Purchase this article with an account.
Ignacio Serrano-Pedraza, Graeme Phillipson, Jenny C. A. Read; Size of vertical disparity pooling and the induced effect. Journal of Vision 2009;9(8):280. doi: 10.1167/9.8.280.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
The fact that vertical disparities can influence perception is demonstrated in the induced effect (Ogle, 1938, Archives of Ophthalmology, 20), in which magnifying one eye's image vertically produces an illusion of slant about a vertical axis. The direction of the slant depends on the “sign” of the vertical magnification, i.e. which eye's image is made larger. Kaneko & Howard (1997, Vision Research, 37, 20) demonstrated that an illusion of a corrugated surface can be produced by alternating the sign of the magnification as a function of horizontal position across the stimulus. They found that illusory corrugations could be detected up to a maximum spatial frequency of 0.04 c/deg, and deduced that vertical disparities are averaged over about 20 deg-wide area. However, their experiments used very large, sparse dot stimuli (dotsize=2 deg), and included only 2 subjects. They also used long presentations (1 sec), in principle allowing subjects to build up a map of vertical disparity across the stimulus in successive saccades. We therefore performed experiments using short presentation times (200 ms), small dots (0.12 deg), and higher dot density, with the sign of vertical magnification alternating as a square-wave across the stimulus. The task was to discriminate the sign of the illusory slant for the central strip of the magnification grating. Despite the considerable experimental differences, our results are compatible with those of Kaneko & Howard, but reveal a wide variability between subjects. The estimated area over which vertical disparities are averaged, ranged over an order of magnitude from 3 deg to 30 deg in diameter, calling into question the conclusion of a uniformly broad spatial limitation for the area over which vertical disparities are pooled.
This PDF is available to Subscribers Only