Visual perception of the third dimension

Chas. H. Judd
1898 Psychological review  
Since the time of Berkeley the most important particular problem in the general discussion of space-perception has been the explanation of the visual perception of depth. The objective conditions on which such perception of depth depends may be isolated more easily than the conditions for any other form of space-perception. As a result, the analysis of the subjective phenomena is here very much easier than in other cases. The conclusions reached in regard to this particular form of perception
more » ... orm of perception are, however, applicable to the more general problem ; for the visual perception of depth must be regarded as similar in kind to all other forms of space-perception. When the particular case is taken up for discussion, then, as it is to be in the present paper, the aim must be to reach general conclusions which shall bring the whole problem nearer to a final solution. And it will be possible in the course of such a discussion to test in this particular sphere some of the general theories that have been advanced. First of all, then, let us raise the question, Does the presence of a third dimension in ordinary binocular and monocular fields of vision justify the doctrine that the sensation factors, which are the elements of the completed percepts, have an original attribute of extension, analogous to quality and intensity but differing from these ? This doctrine has been advanced by a number of recent writers, and it'must be granted that it seems a simple and direct hypothesis. It is true that we never observe a sensation except as part of a percept, and every visual percept has its projection into the third dimension. It follows from this that we can never observe visual sensations apart from some spacial relation. But while granting this, it is not necessary to conclude further that these spacial attributes are attributes of the sensa-388
doi:10.1037/h0074682 fatcat:lezwzluzrbbzdjf3c5q3664fne