How memory works

The role of emotion in memory

Does emotion help us remember? That's not an easy question to answer, which is unsurprising when you consider the complexities of emotion.

First of all, there are two, quite different, elements to this question. The first concerns the emotional content of the information you want to remember. The second concerns the effect of your emotional state on your learning and remembering.

The effect of emotional content

It does seem clear that, as a general rule, we remember emotionally charged events better than boring ones.

Latest research suggests that it is the emotions aroused, not the personal significance of the event, that makes such events easier to remember.

The memory of strongly emotional images and events may be at the expense of other information. Thus, you may be less likely to remember information if it is followed by something that is strongly emotional. This effect appears to be stronger for women.

It does seem that memories are treated differently depending on whether they are associated with pleasant emotions or unpleasant ones, and that this general rule appears to be affected by age and other individual factors. Specifically, pleasant emotions appear to fade more slowly from our memory than unpleasant emotions, but among those with mild depression, unpleasant and pleasant emotions tend to fade evenly, while older adults seem to regulate their emotions better than younger people, and may encode less information that is negative.

An investigation of autobiographical memories found that positive memories contained more sensorial and contextual details than neutral or negative memories (which didn't significantly differ from each other in this regard). This was true regardless of individual's personal coping styles.

  • Emotionally charged events are remembered better
  • Pleasant emotions are usually remembered better than unpleasant ones
  • Positive memories contain more contextual details (which in turn, helps memory)
  • Strong emotion can impair memory for less emotional events and information experienced at the same time
  • It's the emotional arousal, not the importance of the information, that helps memory

The effect of mood

Another aspect of emotion is mood - your emotional state at the time of encoding or retrieving. There has been quite a lot of research on the effect of mood on memory. It is clear that mood affects what is noticed and encoded. This is reflected in two (similar but subtly different) effects:

  • mood congruence: whereby we remember events that match our current mood (thus, when we're depressed, we tend to remember negative events), and
  • mood dependence: which refers to the fact that remembering is easier when your mood at retrieval matches your mood at encoding (thus, your chances of remembering an event or fact are greater if you evoke the emotional state you were in at the time of experiencing the event or learning the fact).

An interesting issue in the study of emotion is the degree to which what we feel is influenced by our expression of it. In other words, does a person who conceals what they are feeling feel as deeply as a person who openly displays their emotion? Does the expression of emotion, in itself, affect what we feel?

I remember reading Paul Ekman (the guru of interpreting facial expressions, and author of several books on the subject) say that, when practicing the expressions, he found himself experiencing the emotions they expressed. However, accurate expression of emotion does seem to require considerable expertise (if the emotion is not, in fact, being felt) - people are very good at distinguishing false expressions of emotion.

The way people go about controlling their reactions to emotional events does seem to affect their memory of the event. People shown a video of an emotional event and instructed not to let their emotions show were found to have a poorer memory for what was said and done than did those who were given no such instructions.

However, as with emotional content, we cannot simply say that emotional state affects memory. The nature of the emotion being felt is also important. And this, too, is not straightforward. We cannot simply say, for example, that anxiety impairs memory and happiness improves it.

A small study in which participants performed difficult cognitive tasks after watching short videos designed to elicit one of three emotional states ( pleasant, neutral or anxious), found that mild anxiety improved performance on some tasks, but hurt performance on others. Similarly, being in a pleasant mood boosted some kinds of performance but impaired other kinds.

This may have something to do with different emotions being involved with different brain regions.

  • Remembering is easier when your mood matches the mood you were in when experiencing/learning the information
  • The stronger the emotions aroused, the greater the effect on memory
  • Emotions can be evoked, or minimized, by displaying or suppressing expressions of emotion
  • Different emotional states may impair or help memory, for different memory tasks

Brain regions involved in the emotion-memory interaction

The brain region most strongly implicated in emotional memory is the amygdala. The amygdala is critically involved in calculating the emotional significance of events, and, through its connection to brain regions dealing with sensory experiences, also appears to be responsible for the influence of emotion on perception - alerting us to notice emotionally significant events even when we're not paying attention. The amygdala appears to be particularly keyed to negative experiences.

But it is not only the amygdala that is involved in this complex interaction. The cerebellum, most strongly associated with motor coordination skills, may also be involved in remembering strong emotions, in particular, in the consolidation of long-term memories of fear.

Parts of the prefrontal cortex also appear to be involved. One study found that a region of the prefrontal cortex was jointly influenced by a combination of mood state and cognitive task, but not by either one alone. Another study found that the dorsolateral prefrontal cortex is more active when the participants were surprised by unexpected responses.

Is surprise an emotion? I think surprise is right there in the fuzzy border between two related phenomena - emotion and attention. Interestingly, our understanding of these two phenomena is about on a par - still woefully inadequate (but greatly improving!).

The relationship between emotion and attention

Research suggests that emotional stimuli and "attentional functions" move in parallel streams through the brain before being integrated in a specific part of the brain's prefrontal cortex (the anterior cingulate). This is why emotional stimuli are more likely than simple distractions to interfere with your concentration on a task such as driving.

We now think that attention is not, as has been thought, a global process, but consists of at least three distinct processes, each located in different parts of the frontal lobes. These are:

  1. a system that helps us maintain a general state of readiness to respond;
  2. a system that sets our threshold for responding to an external stimulus; and
  3. a system that helps us selectively attend to appropriate stimuli.

Correspondingly, emotional arousal helps us maintain a "readiness to respond", and also has a selective effect on the particular stimuli we notice and encode. Perhaps, indeed, attention may be thought of as a state of activity that is triggered by various kinds of emotional arousal, and modulated by such arousal.

How do emotions affect memory?

Well, we're still foggy on details, but there appear to be two main aspects to this. One is that stress hormones, such as cortisol, interact with the amygdala. The other is that the amygdala can alter the activity of other brain regions. One of the ways in which it does this is by acting on consolidation processes (principally in the hippocampus).

It is perhaps this effect on consolidation that is reflected in a study using facial stimuli (involving inversion of eyes and mouth to change the emotional impact of a face without significantly changing its visual features), that indicated that the emotional load of a stimulus does not in fact affect the way we perceive it but does have an effect on how we become used to it if we see it many times.

Notwithstanding this study, however, it does seem clear that, in some circumstances and for some types of stimuli, at least, the emotional attributes of a stimulus do affect the way we perceive it and process it - that is, the encoding of the memory.

One of the ways in which it might do this is through the involvement of different brain regions depending on the nature of the emotion experienced. A recent imaging study found that positive emotional contexts evoked activity in the right fusiform gyrus (among other regions), and negative emotional contexts evoked activity in the right amygdala.

Another way in which emotions might affect memory encoding is through working memory. It has been suggested that, in the case of anxiety, part of working memory may be taken up with our awareness of fears and worries, leaving less capacity available for processing. In support of this theory, one study found that math-anxious people have working memory problems as they do math.

Age and gender differences

It also seems that there are differences in the way men and women process emotional memories. Women are better at remembering emotional memories. They also seem to be more likely to forget information presented immediately before emotionally charged information. This suggests that women are more affected by emotional content - a suggestion compatible with the finding that women and men tend to encode emotional experiences in different parts of the brain. In women, it seems that evaluation of emotional experience and encoding of the memory is much more tightly integrated.

There is also an age difference. The tendency to let unpleasant memories fade faster than pleasant ones gets stronger as we age. This is perhaps a reflection of older people's apparent ability to regulate their emotions more effectively than younger people, by maintaining positive feelings and lowering negative feelings. Preliminary brain research suggests that in older adults, the amygdala is activated equally to positive and negative images, whereas in younger adults, it is activated more to negative images. It may be that older adults encode less information about negative images.

It has also been speculated that age-related cognitive decline may be partly caused by a greater cortisol responsivity to stress.

  • The key player in the processing of emotional memories appears to be the amygdala
  • Other brain regions, in particular the prefrontal cortex and the cerebellum, are also involved
  • While these regions are important for all, men and women do show differences in the parts of the brain they use to encode emotion
  • Emotion and attention are related phenomena
  • Emotion acts on memory at all points of the memory cycle - at encoding, consolidation, and retrieval
  • Emotion acts on memory in various ways, including the production of stress hormones, use of working memory capacity, and involvement of particular brain regions
References: 
  • Anderson, A.K. & Phelps, E.A. 2001. Lesions of the human amygdala impair enhanced perception of emotionally salient events. Nature, 411, 305-309.
  • Canli, T., Desmond, J.E., Zhao, Z. & Gabrieli, J.D.E. 2002. Sex differences in the neural basis of emotional memories. Proceedings of the National Academy of Sciences, 99, 10789-10794.
  • Charles, S.T., Mather, M. & Carstensen, L.L. 2003. Aging and Emotional Memory: The Forgettable Nature of Negative Images for Older Adults. Journal of Experimental Psychology: General, 132(2), 310-24.
  • D'Argembeau, A., Comblain, C. & Van der Linden, M. 2002. Phenomenal characteristics of autobiographical memories for positive, negative, and neutral events. Applied Cognitive Psychology, 17(3), 281-94.
  • Erk, S. et al. 2003. Emotional context modulates subsequent memory effect. Neuroimage, 18, 439-447.
  • Fletcher, P.C., Anderson, J.M., Shanks, D.R., Honey, R., Carpenter, T.A., Donovan, T., Papadakis, N. & Bullmore, E.T. 2001. Responses of human frontal cortex to surprising events are predicted by formal associative learning theory. Nature Neuroscience, 4, 1043-1048.
  • Gray, J.R., Braver, T.S. & Raichle, M.E. Integration of emotion and cognition in the lateral prefrontal cortex. Proceedings of the National Academy of Sciences, 99, 4115-4120.
  • Hamann, S. 2001. Cognitive and neural mechanisms of emotional memory. Trends in Cognitive Sciences, 5 (9), 394-400.
  • Lewis, P.A. & Critchley, H.D. 2003. Mood-dependent memory. Trends in Cognitive Sciences, 7 (9).
  • Lupien, S.J., Gaudreau, S., Tchiteya, B.M., Maheu, F., Sharma, S., Nair, N.P.V., Hauger, R.L., McEwen, B.S. & Meaney, M.J. 1997. Stress-Induced Declarative Memory Impairment in Healthy Elderly Subjects: Relationship to Cortisol Reactivity. The Journal of Clinical Endocrinology & Metabolism, 82 (7), 2070-2075.
  • Nielson, K.A., Yee, D. & Erickson, K.I. 2002. Modulation of memory storage processes by post-training emotional arousal from a semantically unrelated source. Paper presented at the Society for Neuroscience annual meeting in Orlando, Florida, 4 November.
  • Nijholt, I., Farchi, N., Kye, M-J., Sklan, E.H., Shoham, S., Verbeure, B., Owen, D., Hochner, B., Spiess, J., Soreq, H. & Blank, T. 2003. Stress-induced alternative splicing of acetylcholinesterase results in enhanced fear memory and long-term potentiation. Molecular Psychiatry advance online publication, 28 October 2003.
  • Richards, J.M. & Gross, J.J. (2000). Emotion Regulation and Memory: The Cognitive Costs of Keeping One's Cool. Journal of Personality and Social Psychology, 79 (3), 410-424.
  • Richeson, J. & Shelton, N. 2003. When Prejudice Does Not Pay: Effects of Interracial Contact on Executive Function. Psychological Science, 14(3).
  • Sacchetti, B., Baldi, E., Lorenzini, C.A. & Bucherelli, C. 2002. Cerebellar role in fear-conditioning consolidation. Proc. Natl. Acad. Sci. U.S.A., 99 (12), 8406-8411.
  • Strange, B.A., Hurleman, R. & Dolan, R.J. In press. An emotion-induced retrograde amnesia in humans is amygdala and b-adrenergic dependent. Proceedings of the National Academy of Sciences.
  • Stuss, D.T., Binns, M.A., Murphy, K.J. & Alexander, M.P. 2002. Dissociations Within the Anterior Attentional System: Effects of Task Complexity and Irrelevant Information on Reaction-Time Speed and Accuracy. Neuropsychology, 16 (4), 500–513.
  • Walker, W.R., Skowronski, J.J. & Thompson, C.P. 2003. Life Is Pleasant -- and Memory Helps to Keep It That Way! Review of General Psychology, 7(2),203-10.
  • Yamasaki, H., LaBar, K.S. & McCarthy, G. Dissociable prefrontal brain systems for attention and emotion. Proc. Natl. Acad. Sci. USA, 99(17), 11447-51.

Each memory experience biases how you approach the next one

A new study provides evidence that our decision to encode information as new or try and retrieve it from long-term memory is affected by how we treated the last bit of information processed.

Our life-experiences contain a wealth of new and old information. The relative proportions of these change, of course, as we age. But how do we know whether we should be encoding new information or retrieving old information? It’s easy if the information is readily accessible, but what if it’s not? Bear in mind that (especially as we get older) most information / experiences we meet share some similarity to information we already have.

This question is made even more meaningful when you consider that it is the same brain region — the hippocampus — that’s involved in both encoding and retrieval, and these two processes depend (it is thought) on two quite opposite processes. While encoding is thought to rely on pattern separation (looking for differences), retrieval is thought to depend on pattern completion.

A recent study looked at what happens in the brain when people rapidly switch between encoding new objects and retrieving recently presented ones. Participants were shown 676 pictures of objects and asked to identify each one as being shown for the first time (‘new’), being repeated (‘old’), or as a modified version of something shown earlier (‘similar’). Recognizing the similar items as similar was the question of interest, as these items contain both old and new information and so the brain’s choice between encoding and retrieval is more difficult.

What they found was that participants were more likely to recognize similar items as similar (rather than old) if they had viewed a new item on the preceding trial. In other words, the experience of a new item primed them to notice novelty. Or to put it in another way: context biases the hippocampus toward either pattern completion or pattern separation.

This was supported by a further experiment, in which participants were shown both the object pictures, and also learned associations between faces and scenes. Critically, each scene was associated with two different faces. In the next learning phase, participants were taught a new scene association for one face from each pair. Each face-scene learning trial was preceded by an object recognition trial (new and old objects were shown and participants had to identify them as old or new) — critically, either a new or old object was consistently placed before a specific face-scene association. In the final test phase, participants were tested on the new face-scene associations they had just learned, as well as the indirect associations they had not been taught (that is, between the face of each pair that had not been presented during the preceding phase, and the scene associated with its partnered face).

What this found was that participants were more likely to pair indirectly related faces if those faces had been consistently preceded by old objects, rather than new ones. Moreover, they did so more quickly when the faces had been preceded by old objects rather than new ones.

This was interpreted as indicating that the preceding experience affects how well related information is integrated during encoding.

What all this suggests is that the memory activities you’ve just engaged in bias your brain toward the same sort of activities — so whether or not you notice changes to a café or instead nostalgically recall a previous meal, may depend on whether you noticed anyone you knew as you walked down the street!

An interesting speculation by the researchers is that such a memory bias (which only lasts a very brief time) might be an adaptive mechanism, reflecting the usefulness of being more sensitive to changes in new environments and less sensitive to irregularities in familiar environments.

How emotion keeps some memories vivid

Emotionally arousing images that are remembered more vividly were seen more vividly. This may be because the amygdala focuses visual attention rather than more cognitive attention on the image.

We know that emotion affects memory. We know that attention affects perception (see, e.g., Visual perception heightened by meditation training; How mindset can improve vision). Now a new study ties it all together. The study shows that emotionally arousing experiences affect how well we see them, and this in turn affects how vividly we later recall them.

The study used images of positively and negatively arousing scenes and neutral scenes, which were overlaid with varying amounts of “visual noise” (like the ‘snow’ we used to see on old televisions). College students were asked to rate the amount of noise on each picture, relative to a specific image they used as a standard. There were 25 pictures in each category, and three levels of noise (less than standard, equal to standard, and more than standard).

Different groups explored different parameters: color; gray-scale; less noise (10%, 15%, 20% as compared to 35%, 45%, 55%); single exposure (each picture was only presented once, at one of the noise levels).

Regardless of the actual amount of noise, emotionally arousing pictures were consistently rated as significantly less noisy than neutral pictures, indicating that people were seeing them more clearly. This was true in all conditions.

Eye-tracking analysis ruled out the idea that people directed their attention differently for emotionally arousing images, but did show that more eye fixations were associated both with less noisy images and emotionally arousing ones. In other words, people were viewing emotionally important images as if they were less noisy.

One group of 22 students were given a 45-minute spatial working memory task after seeing the images, and then asked to write down all the details they could remember about the pictures they remembered seeing. The amount of detail they recalled was taken to be an indirect measure of vividness.

A second group of 27 students were called back after a week for a recognition test. They were shown 36 new images mixed in with the original 75 images, and asked to rate them as new, familiar, or recollected. They were also asked to rate the vividness of their recollection.

Although, overall, emotionally arousing pictures were not more likely to be remembered than neutral pictures, both experiments found that pictures originally seen as more vivid (less noise) were remembered more vividly and in more detail.

Brain scans from 31 students revealed that the amygdala was more active when looking at images rated as vivid, and this in turn increased activity in the visual cortex and in the posterior insula (which integrates sensations from the body). This suggests that the increased perceptual vividness is not simply a visual phenomenon, but part of a wider sensory activation.

There was another neural response to perceptual vividness: activity in the dorsolateral prefrontal cortex and the posterior parietal cortex was negatively correlated with vividness. This suggests that emotion is not simply increasing our attentional focus, it is instead changing it by reducing effortful attentional and executive processes in favor of more perceptual ones. This, perhaps, gives emotional memories their different ‘flavor’ compared to more neutral memories.

These findings clearly need more exploration before we know exactly what they mean, but the main finding from the study is that the vividness with which we recall some emotional experiences is rooted in the vividness with which we originally perceived it.

The study highlights how emotion can sharpen our attention, building on previous findings that emotional events are more easily detected when visibility is difficult, or attentional demands are high. It is also not inconsistent with a study I reported on last year, which found some information needs no repetition to be remembered because the amygdala decrees it of importance.

I should add, however, that the perceptual effect is not the whole story — the current study found that, although perceptual vividness is part of the reason for memories that are vividly remembered, emotional importance makes its own, independent, contribution. This contribution may occur after the event.

It’s suggested that individual differences in these reactions to emotionally enhanced vividness may underlie an individual’s vulnerability to post-traumatic stress disorder.

Reference: 

Second language processing differs for negative words

A study involving Chinese-English bilinguals shows how words with negative emotional connotations don’t automatically access native translations, while those with positive or neutral emotions do.

Here’s an intriguing study for those interested in how language affects how we think. It’s also of interest to those who speak more than one language or are interested in learning another language, because it deals with the long-debated question as to whether bilinguals working in their non-native language automatically access the native-language representations in long-term memory, or whether they can ‘switch off’ their native language and use only the target language memory codes.

The study follows on from an earlier study by the same researchers that indicated, through the demonstration of hidden priming effects, that bilinguals subconsciously access their first language when reading in their second language. In this new study, 45 university students (15 native English speakers, 15 native Chinese speakers, and 15 Chinese-English bilinguals) were shown two blocks of 90 word pairs. The pairs could have positive emotional value (e.g., honesty-program), negative valence (failure-poet), or neutral valence (aim-carpenter); could be semantically related (virus-bacteria; love-rose) or unrelated (weather-gender). The English or Chinese words were flashed on the screen one at a time, with a brief interval between the first and second word. The students had to indicate whether the second word was related in meaning to the first, and their brain activity was monitored.

The English and Chinese speakers acted as controls — it was the bilinguals, of course, who were the real interest. Some of the English word pairs shared a sound in the Chinese translation. If the Chinese words were automatically activated, therefore, the sound repetition would have a priming effect.

This is indeed what was found (confirming the earlier finding and supporting the idea that native language translations are automatically activated) — but here’s the interesting thing: the priming effect occurred only for positive and neutral words. It did not occur when the bilinguals saw negative words such as war, discomfort, inconvenience, and unfortunate.

The finding, which surprised the researchers, is nonetheless consistent with previous evidence that anger, swearing or discussing intimate feelings has more power in a speaker's native language. Parents, too, tend to speak to their infants in their native tongue. Emotion, it seems, is more strongly linked to our first language.

It’s traditionally thought that second language processing is fundamentally determined by the age of acquisition and the level of proficiency. The differences in emotional resonance have been, naturally enough, attributed to the native language being acquired first. This finding suggests the story is a little more complicated.

The researchers theorize that they have touched on the mechanism by which emotion controls our fundamental thought processes. They suggest that the brain is trying to protect us by minimizing the effect of distressing or disturbing emotional content, by shutting down the unconscious access to the native language (in which the negative words would be more strongly felt).

A few more technical details for those interested:

The Chinese controls demonstrated longer reaction times than the English controls, which suggests (given that 60% of the Chinese word pairs had overt sound repetitions but no semantic relatedness) that this conjunction made the task substantially more difficult. The bilinguals, however, had reaction times comparable to the English controls. The Chinese controls showed no effect of emotional valence, but did show priming effects of the overt sound manipulation that were equal for all emotion conditions.

The native Chinese speakers had recently arrived in Britain to attend an English course. Bilinguals had been exposed to English since the age of 12 and had lived in Britain for an average of 20.5 months.

Reference: 

[2969] Wu, Y. J., & Thierry G. (2012).  How Reading in a Second Language Protects Your Heart. The Journal of Neuroscience. 32(19), 6485 - 6489.

Walking through doorways causes forgetting

A series of experiments indicates that walking through doorways creates event boundaries, requiring us to update our awareness of current events and making information about the previous location less available.

We’re all familiar with the experience of going to another room and forgetting why we’ve done so. The problem has been largely attributed to a failure of attention, but recent research suggests something rather more specific is going on.

In a previous study, a virtual environment was used to explore what happens when people move through several rooms. The virtual environment was displayed on a very large (66 inch) screen to provide a more immersive experience. Each ‘room’ had one or two tables. Participants ‘carried’ an object, which they would deposit on a table, before picking up a different object. At various points, they were asked if the object was, say, a red cube (memory probe). The objects were not visible at the time of questioning. It was found that people were slower and less accurate if they had just moved to a new room.

To assess whether this effect depends on a high degree of immersion, a recent follow-up to this study replicated the study using standard 17” monitors rather than the giant screens. The experiment involved 55 students and once again demonstrated a significant effect of shifting rooms. Specifically, when the probe was positive, the error rate was 19% in the shift condition compared to 12% on trials when the participant ‘traveled’ the same distance but didn’t change rooms. When the probe was negative, the error rate was 22% in the shift condition vs 7% for the non-shift condition. Reaction time was less affected — there was no difference when the probes were positive, but a marginally significant difference on negative-probe trials.

The second experiment went to the other extreme. Rather than reducing the immersive experience, researchers increased it — to a real-world environment. Unlike the virtual environments, distances couldn’t be kept constant across conditions. Three large rooms were used, and no-shift trials involved different tables at opposite ends of the room. Six objects, rather than just one, were moved on each trial. Sixty students participated.

Once again, more errors occurred when a room-shift was involved. On positive-probe trials, the error rate was 28% in the shift condition vs 23% in the non-shift. On negative-probe trials, the error rate was 21% and 18%, respectively. The difference in reaction times wasn’t significant.

The third experiment, involving 48 students, tested the idea that forgetting might be due to the difference in context at retrieval compared to encoding. To do this, the researchers went back to using the more immersive virtual environment (the 66” screen), and included a third condition. In this, either the participant returned to the original room to be tested (return) or continued on to a new room to be tested (double-shift) — the idea being to hold the number of spatial shifts the same.

There was no evidence that returning to the original room produced the sort of advantage expected if context-matching was the important variable. Memory was best in the no-shift condition, next best in the shift and return conditions (no difference between them), and worst in the double shift condition. In other words, it was the number of new rooms entered that appears to be important.

This is in keeping with the idea that we break the action stream into separate events using event boundaries. Passing through a doorway is one type of event boundary. A more obvious type is the completion of an action sequence (e.g., mixing a cake — the boundary is the action of putting it in the oven; speaking on the phone — the boundary is the action of ending the call). Information being processed during an event is more available, foregrounded in your attention. Interference occurs when two or more events are activated, increasing errors and sometimes slowing retrieval.

All of this has greater ramifications than simply helping to explain why we so often go to another room and forget why we’re there. The broader point is that everything that happens to us is broken up and filed, and we should look for the boundaries to these events and be aware of the consequences of them for our memory. Moreover, these contextual factors are important elements of our filing system, and we can use that knowledge to construct more effective tags.

Reference: 

[2660] Radvansky, G. A., Krawietz S. A., & Tamplin A. K. (2011).  Walking Through Doorways Causes Forgetting: Further Explorations. The Quarterly Journal of Experimental Psychology.

Repetition is behind our improved memory for emotional events

A new study concludes that positive events tend to be remembered better than negative, but the more important finding is that being repeatedly reminded of the event is the main factor behind improved memory for emotional experiences.

Certainly experiences that arouse emotions are remembered better than ones that have no emotional connection, but whether negative or positive memories are remembered best is a question that has produced equivocal results. While initial experiments suggested positive events were remembered better than negative, more recent studies have concluded the opposite.

The idea that negative events are remembered best is consistent with a theory that negative emotion signals a problem, leading to more detailed processing, while positive emotion relies more heavily on general scripts.

However, a new study challenges those recent studies, on the basis of a more realistic comparison. Rather than focusing on a single public event, to which some people have positive feelings while others have negative feelings (events used have included the OJ Simpson trial, the fall of the Berlin Wall, and a single baseball championship game), the study looked at two baseball championships each won by different teams.

The experiment involved 1,563 baseball fans who followed or attended the 2003 and 2004 American League Championship games between the New York Yankees (2003 winners) and the Boston Red Sox (2004 winners). Of the fans, 1,216 were Red Sox fans, 218 were Yankees fans, and 129 were neutral fans. (Unfortunately the selection process disproportionately collected Red Sox fans.)

Participants were reminded who won the championship before answering questions on each game. Six questions were identical for the two games: the final score for each team, the winning and losing pitchers (multiple choice of five pitchers for each team), the location of the game, and whether the game required extra innings. Participants also reported how vividly they remembered the game, and how frequently they had thought about or seen media concerning the game.

Both Yankee and Red Sox fans remembered more details about their team winning. They also reported more vivid memories for the games their team won. Accuracy and vividness were significantly correlated. Fans also reported greater rehearsal of the game their team won, and again, rehearsal and accuracy were significantly correlated.

Analysis of the data revealed that rehearsal completely mediated the correlation between accuracy and fan type, and partially mediated the correlation between vividness and fan type.

In other words, improved memory for emotion-arousing events has everything to do with how often you think about or are reminded of the event.

PTSD, for example, is the negative memory extreme. And PTSD is characterized by the unavoidable rehearsal of the event over and over again. Each repetition makes memory for the event stronger.

In the previous studies referred to earlier, media coverage provided a similarly unavoidable repetition.

While most people tend to recall more positive than negative events (and this tendency becomes greater with age), individuals who are depressed or anxious show the opposite tendency.

So whether positive or negative events are remembered better depends on you, as well as the event.

When it comes down to it, I'm not sure it's really a helpful question - whether positive or negative events are remembered better. An interesting aspect of public events is that their portrayal often changes over time, but this is just a more extreme example of what happens with private events as well — as we change over time, so does our attitude toward those events. Telling friends about events, and receiving their comments on them, can affect our emotional response to events, as well as having an effect on our memory of those events.

Reference: 

[2591] Breslin, C. W., & Safer M. A. (2011).  Effects of Event Valence on Long-Term Memory for Two Baseball Championship Games. Psychological Science. 22(11), 1408 - 1412.

Memory genes vary in protecting against age-related cognitive decline

New findings show the T variant of the KIBRA gene improves episodic memory through its effect on hippocampal activity. Another study finds the met variant of the BDNF gene is linked to greater age-related cognitive decline.

Previous research has found that carriers of the so-called KIBRA T allele have been shown to have better episodic memory than those who don’t carry that gene variant (this is a group difference; it doesn’t mean that any carrier will remember events better than any non-carrier). A large new study confirms and extends this finding.

The study involved 2,230 Swedish adults aged 35-95. Of these, 1040 did not have a T allele, 932 had one, and 258 had two.  Those who had at least one T allele performed significantly better on tests of immediate free recall of words (after hearing a list of 12 words, participants had to recall as many of them as they could, in any order; in some tests, there was a concurrent sorting task during presentation or testing).

There was no difference between those with one T allele and those with two. The effect increased with increasing age. There was no effect of gender. There was no significant effect on performance of delayed category cued recall tests or a visuospatial task, although a trend in the appropriate direction was evident.

It should also be noted that the effect on immediate recall, although statistically significant, was not large.

Brain activity was studied in a subset of this group, involving 83 adults aged 55-60, plus another 64 matched on sex, age, and performance on the scanner task. A further group of 113 65-75 year-olds were included for comparison purposes. While in the scanner, participants carried out a face-name association task. Having been presented with face-name pairs, participants were tested on their memory by being shown the faces with three letters, of which one was the initial letter of the name.

Performance on the scanner task was significantly higher for T carriers — but only for the 55-60 age group, not for the 65-75 age group. Activity in the hippocampus was significantly higher for younger T carriers during retrieval, but not encoding. No such difference was seen in the older group.

This finding is in contrast with an earlier, and much smaller, study involving 15 carriers and 15 non-carriers, which found higher activation of the hippocampus in non-T carriers. This was taken at the time to indicate some sort of compensatory activity. The present finding challenges that idea.

Although higher hippocampal activation during retrieval is generally associated with faster retrieval, the higher activity seen in T carriers was not fully accounted for by performance. It may be that such activity also reflects deeper processing.

KIBRA-T carriers were neither more nor less likely to carry other ‘memory genes’ — APOEe4; COMTval158met; BDNFval66met.

The findings, then, fail to support the idea that non-carriers engage compensatory mechanisms, but do indicate that the KIBRA-T gene helps episodic memory by improving the hippocampus function.

BDNF gene variation predicts rate of age-related decline in skilled performance

In another study, this time into the effects of the BDNF gene, performance on an airplane simulation task on three annual occasions was compared. The study involved 144 pilots, of whom all were healthy Caucasian males aged 40-69, and 55 (38%) of whom turned out to have at least one copy of a BDNF gene that contained the ‘met’ variant. This variant is less common, occurring in about one in three Asians, one in four Europeans and Americans, and about one in 200 sub-Saharan Africans.  

While performance dropped with age for both groups, the rate of decline was much steeper for those with the ‘met’ variant. Moreover, there was a significant inverse relationship between age and hippocampal size in the met carriers — and no significant correlation between age and hippocampal size in the non-met carriers.

Comparison over a longer time-period is now being undertaken.

The finding is more evidence for the value of physical exercise as you age — physical activity is known to increase BDNF levels in your brain. BDNF levels tend to decrease with age.

The met variant has been linked to higher likelihood of depression, stroke, anorexia nervosa, anxiety-related disorders, suicidal behavior and schizophrenia. It differs from the more common ‘val’ variant in having methionine rather than valine at position 66 on this gene. The BDNF gene has been remarkably conserved across evolutionary history (fish and mammalian BDNF have around 90% agreement), suggesting that mutations in this gene are not well tolerated.

Another challenge to idea that men are better at spatial thinking

A cross-cultural study finds a significant gender difference on a simple puzzle problem for one culture but no gender difference for another. The difference was only partly explained by education.

Here’s an intriguing approach to the long-standing debate about gender differences in spatial thinking. The study involved 1,279 adults from two cultural groups in India. One of these groups was patrilineal, the other matrilineal. The volunteers were given a wooden puzzle to assemble as quickly as they could.

Within the patrilineal group, men were on average 36% faster than women. Within the matrilineal group, however, there was no difference between the genders.

I have previously reported on studies showing how small amounts of spatial training can close the gap in spatial abilities between the genders. It has been argued that in our culture, males are directed toward spatial activities (construction such as Lego; later, video games) more than females are.

In this case, the puzzle was very simple. However, general education was clearly one factor mediating this gender difference. In the patrilineal group, males had an average 3.67 more years of education, while in the matrilineal group, men and women had the same amount of education. When education was included in the statistical analysis, a good part of the difference between the groups was accounted for — but not all.

While we can only speculate about the remaining cause, it is interesting to note that, among the patrilineal group, the gender gap was decidedly smaller among those who lived in households not wholly owned by males (in the matrilineal group, men are not allowed to own property, so this comparison cannot be made).

It is also interesting to note that the men in the matrilineal group were faster than the men in the patrilineal group. This is not a function of education differences, because education in the matrilineal group was slightly less than that of males in the patrilineal group.

None of the participants had experience with puzzle solving, and both groups had similar backgrounds, being closely genetically related and living in villages geographically close. Participants came from eight villages: four patrilineal and four matrilineal.

Reference: 

[2519] Hoffman, M., Gneezy U., & List J. A. (2011).  Nurture affects gender differences in spatial abilities. Proceedings of the National Academy of Sciences. 108(36), 14786 - 14788.

Brain flexibility predicts learning speed

New analytic techniques reveal that functional brain networks are more fluid than we thought.

A new perspective on learning comes from a study in which 18 volunteers had to push a series of buttons as fast as possible, developing their skill over three sessions. New analytical techniques were then used to see which regions of the brain were active at the same time. The analysis revealed that those who learned new sequences more quickly in later sessions were those whose brains had displayed more 'flexibility' in the earlier sessions — that is, different areas of the brain linked with different regions at different times.

At this stage, we don’t know how stable an individual’s flexibility is. It may be that individuals vary significantly over the course of time, and if so, this information could be of use in predicting the best time to learn.

But the main point is that the functional modules, the brain networks that are involved in specific tasks, are more fluid than we thought. This finding is in keeping, of course, with the many demonstrations of damage to one region being compensated by new involvement of another region.

Reference: 

[2212] Bassett, D. S., Wymbs N. F., Porter M. A., Mucha P. J., Carlson J. M., & Grafton S. T. (2011).  Dynamic reconfiguration of human brain networks during learning. Proceedings of the National Academy of Sciences. 108(18), 7641 - 7646.

New insight into insight, and the role of the amygdala in memory

A new study suggests that one-off learning (that needs no repetition) occurs because the amygdala, center of emotion in the brain, judges the information valuable.

Most memory research has concerned itself with learning over time, but many memories, of course, become fixed in our mind after only one experience. The mechanism by which we acquire knowledge from single events is not well understood, but a new study sheds some light on it.

The study involved participants being presented with images degraded almost beyond recognition. After a few moments, the original image was revealed, generating an “aha!” type moment. Insight is an experience that is frequently remembered well after a single occurrence. Participants repeated the exercise with dozens of different images.

Memory for these images was tested a week later, when participants were again shown the degraded images, and asked to recall details of the actual image.

Around half the images were remembered. But what’s intriguing is that the initial learning experience took place in a brain scanner, and to the researchers’ surprise, one of the highly active areas during the moment of insight was the amygdala. Moreover, high activity in the amygdala predicted that those images would be remembered a week later.

It seems the more we learn about the amygdala, the further its involvement extends. In this case, it’s suggested that the amygdala signals to other parts of the brain that an event is significant. In other words, it gives a value judgment, decreeing whether an event is worthy of being remembered. Presumably the greater the value, the more effort the brain puts into consolidating the information.

It is not thought, from the images used, that those associated with high activity in the amygdala were more ‘emotional’ than the other images.

Syndicate content