The nature of perception

From David Kelley's classic, The Evidence of the Senses: " ... The normal adult human is not a tabula rasa. We bring to perception an enormous fund of background knowledge, and the act of perceiving is usually guided by the conscious purposes of expanding or applying that knowledge. Consider, for example, the role of attention. At any moment, the way in which one directs his attention affects what is perceived from among all the things that could be perceived, given present stimulation. It is doubtful that an act of attention is necessary for perceiving every object. Stimuli such as sudden chills, loud explosions, or noxious odors intrude themselves upon us quite apart from any conscious choice. But attention certainly can make the difference between perceiving or not perceiving an object-the classic examples being one's awareness of his clothes or of a low hum in the background. And the degree of attention to an object has a marked effect on the character of one's perceptual awareness of it. Thus there are major differences in the scope, clarity, and specificity of awareness-that is, in how much of the object is perceived-along a continuum of attention from objects at the edge of the visual field, to pocket change fingered absentmindedly, to the road ahead while one is driving, to a pen one has found at last among the litter on the desk, to the face of another person in conversation, to the riveting sound of a scratching at one's door late at night. ..."

The history of what a person attends to affects what it is possible for him to perceive in a given situation. Attention is the major factor in perceptual learning.

As you can see now, after a few posts on David Kelley's book, that the science of perception - and the philosophy of perception - are quite different.

Enjoy.