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Benjamin Backus, Baptiste Caziot; Vertical size disparity pooling across attended color and contrast. Journal of Vision 2015;15(12):833. doi: 10.1167/15.12.833.
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© ARVO (1962-2015); The Authors (2016-present)
Modifying the interocular vertical size ratio (VSR) to be different from unity causes a frontal surface to appear slanted. This “induced effect” normally functions to correct the stereo slants of surfaces located to the side of straight ahead. VSR is pooled regionally within the visual field (Kaneko & Howard, 1997; Adams, Frisby & Buckley, 1996; Porrill et al, 1999), but details about VSR measurement remain unknown. Duke and Howard (2005, 2012) reported a refinement of pooling: VSR had separate effects within different transparent surfaces that were separated in depth by horizontal disparity. Duke and Howard interpreted their result as showing that VSR measurement occurs separately within horizontal-disparity defined surfaces. An intriguing and more general alternative, however, is that individual display elements (e.g. dots) in one surface were simply selected by attention through parallel processing, with VSR being computed across the attended (and therefore salient) display elements. If so, top-down attention to spatial locations would be acting remarkably early, and with great precision. To test this idea we constructed mixed-VSR displays in which two populations of dots had different colors (black/white, green/red, or black/dark gray) that carried different VSR signals. Observers were instructed to attend to one or the other color within blocks of 40 trials, and to indicate which side of the display appeared near. Attended colors had greater subjective salience. However, although color itself had a significant effect on sign-of-slant judgments, attended color did not. Thus, higher luminance contrast, but not attention to color, increased the contribution of a dot during the measurement of VSR. Thus, Duke and Howard’s interpretation still stands: VSR measurement occurs separately within surfaces separated by horizontal disparity.
Meeting abstract presented at VSS 2015
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