The following situation will illustrate how perception correlates with previous experience:

Suppose a person parked his car and walks away from it while continuing to look back at it. As he goes further and further away from his car, it will appear to him as if his car is gradually getting smaller and smaller. In such a situation none of us, however, would gasp in horror and cry out, "My car is shrinking!" Although the sensory perception is that the car is shrinking rapidly, we do not interpret that the car is changing size. Through past experiences we have learned that objects do not grow or shrink as we walk toward or away from them. You have learned that their actual size remains constant, despite the illusion. Even when one is five blocks away from one's car and it seems no larger than one's fingernail, one would interpret it as that it is still one's car and that it hasn't actually changed size. This learned perception is known as size constancy.

Pygmies, however, who live deep in the rain forests of tropical Africa, are not often exposed to wide vistas and distant horizons, and therefore do not have sufficient opportunities to learn size constancy. One Pygmy, removed from his usual environment, was convinced he was seeing a swarm of insects when he was actually looking at a herd of buffalo at a great distance. When driven toward the animals he was frightened to see the insects "grow" into buffalo and was sure that some form of witchcraft had been at work.

A person needs to INTERPRET sensory phenomena, and this can only be done on the basis of past experience of the same, similar or related phenomena. Perceptual ability, therefore, heavily depends upon the amount of perceptual practice and experience that the subject has already enjoyed. This implies that perception is a cognitive skill that can be improved tremendously through judicious practice and experience.

MEMORY

A variety of memory problems are evidenced in the learning disabled. Some major categories of memory functions wherein these problems lie are:

Receptive memory: This refers to the ability to note the physical features of a given stimulus to be able to recognize it at a later time. The child who has receptive processing difficulties invariably fails to recognize visual or auditory stimuli such as the shapes or sounds associated with the letters of the alphabet, the number system, etc.