Implicit vs. Explicit Memory

Certain forms of memory do not require conscious executive control. An example is remembering how to brush your teeth. You probably do not need to think about it. These forms of memory—called implicit memory —are usable even if a person suffers severe brain damage from organic brain syndromes such as Alzheimer's Syndrome.

What is the difference between implicit and explicit memory?

People who are drunk, or who suffer from organic brain syndromes, may perform very poorly on memory tasks requiring conscious control: explicit memory tasks. An example of an explicit memory task would be reciting everything you remember reading on the last page. By contrast, implicit memory tasks are automatic responses, drawn out or elicited by a situation, like clapping after a performance.

In the following columns, tasks on the left are examples of implicit memory that do not require executive control. Brain-damaged or intoxicated humans can still perform them. Tasks on the right are examples of explicit memory that do require some conscious control. They are performed poorly by people who are brain-damaged or drunk.

Tasks requiring implicit memory

Tasks requiring explicit memory

 

 

mirror tracing

recalling last year

reading reversed text

paired associate learning

doing a word-completion task

identifying the head of state

singing part of a familiar song

writing a term paper

Items in the left column are all indirect forms of memory. They do not involve a conscious strategy for retrieving information. If you once learned to read text that is printed backwards, chances are you will be able to do it later, even if you suffer a brain disorder. The same is true of the other tasks on the left.

How does implicit memory help old people who stay in their own homes?

The importance and power of implicit memory helps explain why old people are often more comfortable and capable when they stay in a familiar place. Years of living in the same rooms produces implicit memory such as knowing where to find a broom and other useful knowledge and skills. When an old person is put in a nursing home or other unfamiliar environment, the same person may seem disabled, because none of the old automatic routines work in the new environment.

What was discovered in the study of "alcohol amnesia?

Hashtroudi, Parker, DeLisi, Wyatt, and Mutter (1984) studied the effects of alcohol on implicit and explicit memory. Ninety-six male volunteers between the ages of 21 and 35 were recruited for the all-day experiment (they were kept at the lab until their blood alcohol returned to zero). The researchers found that alcohol intoxication had effects similar to brain injury. It damaged explicit memory but not implicit memory.

The subjects were divided into 6 groups of 16. Three groups received alcoholic drinks; three groups received placebos. Each received 4 drinks in 40 minutes, then the memory tests began. Subjects saw a list of words for 2 seconds each. They performed an arithmetic task for 5 minutes, then they were tested on one of three memory tests: (1) recalling the words, (2) recognizing the words, (3) identifying the words in degraded form.


Degraded words progressively filled in

What tasks were affected by alcohol, and what were not?

The figure shows some degraded words used in the experiment. Each subject had to indicate as quickly as possible the word seen a few minutes earlier for 2 seconds. First they saw the word in severely degraded form (top) then with more and more of the word revealed.(as shown top to bottom).

Alcohol-intoxicated subjects performed just as well as sober subjects on the last two tasks: recognizing the degraded words and recognizing other words in a Yes/No recognition test. (Actually the drunk subjects identified fewer words from the list, but they also made fewer errors of false identification, so the recognition scores came out the same.) Both forms of recognition are examples of implicit memory, because a person does not have to perform any elaborate or deliberate mental activity to recognize a word. You see the word, later on you recognize it, and it is all somewhat automatic and effortless.

However, on the recall task, a big difference appeared. Drunk subjects recalled only half as many words as sober subjects. This was a task that involved explicit memory. Subjects knew they would be asked to recall the words later, so they probably tried to memorize them during the initial presentation of the list. Sober subjects were better at this consciously controlled process.

With what type of memory are preschool children just as good as adults?

Implicit memory occurs under the surface all the time. As you explore the environment, you absorb information about it continuously without trying. If somebody asks you where a certain missing object is located, you may reply, "Oh, I saw that in such-and-such a place." You did not make a conscious effort to memorize its location when you saw it, nor did you have to make much of a conscious effort to retrieve this information when the person asked you about it.

Implicit memory operates almost without conscious intervention. No sophisticated executive control is required. That is why preschool children are sometimes as good as adults at tasks requiring only implicit memory. Ask a 3 year old where a favorite toy is, and the child is as likely as you are to remember where it was last seen. Ask a 3 year old to hold a series of numbers in memory and he or she will not perform well, because a child does not know to rehearse such a series to "hold it in memory." This is something learned, and it requires executive control.

What did Crowder say about implicit memory?

Implicit memory is very pervasive or widespread in human cognitive processing. Robert G. Crowder of Yale University pointed out, "Most researchers now agree that implicit memory is more influential than explicit, conscious memory" (Bower, 1990).


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Copyright © 2007 Russ Dewey