Visual interactions with luminance and chromatic stimuli

Abstract

The visibility of a 1 degree, 200-msec flash on a large yellow field was measured as a function of the intensity of a coincident pedestal flash (a flash that was the same in both temporal intervals of a two-alternative forced-choice trial). The various flashes were incremental (+Lum) or decremental (-Lum) yellow luminance flashes or green (+Chr) or red (-Chr) isoluminant chromatic flashes. With uncrossed conditions (Lum tests on Lum pedestals or Chr tests on Chr pedestals), we obtained the conventional dipper function, that is, the function of threshold test intensity was highly asymmetric about zero pedestal intensity, and strong pedestals induced strong masking. Crossed conditions produced neither effect: for example, with Chr tests on Lum pedestals, there was no dipper function: the function of threshold test intensity was symmetric about zero pedestal intensity, and strong pedestals produced no masking. Instead, the suprathreshold luminance pedestals facilitated chromatic detection by as much as 2-3X and also linearized the chromatic psychometric function, further enhancing sensitivity to weak chromatic stimuli. (Chromatic sensitivity on the suprathreshold luminance pedestal was approximately 25X higher than luminance sensitivity on the uniform field.) A pedestal consisting of a thin luminance ring that surrounded the chromatic test produced facilitation equal to that of the uniform-luminance pedestal: the pedestal may thus act to demarcate the test spatially and promote chromatic comparison with the surround. Removing the uniform yellow surround eliminated this crossed facilitation but did not eliminate the uncrossed facilitation (the dipper function), suggesting that different mechanisms mediate the crossed and uncrossed facilitations.

Contributions of human long‐wave and middle‐wave cones to motion detection.

“…Thus the grating can be detected with high probability (by RG) before a significant motion response is generated (by SPO). Cole et al (1990) also obtained an exponent of -2 for detection of a chromatic flash. The exponent for motion of this chromatic pattern is considerably higher than for detection.…”

The effect of notched noise on flicker detection and discrimination

“…It has been used extensively in the spatial domain to investigate the response characteristics of channels or mechanisms that are differentially sensitive to spatial frequency and orientation (e.g., Bird, Henning, & Wichmann, 2002;Henning & Wichmann, 2007;Nachmias & Sansbury, 1974;Wichmann, 1999;Yang & Makous, 1995). But it has also been used to investigate the properties of, for example, color and luminance mechanisms (e.g., Chen, Foley, & Brainard, 2000;Cole, Stromeyer, & Kronauer, 1990;Mullen & Losada, 1994;Switkes, Bradley, & De Valois, 1988); and ON-and OFF-channels (e.g., Bowen, 1995). The effect has also been reported with flickering or drifting gratings (e.g., Anderson & Vingrys, 2001;Boynton & Foley, 1999;Stromeyer, Kronauer, & Madsen, 1984) and with uniform flickering targets (Anderson & Vingrys, 2000;Stockman & MacLeod, 1985).…”

Informational primacy of visual dimensions: Specialized roles for luminance and chromaticity in figure-ground perception

“…Empirical evidence in support of the primacy of luminance comes from studies showing impaired perception of figural boundaries at isoluminance, whether contours are real (Eskew & Boynton, 1987) or illusory (Livingstone & Hubel, 1987, 1988. Furthermore, chromatic discrimination is disrupted at isoluminance (Boynton, Hayhoe, & MacLeod, 1977) and enhanced by luminance pedestals (Cole, Stromeyer, & Kronauer, 1990), findings that suggest that chromatic processing is perceptually dependent on discontinuities in luminance. Cavanagh (1985Cavanagh ( , 1987, among others (McIlhagga & Mullen, 1996;Ramachandran, 1992;Ware & Cowan, 1983), has been critical of Gregory's (1977Gregory's ( , 1979 position, arguing instead that two-dimensional figure-ground perception is accomplished as easily by color or textural differences as by luminance differences.…”