15 September 2008

Memory surprisingly unreliable, study shows

Cosmos Online
Our memories of major past events can be surprisingly unreliable, says a new study of the July 2005 London bombings, which found that people can easily convince themselves they've seen things that never happened.
Bombed bus

Strange memories: The remains of a London bus that was destroyed by a bomb sit near Tavistock Square in London on 7 July 2005. Credit: AFP

LIVERPOOL, UK: Our memories of major past events can be surprisingly unreliable, says a new study of the July 2005 London bombings, which found that people can easily convince themselves they’ve seen things that never happened.

“Some people think that our memories are like video recorders and that if you press play the memories come flooding back. It doesn’t work like that at all and should not form the basis of legal decision making” said James Ost, a psychologist from the University of Portsmouth, England.

Explicit details of non-existant footage

Ost said that when DNA testing became available in the U.S. in the early 90s, 80 per cent of death row cases that were exonerated, were found to have been wrongly convicted on the strength of mistaken identity. His research demonstrates how this can happen.

To investigate how reliable our memories are, he asked people in the U.K. and Sweden if they’d seen CCTV footage of the bus bombing in the city’s Tavistock Square. Eighty-four per cent of U.K. respondents said that they had, compared to 50 per cent of Swedish participants, when in fact, no such footage exists.

His research was presented last week at the British Association for the Advancement of Science (BA) Festival of Science, held in Liverpool, England.

Some respondents in the false memory investigation also gave explicit details of the events they had seen in the non-existant footage.

In response to the question, “Was the bus moving when the bomb went off?” Ost received detailed responses such as: “The bus had just stopped to let two people off when two women got on and a man. He placed the bag by his side, the woman sat down and doors closed. As the bus left there was an explosion and then everyone started to scream.”

The study was conducted over two weeks in October 2005, three months after the attacks on the bus and underground system in central London. In the U.K., reports and analysis of the events continued relentlessly for weeks and months, said Ost, whereas in Sweden the bombings were headline news for only a few days.

“Fantasy proneness”

Ost said that people who were more likely to come up with false memories scored higher on a scale of “fantasy proneness” than those that did not.

“Some people who are more imaginative or more creative are better able to assimilate information, put it all together and weave a story out of it. They often have a lower threshold for accepting something as memory rather than imagination,” he added.

Memory footprint

Peter Naish is senior lecturer in cognitive psychology at the Open University in Milton Keynes, England. He explained that as memories form, sensory information enters the brain from a variety of sources and leaves a footprint.

“Other brain structures monitor these memories and resurrect them as and when required. But it is very easy to make errors when there are a lot of sources or effectively, memory ingredients stored, then it is easy to add in the wrong one that does not actually belong to that memory,” Naish told Cosmos Online.

In a courtroom this can spell disaster. Many child abuse cases have been brought to court based on testimony from adults who made false claims about things that happened many tens of years ago. Naish explains that certain people are susceptible to suggestibility and convincing themselves that things happened that never did.

“Approximately, 25 per cent of people are prone to false memory. In repeated experiments asking university students to recall childhood events, 25 per cent claimed that a particular fabricated event had really occurred after the psychologist suggested it had,” said Naish.


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