PSYCHOLOGY AS A NATURAL SCIENCE

Psychology As A Natural Science

Psychology as a Natural Science

Introduction

When we open our eyes on a familiar scene, we form an immediate impression of recognizable objects, organized coherently in a spatial framework. Analysis of our experience into more elementary sensations is difficult, and appears subjectively to require an unusual type of perceptual activity. In contrast, the physiological evidence suggests that the visual scene is analyzed at an early stage by specialized populations of receptors that respond selectively to such properties as orientation, color, spatial frequency, or movement, and map these properties in different areas of the brain (Zeki, 1976). The controversy between analytic and synthetic theories of perception goes back many years: the Associationists asserted that the experience of complex wholes is built by combining more elementary sensations, while the Gestalt psychologists claimed that the whole precedes its parts, that we initially register unitary objects and relationships, and only later, if necessary, analyze these objects into their component parts or properties. This view is still active now (e.g., Monahan & Lockhead, 1977; Neisser, 1976).

The Gestalt belief surely conforms to the normal subjective experience

Address reprint requests to Anne Treisman, Department of Psychology, University of British Columbia, 2075 Wesbrook Mall, Vancouver, B.C. V6T IW5, Canada. We are grateful to the British Medical Research Council, the Canadian Natural Sciences and Engineering Research Council, the Center for Advanced Study in the Behavioral Sciences, Stanford, California, and the Spencer Foundation for financial support, to Melanie Meyer, Martha Nagle, and Wendy Kellogg of the University of Santa Cruz for running four of the subjects in Kxperiment V. and to Daniel Kahneman for many helpful comments and suggestions.

of perception. However the immediacy and directness of an impression are no guarantee that it reflects an early stage of information processing in the nervous system. It is logically possible that we become aware only of the final outcome of a complicated sequence of prior operations. "Top-down" processing may describe what we consciously experience; as a theory about perceptual coding it needs more objective support (Treisman, 1979).

We have recently proposed a new account of attention which assumes that features come first in perception (Treisman, Sykes, & Gelade, 1977). In our model, which we call the feature-integration theory of attention, features are registered early, automatically, and in parallel across the visual field, while objects are identified separately and only at a later stage, which requires focused attention. We assume that the visual scene is initially coded along a number of separable dimensions, such as color, orientation, spatial frequency, brightness, direction of movement. In order to recombine these separate representations and to ensure the correct synthesis of features for each object in a complex display, stimulus locations are processed serially with focal attention. Any features which are present in the same central "fixation" of attention are combined to form a single object. Thus focal attention provides the "glue" which integrates the initially separable features into unitary objects. Once they have been correctly registered, the compound objects continue ...