Varying luminance of distracters in alignment task A Bielevicius, A Bertulis, A Bulatov |
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Institute of Biological Systems and Genetics, Lithuanian University of Health Sciences, Lithuania
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| The magnitude of misalignment was measured in psychophysical experiments with the horizontal three-spot stimulus (the interval distance, 30 min-of-arc) and three distracter-spots situated one at a time below the medial and above both lateral stimulus terminators at the distances: 0.75, 1.5, 2.25, 3, or 3.75 min-of-arc. The terminator and background luminance was fixed at 75 and 15 cd/m2, respectively, and the distracter luminance varied from 3 to 31 cd/m2. The subjects adjusted the middle stimulus spot (together with the flanking spot) into a position which made all three terminators to be aligned perceptually. The error magnitude varied in dependence on the terminator-distracter distance and luminance difference, like in the previous experiments [Bielevicius et al, 2007, Perception, 36 ECVP Supplement, 38]. However, the maximum values of two misalignment types were found at different terminator-distracter distances: those of the attraction effect produced by the bright distracters were observed within the 1.5-3 min-of-arc distance range, and the maxima of the repulsion induced by the dark distracters were registered at the 0.75-1.5 min-of-arc distances. The results might be interpreted in terms of functional properties of the retinal ON and OFF receptive fields [E.J.Chichilnicky and R.S.Kalmar, 2002, The Journal of Neuroscience, 22(7)]. |
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