The study of perception has a long history, as long as the history of science itself. The framework for science and for the study of perception was outlined by Greek philosophers, but we have concentrated upon the advances made in the modern era, following the scientific revolution in the seventeenth century. Our current theories of perception have been shaped by ideas in physics, art, physiology, biology, philosophy, psychology, and more recently computer science. Physics contributed an understanding of the nature of light and of the laws of optical transmission in air and in the eye. The former led to a recognition that vision is not due to the emission of energy from the eye, and the latter made it possible to understand how objects in the external world were represented as images on the retinal surface. The laws of optics were also employed in artistic representation: The formation of an image on a transparent screen at a fixed distance in front of the eye will produce a picture in linear perspective; if the screen is considered to lie at the back of the eye then a similar pattern will be produced (though inverted and reversed with respect to the external picture). When this similarity between image formation in the eye, in cameras, and in art was appreciated the problem of perception was thought of in terms of extracting information from a two-dimensional image. The retinal image was conceived in terms of a static picture, which has had profound effects upon both theory and experiment. It has meant that pictorial representations of objects could be considered as adequate experimental substitutes for the objects themselves, and that the dynamic aspects of vision could be too readily ignored. Because our eyes are in constant motion, the retinal image is an abstraction, not actually present in the eye unless a scene is viewed for a very brief interval, too short for the eyes to move. Anatomists examined the structure of the retina and of the optic nerves. Physiologists conjectured how the brain could distinguish between neural signals arising from different sense organs.
Towards the end of the nineteenth century specific cortical regions were found that received neural signals from the different sense organs. The biological perspective, following Darwin's theory, placed humans in a closer relationship to other animals and so added to the relevance of experiments on animal perception to interpretations of human perception. It emphasised