Page:Mind (Old Series) Volume 11.djvu/540

 THE PERCEPTION OF SPACE BY DISPARATE SENSES. By JOSEPH JASTROW, Psychophysical Laboratory, Johns Hopkins University, Baltimore. Introductory. In the philosophic doctrine of " common sensibles " the KOIVU niaQipa of Aristotle the general problem of the relation of space- conceptions to the senses which furnish them receives its first notice. Hobbes regards motion, rest, size and shape as notions common to sight and touch. Locke names as a distinct class of simple ideas those which owe their origin to two senses ; thus space, extension, figure and motion are made common to sight and touch. Either sense gives an adequate idea of space ; and the two ideas are in perfect agreement. Berkeley, 1 however, held that these two notions of space were distinct and hetero- geneous ; that they were regarded as one because they were constantly joined in experience. By a proposal of Molyneux the discussion was brought to an issue by testing the space- ideas of persons born blind and restored to sight by a sur- gical operation. Such persons are unable to identify the object now seen with the object formerly touched until this identification has been slowly learnt by experience. In this pro- cess touch is the teacher and sight the scholar. 2 Mr. T. K. Abbott 3 opposes Berkeley and regards each sense as having its own space-idea, which is little influenced by association with another. Prof. Stumpf 4 ascribes some space-relations to each of the five senses, and regards the resulting conception as essentially innate and single. A more recent writer, Dr. E. Montgomery, 5 supposes an organically evolved pre-established harmony between the several space-senses. He assumes a central organ which gives sensations their spacial value, and puts the matrix of tactile space in the optic thalami, of the knowledge of the position of our body in the cerebellum, of visual space in the corpora quadrigernina. 1 " It is a mistake to suppose that we see and feel the same object." 2 One patient did not realise the impressions of his new sense until " he perceived the sensations of what he saw in the points of his fingers as if he really touched the objects ". Another was quite confused by not being able to combine sight and touch. " I cannot tell what I do see." " I am quite stupid." 3 Sight and Touch, London, 1867. 4 Ueber den psychologischen Ursprung der Raumvorstellung, Leipzig, 1873. " Space and Touch," in MIND 38, 39, 40.