autobiographical memory

Autobiographical memory

Autobiographical memory contains information about yourself, and about personal experiences.

Emotions, the "facts" that describe you and make you unique, the facts of your life, and the experiences you have had, are all contained in separate domains, and processed differently.

Your memory for emotions can help you modify your moods.

Specific events you have experienced are only memorable to the extent that they include details special to that specific occasion.

Most events in our lives are routine, and are merged in memory into one generic memory containing the common elements of the experience.

Autobiographical memory contains the information you have about yourself. It includes several domains:

  • self-description (the source of a large part of your sense of identity), containing information such as:
    • whether or not you like ice-cream
    • what your favorite color is
    • what you think about a political party
  • emotional memory, which not only contains our memories of emotional experiences, but also helps us control our moods. By dwelling on appropriate memories, we can sustain a mood. By recalling memories that involve a contrasting emotion, we can change a mood.
  • event memory

diagram

Your memory for events

This is the largest component of autobiographical memory, containing three separate but related domains:

  • memory for specific events that have happened to you
  • memory for general events, which tells you the broad sequence of actions in events such as going to a restaurant or going to the dentist
  • a potted summary of your life, which enables you to answer such questions as, “Where did you go to school?”, “Where were you working last year?”.

These may be thought of as being connected hierarchically:

diagram

Recalling specific events

Event memory is usually entered via the general-event level, although the information we are searching for is usually at the specific-event level. Thus, if you're trying to retrieve the memory of going to see the movie Titanic, you will probably start by accessing the general event "going to the pictures"

Specific events over time become merged into a general event - all the occasions you've been to the dentist, for example, have blurred into a generic "script", which encapsulates the key experiences and actions that are typical of the going-to-the-dentist event. After the specific event has become consolidated into the script, only distinctive events are likely to be specifically remembered. That is, events when something unusual/interesting/humorous happened.

The power of these scripts is such that people often "remember" details of a specific event that never happened, merely because they are typical of the script for that event.

Our memory for events reflects what we expect to happen.

It is perhaps because of this that unexpected events and new events (first-time experiences) are better remembered. If you don't have an existing script for the event, or if the event is atypical enough not to easily fit an existing script, then you can't mould the experience to your expectations.

The more distinctive an event - the more the event breaks with your script for that type of event - the better your memory for that particular event will be. (Failures to remember trivial events, such as where you’ve put something, or whether you’ve done something, are reflections of the fact that we pay little attention to routine actions that are, as it were, already scripted).

To remember an event therefore, you should look for distinctive details.

What makes a good cue for remembering events?

One of the most interesting areas of research in the study of event memory is a small set of diary studies. In one such study, a Dutch psychologist called Willem Wagenaar recorded his day's events every day for six years, noting down:

  • who was involved
  • what the event was
  • where it occurred
  • when it occurred

Researchers at Duke University and the University of Amsterdam are conducting an experiment into autobiographical memory on the Internet, that basically tests your memory for personal events — you're given a word and you have to respond with the first personal event that comes to mind. Who can resist? To participate, go to http://memory.uva.nl/testpanel/gc/en/

Wagenaar was hoping to discover which of these different bits of information were the best retrieval cues. At the conclusion of his study he reported that what was the best cue, followed by who and where. When was the least effective (have you ever tried to remember an event on the basis of its approximate date?).

There is nothing particularly special about these types of information however. Later, Wagenaar reanalyzed his data, and found that most of the difference in the memorability of these cues was due to their relative distinctiveness. Thus, the nature of the event is usually the most distinctive aspect of the event, and the people involved, and the location, are usually more distinctive bits of information than the date or time of occurrence.

To remember a specific event, we need a key - a unique feature that allows us to readily distinguish that event from similar events.

References: 
  • Barsalou, L.W. 1988. The content and organization of autobiographical memories. In U. Neisser & E. Winograd (eds.) Remembering reconsidered: Ecological and traditional approaches to the study of memory. Cambridge: Cambridge University Press.
  • Robinson, J.A. 1992. Autobiographical memory. In M.M. Gruneberg, & P. Morris (eds). Aspects of memory. Vol.1: The practical aspects. 2nd ed. London: Routledge.
  • Diagrams taken from The Memory Key.

For more, see the research reports

How your brain chunks ‘moments’ into ‘events’

We talk about memory for ‘events’, but how does the brain decide what an event is? How does it decide what is part of an event and what isn’t? A new study suggests that our brain uses categories it creates based on temporal relationships between people, objects, and actions — i.e., items that tend to—or tend not to—pop up near one another at specific times.

05/2013

Why we remember more from young adulthood than from any other period

Autobiographical memory is an interesting memory domain, given its inextricable association with identity. One particularly fascinating aspect of it is its unevenness - why do we remember so little from the first years of life ('childhood amnesia'), why do we remember some periods of our life so much more vividly than others? There are obvious answers (well, nothing interesting happened in those other times), but the obvious is not always correct. Intriguing, then, to read about a new study that links those memorable periods to self-identity.

Improving memory for specific events can help depression

November, 2012

A small study suggests that training in recalling personal memories can significantly help those with depression.

We know that people with depression tend to focus on, and remember, negative memories rather than positive. Interestingly, it’s not simply an emotion effect. People with depression, and even those at risk of depression (including those who have had depression), tend to have trouble remembering specific autobiographical memories. That is, memories of events that happened to them at a specific place and time (as opposed to those generalized event memories we construct from similar events, such as the ‘going to the dentist’ memory).

This cognitive difficulty seems to exacerbate their depression, probably through its effect on social encounters and relationships.

A new study, however, has found that a particular training program (“Memory Specificity Training”) can help both their memory for specific events and their symptoms of depression.

The study involved 23 adolescent Afghani refugees in Iran, all of whom had lost their fathers in the war in Afghanistan and who showed symptoms of depression. Half were randomly assigned to the five-week memory training program and half received no training.

The training program involved a weekly 80-minute group session, in which participants learned about different types of memory and memory recall, and practiced recalling specific memories after being given positive, neutral, and negative keywords.

Participants’ memory for specific events was tested at the start of the study, at the end of the five-week training period, and two months after the end of the training. Compared to the control group, those given the training were able to provide more specific memories after the training, and showed fewer symptoms of depression at the two month follow-up (but not immediately after the end of training).

The study follows on from a pilot study in which ten depressed female patients were given four weekly one-hour sessions of memory training. Improvements in memory retrieval were associated with less rumination (dwelling on things), less cognitive avoidance, and improvements in problem-solving skills.

It’s somewhat unfortunate that the control group were given no group sessions, indeed no contact (apart from the tests) of any kind. Nevertheless, and bearing in mind that these are still very small studies, the findings do suggest that it would be helpful to include a component on memory training in any cognitive behavioral therapy for depression.

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Quick therapy may reduce post-traumatic stress when delivered immediately

July, 2012

A pilot study supports the value of brief cognitive therapy for victims of traumatic events, when delivered as soon as possible after the event. The benefit appears greatest for sexual assault victims.

A new study has found that, when delivered quickly, a modified form of prolonged exposure therapy reduces post-traumatic stress reactions and depression.

The study involved 137 patients being treated in the emergency room of a major trauma center in Atlanta. The patients were chosen from survivors of traumatic events such as rape, car or industrial accidents, and shooting or knife attacks. Participants were randomly assigned to either receive three sessions of therapy beginning in the emergency department (an average of 12 hours after the event), or assessment only. Stress reactions were assessed at 4 and 12 weeks, and depression at baseline and 4 weeks.

Those receiving the therapy reported significantly lower post-traumatic stress at 4 weeks and 12 weeks, and significantly lower depression at 4 weeks. Analysis of subgroups revealed that the therapy was most effective in rape victims. In the cases of transport accidents and physical (non-sexual) assault, the difference between therapy and assessment-only was only barely significant (for transport at 4 weeks) or non-significant. In both subgroups, the effect was decidedly less at 12 weeks than at 4 weeks.

The therapy, carried out by trained therapists, involved participants describing the trauma they had experienced while the therapist recorded the description. The bulk of the hour-long session was taken up with reliving and processing the experience. There were three sessions spaced a week apart. The patients were instructed to listen to their recordings every day, and 85% were compliant. The therapists also explained normal reactions to trauma, helped the patients look at obtrusive thoughts of guilt or responsibility, and taught them a brief breathing or relaxation technique and self care.

While this study doesn’t itself compare the effects of immediate vs delayed therapy, the assumption that delivering the therapy so soon after the trauma is a crucial factor in its success is in line with other research (mainly to do with fear-conditioning in rodent and human laboratory studies). Moreover, while brief cognitive-behavioral therapy has previously been shown to be effective with people diagnosed with acute stress disorder, such therapy is normally begun some 2-4 weeks after trauma, and a study of female assault survivors found that although such therapy did indeed accelerate recovery compared with supportive counseling, after 9 months, PTSD severity was similar in both groups.

Another, severe, limitation of this study is that the therapy involved multiple items. We cannot assume that it was the repeated re-experiencing of the event that is critical.

However, this study is only a pilot study, and its findings are instructive rather than decisive. But at the least it does support the idea that immediate therapy is likely to help victims of trauma recover more quickly.

One final, important, note: It should not, of course, be assumed that simply having the victim describe the events — say to police officers — is in itself therapeutic. Done badly, that experience may itself be traumatic.

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Sleep preserves your feelings about traumatic events

January, 2012

New research suggests that sleeping within a few hours of a disturbing event keeps your emotional response to the event strong.

Previous research has shown that negative objects and events are preferentially consolidated in sleep — if you experience them in the evening, you are more likely to remember them than more neutral objects or events, but if you experience them in the morning, they are not more likely to be remembered than other memories (see collected sleep reports). However, more recent studies have failed to find this. A new study also fails to find such preferential consolidation, but does find that our emotional reaction to traumatic or disturbing events can be greatly reduced if we stay awake afterward.

Being unable to sleep after such events is of course a common response — these findings indicate there’s good reason for it, and we should go along with it rather than fighting it.

The study involved 106 young adults rating pictures on a sad-happy scale and their own responses on an excited-calm scale. Twelve hours later, they were given a recognition test: noting pictures they had seen earlier from a mix of new and old pictures. They also rated all the pictures on the two scales. There were four groups: 41 participants saw the first set late in the day and the second set 12 hours later on the following day (‘sleep group’); 41 saw the first set early and the second set 12 hours later on the same day; 12 participants saw both sets in the evening, with only 45 minutes between the sets; 12 participants saw both sets in the morning (these last two groups were to rule out circadian effects). 25 of the sleep group had their brain activity monitored while they slept.

The sleep group performed significantly better on the recognition test than the same-day group. Negative pictures were remembered better than neutral ones. However, unlike earlier studies, the sleep group didn’t preferentially remember negative pictures more than the same-day group.

But, interestingly, the sleep group was more likely to maintain the strength of initial negative responses. The same-day group showed a weaker response to negative scenes on the second showing.

It’s been theorized that late-night REM sleep is critical for emotional memory consolidation. However, this study found no significant relationship between the amount of time spent in REM sleep and recognition memory, nor was there any relationship between other sleep stages and memory. There was one significant result: those who had more REM sleep in the third quarter of the night showed the least reduction of emotional response to the negative pictures.

There were no significant circadian effects, but it’s worth noting that even the 45 minute gap between the sets was sufficient to weaken the negative effect of negative scenes.

While there was a trend toward a gender effect, it didn’t reach statistical significance, and there were no significant interactions between gender and group or emotional value.

The findings suggest that the effects of sleep on memory and emotion may be independent.

The findings also contradict previous studies showing preferential consolidation of emotional memories during sleep, but are consistent with two other recent studies that have also failed to find this. At this stage, all we can say is that there may be certain conditions in which this occurs (or doesn’t occur), but more research is needed to determine what these conditions are. Bear in mind that there is no doubt that sleep helps consolidate memories; we are talking here only about emphasizing negative memories at the expense of emotionally-neutral ones.

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Repetition is behind our improved memory for emotional events

December, 2011

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.

What transient amnesia tells us about autobiographical memory and brain plasticity

November, 2011

Brain scans of those suffering from transient global amnesia indicate a permanent role of the hippocampus in autobiographical memory, and demonstrate the brain’s ability to self-repair.

When a middle-aged woman loses her memory after sex, it naturally makes the headlines. Many might equate this sort of headline to “Man marries alien”, but this is an example of a rare condition — temporary, you will be relieved to hear — known as transient global amnesia. Such abrupt, localized loss of autobiographical memory is usually preceded by strenuous physical activity or stressful events. It generally occurs in middle-aged or older adults, but has been known to occur in younger people. In those cases, there may be a history of migraine or head trauma.

Following an earlier study in which 29 of 41 TGA patients were found to have small lesions in the CA1 region of the hippocampus, scanning of another 16 TGA patients has revealed 14 had these same lesions. It seems likely that all the patients had such lesions, but because they are very small and don’t last long, they’re easy to miss. The lesion is best seen after 24-72 hours, but is gone after 5-6 days.

At the start of one of these attacks, memory for the first 30 years of life was significantly impaired, but still much better than memory for the years after that. There was a clear temporal gradient, with memory increasingly worse for events closer in time. There was no difference between events in the previous year and events in the previous five years, but a clear jump at that five-year point.

The exact location of the lesions was significant: when the lesion was in the anterior part of the region, memory for recent events was more impaired.

The hippocampus is known to be crucially involved in episodic memory (memory for events), and an integral part of the network for autobiographical memory. In recent years, it has come to be thought that such memories are only hosted temporarily by the hippocampus, and over a few years come to be permanently lodged in the neocortex (the standard consolidation model). Evidence from a number of studies of this change at the five-year mark has been taken as support for this theory. According to this, then, older memories should be safe from hippocampal damage.

An opposing theory, however, is that the hippocampus continues to be involved in such memories, with both the neocortex and the hippocampus involved in putting together reconsolidated memories (the multiple trace model). According to this model, each retrieval of an episodic memory creates a new version in the hippocampus. The more versions, the better protected a memory will be from any damage to the hippocampus.

The findings from this study show that while there is indeed a significant difference between older and more recent memories, the CA1 region of the hippocampus continues to be crucial for retrieving older memories, and for our sense of self-continuity.

Interestingly, some studies have also found a difference between the left and right hemispheres, with the right hippocampus showing a temporal gradient and the left hippocampus showing constant activation across all time periods. Such a hemisphere difference was not found in the present study. The researchers suggest that the reason may lie in the age of the participants (average age was 68), reflecting a reduction in hemispheric asymmetry with age.

There’s another message in this study. In these cases of TGA, memory function is restored within 24 hours (and generally sooner, within 6-10 hours). This shows how fast the brain can repair damage. Similarly, the fact that such tiny lesions have temporary effects so much more dramatic than the more lasting effects of larger lesions, is also a tribute to the plasticity of the brain.

The findings are consistent with findings of a preferential degeneration of CA1 neurons in the early stages of Alzheimer's disease, and suggest a target for treatment.

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Childhood amnesia shifts with time

August, 2011

A new study finds that the earliest memories children can recall shifts with time, providing support for the theory that children’s memories don’t consolidate in the way adults’ memories do.

Childhood amnesia — our inability to remember almost everything that happened to us when very young — is always interesting. It’s not as simple as an inability to form long-term memories. Most adults can’t remember events earlier than 3-4 years (there is both individual and cultural variability), even though 2-year-olds are perfectly capable of remembering past events (side-note: memory durability increases from about a day to a year from age six months to two years). Additionally, research has shown that young children (6-8) can recall events that happened 4-6 years previously.

Given that the ability to form durable memories is in place, what governs which memories are retained? The earliest memories adults retain tend to be of events that have aroused emotions. Nothing surprising about that. More interesting is research suggesting that children can only describe memories of events using words they knew when the experience occurred — the study of young children (27, 33 or 39 months) found that, when asked about the experimental situation (involving a "magic shrinking machine") six months later, the children easily remembered how to operate the device, but were only able to describe the machine in words they knew when they first learned how to operate it.

Put another way this isn’t so surprising: our memories depend on how we encode them at the time. So two things may well be in play in early childhood amnesia: limited encoding abilities (influenced but not restricted to language) may mean the memories made are poor in quality (whatever that might mean); the development of encoding abilities means that later attempts to retrieve the memory may be far from matching the original memory. Or as one researcher put it, the format is different.

A new study about childhood amnesia looks at a different question: does the boundary move? 140 children (aged 4-13) were asked to describe their three earliest memories, and then asked again two years later (not all could provide as many as three early memories; the likelihood improved with age).

While more than a third of the 10- to 13-year-olds described the same memory as their very earliest on both occasions, children between 4 and 7 at the first interview showed very little overlap between the memories (only 2 of the 27 4-5 year-olds, and 3 of the 23 6-7 year-olds). There was a clear difference between the overlap seen in this youngest group (4-7) and the oldest (10-13), with the in-between group (8-9) being placed squarely between the two (20.7% compared to 10% and 36%).

Moreover, children under 8 at the first interview mostly had no overlap between any of the memories they provided at the two interviews, while those who were at least 8 years old did. For the oldest groups (10-13), more than half of all the memories they provided were the same.

The children were also given recall cues for memories they hadn’t spontaneously recalled. That is, they were told synopses of memories belonging to both their own earlier memories, and other children’s earlier memories. Almost all of the false memories were correctly rejected (the exceptions mostly occurred with the youngest group, those initially aged 4-5). However, the youngest children didn’t recognize over a third of their own memories, while almost all the oldest children’s memories were recognized (90% by 8-11 year-olds; all but one by 12-13 year-olds). Their age at the time of the event didn’t seem to affect the oldest or the very youngest groups, but 6-9 year-olds were more likely to recall after cuing events that happened at least a year later than those events that weren’t recalled after cuing.

In general, the earliest memories were several months later at the follow-up than they had been previously. The average age at the time of the earliest memory was 32 months, and 39.6 months on the follow-up interview. This shift in time occurred across all ages. Moreover, for the very earliest memory, the time-shift was even greater: a whole year.

In connection with the earlier study I mentioned, regarding the importance of language and encoding, it is worth noting that by and large, when the same memories were recalled, the same amount of information was recalled.

There was no difference between the genders.

The findings don’t rule out theories of the role of language. It seems clear to me that more than one thing is going on in childhood amnesia. These findings bear on another aspect: the forgetting curve.

It has been suggested that forgetting in children reflects a different function than forgetting in adults. Forgetting in adults matches a power function, reflecting the fact that forgetting slows over time (as is often quoted, most forgetting occurs in the first 24 hours; the longer you remember something, the more likely you are to remember it forever). However, there is some evidence that forgetting in children is best modeled in an exponential function, reflecting the continued vulnerability of memories. It seems they are not being consolidated in the way adults’ memories are. This may be because children don’t yet have the cognitive structures in place that allow them to embed new memories in a dense network.

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Change in our understanding of memory development

September, 2010

Children’s slowly developing memory for past events may not be due to the slow development of the prefrontal cortex, as was thought, but to changes in the hippocampus.

Children’s ability to remember past events improves as they get older. This has been thought by many to be due to the slow development of the prefrontal cortex. But now brain scans from 60 children (8-year-olds, 10- to 11-year-olds, and 14-year-olds) and 20 young adults have revealed marked developmental differences in the activity of the mediotemporal lobe.

The study involved the participants looking at a series of pictures (while in the scanner), and answering a different question about the image, depending on whether it was drawn in red or green ink. Later they were shown the pictures again, in black ink and mixed with new ones. They were asked whether they had seen them before and whether they had been red or green.

While the adolescents and adults selectively engaged regions of the hippocampus and posterior parahippocampal gyrus to recall event details, the younger children did not, with the 8-year-olds indiscriminately using these regions for both detail recollection and item recognition, and the 10- to 11-year-olds showing inconsistent activation. It seems that the hippocampus and posterior parahippocampal gyrus become increasingly specialized for remembering events, and these changes may partly account for long-term memory improvements during childhood.

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