The world around us seems concrete and immediate, and our ability to perceive it is easily taken for granted. Objects have positions, shapes, and colours that seem to be perceived instantly, and we can reach for them or move to where they are, without any apparent effort. Clearly, there must be some process that gives rise to visual experience, and it is not surprising that throughout history people have found it fascinating. If what we perceive is what we take to be true or factual about the world, are everyone's experiences the same? What is the perceptual world of animals, or infants, like? What sorts of errors do we make in perceiving? Can perceptual experience be communicated to others? Philosophers, artists, physicians, and, more recently, psychologists have tried to find ways to answer such questions, which are among the most fundamental that can be posed about the human mind.
Although we perceive the world around us, we have no direct knowledge of how this experience comes about. In fact, it can often be hard to believe that there is any mechanism involved in perception at all; for most people, most of the time, perceptions are simply “given” as facts about the world that are obviously correct. Perception is indeed a fundamental psychological process, and a very remarkable one. Its success in providing us with accurate information about the characteristics of the world around us is an index of its power, because there are relatively few situations in which it is seriously in error. A perceptual process that gave rise to subjective experiences grossly different from physical reality would make survival virtually impossible.
This chapter provides an overview of central issues in the study of visual perception, many of which will be discussed in more detail in later chapters. It is important to understand the functions that any visual system must perform if there is to be coordinated, effective action, and the problems of devising explanations for how this comes about. If perception is to be explained, appropriate measurements of its characteristics must be obtained, and related to the information potentially available from the physical environment. Each of these issues contributes to the general framework of ideas that guides the investigation of vision.