Some informational aspects of visual perception.

ing the invariance and utilizing it appropriately, but we actually know very little about the limits of the human perceptual machinery with respect to such abilities. A group of psychophysiINFORMATIONAL ASPECTS OF VISUAL PERCEPTION 187 cal studies determining the accuracy with which observers are able to extrapolate certain discrete and continuous functions of varying complexity must be carried out before we can usefully discuss any but the simplest cases. A troublesome question arises in this connection: where does perception leave off and inductive reasoning begin? The abstraction of simple homogeneities from a visual field does not appear to be different, in its formal aspects, from the induction of a highly general scientific law from a mass of experimental data. Certain subjective differences are obvious enough: thus reasoning seems to involve conscious effort, whereas perception seems to involve a set of processes whereby information is predigested before it ever reaches awareness. When extrapolations are required of a subject in an experimental situation, however, it is difficult or impossible for the experimenter to be certain whether the subject is responding on an "intuitive" or a "deliberative" basis. I do not know any general solution to this problem, and can only suggest that a limited control may be exercised by way of the establishment of a desired set in the