A series of experiments was done to determine how completely and accurately people remember the visual details of a common object, a United States penny.
People were asked to:
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draw a penny from unaided recall;
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draw a penny given a list of its visual features;
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choose from among a list of possible features those which do appear on a penny;
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indicate what was wrong with an erroneous drawing of a penny; and
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select the correct representation of a penny from among a set of incorrect drawings.
Performance was surprisingly poor on all tasks. On balance, the results were consistent with the idea that the visual details of an object, even a very familiar object, are typically available from memory only to the extent that they are useful in everyday life. It was also suggested that recognition tasks may make much smaller demands on memory than is commonly assumed.
…These results violate our intuitions regarding what we know about the way things look. Most people, we suspect, would be willing to say that they know what a penny looks like or at least that they would have no trouble recognizing one when they saw it. A typical reaction of our subjects after participating in this study was one of surprise, and sometimes embarrassment, at how difficult their tasks, which initially sounded so simple, turned out to be. Certainly, all of our subjects had seen pennies many thousands of times during their lives; some had collected them as a hobby. And we had, after all, selected a penny as our stimulus because we thought it would be at least as familiar to most people as any other object we might have used.
…One plausible explanation is that there is no need for them to be any better. Perhaps what we mean when we say that we know what a penny looks like is that we can distinguish a penny from other things from which we normally have to distinguish it, for example, from other coins. This does not require that we know what a penny looks like in any detail. The features that are salient for distinguishing a penny from other US coins are probably its color and size. And even when one has occasion to distinguish a penny from a foreign coin of similar color and size, a gross comparison of their features will generally suffice. (In view of our subjects’ relatively good memory for the date, it is noteworthy that of the features considered in this study, it is the only one that many of us find valuable for distinguishing among pennies.) What is interesting about this explanation is that it suggests that many of the numerous things we all can “recognize”, we may recognize on the basis of memory representations that are as incomplete and imprecise as our representations of pennies appear to be. Skeptics are invited to try to draw from memory a telephone dial or their watch face or any other thing at which they frequently look.
We should note that our subjects’ underlying memory representations may have been even more vague than our results suggest. The fact that a subject drew a particular feature in the first of our experiments does not prove that he or she relied on stored information about pennies in particular to do so. All current US coins have a head on one side. Moreover, they all contain a date and the words LIBERTY, E PLURIBUS UNUM and UNITED STATES OF AMERICA. Even if one were not aware of this fact, one might expect any coin to display its denomination, the name of the country of coinage, and the year of mint. Remembering, or being able to guess, that the building on the back side of the penny is the Lincoln Memorial, coupled with a memory representation—from some source other than a penny—of what that looks like, could provide a basis for an accurate drawing. More generally, many correct responses may have been derived from memories for different but related information. Inference may be seen as the productive counterpart of interference. These considerations illustrate a methodological difficulty that characterizes much long-term memory research: namely, the difficulty (perhaps impossibility) of distinguishing between what is remembered and what is inferred.
…The results from these experiments should at least give us pause about the accuracy of testimonies on topics that we know like the “backs of our hands.”