Some problems of sensory integration / by Henry J. Watt.

  • Henry J. Watt
Date:
1910
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Licence: In copyright

Credit: Some problems of sensory integration / by Henry J. Watt. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    uniocularly when the eye or the objects of regard are in motion, is no serious objection to this view, because it is well known that very many animals notice well defined near objects when these are motionless, important or dangerous though they be, just as little as we notice motionless objects situated in the periphery of our uniocular field of vision. Binocular stereoscopic vision would then be an adaptation of vision to the demands of a life of comparative or frequent bodily repose. The life of a beast of prey would also seem to bring many moments which demand long-continued observation of objects towards which it must turn its head with little or no progressive or regressive motion. Herbivorous animals and birds on the other hand, however swiftly they may move, seldom need to observe near objects in front of the head for any length of time, and are more dependent upon a wide field of vision for secure motion and feeding. Simultaneous use of both fields of vision would therefore seem to be necessary if motionless depth is to be obtained. Binocular depth-vision might, accordingly, be called static in distinction to uniocular or progressive depth-vision. Comparative study of the vision of animals lead Harris to recognize the influence of the carnivorous habit upon the position of the eyes. “ Binocular vision is originally associated with carnivorous habits, and is found to a moderate degree amongst carnivorous fishes in a few of the sharks and rays, in some amphibia, as the toad, which lives on flies and insects and in many carnivorous birds, especially the larger gulls some penguins, hawks, owls and vultures. Amongst mammals binocular vision is especially developed in the carnivora and in the primates1.” Many animals besides the chameleon2, may make a momentary convergent movement of the eyes at the moment of striking their prey, especially if their mode of pursuit happens to be that of rapid flight or chase, without long fixation or combat. “ Though many of these animals have fair binocular vision, yet in all vertebrates below mammals there is total decussation of the optic nerves at the chiasma3.” It is obvious then, that if the presence of total decussation is no barrier to the occurrence of static stereoscopic vision in the chameleon and owl, it can also be no argument against the presence of progressive stereoscopic vision in the birds and in all animals with fixed or laterally projecting Lageverhaltnissen der Netzhautprojectionen. (Diese) stehen in eindeutiger und ganz gesetzmassiger Beziehung zur Tiefendimension und werden wahrscheinlich vom Gesichts- sinne als Hilfsmittel zur Gewinnung einer monocularen Tiefenwahrnehmung verwandt.” Cf. also the same author, Philos. Studien, xi. 1895, p. 188. 1 loc. cit. p. 108. 3 loc. cit. p. 108. 2 loc. cit. pp. 113, 114.