The psychology of visual motion / by Henry J. Watt.

  • Henry J. Watt
Date:
1913
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Licence: In copyright

Credit: The psychology of visual motion / 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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    unitary quality of continuity, namely “ ein Hindurchgehen durcli die zwischenliegenden Raume1.” But can motion really be treated in this way ? Is it not rather the case that motion has a direction of its own, which may coincide with, or be opposed to, some other direction of which we are conscious apart from any motion ? Is not also the velocity of a motion a characteristic of its own? Are not the motion, the direction, and the velocity, of motion—whether it correspond to a real motion or be pure motion in the sense of the after-effect—the essential aspects of this experience, its vividness being necessary in some degree, but as such relatively unimp rtant ? The vividness of the experience may be to some extent interchangeable with its velocity, in so far as an increase in velocity is accompanied by an increase in vividness; but surely it would be contrary to experience to allow this vividness to usurp the place of the velocity of the motion itself, not to speak of its direction. And if motion presents a continuity that is not given in, or derivable from, the data of our space and time Anschauungen, should we not expect to find an explanation of this continuity included in the physiological theory of motion ? But it is evident that this continuity is taken for granted in the theory as stated. It seems then that the theory in question offers an explanation really only of the vividness of the experience; and if against this must be written the arbitrary assumption which I have stated under (a), the balance leaves nothing to the credit of the theory. We must discover first of all what is the neural basis of pure motion, its direction, and its velocity; it will hardly be very difficult thereafter to find a basis for its vividness. On page 19 Wohlgemuth says that Borschke and Hescheles admit that, as seen, the movement of two sets of straight rods at right angles to one another “ can only be regarded as squares, moving in an oblique direction.” This movement can, of course, be described as one pleases; but if it is felt as the movement of squares in an oblique direction, that must be due to psychical, or shall we say, central, reasons; for it is essentially the Gestalt of the square which determines the apparent movement. If a point on one of the rods were marked out by colour or shape, we should at once in so far be free from this apparent oblique motion of the squares2. In connexion with this the 1 Cf. Ebbinghaus, as quoted by Wohlgemuth, op. cit., p. 108. 2 Cf. Pleikart Stumpf, “Ueber die Abhangigkeit der visuellen Bewegungsempfindung und ihres negativen Nachbildes von den Reizvorgangen auf der Netzhaut.” Ztschr.f.