Tag Archives: Unpleasant


Unpleasant smells make for more powerful memories, a new study finds

Stinky smells make for stronger memories, it seems.


Literally unforgettable.
Image via Pixabay.

New research from the New York University’s Department of Psychology suggests that memories are stronger when the original experience was accompanied by unpleasant odors. The findings broaden our understanding of the mechanisms that underpin memory and of how negative experiences help shape our ability to recall past events.

Smells… familiar

“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,” explains Catherine Hartley, an assistant professor in New York University’s Department of Psychology and the senior author of the study.

“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,” adds lead author Alexandra Cohen, an NYU postdoctoral fellow.

Negative experiences are known to impact our memory. If you get bitten by a dog, for example, you can develop a negative memory of that particular animal — and that negative association may eventually eneralize to all dogs. You’re also much more likely to have a vivid, powerful memory of that particular interaction than your other past experiences with dogs due to the trauma associated with the event.

“The generalization and persistence in memory of learned negative associations are core features of anxiety disorders, which often emerge during adolescence,” notes Hartley.

In order to get a better idea of how these learned negative associations shape the way our memories form during this age, the team designed and administered a Pavlovian learning task to individuals aged 13 to 25. Such tasks usually employ mild electrical shocks; however, the researchers used bad smells because they can be ethically administered in studying children.

The task included viewing a series of images belonging to one of two conceptual categories: objects (e.g., a chair) and scenes (e.g., a snow-capped mountain). Participants wore a nasal mask connected to an olfactometer (an instrument used to detect and measure odor dilution) as they viewed the images. When images from one category were shown, participants were given unscented air. While participants viewed images from the other category, unpleasant smells were sometimes circulated through the device to the mask.

In order to determine which odors the participants found unpleasant, the researchers had the subjects breathe in a variety of odors and indicate which ones they thought were unpleasant prior to the study. The odors were blends of chemical compounds provided by a local perfumer and included scents such as rotting fish and manure.

This allowed the team to quantify the effect of a bad smell on individual memories as well as generalization to related images. In other words, they could measure if the image of a chair was stronger when associated with a bad smell, and whether this would happen only for this image or images in general. The team measured perspiration in the participants’ hands as a proxy for arousal levels. One day after the task, researchers tested participants’ memory for the images.

Their findings showed that both adolescents and adults showed better memory specifically for images paired with the bad smell 24 hours after the task. They also found that individuals with higher arousal levels during while viewing images that may have been associated with an unpleasant smell had better memory of the images 24 hours later regardless of whether or not a smell was actually delivered. This suggests that unpredictability or surprise associated with the outcome leads to better memory.

The paper “Aversive learning strengthens episodic memory in both adolescents and adults” has been published in the journal Learning & Memory.

Buddhist monk meditating.

Around one-quarter of those who meditate experience unpleasant symptoms — we don’t know why

About a quarter of those trying meditation report having at least one ‘particularly unpleasant’ psychological experience regarding this practice.

Buddhist monk meditating.

Image credits Sasin Tipchai.

Meditation gets a lot of attention these days, and there is some data to support their beneficial effect. But it’s not all mantras and roses, a new study found — a sizeable chunk of those who try their hand at the practice reported experiencing unpleasant effects.

The deep within

“These findings point to the importance of widening the public and scientific understanding of meditation beyond that of a health-promoting technique,” says first author Marco Schlosser, a researcher at the University College London (UCL) Division of Psychiatry.

“Very little is known about why, when, and how such meditation-related difficulties can occur: more research is now needed to understand the nature of these experiences. When are unpleasant experiences important elements of meditative development, and when are they merely negative effects to be avoided?”

These ‘particularly unpleasant’ experiences include feelings of fear and distorted emotions, the team reports. People who only practice deconstructive types of meditation — for example Vipassana (insight) and Koan practice (used in Zen Buddhism) — were more likely to experience such effects, as were those with higher levels of repetitive negative thinking, the team reports. However, female participants and those with religious beliefs were less likely to go through an unpleasant meditation-related experience.

The team used an online survey through which they questioned 1,232 people across the world who had at least two months’ meditation experience. Researchers at Witten/Herdecke University, Germany, and the University of Ljubljana, Slovenia, also participated in the study. They wanted to understand why some people experience unpleasant psychological effects during meditative practice — a trend illustrated by a growing number of research reports and case studies, they add. A collection of traditional Buddhist texts also tell of similar experiences in practitioners of yore, which further piqued the team’s interest.

Participants were asked whether they have “ever had any particularly unpleasant experiences (e.g. anxiety, fear, distorted emotions or thoughts, altered sense of self or the world), which you think may have been caused by your meditation practice?” They were also asked about how long they’ve been practicing meditation, the frequency with which they practice, whether or not they had attended a meditation retreat at any point in their life, and what form of meditation they practiced (attentional, constructive, or deconstructive). They also completed measures of repetitive negative thinking and self-compassion.

The results

Of the 1,232 participants:

  • 25.6% said that they had previously encountered particularly unpleasant meditation-related experiences.
  • More male participants experienced a particularly unpleasant experience than female participants (28.5% vs 23% ).
  • More of those who did not have a religious belief had a particularly unpleasant experience, compared to those who had a religious belief (30.6% vs 22%).
  • 29.2% of the participants who practiced only deconstructive types of meditation reported a particularly unpleasant experience, compared to 20.3% who only engaged in other meditation types.
  • 29% of those who had been on a meditation retreat (at any point in life) had a particularly unpleasant experience, compared to 19.6%, who had never been on a retreat.

“Most research on meditation has focused on its benefits, however, the range of meditative experiences studied by scientists needs to be expanded,” Schlosser adds.

“It is important at this point not to draw premature conclusions about the potential negative effects of meditation. Longitudinal studies will help to learn when, for whom, and under what circumstances these unpleasant experiences arise, and whether they can have long-term effects. This future research could inform clinical guidelines, mindfulness manuals, and meditation teacher training.”

It’s important to note that the present study doesn’t provide any indication of what these ‘unpleasant experiences’ were. In other words, it doesn’t have any way to quantify their severity and impact — which is a common limitation of self-reported data. Furthermore, the team writes that their inclusion of a list of specific examples (i.e., anxiety, fear, distorted emotions or thoughts, altered sense of self or the world) in the questionnaire may have biased participants’ responses towards recalling these particular experiences over others. The study also didn’t assess possible pre-existing mental health problems, which could have confounded the prevalence estimate of particularly unpleasant meditation-related experiences.

In less-fancy, less-science speak, this study cannot and should not be used as an indication that meditation caused these unpleasant experiences. However, it does show that the two can go hand-in-hand, and do so for a meaningful number of participants. Exactly why, how, and what that means, however, is something we still have to work to understand.

The paper “Unpleasant meditation-related experiences in regular meditators: Prevalence, predictors, and conceptual considerations” has been published in the journal PLOS ONE.