Induced steady color shifts from temporally varying surrounds

Abstract

The color appearance of a physically steady central region can appear to vary over time if a surrounding chromatic light varies in time. The induced temporal variation, however, is strongly attenuated at surround temporal frequencies above ∼3 Hz. At these higher temporal frequencies, the central region appears steady (De Valois et al., 1986). The posited explanation is a cortical low-pass temporal filter. Here, we investigate whether higher temporal-frequency surrounds induce color shifts in the steady appearance of the central test. Surrounds modulated in time along the l or s chromatic direction of MacLeod-Boynton color space were symmetric around equal-energy white (EEW). The temporal frequency of the surround was varied. If observers perceived the central test to be temporally modulating between two points in time, they set two separate matches to the extreme points of this modulation. If the central test appeared steady in time, then color matches were made to this steady appearance. Corroborating previous reports, measurements showed that surround temporal frequencies below ∼3 Hz induced temporal modulation. At higher temporal frequencies, however, the surround induced steady color shifts, compared to a steady surround at its time average (EEW). The measurements imply that a nonlinear neural process affects chromatic induction from time-varying context.