: 24248358

--Further reading--
Digest interview: Meet the woman who remembers most of her life in extraordinary detail.
Digest report: Total recall: The man who can remember every day of his life in detail.

Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.

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