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

  • Watt, Henry J. (Henry Jackson), 1879-1925.
Date:
1913
Catalogue details

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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    hand, a well-known fact that orders and distances are clearer when they are regular and symmetrical. Eh—6, 2, which shews that a grey stripe is more effective in alternation with a white one than a black one is, may be supposed to involve a greater clearness of orders. For when black and white are juxtaposed, they must intensify each other by contrast, and so make irregularities of brightness of their surfaces less noticeable than they would be if the black were replaced bv grey. That is to say, grey favours the distinction of positions, or, in other words, it allows of the existence of many orders, besides that given in the contours. With E 26 we may compare what was said above about the apparent movement of squares in an oblique direction, when two sets of parallel rods move at right angles to one another. If the after- effect is correlated with the neural basis of orders, directions, and motions, there is no reason why fatigue for one direction should affect the receptivity towards another direction at right angles to the first {E 28). Wohlgemuth’s explanation of this result, on the contrary, must be said to be highly strained (vide p. 107). As regards E 21,1—4, it is a commonly accepted fact that motion is more insistent in the periphery of the field of vision, but that positions there are not so highly differentiated as in the centre of the field. We might, then, expect a more insistent after-effect of briefer duration, rapidly dis- appearing. It is difficult to see what relation 010, especially as described by Wertheimer, has to the varying intensity of pairs of movement centres. But their relation to differences of order and of time is obvious. The conclusion must, therefore, be that the after-effect is correlated with, and directly or indirectly dependent upon, the order-differences of sensation given by the objective movement which excites the after- effect. There is no fact which suggests that the after-effect is inde- pendent of this attribute of simple visual sensation. El and E 2—4 only imply that the presence of clear qualities and high intensities involves clearer sensational orders than does a darker or obscurer field. Of G 9 Wohlgemuth says: ‘‘This result is probably merely a question of fusion of two retinal fields like results Nos. [G] 6 and 7 ” (p. 103). These binocular cases do surely belong to quite a different class of integrative processes to be studied separately from uniocular cases. (d) The only other attribute which could come into question at all is that of 'position in time which represents rate of succession of stimuli.