Forgetting

I’ve discussed before how hard it is to correct false knowledge. This is not only a problem for the classroom — the preconceptions students bring to a topic, and the difficulty of replacing them with the correct information — but, in these days of so much misinformation in the media and on the web, an everyday problem.

An internet study involving 574 adults presented them with an article discussing the issue of electronic health records (EHRs). They were then shown another article on the subject, supposedly from a "political blog". This text included several false statements about who was allowed access to these records (for example, that hospital administrators, health insurance companies, employers, and government officials had unrestricted access).

For some participants, this article was annotated so that the false statements were clearly marked, and directions explained that an independent fact-checking organization had found these factual errors. Other participants completed an unrelated three-minute task at the end of reading the text before being presented with the same corrections, while a third group was not advised of the inaccuracies at all (until being debriefed).

After reading the text, participants were given a questionnaire, where they listed everything they had learned about EHRs from the text, rated their feelings about each item, and marked on a 7-point scale how easy it would be for specific groups to access the records. They were also asked to judge the credibility of the fact-checking message.

Those who received the immediate corrections were significantly more accurate than those who received the delayed corrections, and both were significantly more accurate than those receiving no corrections — so at least we know that correcting false information does make a difference! More depressingly, however, the difference between any of the groups, although significant, was small — i.e., correcting false statements makes a difference, but not much of one.

Part of the problem lies, it appears, in people’s preconceptions. A breakdown by participant’s feelings on the issue revealed that the immediate correction was significantly more effective for those who were ‘for’ EHRs (note that the corrections agreed with their beliefs). Indeed, for those unfavorably disposed, the immediate corrections may as well have been no corrections at all.

But, intriguingly, predisposition only made a difference when the correction was immediate, not when it was delayed.

Mapping these results against participants’ responses to the question of credibility revealed that those unfavorably disposed (and therefore prone to believing the false claims in the text) assigned little credibility to the corrections.

Why should this, perfectly understandable, difference apply only when corrections were immediate? The researchers suggest that, by putting the corrections in direct competition with the false statements, more emphasis is put on their relative credibility — assessments of which tend to be biased by existing attitudes.

The findings suggest it is naïve to expect that it is enough to simply tell people something is false, if they have a will to believe it. It also suggests the best approach to correcting false knowledge is to emphasize the credibility of the corrector.

Of course, this study used politically charged information, about which people are likely to have decided opinions. But the results are a reminder that, as the researcher says: "Humans aren't vessels into which you can just pour accurate information. Correcting misperceptions is really a persuasion task.”

This is true even when the information is something as ‘factual’ as the cause of the seasons! Even teachers should take on board this idea that, when new information doesn’t fit in with a student’s world-view, then credibility of the source/authority (the teacher!) is paramount.

Garrett, R., & Weeks, B. (2013). The Promise and Peril of Real-Time Corrections to Political Misperceptions. Proceedings of the Computer Supported Cooperative Work and Social Computing conference. Retrieved from http://wp.comm.ohio-state.edu/misperceptions/wp-content/uploads/2012/07/...

I reported recently on how easily and quickly we can get derailed from a chain of thought (or action). In similar vein, here’s another study that shows how easy it is to omit important steps in an emergency, even when you’re an expert — which is why I’m a great fan of checklists.

Checklists have been shown to dramatically decrease the chances of an error, in areas such as flying and medicine. However, while surgeons may use checklists as a matter of routine (a study a few years ago found that the use of routine checklists before surgery substantially reduced the chances of a serious complication — we can hope that everyone’s now on board with that!), there’s a widespread belief in medicine that operating room crises are too complex for a checklist to be useful. A new study contradicts that belief.

The study involved 17 operating room teams (anesthesia staff, operating room nurses, surgical technologists, a surgeon), who participated in 106 simulated surgical crisis scenarios in a simulated operating room. Each team was randomized to manage half of the scenarios with a set of crisis checklists and the remaining scenarios from memory alone.

When checklists were used, the teams were 74% less likely to miss critical steps. That is, without a checklist, nearly a quarter (23%) of the steps were omitted (an alarming figure!), while with a checklist, only 6% of the steps were omitted on average. Every team performed better when the checklists were available.

After experiencing these situations, almost all (97%) participants said they would want these checklists used if they experienced such a crisis if they were a patient.

It’s comforting to know that airline pilots do have checklists to use in emergency situations. Now we must hope that hospitals come on board with this as well (up-to-date checklists and implementation materials can be found at www.projectcheck.org/crisis).

For the rest of us, the study serves as a reminder that, however practiced we may think we are, forgetting steps in an action plan is only too common, and checklists are an excellent means of dealing with this — in emergency and out.

In the study, 64 older adults (60-74; average 70) and 64 college students were compared on a word recognition task. Both groups first took a vocabulary test, on which they performed similarly. They were then presented with 12 lists of 15 semantically related words. For example, one list could have words associated with "sleep," such as "bed," "rest," "awake," "tired" and "night" — but not the word “sleep”. They were not told they would be tested on their memory of these, rather they were asked to rate each word for pleasantness.

They then engaged in a five-minute filler task (a Sudoku) before a short text was read to them. For some, the text had to do with age-related declines in memory. These participants were told the experiment had to do with memory. For others, the text concerned language-processing research. These were told the experiment had to do with language processing and verbal ability.

They were then given a recognition test containing 36 of the studied words, 48 words unrelated to the studied words, and 12 words related to the studied words (e.g. “sleep”). After recording whether or not they had seen each word before, they also rated their confidence in that answer on an 8-point scale. Finally, they were given a lexical decision task to independently assess stereotype activation.

While young adults showed no effects from the stereotype manipulation, older adults were much more likely to falsely recognize related words that had not been studied if they had heard the text on memory. Those who heard the text on language were no more likely than the young adults to falsely recognize related words.

Note that there is always quite a high level of false recognition of such items: young adults, and older adults in the low-threat condition falsely recognized around half of the related lures, compared to around 10% of unrelated words. But in the high-threat condition, older adults falsely recognized 71% of the related words.

Moreover, older adults’ confidence was also affected. While young adults’ confidence in their false memories was unaffected by threat condition, older adults in the high-threat condition were more confident of their false memories than older adults in the low-threat condition.

The idea that older adults were affected by negative stereotypes about aging was supported by the results of the lexical decision task, which found that, in the high-threat condition, older adults responded more quickly to words associated with negative stereotypes than to neutral words (indicating that they were more accessible). Young adults did not show this difference.

Thomas, A. K., & Dubois, S. J. (2011). Reducing the burden of stereotype threat eliminates age differences in memory distortion. Psychological science, 22(12), 1515-7. doi:10.1177/0956797611425932

A number of studies have found that source memory (knowing where you heard/read/experienced something) is a particular problem for older adults. Destination memory (knowing who you’ve told) is an area that has been much less studied. Last year I reported on why destination memory is difficult for all of us (my report is repeated below). A follow-up study has found not only that destination memory is a particular problem for older adults, but that it is in fact a worse problem than source memory. Moreover, destination amnesia (falsely believing you've told someone something) is not only more common among older adults, but is associated with greater confidence in the false belief.

The study compared the performance of 40 students (aged 18-30) and 40 healthy older adults (aged 60-83). In the first task, the participant read out loud 50 interesting facts to 50 celebrities (whose faces appeared on a computer screen), and were then tested on their memory of which fact they told to which famous person. In the second task, they had to remember which famous person told them which particular fact. Older adults' performance was 21% worse than their younger counterparts on the destination memory test, but only 10% worse (50% vs 60%) on the source memory test. This latter difference was not statistically significant.

The 2009 study, involving 60 students, found good reason for destination memory to be so poor — apparently outgoing information is less integrated with context than incoming information is. In the study, 50 random facts were linked with the faces of 50 famous people; half the students then “told” each fact to one of the faces, reading it aloud to the celebrity’s picture. The other half read each fact silently and saw a different celebrity moments afterward. In the subsequent memory test, students who simulated telling the facts did 16% worse. In another experiment using personal facts, it was significantly worse.

However, the final experiment found that you could improve your destination memory by saying the name of the person you’re speaking to, as you tell them. The findings also suggest that self-focus is an important factor: increasing self-focus (e.g. by telling a personal story) worsened destination memory; reducing self-focus (e.g. by naming the listener) improved it.

[1809] Gopie N, Craik FIM, Hasher L. Destination memory impairment in older people. Psychology and Aging [Internet]. 2010 . Available from: http://psycnet.apa.org/psycinfo/2010-16740-001/

[396] Gopie N, MacLeod CM. Destination Memory: Stop Me if I've Told You This Before. Psychological Science [Internet]. 2009 ;20(12):1492 - 1499. Available from: http://dx.doi.org/10.1111/j.1467-9280.2009.02472.x

When we tell people about things that have happened to us, we shape the stories to our audience and our purpose. The amount of detail we give and the slant we give to it depends on our perceptions of our audience and what we think they want to hear. Does this change our memory for the event? Certainly we are all familiar with the confusion we get after we have been telling a particular story for years — we’re no longer sure what really happened and what we’ve added or subtracted to make a better story.

There is a popular misconception that dramatic public events such as earthquakes, the Challenger disaster, JFK’s assassination, etc, are given a special status in memory (“flashbulb memories”). It is true that people often have very clear memories of these events, but research has shown that such memories are as likely as any other event memory to be inaccurate1. Vividness, I regret to say, is no reliable measure of the accuracy of a memory.

This study used two invented stories rich in detail that could be told from more than one point of view. After studying one or other of the stories, subjects were asked to write a letter about one of the characters, the letter to be biased either for or against the character. Control subjects were simply asked to write as much as they could remember about the specified character. Subjects were later tested on their recall of the original story. Different aspects of memory were investigated in a series of four experiments.

It was found that subjects who wrote the biased letters recalled more information about the specified character that was related to the biased perspective. Their recall of the other character in the story was unaffected. They also added more (erroneous) details about the character — these errors being consistent with the particular bias they’d been given.

Although selective rehearsal (the fact that these subjects had had an opportunity to rehearse the information that supported the appropriate bias, at the expense of other information) plays a part in this, biased memory was found even when the subjects, in the fourth experiment, were asked to write a biased evaluation instead of a biased retelling (to avoid rehearsal of specific items).

The slant we give to information guides our encoding of the memory, the way we organize it, and the connections we make to other memories.

References

1. Neisser, U. & Harsch, N. 1992. Phantom flashbulbs: False recollections of hearing the news about Challenger. In E. Winograd & U. Neisser (eds.) Affect and accuracy in recall: Studies of 'Flashbulb Memories'. New York: Cambridge University Press.

Larsen, S.F. 1992. Potential flashbulbs: Memories of ordinary news as the baseline. In E. Winograd & U. Neisser (eds.) Affect and accuracy in recall: Studies of 'Flashbulb Memories'. New York: Cambridge University Press.

Tversky, Barbara & Marsh, Elizabeth J. 2000. Biased retellings of events yield biased memories. Cognitive Psychology, 40, 1-38.

Older news items (pre-2010) brought over from the old website

Relearning a forgotten language is easier for those under 40

A small study involving 7 native English speakers who had learned either Hindi or Zulu as children when living abroad, but now had no memory of the neglected language, found that the three who were under 40 could relearn certain phonemes that are difficult for native English speakers to recognize, but those over 40, like those who had never been exposed to the language in childhood, could not. The amount of experience of exposure in childhood ranged from 4 to 10 years, and it’s especially notable that the 47-year old individual who had 10 years exposure, having become almost fluent, still could not recover the ability to distinguish these difficult sounds. It should also be noted that where the ability was recovered (and recovered almost to native ability), it took about 15-20 training sessions. The findings point to the value of early foreign language learning.

Bowers, J.S., Mattys, S.L. & Gage, S.H. 2009. Preserved Implicit Knowledge of a Forgotten Childhood Language. Psychological Science, 20 (9), 1064–1069.

http://www.eurekalert.org/pub_releases/2009-09/afps-uio092409.php

Forgotten memories still there

In an imaging study in which 16 college students were shown a list of words, asked to say each word backwards, think of how it could be used, and imagine how an artist would draw it, then shown the list again 20 minutes later and asked to remember what they could of each word, brain activity showed that recollection reinstated the original pattern of activity, and its strength correlated with the strength of the memory. Moreover, even when the student had no conscious memory, the pattern was still there, although weak. Follow-up studies will explore the degradation over time.

Johnson, J.D. et al. 2009. Recollection, Familiarity, and Cortical Reinstatement: A Multivoxel Pattern Analysis. Neuron, 63 (5), 697-708.

http://www.wired.com/wiredscience/2009/09/forgottenmemories/
http://www.eurekalert.org/pub_releases/2009-09/uoc--mee090809.php

New insights into memory without conscious awareness

An imaging study in which participants were shown a previously studied scene along with three previously studied faces and asked to identify the face that had been paired with that scene earlier has found that hippocampal activity was closely tied to participants' tendency to view the associated face, even when they failed to identify it. Activity in the lateral prefrontal cortex, an area required for decision making, was sensitive to whether or not participants had responded correctly and communication between the prefrontal cortex and the hippocampus was increased during correct, but not incorrect, trials. The findings suggest that conscious memory may depend on interactions between the hippocampus and the prefrontal cortex.

Hannula, D.E. & Ranganath, C. 2009. The Eyes Have It: Hippocampal Activity Predicts Expression of Memory in Eye Movements. Neuron, 63 (5), 592-599.

http://www.eurekalert.org/pub_releases/2009-09/cp-ycb090309.php
http://sciencenow.sciencemag.org/cgi/content/full/2009/910/4?etoc

How we forget over the short term

Information in short-term memory is rapidly forgotten once attention is diverted, but why? Is it because memory traces decay in the absence of attention? Or is it because older traces interfere with new traces? In a study in which volunteers were shown a string of 3 letters, then told to count backwards for 4, 8, 12, or 16 seconds, before recalling the letters, it was found that those who counted backwards for the longest time were better able to recall the letters than those who counted backwards for shorter times. This suggests that temporal confusability, not decay, is the main culprit in short-term forgetting. The finding is consistent with research indicating that interference is more important than decay in long-term forgetting as well.

Unsworth, N., Heitz, R.P. & Parks, N.A. 2008. The Importance of Temporal Distinctiveness for Forgetting Over the Short Term. Psychological Science, 19 (11), 1078-1081.

http://www.eurekalert.org/pub_releases/2008-12/afps-src121208.php

Forgotten but not gone

We all know it’s easier to re-learn something than learn it for the first time. But why? When we learn, as we know, a neuron makes new connections with other neurons, and these connections are made through synapses. If that connection breaks down, we forget. A new study sheds light on what happens when we re-learn something we thought was forgotten. It appears that in the case of information (synaptic connections) that isn’t needed any more, the synapses are disabled, not destroyed. When needed again, they just need to be reactivated.

Hofer, S.B. et al. 2008. Experience leaves a lasting structural trace in cortical circuits. Nature, Published online November 12, 2008

http://www.eurekalert.org/pub_releases/2008-11/m-fbn111708.php

A new perspective on forgetting

A new mathematical model may shed light on forgetting. The model has found that "free-lunch learning" (the way in which forgotten material is called back to mind when we relearn some part of it — as when a few words in a foreign language we learned at school brings back many other words) occurs when forgetting was induced by random fluctuations in the strength of synaptic connections (‘synaptic drift'). But when forgetting is induced by progressive decay in synaptic strength (which is how forgetting has traditionally been thought of), then "negative free-lunch learning" (where relearning parts of forgotten associations decreases the recall of associated knowledge) occurs. This suggests that forgetting occurs because of random drift rather than a decay in the strength of synaptic connections.

Stone, J.V. & Jupp P.E. 2008. Falling towards Forgetfulness: Synaptic Decay Prevents Spontaneous Recovery of Memory. PLoS Computational Biology, 4(8), e1000143. Full text available at http://dx.plos.org/10.1371/journal.pcbi.1000143

http://www.eurekalert.org/pub_releases/2008-08/plos-rpn082108.php

New research shows why too much memory may be a bad thing

People who are able to easily and accurately recall historical dates or long-ago events may have a harder time with word recall or remembering the day's current events. A mouse study reveals why. Neurogenesis has been thought of as a wholly good thing — having more neurons is surely a good thing — but now a mouse study has found that stopping neurogenesis in the hippocampus improved working memory. Working memory is highly sensitive to interference from information previously stored in memory, so it may be that having too much information may hinder performing everyday working memory tasks.

Saxe, M.D. et al. 2007. Paradoxical influence of hippocampal neurogenesis on working memory. Proceedings of the National Academy of Sciences, 104 (11), 4642-4646.
Full text is available at http://www.pnas.org/cgi/reprint/104/11/4642

http://www.physorg.com/news94384934.html
http://www.eurekalert.org/pub_releases/2007-03/cumc-nrs032807.htm

More insight into why we forget

Increasingly researchers have come to believe interference is far more important for forgetting than the traditional notion of decay over time. A technique called "transcranial magnetic stimulation" (TMS) has now revealed that an area within the prefrontal cortex called the left inferior frontal gyrus, known to be active when volunteers take memory tests while confronting interference, is essential for blocking interference.

Feredoes, E., Tononi, G. & Postle, B.R. 2006. Direct evidence for a prefrontal contribution to the control of proactive interference in verbal working memory. Proceedings of the National Academy of Sciences, 103 (51), 19530-19534.

http://www.eurekalert.org/pub_releases/2006-12/uow-ccr120406.php

Memories are harder to forget than recently thought

Previous rodent studies have shown that the process of encoding a memory can be blocked by the use of a protein synthesis inhibitor called anisomycin (http://www.eurekalert.org/pub_releases/2000-08/NYU-Nnfl-1508100.htm). Experiments with anisomycin helped lead to the acceptance of a theory in which a learned behavior is consolidated into a stored form and that then enters a 'labile' - or adaptable - state when it is recalled. According to these previous studies, the act of putting a labile memory back into storage involves a reconsolidation process identical to the one used to store the memory initially. Indeed, experiments showed that anisomycin could make a mouse forget a memory if it were given anisomycin directly after remembering an event. In a new study, however, researchers have showed that disruption of a "re-remembered" memory was not permanent. Mice demonstrated that they could remember the original learned behavior 21 days later. This research thus casts doubt on the concept of “reconsolidation”, or at least demonstrates that we still have much to learn about this process.

Lattal, K.M. & Abel, T. 2004. Behavioral impairments caused by injections of the protein synthesis inhibitor anisomycin after contextual retrieval reverse with time. PNAS, 101, 4667-4672.

http://www.eurekalert.org/pub_releases/2004-03/uop-mah031504.php

More evidence for active forgetting

In an imaging study involving 24 people aged 19 to 31, participants were given pairs of words and told to remember some of the matched pairs but forget others. Trying to shut out memory appeared more demanding than remembering, in that some areas of the brain were significantly more when trying to suppress memory. Both the prefrontal cortex and the hippocampus were active. Those whose prefrontal cortex and hippocampus were most active during this time were most successful at suppressing memory.

Anderson, M.C., Ochsner, K.N., Kuhl, B., Cooper, J., Robertson, E., Gabrieli, S.W., Glover, G.H. & Gabrieli, J.D.E. 2004. Neural Systems Underlying the Suppression of Unwanted Memories. Science, 303 (5655), 232-235.

http://www.eurekalert.org/pub_releases/2004-01/su-rrb010604.php

You may not be able to recall it, but it influences you anyway

“Forgetting” doesn’t mean the memory is erased from your brain. “Forgotten” information may in fact influence you more than it would if it hadn’t been forgotten — because you’re unaware of the influence. This somewhat alarming possibility has been raised by a recent study in which college students studied lists of nonfamous and famous names. Some participants were told to remember the nonfamous names, while the others were told to forget them. Later, both groups were asked to judge whether or not a name was famous from a mixed list of famous and nonfamous names. Those who were told to forget misidentified more nonfamous names as famous than those who had been told to remember.
Such a judgment is of course made on the basis of the familiarity of the name. It is exposure to an item that affects its familiarity – not whether or not you consciously remember it. By telling the participants to “forget” what they’d seen, the experimenters were removing the participants’ awareness of the source of the familiarity, not the familiarity itself.

Bjork, E.L. & Bjork, R.A. 2003. Intentional Forgetting Can Increase, Not Decrease, Residual Influences of To-Be-Forgotten Information. Journal of Experimental Psychology: Learning, Memory, and Cognition, 29 (4), 524–531.

Failing recall not an inevitable consequence of aging

New research suggests age-related cognitive decay may not be inevitable. Tests of 36 adults with an average age of 75 years found that about one out of four had managed to avoid memory decline. Those adults who still had high frontal lobe function had memory skills “every bit as sharp as a group of college students in their early 20s." (But note that most of those older adults who participated were highly educated – some were retired academics). The study also found that this frontal lobe decline so common in older adults is associated with an increased susceptibility to false memories – hence the difficulty often experienced by older people in recalling whether they took a scheduled dose of medication.

The research was presented on August 8 at the American Psychological Association meeting in Toronto.

http://www.eurekalert.org/pub_releases/2003-08/wuis-fmf080703.php

Selective erasure of memories one step closer

It is now believed that memories become “labile” (able to be changed) every time they are reactivated. If so, it would seem that we could, by re-activating a memory, “erase” it – even though the memory is very old. Researchers have, however, had mixed success in achieving this. A new report suggests why. Any memory is made up of a number of different associations, but only one association will be “dominant” (will determine our reaction). It is this dominant association that is susceptible to change, and thus, to erasure.

Eisenberg, M., Kobilo, T., Berman, D.E. & Dudai, Y. 2003. Stability of Retrieved Memory: Inverse Correlation with Trace Dominance. Science, 301 (5636), 1102-1104.

http://www.eurekalert.org/pub_releases/2003-08/wi-npg082003.php

Older adults better at forgetting negative images

It seems that this general tendency, to remember the good, and let the bad fade, gets stronger as we age. Following recent research suggesting that older people tend to regulate their emotions more effectively than younger people, by maintaining positive feelings and lowering negative feelings, researchers examined age differences in recall of positive, negative and neutral images of people, animals, nature scenes and inanimate objects. The first study tested 144 participants aged 18-29, 41-53 and 65-80. Older adults recalled fewer negative images relative to positive and neutral images. For the older adults, recognition memory also decreased for negative pictures. As a result, the younger adults remembered the negative pictures better. 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. This suggests that older adults encode less information about negative images, which in turn would diminish recall.

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.

Memories may be hard to find when thalamus fails to synchronize rhythms

Memory codes - the representation of an object or experience in memory - are patterns of connected neurons. The neurons that are linked are not necessarily in the same region of the brain. Exciting new research has measured the electrical rhythms that parts of the brain use to communicate with each other and found that the thalamus regulates these rhythms. "Memory appears to be a constructive process in combining the features of the items to be remembered rather than simply remembering each object as a whole form. The thalamus seems to direct or modulate the brain's activity so that the regions needed for memory are connected." The authors suggest that tips of the tongue experiences (when only part of a memory is recalled) may occur when the rhythms don't synchronize with the regions properly.

Slotnick, S.D., Moo, L.R., Kraut, M.A., Lesser, R.P. & Hart, J. Jr. 2002. Interactions between thalamic and cortical rhythms during semantic memory recall in human. Proc. Natl. Acad. Sci. U.S.A., 99, 6440-6443.

http://www.eurekalert.org/pub_releases/2002-05/uoaf-mi050902.php