No abstract

This is a descriptive study of the various judgments of shape which are spontaneously made when the inclination of an object is varied. The full range of inclinations is examined, using independent and unsophisticated subjects at each inclination, and recording subjects' descriptions.The chief findings are: (1) T w o main judgments are possible: judgments of real shape (R), which approximate to the true shape at all inclinations; and judgments contrasted with these (not-real or N), which show typically a compromise between true and retinal shape. (2) Some subjects (group RN) are spontaneously aware of both possibilities. They describe the N judg ment as an attempt to equate on the basis of a direct, instantaneous, visual impression; whereas the R judgment involves 'allowing for the slope'. Those subjects predominate at greater inclinations. (3) The remaining subjects (group RO) are spontaneously aware of the R possibility only. For these subjects, the R judgment seems to approximate closely to that quality of direct visual impression which for group RN characterizes the N judgment.It is suggested that judgments of real shape involve a skill. Group RN are in an 'investigating' frame of mind, and offer an analysis of this skill. Group RO, in an 'unreflecting' frame of mind, take it for granted. Determining factors are also noted in the experimental situation and the instructions. It is suggested that previous studies fail to take adequate notice of these factors, and so give partial accounts.

A number of studies have led to the generalization that there is a tendency to “overconstancy” in the perception of size. The experiments reported here suggest that over-estimation is limited to objects subtending angles of approximately 2° or less, and that objects subtending greater angles are judged fairly accurately. This raises the possibility that foveal diameter (approximately 2°) is involved.

Michotte's account of his experiments on the perception of causality is incomplete and imprecise. There is considerable evidence, however, that subjective variables were very poorly controlled. It follows that little reliance can be placed on his conclusions.

The Associationists state that our everyday impressions of size are a product of past experience. The Gestalt psychologists state that they are immediately or directly given in present experience. The experiment described here suggests that both past and present experience are simultaneously involved, and that a synthesis of the two accounts is required.