Depending on your favorite poet, memory is sweet (Cowper), pleasing (Pope), green (Shakespeare) or fond (Moore). If you prefer science to poetry, though, memory is, above all else, faulty. Memory’s essential imperfection is no secret. Everybody sometimes suffers from forgetfulness. And psychologists have long known that not only do people forget, they also misremember. Still, scientists are only beginning to learn just how strangely flawed human memory can be. One new study, for example, suggests that the worst thing you can do for a memory is recall it. In other words, practice makes imperfect. If you use a memory, you can lose it.
“Whenever we bring a memory to mind,” writes neurobiologist Yadin Dudai, “it may turn shaky and slip into oblivion.” Dr. Dudai, of the Weizmann Institute in Israel, cites a new study reported this month in the journal Nature by scientists at New York University. In essence, they showed how to erase a rat’s memory of a fearful event. The New York scientists used a standard experimental set-up: playing a short tone followed by an electric shock to the rat’s feet. It doesn’t take the rat long to remember that a tone means a shock. Bring the rat back the next day, and it will freeze with fear when it hears the tone, even without the accompanying shock.
Biologists have a vague idea of what happens in the brain to form such a long-term memory. Specific links between nerve cells are somehow strengthened. Part of that process involves the need for the nerve cells to make new proteins. An event is stored in long-term memory only after this protein production, which can take a few hours. “Most memories, like humans and wine, do not mature instantly,” Dr. Dudai observes. Before protein production completes the memory maturation, the memory of the event is fragile, subject to change or loss.
It’s easy to disrupt a rat’s memory during the fragile period, previous research had shown. Simply injecting a chemical that blocks protein production prevents the rat from forming a long-term memory of its fear. Bring the rat back the next day and the tone doesn’t faze it. Now take a rat that does remember to freeze at the sound of the tone. Inject it with the protein blocker, the New York scientists found, and the rat will lose its fearful memory — but only if it has first been forced to remember its fear.
“This effect … requires that the memory be actively retrieved,” wrote researchers Karim Nader, Glenn Schafe and Joseph Le Doux. In other words, if you bring a rat back the second day and merely inject the protein blocker, the rat retains its memory of the tone-shock connection. Only if you first play the tone, activating the rat’s memory, will the protein blocker erase the fear. “It now appears that new proteins are … required to maintain memories that have been reactivated,” the scientists wrote in Nature.
These findings imply that calling up a long-term memory exposes that memory to distortion or loss. Whenever you recall a memory, it must be re-stored, requiring new protein production in your nerve cells. And re-storing a memory means that it must be encoded again, with all the potential for memory error that occurs when a memory is encoded the first time. In a commentary in the same issue of Nature, Dr. Dudai notes that scientists already knew that memories are reconstructed with use. Any memory, he points out, involves mingling present perceptions with representations of the past stored in our brain.
Two people can bring a different memory away from the same event because they perceived it through different “filters” colored by the details of their personal pasts. Then, when a person recalls a long-term memory later on, it mixes with an expanded set of additional memories and perceptions. So that memory will be re-stored in a modified way, even without any protein-blocking injections.
Of course, it’s a little too soon for biologists to erase their memory of what they used to think about memory. Questions remain, Dr. Dudai reminds everybody. For one thing, perhaps the protein blocker didn’t really erase the fear memory, but merely covered it up, and maybe there’s some way to trigger it again. Furthermore, it may be that other forms of memory don’t work the same way as memory of fear. And there’s the obvious issue that even though humans mimic rats in many ways, there are differences.
Even so, recent findings about memory and its flaws may have important impacts on various realms of human interaction. Imagine the possible benefit for people traumatized by haunting memories of terror or tragedy. The day may come when the cure is recalling the trauma, and then erasing it with a shot. Other relevant issues range from the credibility of eyewitness testimony to the frequency of “false” memories that confound some allegations of sexual abuse. New and improved knowledge about how memory works can suggest novel solutions to such problems, and perhaps even make it easier to memorize poetry. (The Dallas Morning News)
Memories may be beautiful & yet they’re often wrong
Michael Turner
Dallas Morning News
You shouldn’t always believe what you remember. Memories, whether misty and watercolored or as sharp as Dr. Laura’s tongue, are no more reliable than presidential campaign promises. What people remember is not reality, but the mind’s reconstruction of what the senses sense. Sounds and sights and other sensations are not taped by a mental video camera; they are encoded by the mind’s version of a computer, storing images distorted by special effects.
“Remembering an episode from even the recent past may involve a blend of fiction and fact,” write psychologists Henry Roediger III and Kathleen McDermott. “Memories are not recordings but rather recodings; that is, they are not audio or video recordings but a recoded blend of events from the external world.” Recoding events in this way might seem like a flawed approach to life. But in fact it’s an essential part of the brain’s ability to figure out what’s going on in the world.
“Memory illusions … are a consequence of normal human information processing,” say Drs. Roediger and McDermott, of Washington University in St. Louis. “Whenever people engage in conversation, listen to a talk, read a newspaper article, or watch a television program, they recode events from the outside world as they try to understand them.” As a result of such recoding, vivid and clear memories may actually be inaccurate. Drs. Roediger and McDermott have tested people by reading them a list of 15 related words (at a rate of one every 1.5 seconds), then asking the people to repeat all the words. Try it yourself by reading the following words aloud (unless you are in a library): bed, rest, awake, tired, dream, wake, snooze, blanket, doze, slumber, snore, nap, peace, yawn, drowsy.
Now, cover the list with your hand. Was the word wake on the list? Yes, but in these experiments, fewer than half the people tested will recall it. Was the word sleep on the list? No, but many people who hear the words insist that it was. In a typical experiment of this sort, people will remember the first word on the list roughly 9 times out of 10 and will nearly always remember the last word. Middle-of-the-list words are harder to remember; those in positions 4 through 10 are usually recalled less than half the time. Yet more than half the time, people tested will say they heard the word sleep, even though it was not on the list.
After studying numerous lists, people are then asked specifically if they had heard particular words — some that they had and some that they hadn’t. Of the words the people hadn’t heard, some were related to the words on the list (like sleep) and some weren’t (like spider). Only a few people will contend that they heard the word spider. But people are just as likely to say they’ve heard sleep as they are to say they’ve heard words that actually had been presented.
Warning people to be careful doesn’t matter. Even when people are told precisely what the experiment is about and asked to try to avoid making the false memory error, some still insist they heard a word they didn’t hear. “Informing subjects about the nature of the effect and asking them to avoid false recognition does not come close to eliminating the effect,” the researchers wrote last month in Current Directions in Psychological Science.
Of course, not everybody makes the mistake of “remembering” a word that wasn’t really heard. Susceptibility to false memory afflicts some individuals more than others. Some studies indicate that people with vivid imaginations, and those who succumb easily to hypnosis, are more likely to fall for the missing word trick. Drs. Roediger and McDermott think the false memory effect has something to do with the way a “critical” word, missing from a list of related terms, triggers information already in a person’s brain.
It’s only natural. Calling words or ideas to mind is an important part of the way people interpret events and draw inferences about them. A list of related words creates an informational context that gets a brain thinking. “The information may spark related thoughts, and these thoughts may later be remembered as having been made as explicit statements,” the researchers write. A susceptibility to false memories, therefore, does not mean that a person is irrational. Memories may be prone to errors, but they are “intelligent” errors — the kind of mistakes only an intelligent system would make.
“Part of what makes humans clever is the ability to make inferences,” Drs. Roediger and McDermott declare. “The fact that such inferences can lead one astray, and that people can recollect vividly events that they only inferred, is a small price to pay for the inventiveness and adaptiveness of the human mind.”
Source: Michael Turner, Dallas Morning News
[Now with this information in mind, tell me again about the credibility of all that supposed “eyewitness” testimony of the so-called “Holocaust” — and not to mention making it a crime in some countries to question these “memories”!]