Bad smells, better memory?
A series of experiments with volunteers aged 13 to 25 showed that they were better able to recall images that were associated with unpleasant odours.
Unpredictability or surprise
Specifically, they had better recall of images 24 hours after seeing them if the images were paired with a bad smell.
The study also found that people who had greater arousal responses (measured by palm perspiration) at the instant when they might be exposed to either a bad smell or clean air while viewing the image – regardless of whether or not they were actually exposed to a smell – had better recall of the images 24 hours later.
This suggests that unpredictability or surprise associated with the outcome leads to better memory, according to the New York University researchers.
"These results demonstrate that bad smells are capable of producing memory enhancements in both adolescents and adults, pointing to new ways to study how we learn from and remember positive and negative experiences," senior author Catherine Hartley said in a university news release. Hartley is an assistant professor of psychology cognition and perception.
"Because our findings spanned different age groups, this study suggests that aversive odors might be used in the future to examine emotional learning and memory processes across development," said study author Alexandra Cohen, a postdoctoral fellow.
People have different opinions about what constitutes a bad smell, so before the start of the study, the researchers exposed the participants to a variety of odours and asked which of them they found unpleasant.
The odours were blends of chemical compounds and included smells such as rotting fish and manure.
The study participants wore nasal masks hooked to an olfactometer – an instrument used to produce and measure smells – and were shown a series of images of objects or scenes. While they viewed one category, unpleasant smell circulated through their masks. For the other category, unscented air was used. The researchers monitored their responses.
It's long been known that negative experiences have a significant impact on memory. For example, people who suffer a dog bite may develop a negative memory of the dog, which may expand into a negative association with all dogs, according to the researchers.
The trauma linked with the bite might also make that experience stronger in the memory than other interactions with dogs.
"The generalisation and persistence in memory of learned negative associations are core features of anxiety disorders, which often emerge during adolescence," Hartley said.
The study will be published in the journal Learning and Memory.
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