Some factors affecting response in recognition tests

Experiments were designed to investigate some of the factors which might affect a subject's responses in a recognition test. Two experiments are described. In the first, subjects were shown 12 similar photographs. They were then given a recognition test of 12 photographs, of which a number varying from o to 12 had been shown in the original display. All the photographs were sufficiently alike to render some guessing essential. It was found that subjects tended to select approximately 50 per cent. as having been seen previously and to reject 50 per cent. When a second and similar display and recognition test followed immediately, there was a tendency for subjects to make more “yes” responses, without any improvement in accuracy. The effect of giving serial presentation first was to increase the number accepted not only in that test but also in a test using simultaneous presentation which succeeded it. It was also shown that when a correct decision was possible but difficult a positively correct response (in this case recognizing something seen before) was easier than a negatively correct one (rejecting something not seen before).

In the second experiment subjects were shown a picture and were then asked to describe it from memory. Immediately afterwards half the group was given a multiple-choice recognition test while the other half was given a single-choice recognition test. It was found that accuracy and certainty of decision varied with the nature of the choice situation. The results are discussed in relation to a theory of adaptation levels.