A type of experimental chamber often used in the laboratory analysis of behaviour, named after the American psychologist
B. F. Skinner. As a graduate student at Harvard in 1929 he invented the first such chamber to facilitate the study of eating behaviour in rats, and he later developed many versions.
The prototypical Skinner box for, say, a rat (Fig. 1) would be cubic in shape, 30 cm (1 foot) long on each edge, and would contain the following elements: (i) an 'operandum', such as a lever that protrudes from one wall, and (ii) an opening in that wall where the rat could obtain a small pellet of food, delivered by a mechanical feeding device. The box would be light-and soundproof to minimize distractions and maximize the effectiveness of events that occur inside the box. If lever pressing produces a pellet of food in this situation, a hungry rat will typically press the lever repeatedly and thereby eat.
Since its invention, the Skinner box has been adapted to study many organisms besides the rat, behaviours other than bar pressing, and consequences other than food presentation. Behaviour has been studied in the context of auditory and visual stimuli, such as coloured lights and pure tones, as well as more complex stimuli, such as other organisms and slides of the natural environment projected on a screen inside the chamber. In general, the term is now applied to almost any experimental chamber used in the study of the relationships of behaviour, its antecedent stimuli, and its consequences.
The use of the term probably began with
Clark Hull, who made use of what he called a 'modified Skinner box', described in his
Principles of Behavior. Skinner himself objected to the use of the term and in particular to its erroneous extension to the 'air-crib', an enclosed crib for human infants that he invented in the 1940s.

Fig. 1. The interior of a typical Skinner box. A hungry rat is poised over a lever protruding from the front wall. Pressing the lever one or more times will operate a feeder; the rat can retrieve a pellet of food which is dispensed at the small opening in the wall. The rat can easily learn to make discriminations; for example, to press the lever when a light is on and not to press it when the light is off. Chambers for other animals may vary considerably from this one.
(Published 1987)— Robert Epstein