Fundamentally different representations of color and motion revealed by individual differences in perceptual scaling.

The coordinate frames for color and motion are often defined by three dimensions (e.g., responses from the three types of human cone photoreceptors for color and the three dimensions of space for motion).

Comparison of two methods of hue scaling.

Hue-scaling functions are designed to characterize color appearance by assessing the relative strength of the red versus green and blue versus yellow opponent sensations comprising different hues. However, these judgments can be non-intuitive and may pose difficulties for measurement and analysis. We explored an alternative scaling method based on positioning a dial to represent the relative similarity or distance of each hue from the labeled positions for the opponent categories.

Variations in normal color vision. VII. Relationships between color naming and hue scaling.

A longstanding and unresolved question is how observers construct a discrete set of color categories to partition and label the continuous variations in light spectra, and how these categories might reflect the neural representation of color. We explored the properties of color naming and its relationship to color appearance by analyzing individual differences in color-naming and hue-scaling patterns, using factor analysis of individual differences to identify separate and shared processes underlying hue naming (labeling) and hue scaling (color appearance). Observers labeled the hues of 36 stimuli spanning different angles in cone-opponent space, using a set of eight terms corresponding to primary (red, green, blue, yellow) or binary (orange, purple, blue-green, yellow-green) hues.

Variations in normal color vision. VI. Factors underlying individual differences in hue scaling and their implications for models of color appearance.

Observers with normal color vision vary widely in their judgments of color appearance, such as the specific spectral stimuli they perceive as pure or unique hues. We examined the basis of these individual differences by using factor analysis to examine the variations in hue-scaling functions from both new and previously published data. Observers reported the perceived proportion of red, green, blue or yellow in chromatic stimuli sampling angles at fixed intervals within the LM and S cone-opponent plane.

Binocular vs. monocular hue perception.

Hue perception has been shown to differ for the same stimulus when presented to the temporal and the nasal areas of the retina. The present study investigated perceptual differences in stimuli viewed binocularly or monocularly in the peripheral retina to determine how hue information combines across the two retinas for a stimulus falling on the temporal retina of one eye and the nasal retina of the other. A hue-scaling procedure was utilized to ascertain hue perception for three color- and binocular-normal observers viewing monochromatic stimuli (450-670nm, 20nm steps) ranging in size from 1.

Small field tritanopia in the peripheral retina.

If stimuli are made sufficiently small, color-normal individuals report a loss in hue perception, in particular a decrease in the perception of green, in both the fovea and peripheral retina. This effect is referred to as small field tritanopia. It is not clear, however, how rod input may alter the dynamics of small field tritanopia in the peripheral retina.

Supersaturation in the peripheral retina.

Foveal and peripheral hue-scaling data were obtained for a 1° foveal stimulus and a 3° stimulus presented at 10° retinal eccentricity under both bleach (reducing rod input) and no-bleach (permitting rod input) conditions. Uniform appearance diagrams (UADs) were generated from the data. Peripheral stimuli appeared more saturated than foveal stimuli (i.

Color appearance at ±10° along the vertical and horizontal meridians.

Hue-scaling data were collected from three observers using the "4+1" color-naming procedure for circular (0.25°-5°), monochromatic (440-660 nm) stimuli. Stimuli were presented at ±10° along the vertical and horizontal meridians under conditions chosen to include both rod and cone signals (no bleach) and to minimize rod contribution (bleach).

Middle- and long-wavelength discrimination declines with rod photopigment regeneration.

Hue-discrimination functions were derived from hue-naming data (480-620 nm, 20 nm steps) obtained in 4 min intervals from 4 min to 28 min postbleach at 10° temporal retinal eccentricity. Hue-naming data were also obtained in the fovea. Hue-discrimination functions derived at the 4, 8, and 12 min intervals were very similar to those derived in the fovea.

Unique hue loci differ with methodology.

Background: Studies investigating the effect of rods on unique hue loci in the peripheral retina generally obtain measures at two time points associated with the dark adaptation function - the cone plateau and the rod plateau. In comparison, this study used a color-naming procedure to identify the loci of unique green and unique yellow as a function of time associated with the entire dark adaptation function. The unique hue loci derived by this procedure were then compared to those obtained directly with a staircase procedure.

Scotopic spatiotemporal sensitivity differences between young and old adults.

Background: Our lab has previously demonstrated losses in contrast sensitivity to low spatial frequencies under scotopic conditions with older adults. It is not clear, however, whether the temporal frequency of a stimulus alters the relation between age and the spatial contrast sensitivity function (sCSF) under scotopic conditions.

Methods: A maximum-likelihood, two-alternative, temporal forced-choice QUEST procedure was used to measure threshold to spatially and temporally modulated stimuli in both young (mean = 26 years) and old (mean = 75 years) adults.

Chromatic perceptive field sizes measured at 10 degrees eccentricity along the horizontal and vertical meridians.

The different hemifields in the retina are known to vary in photoreceptor density as well as in the number of photoreceptors converging onto one ganglion cell. The effect of these differences among the retinal hemifields at 10 degrees retinal eccentricity was investigated using a color-naming procedure to derive perceptive field sizes for the hue terms of blue, green, yellow, and red. Color-naming data were obtained under two conditions: (1) after a bleach condition, chosen to minimize rod contribution, and (2) after 30 min dark adaptation, chosen to maximize rod contribution.

Effect of stimulus intensity on the sizes of chromatic perceptive fields.

The effects of intensity on chromatic perceptive field size were investigated along the horizontal meridian at 10 degrees temporal eccentricity by manipulating stimulus intensity from 0.3 to 3.3 log trolands.

Chromatic perceptive field sizes change with retinal illuminance.

The effect of retinal illuminance (0.3-3.3 log td) on chromatic perceptive field size was investigated at 10 degrees eccentricity along the horizontal meridian of the temporal retina.

A new look at the Bezold-Brücke hue shift in the peripheral retina.

Experiments were conducted with a bipartite field to better understand the Bezold-Brücke hue shift in the peripheral retina. The first experiment measured hue shift in the fovea and at 1 degrees and 8 degrees along the horizontal meridian of the nasal retina for nominal test wavelengths of 430, 450, 490, 520 and 610 nm. Peripheral measurements were obtained under two adaptation conditions: after 30 min dark adaptation and following a rod-bleach.

Ricco's Areas for S- and L-Cone Mechanisms Across the Retina.

The purposes of this study were to measure areas of complete spatial summation (i.e., Ricco's area) for S- and L-cone mechanisms and to evaluate whether the sizes of Ricco's area could be explained in terms of either the densities of photoreceptors or ganglion cells.