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Emotion Critical to Memory Retention

According to a study led by psychologists at the University of Toronto, the differences in human memory – remembering something long ago that is crystal clear, versus something the other night that is lost in haze – are triggered by the varying levels of emotional involvement in that memory's formation.

This is a critical feature if we wish to create truly memorable worlds, and memorable experiences within those worlds. It seems that increased drama may actually be good for the memory.

"We've discovered that we see things that are emotionally arousing with greater clarity than those that are more mundane," says Rebecca Todd, a post doctoral fellow in U of T's Department of Psychology and lead author of the study published recently in the Journal of Neuroscience. "Whether they're positive – for example, a first kiss, the birth of a child, winning an award – or negative, such as traumatic events, breakups, or a painful and humiliating childhood moment that we all carry with us, the effect is the same."

"What's more, we found that how vividly we perceive something in the first place predicts how vividly we will remember it later on," says Todd. "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.”

By studying brain activity, Todd, psychology professor Adam Anderson and other colleagues at U of T, along with researchers at the University of Manchester and the University of California, San Diego found that the part of the brain responsible for tagging the emotional or motivational importance of things according to one's own past experience – the amygdala – is more active when looking at images that are rated as vivid. This increased activation in turn influences activity in both the visual cortex, enhancing activity linked to seeing objects, and in the posterior insula, a region that integrates sensations from the body.

Psychologists overlaid images with visual noise to measure perception. After accounting for other features of images that contribute to perceptual vividness, such as contrast, color, and scene complexity, they found emotionally arousing images to be perceived more vividly, and thus contributing partly to more vivid memories of certain images later.


"The experience of more vivid perception of emotionally important images seems to come from a combination of enhanced seeing and gut feeling driven by amygdala calculations of how emotionally arousing an event is," says Todd.

So, how do you begin measuring something as subjective as perception? Well, it helps to add definite measurable elements into the item being perceived, and go from there. Specifically, adding noise and making the perceived items harder and harder to determine in progressive stages until the emotional effect is annulled by the difficulty.

They took a plethora of pictures of scenes that would trigger different emotions. Each ione had to trigger strong emotional responses, so scenes of horrific bodily mutilation ranked equally as valuable as erotic imagery. In addition they took some neutral scenes – such as empty offices and escalators to serve as a baseline. These were then digitally treated with varying levels of white noise before being shown to study participants who were asked to say whether each image had the same, more, or less noise than a standard image with a fixed amount of noise.

"We 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," says Todd. "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."

The researchers used additional tests to rule out other explanations of their findings, such as how 'noisy' a picture seems due to less vibrant colours or a more complex scene. They also used eye-tracking measures to eliminate the possibility that people look at emotionally arousing images differently, causing them to rate some as more vivid.

"We next wanted to see if this finding of emotionally enhanced vividness influenced memory vividness," says Todd. "So, in two different studies, we measured memory for the images, both right after seeing them in the first place and one week later."

In the first study, 45 minutes after they did the noise task, participants were asked to write down all the details they could about pictures they remembered seeing. How much detail they remembered was a measure of vividness. In the second study, participants were shown the pictures again one week later and asked if they remembered them and, if so, how vividly they remembered them from very vague to very detailed.

"Both studies found that pictures that were rated higher in emotionally enhanced vividness were remembered more vividly," says Todd.

Finally, the researchers used brain imaging measures to look at when the brain responded to emotionally enhanced vividness and what regions of the brain responded. Using electrophysiology (EEG) to measure the timing of activity in the cortex to see when the brain is sensitive to vividness, gave them a sense of whether this subjective vividness was more about seeing vividly, or thinking that it was more vivid when you're considering it after the fact.

"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," says Todd. "Emotion alters activity in the visual cortex, which in turn influences how we see."

"We know now why people perceive emotional events so vividly – and thus how vividly they will remember them – and what regions of the brain are involved," says Todd. "Knowing that there are going to be differences among people as to how strongly they show this emotionally enhanced vividness and the strength of the brain activation patterns underlying them, could be useful in predicting an individual's vulnerability to trauma, including intrusive memories experienced by people with post-traumatic stress disorder."

It is also going to be absolutely vital in making sure their next visit to your virtual environment is a memorable one. Unless you successfully play on their emotional heartstrings, there is a very, very good chance the experience will fade into the background in short order.

References

Psychologists link emotion to vividness of perception and creation of vivid memories
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