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Preliminary evidence that stress makes negative memories less distinctive, with implications for witness testimony
Studies on stress and memory have often given conflicting results.
Stress has complicated effects on our memories.
Whereas some studies have found that we are better at remembering events that occurred during stressful situations, such as while watching disturbing videos, others have shown that stress impairs memory. Now a study published in Brain and Cognitionsuggests that stress doesn't influence the strength of our emotional memories at all. Instead, the researchers claim, it is the fidelity of those memories – how distinct and precise they are – that changes when we go through stressful experiences.
Maheen Shermohammeda from Harvard University and colleagues recruited 56 young adults between 18 and 23, and asked them to view a series of negative and neutral pictures. That might seem painless enough – except that half of the participants looked at the pictures while feeling rather stressed. Before they began looking at the pictures, they were told that they would later have to give a speech to a panel of judges. To make matters worse, before seeing each block of pictures they had to complete complicated maths problems. They were given just a short time to complete these, and while doing so they were told that they were performing poorly and their data would be unusable if they didn't do well. In contrast, the control group had a fairly relaxing time: instead of a speech, they were told they would have to write a story, and they only had to complete simple maths problems at their own pace.
About two weeks later, all the participants were given a surprise memory task, in which they again saw the earlier pictures alongside new images they hadn't seen before. They had to indicate whether each picture was an old one that had been in the original task or a new image they hadn't seen before.
At several points throughout the study, all participants were asked how stressed they were, and also had their heart rate measured and saliva samples taken to analyse levels of the stress hormone cortisol. As expected, the group that went through the stressful experience reported higher levels of stress, and had increased heart rates and cortisol levels (although the team had to exclude a handful of participants who, surprisingly, didn't report feeling stressed).
Overall, participants in both groups were better at remembering negative images – this replicates a well-established finding that emotional material tends to be more memorable. Also, the stressed group correctly remembered just as many of the earlier images as the control group (i.e. their "hit rate" was the same). Crucially, where the groups differed was in their patterns of "false alarms" – how often they falsely remembered new images as being from the original task. The stressed participants were more prone to false alarms for negative images compared neutral images, and the more stressed they were, the larger this difference.The control group didn't show any difference between the two kinds of images.
Based on these results, the researchers suggest it's not the strength of our memories that is influenced by stress, but rather their fidelity, or how distinct they are from other information. For the stressed group, neutral memories became more distinct, making it easier to distinguish them from new neutral material, while negative memories were more vague or blurred, making it harder to distinguish them from new negative material. The results demonstrate the importance of separating out memory into its constituent parts (strength and fidelity), the researchers add, rather than just looking at overall performance or correct "hits".
It's clearly a rather preliminary result. The pool of participants was small to begin with, and made even smaller after the researchers had to remove those participants who didn't respond to their stress intervention. And the participants all came from a very young, narrow age range, raising the question of whether older people respond in similar ways.
Nevertheless, the idea that stress has different effects on different components of memory is an interesting proposition that deserves further attention – particularly as understanding memory during periods of stress has important real-world implications for situations like eyewitness accounts of crimes. For example, the researchers said, a "stressed witness to [a] crime … may indeed have a strong recollection of the criminal, but may also have an impoverished ability to discriminate the assailant from other individuals in a police lineup."
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Ever since we've had the technology, we've looked to the stars in search of alien life. It's assumed that we're looking because we want to find other life in the universe, but what if we're looking to make sure there isn't any?
Here's an equation, and a rather distressing one at that: N = R* × fP × ne × f1 × fi × fc × L. It's the Drake equation, and it describes the number of alien civilizations in our galaxy with whom we might be able to communicate. Its terms correspond to values such as the fraction of stars with planets, the fraction of planets on which life could emerge, the fraction of planets that can support intelligent life, and so on. Using conservative estimates, the minimum result of this equation is 20. There ought to be 20 intelligent alien civilizations in the Milky Way that we can contact and who can contact us. But there aren't any.
Frequent shopping for single items adds to our carbon footprint.
- A new study shows e-commerce sites like Amazon leave larger greenhouse gas footprints than retail stores.
- Ordering online from retail stores has an even smaller footprint than going to the store yourself.
- Greening efforts by major e-commerce sites won't curb wasteful consumer habits. Consolidating online orders can make a difference.
A pile of recycled cardboard sits on the ground at Recology's Recycle Central on January 4, 2018 in San Francisco, California.
Photo by Justin Sullivan/Getty Images<p>A large part of the reason is speed. In a competitive market, pure players use the equation, <em>speed + convenience</em>, to drive adoption. This is especially relevant to the "last mile" GHG footprint: the distance between the distribution center and the consumer.</p><p>Interestingly, the smallest GHG footprint occurs when you order directly from a physical store—even smaller than going there yourself. Pure players, such as Amazon, are the greatest offenders. Variables like geographic location matter; the team looked at shopping in the UK, the US, China, and the Netherlands. </p><p>Sadegh Shahmohammadi, a PhD student at the Netherlands' Radboud University and corresponding author of the paper, <a href="https://www.cnn.com/2020/02/26/tech/greenhouse-gas-emissions-retail/index.html" target="_blank">says</a> the above "pattern holds true in countries where people mostly drive. It really depends on the country and consumer behavior there."</p><p>The researchers write that this year-and-a-half long study pushes back on previous research that claims online shopping to be better in terms of GHG footprints.</p><p style="margin-left: 20px;">"They have, however, compared the GHG emissions per shopping event and did not consider the link between the retail channels and the basket size, which leads to a different conclusion than that of the current study."</p><p>Online retail is where convenience trumps environment: people tend to order one item at a time when shopping on pure player sites, whereas they stock up on multiple items when visiting a store. Consumers will sometimes order a number of separate items over the course of a week rather than making one trip to purchase everything they need. </p><p>While greening efforts by online retailers are important, until a shift in consumer attitude changes, the current carbon footprint will be a hard obstacle to overcome. Amazon is trying to have it both ways—carbon-free and convenience addicted—and the math isn't adding up. If you need to order things, do it online, but try to consolidate your purchases as much as possible.</p><p>--</p><p><em>Stay in touch with Derek on <a href="http://www.twitter.com/derekberes" target="_blank">Twitter</a>, <a href="https://www.facebook.com/DerekBeresdotcom" target="_blank">Facebook</a> and <a href="https://derekberes.substack.com/" target="_blank">Substack</a>. His next book is</em> "<em>Hero's Dose: The Case For Psychedelics in Ritual and Therapy."</em></p>
Chronic irregular sleep in children was associated with psychotic experiences in adolescence, according to a recent study out of the University of Birmingham's School of Psychology.