Perception is the process of selecting, organizing and interpreting information gained through the senses. It is a major field of study in psychology and cognitive science. It can be considered as either a physiological or a mental process, because it is dependent on anatomical and physiological underpinnings yet gives rise to mental effects.
Human perception depends on the five senses of Sight, Hearing, Smell, Taste and Touch. To these some add a "sixth" sense variously described as precognition (or foretelling) or sometimes telepathy (distance communications without aid other than the human brain). While this is controversial, it is certain that animals of other species do have additional senses: for example some fish can detect electric fields, while pigeons have been shown to detect magnetic fields and to use them in homing.
History of the study of perception
The subjective nature of perception, and hence of cognition, has attracted the attention of philosophers since antiquity, for example in the qualia which have been known since the Sufi thinkers, or in the extreme idealism of George Berkeley.
Perception is one of the oldest fields within scientific psychology, and there are correspondingly many theories about its underlying processes. The oldest quantitative law in psychology is the Weber-Fechner Law, which quantifies the relationship between the intensity of physical stimuli and their perceptual effects. It was the study of perception that gave rise to the Gestalt school of psychology, with its emphasis on holistic approaches.
Perception and reality
Many cognitive psychologists hold that, as we move about in the world, we create a model of how the world works. That is, we sense the objective world, but our sensations map to percepts, and these percepts are provisional, in the same sense that scientific hypotheses are provisional (cf. in the scientific method).
As we acquire new information, our percepts shift. Abraham Pais' biography refers to the 'esemplastic' nature of imagination. In the case of visual perception, some people can actually see the percept shift in their mind's eye. Others who are not picture thinkerss, may not necessarily perceive the 'shape-shifting' as their world changes. The 'esemplastic' nature has been shown by experiment: an ambiguous image has multiple interpretations on the perceptual level.
Just as one object can give rise to multiple percepts, so an object may fail to give rise to any percept at all: if the percept has no grounding in a person's experience, the person may literally not perceive it.
These confusing ambiguity of perception is exploited in human technologies such as camouflage, and also in biological mimicry, for example by Peacock butterflies, whose wings bear eye markings that birds respond to as though they were the eyes of a dangerous predator.