Two major conceptual approaches to the study of visual receptive field physiology can be identified; one, here termed the ''parametric'' approach, which considers all the properties of a cell to be potentially related to that cell''s functional role, and a second, here termed the ''feature extraction'' approach, which regards a particular receptive field property as defining a cell''s role in the visual system. The parametric approach seems most compatible with network theories of visual information processing, while the feature extraction approach suggests a localized single-cell form of visual representation. In this paper we trace the growth and development of these two approaches, from 1938 to the present, by dividing this period into four segments: 1938–1953, during which the foundations of both approaches were laid; 1953–1966, the major period of growth for feature-extraction analyses; 1966–1975, the major period of growth for parametric analyses; and 1975 to the present, during which the parametric approach has been expanded by the incorporation of principles of systematics and population biology to enable groups of neurones to be studied from a biological perspe