Abstract
The color appearance of a uniform region (test) can be altered by a surrounding periodic pattern (inducer) alternating in two colors (Monnier & Shevell, 2003, Nature Neuroscience). We investigated the properties of the mechanisms underlying the contributions of different inducer components by observing how various surrounding patterns affect color contrast discrimination in the test. The bull-eye inducer (3.3 cyc/deg along the radius) had rings alternating in two out of three colors: L-M (“red”), M-L (“green”), and neutral gray. The thirteenth ring (2-degree eccentricity) of the inducer was replaced by the uniform test. The test regions contained either a red or green target superimposed on a pedestal of the same color or the pedestal alone. The pedestal contrast varied from -46 to -26 dB. We used a temporal 2AFC and PSI adaptive staircase to measure the target threshold at a 75% proportional correct level. The observer’s task was to decide which interval contained the target. The target threshold vs. pedestal contrast (TvC) function for a red target surrounded by a nearby green ring and a distanced red ring (full inducer) showed a dipper shape with threshold decrement (facilitation) at low and increment (masking) at high pedestal contrasts. The TvC function for inducers with nearby green and a distanced gray ring shifted downward on log-log coordinates from that of the full inducer and had more pronounced facilitation. The TvC function shifted further downward and produced little masking for inducers with nearby gray and a distanced red ring and that for the uniform gray background had the lowest threshold and had only masking effects. The result for the green target mirrored the red target data. The data is best explained by a divisive inhibition model with an additive short-range and a multiplicative long-range lateral interaction.