We make contact with the world around us through our five primary senses — sight, hearing, touch, smell, and taste. Psychologists distinguish between sensation and perception.
Sensation is the pickup of information by our sensory receptors, for example the eyes, ears, skin, nostrils, and tongue. In vision, sensation occurs as rays of light are collected by the two eyes and focused on the retina. In hearing, sensation occurs as waves of pulsating air are collected by the outer ear and transmitted through the bones of the middle ear to the cochlear nerve.
Perception is the interpretation of what is sensed. The physical events transmitted to the retina may be interpreted as a particular color, pattern, or shape. The physical events picked up by the ear may be interpreted as musical sounds, a human voice, noise, and so forth.
Lack of experience may cause a person to misinterpret what he has sensed. In other words, perception represents our apprehension of a present situation in terms of our past experiences, or, as stated by the philosopher Immanuel Kant (1724-1804): “We see things not as they are but as we are.”
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 used to live deep in the rain forests of tropical Africa, were not often exposed to wide vistas and distant horizons, and therefore did not have sufficient opportunities to learn size constancy. Colin Macmillan Turnbull, an anthropologist and author of The Forest People, wrote about one pygmy who, when 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 witchcraft had been responsible.
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 skill that can be improved tremendously through judicious practice and experience.