Perception

Perception is the process by which a subject identifies, interprets and organizes sensory information in order to represent and understand their surroundings. Although it is often experienced as the passive reception of data, it is a constructive activity shaped by learning, memory, expectation and attention.

The term has a long history in philosophy, where it is distinguished from sensation and from the idea as the mental apprehension of an objective reality. Depending on the school, perception is considered either mediate or immediate: realists tend to understand it as direct access to the external world, while idealists regard it as a representation mediated by the mind. Samuel Bailey argued that perceiving external things through the senses is an immediate mental act that cannot be reduced to anything else, and Mary Shepherd maintained that perception requires an extended reality outside the mind, against Berkeley's idealism.

As a scientific discipline, perception began to be studied in the nineteenth century, when physiology and psychophysics started to relate the magnitude of a physical stimulus to the magnitude of what is perceived. Ernst Heinrich Weber and Gustav Fechner formulated the first quantitative laws of that relation, while the Gestalt school, led by Max Wertheimer, Kurt Koffka and Wolfgang Köhler, held that we perceive organized forms rather than isolated sensations. Two broad positions emerged from this: the empiricist or associationist view, which starts from disordered sensations that the subject organizes on the basis of prior experience, and the innatist or form-based view, which attributes to the mind an automatic organization of data.

A simple example is a ringing telephone: the sound is the distal stimulus, the vibration reaching the ear is the proximal stimulus, and recognizing that "the phone is ringing" is the percept. Rudolph Arnheim insisted that seeing is a form of reasoning, that is, organizing data into meaningful configurations.

Today the debate continues between those who see perception as a kind of hypothesis that the brain tests against reality and those who argue that sensory information is rich enough to make such inference unnecessary. Studies of illusions and ambiguous figures, along with research on the brain's modular organization, keep this discussion alive.