PERCEPTION AND MEMORY AS INFLUENCED BY ATTITUDE AND EXPERIENCE
A camera is a mechanism by means of which patterns of light chemically transform a sensitive film and leave lasting traces upon it. In much the same manner, living organisms are affected by the stimuli which impinge upon them, and the effects of these stimuli persist often over long periods of time. This persistence of the effects of stimulation is what is meant by retention, or memory.
Although the impression left on a photographic film bears a close resemblance to the object which was photographed, it is not a precise copy of that object. A photograph of a tree is smaller than the tree; it commonly lacks the tree's colors; and, unless the camera lens is exceptionally good, the edges of the picture are blurred. What is impressed upon the sensitive film, therefore, is determined not only by the character of the object producing the impression, but also by the structural characteristics of the recording mechanism itself (primarily of the lens and the film). The differences between the object photographed and the resulting photograph depend upon the deficiencies of the camera mechanism.
In some respects, the functioning of the human memory mechanism resembles that of the camera. As a rule, what we remember has a definite similarity to the pattern of stimuli which furnished the basis for the memory. But we do not remember perfectly. Memories are generally incomplete and defective in the sense that they do not reproduce in a literal way the past objects or events which they represent. If you were asked to recall the first paragraphs of this chapter, you might be able to state their general import, perhaps reproduce some of the exact phrases, but it is very doubtful that you could achieve a letter-perfect copy. The fallibility of our memory processes is brought home to all of us many times each day. We are frequently confident