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Jan Skerswetat, Monika Formankiewicz, Sarah Waugh; Contrast-modulated stimuli in competition with luminance-modulated stimuli under binocular rivalry conditions. Journal of Vision 2016;16(12):1208. doi: 10.1167/16.12.1208.
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© 2017 Association for Research in Vision and Ophthalmology.
Binocular rivalry demonstrates perceptual competition, when dissimilar stimuli are presented separately to each eye. Results of previous investigations on rivalry suggest that luminance-modulated noise (LM) and contrast-modulated noise (CM) stimuli engage different processing sites because of the different proportions of visual exclusivity reported (Skerswetat et al. VSS 2014, ECVP 2015). We presented an LM grating to one eye and an orthogonal CM grating to the other, to investigate how these are perceived when competing under binocular rivalry conditions. Stimulus size was 2 deg, the spatial frequency was 2 c/deg. Sine-wave gratings were constructed from correlated binary noise with a contrast-amplitude of 0.20. The modulation of the CM-grating was fixed at 1.00 (visibility level of ~7x). LM-grating contrast varied from 0.04 to 0.78 (visibility levels of ~2x to 44x). A trial lasted at least 120 seconds. Each CM/LM condition was carried out 8 times. Ten participants indicated via response box button presses the following perceptual states: exclusively visible, completely superimposed, or piecemeal. When the two stimuli were of similar visibility (~5-7x), the CM stimulus was exclusively visible for 45% of trial time whereas the LM stimulus, for only 7%. An increase in LM visibility, resulted in an increase in visual exclusivity of the LM grating from 2 to 18%, and a reduction of the CM-grating from 78% to 21%; the mean dominance duration for the LM grating increased from 0.9 to 1.3 sec, and reduced for the CM grating from 24 to 1.3 sec. For both visual exclusivity and mean dominance duration, the interaction between stimulus type and LM visibility was significant [p< 0.05]. The results have shown that inter-ocular stimulus strength (Levelt, 1965), does not necessarily drive perceptual predominance during binocular rivalry, but that stimulus type and processing site also need to be considered.
Meeting abstract presented at VSS 2016
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