Understanding the Impact of Emotion on Memory

Emotions are the motive forces of much of human behaviour and are therefore important to understand. But studying emotion is hard. In the laboratory, researchers show participants pictures of angry faces or fluffy bunnies to try to induce emotions, but one always has a lurking doubt that the emotions evoked this way are really the same as what I feel when she says “I do” or when grandad finally lets go.

The problem is compounded when you want to study the effects of emotion on memory. People’s lives are a compilation of vivid experiences – swirling vortexes of people, places, sounds and activities that come boxed in routine and circumstance. Somehow encoding a random list of words for a later recogition memory test doesn’t seem to do it justice.

To try to do a better job, we conducted a study in which we had people install two apps on their phones. For two weeks, the www.unforgettable.me app recorded where they were, short segments of sound every ten minutes and their accelerometry. At the same time, the SEMA3 app queried them 8 times a day asking them to rate how happy, excited, confident, bored, content, angry, anxious, sad, irritable and relaxed they felt. After a week, we asked them a series of questions about where they were at different times. They were given four choices, so we could use the mistakes they made to infer how different aspects of their experience affected their memories.

You can imagine emotion affecting memory in two main ways. Emotions might increase the salience of an event causing you to encode it more strongly in memory. Alternatively, emotions might be encoded as features of events making you more likely to confuse events that have similar emotions.

To test the first possibility, we divided the emotions into four cateogries – positive low arousal emotions (relaxed, content), positive high arousal emotions (happy, excited, confident), negative low arousal emotions (bored, disappointed, sad) and negative high arousal emotions (angry, anxious, irritable) – and looked at how often people got the questions right as a consequence.

The negative emotions had no impact on performance, positive low arousal emotions improved performance and postive high arousal emotions hurt performance. We really didn’t expect these results. If the salience of the emotions made you more likely to encode information in memory then the high arousal positive and negative events should have improved performance. It’s a puzzle.

We also looked at how similarity in the emotional profile of events affected how likely people were to select the wrong choice.

All of the emotions showed robust effects suggesting that emotions are being encoded into memories and can lead people to confuse events during which they experienced similar emotions.

Perhaps unsurprisingly, if there was a choice that was physically close to where they actually were then they were more likely to choose it. Interestingly, however, if there were choices for which the sounds were the same or their patterns of movement were the same they were also more likely to choose them (although much less so than for the location).

The interaction of emotion and memory is a complex topic and we have just scratched the surface in this study. However, we are hopeful that using experience sampling methods like these will provide a deeper understanding of the mechanisms involved than has previously been possible.

If you are interested in learning more about this research feel free to read the preprint.

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