Our memories of the past can be distorted by powerful emotions and pain, according to research.

Psychologists have found that giving small electric shocks to volunteers was enough to distort their memories of things they had seen in the past.

The findings will increase concerns about the reliability of eyewitness accounts during court cases from people who have suffered traumatic experiences.

The findings might help explain why people's memories of what they were doing on the days around 9/11 in 2001 are often distorted by the terrorist attacks that on the Twin Towers in New York (shown above)

Brian Williams, the former NBC Nightly News anchor, also suggested his own memory may have been affected in a similar way while covering the war in Iraq in 2003 due to his fear at being in a warzone for the first time.

FALSE MEMORIES CAN TURN EVEN TURN YOU INTO A CRIMINAL Innocent people can be fooled into believing they have carried out a violent crime that never took place, a study has revealed. Psychologists found that during just three hours of interviews, adults could be convinced they had perpetrated a theft, an assault, or even attacked somebody with a weapon when they were a teenager. Using suggestive memory-retrieval techniques, the researchers were able to trick 70 per cent of the participants into believing they had committed an offence. After hearing a false account of their teenage crime - peppered with true details of their life at that time - the participants appeared to ‘internalise’ the fabricated story. The effect was so strong that the participants ended up providing detailed descriptions of things that had never actually taken place. Advertisement

Last week he was suspended from his job by NBC for making false statements about being in a helicopter that was shot down during the conflict.

Instead he was on an aircraft an hour behind and later spoke to those on board the helicopter that was shot down.

The new research shows that our memories of a seemingly ordinary event can be altered should we experience a powerful emotion like fear in connection with similar events at a later date.

Writing in the journal Nature, Professor Elizabeth Phelps, a psychologist at New York University who led the work, said: 'Humans and other animals continuously monitor the environment, accumulating countless details.

'Much of this information is forgotten. However, meaningful events can selectively preserve memory for previously encountered information that seemed insignificant at the time it was encoded.

'We found that memories for neutral information can be enhanced by a future emotional event that involves conceptually related material.'

The researchers showed 120 volunteers a series of 60 images of animals and tools and were asked to classify each photograph into one of the two categories.

Volunteers in the study were shown images of either animals or tools, like those shown on the left of the diagram above, and then later shown similar images where one category of pictures were associated with an electric shock. When asked to look at another set of images and say if they had seen them before, those similar to the animals or tools associated with the electric shock triggered much stronger recall after 24 hours

Brian Williams, above, claimed his memory of events in the Iraq war in 2003 may have been clouded by fear

Around five minutes later, they conducted a similar task but this time half of the volunteers 30 of the pictures were asociated with electric shocks in a form of fear condition.

The volunteers were then asked asked to look at around 90 pictures and classify whether they had seen them before or not after either six hours or 24 hours.

The researchers found that while there was no immediate difference in recollection between those that had received conditioning and those that had not, after 24 hours significant differences appeared.

Images simlar to those that were paired with shocks were stronger than for objects not associated with shocks.

The researchers suggest that sleep may an important role in altering these old memories.

The findings suggest that traumatic events, like being a victim of crime, and emotions like fear can change our memories and seem to be be able to alter the way we remember things that happened in the past

The findings underline the importance for police to obtain witness statements as soon after an event as possible before memories have the potential to become distorted by emotion.

It may also help to explain why people are often wildly wrong when they try to remember what they were doing during major and shocking events like the terrorist attacks on the Twin Towers in 2001.

The researchers believe the mechanism may also play a role in the development of post-traumatic stress disorders.