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Tests of Recognition

Serial learning and free recall are examples of recall testing. A different variety of memory test is recognition testing. In recognition testing, the subject views stimuli such as words or pictures. After a retention interval, the subject is shown test items and must indicate whether each item is "old" (from the earlier list) or "new" (not shown earlier).

In recognition testing, What is an "old" item? A "new" item?

Notice this does not correspond exactly to what we usually call recognition. Usually we say we recognize an item if we have ever seen it before in our whole lives. In recognition memory research, however, a subject is typically asked to recognize an item seen earlier in the experiment. It may be a familiar word that the subject has known since childhood.

The "subject" in a recognition experiment may be a non-human animal, too. First the animal must be taught to discriminate previously-seen stimuli from others. This is accomplished by reinforcing the animal for picking items seen earlier, a form of differential reinforcement (see p.246). After the animal catches on to the pattern, it can be tested for recognition of new stimuli.

To experience a simple recognition test in the role of a subject, see if you can detect the "old" items in the following list. Three of the syllables appeared in an example several pages ago.

BOF    WUJ    ZEQ    VAF    MIB    DUR    RIQ    SOZ    ZYQ

Could you recognize the items you had seen before? As a rule,recognition memory is more sensitive than recall. Chances are you recognize the three "old" syllables, even if you could not recall them in a free recall test. (Perhaps you would recall them in a free recall test, if you studied the "mibery" example. Natural language mediation is very helpful!)

How do relearning, recognition, and recall compare, as measures of memory?

In another example of how recognition succeeds when recall may fail, most people can recognize the names of their grade-school teachers, even if they cannot recall them in a free recall situation. Relearning is the most sensitive memory measure; it can show the effects of memory when recognition fails. Recognition is next most sensitive; it can show the effects of memory when recall fails. Recall is the least sensitive, most demanding measure of memory.

Why is recognition more sensitive than recall?

Most psychologists agree recall is harder than recognition because retrieval is more of a problem in recall testing. Recognition testing makes retrieval easy, most of the time, by presenting you with a stimulus. As long as you encode the stimulus the same way during testing as you did during the acquisition (learning) phase, recognition is virtually automatic.

When does recognition failure take place?

Recognition failure does occur sometimes, however. People do not always encode stimuli the same way on two different occasions. Recognition failures take place if your current encoding of a stimulus does not match your previous encoding of the same stimulus. Then you may think you did not see it previously, when actually you did. A change of context can cause this. For example, you might not be able to "place" (recognize the identity of) a person usually seen at a grocery store, if you meet the same person at a sporting event. You would probably have a vague feeling of familiarity ( "I know that person!") but you might not be able to retrieve the information about who it is.

The encounter with a person you cannot "place" could be considered a recognition failure, if your criterion of memorization is being able to name the person. The same mental event could be considered a recognition success if the task is to decide if you have seen the person before. Criteria of success are somewhat arbitrary and depend upon what the experimenter is investigating.

How is recognition "probabilistic" in nature?

Even when the criterion of success is clear and simple, like deciding whether you have seen a picture before, recognition memory is often uncertain and probabilistic in nature. You might be "70% sure" you recognize the picture. This would be like saying, "When I feel this level of confidence in my recognition, I might be wrong 3 out of 10 times."

Such subjective judgments do not always correspond with reality, of course. A person can be "100% sure" a stimulus is familiar when actually viewing it for the first time. Déjà vu sensations are a bit like that. A person might feel 100% sure the present situation is familiar, while objective evidence indicates it could not be.

Why does a student who guesses an answer have a good chance of getting it right?

People sometimes underestimate their recognition accuracy. A person who claims to be guessing may perform at levels far above random. In fact, this is a typical finding. Perhaps some sort of unconscious, implicit learning is at work. This is one reason students taking multiple-choice quizzes should guess rather than leave quiz items blank, unless heavily penalized for wrong answers.

The probabilistic nature of recognition puts it in the same category as many other processes in which a person picks a signal out of background noise. The Theory of Signal Detection, a mathematical description of decision-making in uncertain environments discussed in chapter 4, applies well to recognition testing. It can be used to measure the true sensitivity of an organism's recognition abilities.

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