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Charles C.-F. Or, Sieu K. Khuu, Anthony Hayes; The effect of contrast variations on the perception of Glass patterns. Journal of Vision 2006;6(6):583. doi: 10.1167/6.6.583.
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The perception of global structure of a static concentric Glass pattern is difficult, but not impossible, when its dot-pairs are of opposite polarity (see, e.g., Badcock, Clifford, & Khuu, 2005). We investigated whether the addition of motion signals enhance extraction of local orientation from opposite-polarity dot-pairs. The stimuli were random-dot patterns (radius: 14 deg visual arc) consisting of 200 dot-pairs (dot width: 5 min; length of pair: 20 min) orientated along circular trajectories, or at random orientations, on a background at 45.5 cd m−2 luminance. For each dot-pair, one dot was always light increment (90.9 cd m−2), and the other was varied over conditions in the range between 0.0718 cd m−2 and 90.9 cd m−2 (i.e., Weber contrast from approx. −1 to 1). The dot pairs were either stationary (static condition), or randomly re-positioned at a rate of 17 Hz (dynamic condition) in a 1.06 s stimulus presentation. The observer's task was to identify the interval containing the circular structure in a temporal two-interval forced-choice procedure. The detection threshold for each contrast difference within the dot-pair was determined by an adaptive staircase. The results showed that perception of global structure is more salient with dynamic than with static Glass patterns regardless of variations in contrast, and for dynamic presentations salience improvement was greater for opposite-polarity than for same-polarity patterns. These findings suggest that motion processing mechanisms are more capable than form processing mechanisms in tolerating contrast differences for the perception of global structure.
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