The groundwork of psychology / by G.F. Stout.

  • George Frederick Stout
Date:
1903
Catalogue details

Licence: In copyright

Credit: The groundwork of psychology / by G.F. Stout. Source: Wellcome Collection.

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    totally and partially immersed in a bath differ as regards the quantity of resulting sensation. But this difference is not merely one of intensity ; it is also one of massiveness or voluminousness. In other words, it is a difference in extensity. The nature of extensity is best illustrated by experiences which differ from the fully developed per- ception of spatial extension only in the comparative absence of spatial order. Organic sensations, such as those of hunger, thirst, repletion, fatigue, and repose after fatigue, contain at the most very rudimentary internal distinctions of direction, distance, and position. But they are felt as more or less diffused. Professor James speaks of “ the vast discomfort of a colic or a lumbago.” Pres- entations in the extreme margin of the field of view have a peculiar vagueness not differing in its nature from that of objects seen through a fog or in a bad light. This vague- ness consists in the comparative absence of a definitely discernible order of positions, distances, and directions; in particular, it is worth noticing that the field of view as a whole is shapeless at its boundary. In the case of touch, the two points of a pair of compasses separated by a quar- ter of an inch and applied to the lips yield the perception of two discriminated contacts, with a discernible position, distance, and direction relatively to each other. But when they are applied to the forehead there is no discernment of two contacts; there is merely a vaguely extensive touch- sensation without inner distinction of position, distance, and direction. We can no more account psychologically for the exten- sity of visual and tactual sensations than for their intensity and quality. Extensity is a primary datum with which we must start in treating of the development of spatial per- ception. On the other hand, the cognition of spatial
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