Forgetting keys ‘normal’ as study reveals secret of memorable events

Forgetting everyday things like where you left your keys may be normal as the brain is wired to recall the most emotionally charged events most vividly, research shows.

• Emotional power of memory helps brain store thoughts

• Dull items not stored so well

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Within a 5th of a second of seeing an image the brain indexes it by the emotional power of the image which then effects subsequent recall.

Lead author of the study Dr Rebecca Todd from the University of Toronto said: “We call this ‘emotionally enhanced vividness’ and it is like the flash of a flashbulb that illuminates an event as it’s captured for memory.”

She hopes that the new understanding of why people perceive and remember emotional events so vividly could help in treating people who are suffering intrusive memories as a part of post-traumatic stress disorder.

Participants in the study were shown various images and their ability to remember them was tested immediately afterwards as well as a week later. Some images were emotionally arousing and negative, like mutilation or sharks baring their teeth whereas others were arousing and positive, such as mild erotica. The final class of images were neutral which included for example people on an escalator.

In both cases the emotionally arousing images were recalled more vividly with no difference between the positive and negative images.

Dr Todd said: We’ve discovered that we see and remember things that are emotionally arousing with greater clarity than those that are more mundane.

“Whether they’re positive - for example, a first kiss, the birth of a child, winning an award - or negative, such as traumatic events, break-ups, or a painful and humiliating childhood moment that we all carry with us, the effect is the same.”

Brain scans were used to measure the timing of the activity in the visual cortex area of the brain to see when the brain is sensitive to vividness.

Dr Todd explained: “We found that the brain indexes vividness pretty quickly - about a 5th of a second after seeing a picture, which suggests it’s about seeing and not just thinking. Emotion alters activity in the visual cortex, which in turn influences how we see.”

The vividness effect also works when looking at images for the first time. It seems that our brain rates the emotional importance of a picture depending upon past experiences which in turn influences how vividly the image is seen.

The participants were shown similar images to the memory study but in this case overlaid with ‘visual noise’ similar to interference on an old TV screen.

They were asked to rate how noisy the pictures were and the scientists found that while people were good at rating how much noise was on the picture relative to a standard, they consistently rated pictures that were emotionally arousing as less noisy than neutral pictures regardless of the actual level of noise.

Dr Todd said: “When a picture was rated as less noisy, then they actually saw the picture underneath more clearly, as if there is more signal relative to noise in the emotionally arousing picture. The subjective meaning of a picture actually influenced how clearly the participants saw it.”