Abstract
Peripheral vision (20–40° eccentricity) has been characterized as categorically different from foveal, in color and spatial/temporal resolution. Extreme-periphery (40° up) has been neglected, although this is subject to greatest ambiguity, thus the most heavily modulated by attention, inference, and signals from the fovea. We conducted a series of psychophysics, to test our “compensation hypothesis” which proposes that the brain compensates for the sparse, ambiguous visual input in the extreme-periphery, by utilizing inferences from sources such as unambiguous signals from the fovea. Here we examine if the color in fovea affects color perception in the extreme-periphery. Methods: In Experiment 1, each trial consisted of a sequence of three 50 ms flashes of light (500 ms SOA), two pre-target flashes at fixation, followed by a target flash at one of the 4 locations (left/right × near-/extreme-periphery). Near = 39° and far = 70–90°, set by observer’s 50% threshold for flash detection. Initial flashes could be white/red/green, while target could be red/green (perceptually equalized brightness). Observers rated the target’s color on a 7-point scale from Clearly Red to Clearly Green. Experiment 2 was identical, except the second flash was presented at a location halfway between the fixation and target, and SOAs were reduced to 100ms, producing apparent motion. Results: Observers reported the target’s color correctly at 39°, regardless of the pre-target color. In the extreme-periphery, however, the perception of target’s color was affected by the fixation’s color, and vivid illusory color was sometimes perceived (e.g. green target reported as clearly red when preceding flashes were red). Such effects were enhanced in Experiment 2, where the target was bound to the other flashes by apparent motion. Ambiguous chromatic signals in the extreme-periphery may be compensated (even if erroneously) by unambiguous color input to the fovea.
Acknowledgement: Yamaha Motor Corporation U.S.A.