Copyright © 2007-2018 Russ Dewey
Influences on Memory Formation
In the late 1970s, reports of flashbulb memory (Brown & Kulik, 1977) were widely publicized. They seemed consistent with reports of adrenaline affecting on memory. Flashbulb memories were supposed to be formed instantaneously and remembered forever, after shocking events.
The example used in the 1970s was, "Where were you when you heard about Kennedy being shot." That turned into "Where were you when the space shuttle Challenger exploded (1986) in the 1990s, and in the 2000s, "Where were you when the twin towers came down."
This phenomenon has been known for many years. A psychologist (Colegrove) writing in 1899 described how middle-aged people remembered exactly what they were doing when they heard Abraham Lincoln was shot. That was 34 years after the event.
What is "flashbulb memory"?
Neisser (1982) argued that these memories are often inaccurate. He gave a personal example.
For years Neisser had a flashbulb memory of watching a baseball game the day before his 13th birthday. The game was interrupted by the announcement of the Pearl Harbor bombing (December 7, 1941). He rushed upstairs to tell his mother. Neisser continues:
This memory has been so clear for so long that I never confronted its inherent absurdity until last year: no one broadcasts baseball games in December! (It can't have been a football game either; professional football barely existed in 1941, and the college season ended by Thanksgiving.) Apparently flashbulbs can be just as wrong as other kinds of memories; they are not produced by a special quasi-photographic mechanism. (Neisser, 1982, p.45)
What point did Neisser make with his memory of the Pearl Harbor announcement?
Neisser proposed that flashbulb memories were really like historical markers. When a significant historical event occurs, we make it part of our life history.
We think about it and its relationship to our lives. We know the world is changed from that moment onward. In the following years we often think of this landmark in our personal history. So the memories linger, but that does not mean the memory is accurate.
How does Neisser explain flashbulb memories?
Schmolck, Buffalo, and Squire (2000) studied flashbulb memories which American students had for the announcement of the verdict of the O. J. Simpson trial. They found that "the quality of the recollections after 32 months was strikingly different from the quality of recollections after 15 months."
Many errors crept into the memory accounts. Because the researchers collected memory reports from the same people at two intervals, they were able to document changes in memory reports of individuals. For example, one student produced this report 15 months after the verdict:
"I was at the Commuter Lounge at Reville [College] and saw it on T.V. As 10:00 approached, more and more people came into the room. We kept having to turn up the volume, but it was kind of cool. Everyone was talking."
At 32 months post-verdict, the same student produced this recollection:
"I first heard about it while I was watching TV. At home in my living room. My sister and father were with me. Doing nothing in particular, eating and watching how the news station was covering different groups of viewers..."
This provides more evidence (if any is needed) that retrospective self-reports are unreliable. It also shows that memory continues to change and transform between 1 and 3 years after an experience.
What did Linton discover about memory for life events?
Marigold Linton (1982) argued that the distinctiveness of newsworthy events is what makes them memorable. Linton was the researcher described earlier in this chapter who wrote down two personal events every day for six years.
Linton systematically tested her memory for these events. She found that the first time you do almost anything is memorable, compared to later occasions.
For example, she retained a clear memory of submitting the "final draft" of a statistics textbook to her publishing company. But they asked for revisions.
She was less successful in remembering the second time she submitted a "final draft." She had only a vague memory of the third and final submission of the book, which was then published.
If Linton is correct, flashbulb memories, to the extent they are accurate, may be caused by unique, distinctive, first time events. This may not contradict the adrenaline theory. Such novel events probably provoke adrenaline release.
However, Linton's analysis suggests that encoding effects are important. A first-time event is distinctive and therefore easier to retrieve.
Recall of Events during Anesthesia
As mentioned on the previous page, Weinberger, Gold, and Sternberg (1984) reported that adrenaline acted as a switch for turning on memory-formation processes in rats. This occurred even when they were anesthetized and unconscious.
The researchers first gave rats enough anesthetic to eliminate any visible response to electric shock or electronically generated tones. Then they carried out a classical conditioning procedure, pairing the tone with the electric shock.
One group of rats received an injection of adrenaline during the training procedure, the other did not. Only the group receiving the adrenaline showed evidence of conditioning later.
How did Weinberger and colleagues train an anesthetized rat?
The researchers emphasized that the adrenaline did not alter the rats' level of anesthesia. The rats remained "out cold" during the whole conditioning procedure, and their heart rates did not increase when they received the adrenaline injection. Adrenaline seemed to switch on areas of the brain where memories were formed, despite the anesthesia.
These findings may explain why patients who undergo surgery sometimes remember events that occur during deep anesthesia. Years ago doctors assumed these patients simply had overactive imaginations.
Evidence slowly accumulated that patients could indeed remember events that occurred during surgical operations. This was especially likely if the events were somewhat shocking.
What types of events are remembered after surgery?
Mostert (1975) reported this phenomenon during surgery that involved opening the chest wall.
I was one of the anesthetists who helped Levinson study 10 volunteer patients. At deep levels of di-ethyl ether anesthesia as judged from virtual electrical quiescence and only occasional spindles, Levinson presented the patients with a (feigned) alarming comment indicative of a life-threatening crisis.
One month later the patients were hypnotized and regressed to the operation. Four were able to reproduce the words spoken, such as "the lung looks cancerous...it is black from living in the city."
Four patients became anxious and awoke from the hypnosis, and two did not reproduce the suggestion. None of the patients had recall at the conscious level. (p.69)
What was Levinson's experiment?
Mostert maintained that earlier researchers failed to find evidence of memory during anesthesia because they presented patients with trivial stimuli such as word lists. Only arousing or shocking stimuli succeed in penetrating the anesthesia. Perhaps "shocking" remarks stimulate adrenaline release
If sufficiently sensitive measures are used, researchers can demonstrate that regular, non-shocking stimuli also penetrate anesthesia. Kihlstrom, Schachter, Cork, Hurt and Behr (1990) were able to show memory for word lists, presented to anesthetized patients.
The researchers used the paired associates technique, reading pairs of words to the anesthetized patients. After awakening, none of the patients could consciously recall any of the words, nor could they recognize them. Memory effects showed up only in a free association test.
The free association test consisted of reading the stimulus words (the same ones used under anesthesia) one at a time. The patient was supposed to "report the first word that comes to mind" when hearing the stimulus word.
Under those conditions, subjects who heard word-pairs during anesthesia were significantly more likely than control subjects to report the response words they heard under anesthesia.
Rats taught to run a maze under the influence of a depressant drug will often forget the route if tested later without the drug. Given the drug again, they retrieve their memory and run the maze successfully.
This is called state-dependent memory (or state-dependent forgetting). Apparently the animal's chemical state of mind affects the encoding of the memory. When the same conditions are reinstated, it helps memory retrieval.
How can state-dependent learning be demonstrated in rats?
Alcohol-related state-dependent memory is known to occur with humans. Heavy drinkers may forget what they did while drunk, only to remember again the next time they drink. This phenomenon has been documented under experimental conditions using word lists.
What form of drug-induced state-dependent forgetting is known to occur in humans?
Here is an informal example:
While we were studying memory, I remembered a situation in which my friend and I were at a Rush concert at the Omni in Atlanta. We were talking about a particular song that the band was playing.
After the show, the next week, I asked the same fellow if he remembered what he said about the song during the concert. He said that he didn't because he was pretty drunk that evening. I gave him specifics about what he said but he still didn't remember.
Later, after a couple pitchers, he asked me if he had told me about that same song. I told him he had and asked him the same questions again.
This time he remembered that, during the concert, he told me the order of songs to expect. I guess he "stored" this information in some place in his head while drunk and couldn't retrieve it until slightly intoxicated again. [Author's files]
Alcohol-related effects on memory are well established. Does the same sort of state-dependent forgetting occur with caffeine?
Many students drink coffee or soft drinks with caffeine to stay awake while they study. (A counselor at Florida State said that Diet Coke was the most common addiction on campus.)
If caffeine caused state-dependent learning, students should do poorly on a test unless they took caffeine again before the test. But does caffeine produce state-dependent memory? Apparently not!
Does state-dependent forgetting occur with caffeine?
Blount and Cox (1982) tested 80 college students at the University of Minnesota in Morris, looking for evidence of this effect. Subjects who consumed caffeinated drinks during the learning phase were compared with subjects who did not.
Half of each group was given caffeinated drinks before the memory test. There was no effect due to the caffeine. The researchers concluded, "Caffeine's effects on memory are different from the effects of depressants."
Blount, J. P., & Cox, W. M. (1982, August). State-dependent learning with caffeine in a college classroom setting. Paper presented at the Ninetieth Annual Convention of the American Psychological Association, Washington, DC.
Brown, R., & Kulik, J. (1977). Flashbulb memories. Cognition, 5, 73-99.
Kihlstrom, J. F., Schacter, D. L., Cork, R. C., Hurt, C. A., & Behr, S. E. (1990). Implicit and explicit memory following surgical anesthesia. Psychological Science, 1, 303-306.
Linton, M. (1982) Transformations of memory in everyday life. In U. Neisser, (Ed.) Memory Observed: Remembering in Natural Contexts. San Francisco: Freeman.
Mostert, J. W. (1975). States of awareness during anesthesia. Perspectives in Biology and Medicine, 19, 68-76.
Neisser, U. (1982). "Snapshots or benchmarks" in U. Neisser (Ed.) Memory Observed: Remembering in Natural Contexts. pp. 43-48. San Francisco: Freeman.
Schmolck, H., Buffalo, E. A. & Squire, L. R. (2000) Memory distortions develop over time: Recollections of the O. J. Simpson trial verdict after 15 and 32 months. Psychological Science, 11, 39-45.
Weinberger, N. M., Gold, P. E., & Sternberg, D. B. (1984). Epinephrine enables Pavlovian fear conditioning. Science, 223, 605-607.
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