Colour appearance and compensation in the near periphery

Abstract

The spectral sensitivity of the visual system varies markedly between the fovea and surrounding periphery owing in part to the rapid fall in macular pigment density with eccentricity. We examined how colour appearance changes between the fovea and near periphery (8°) by measuring achromatic loci and the loci of unique and binary hues. Chosen colours remained much more similar at the two locations than predicted by the change in spectral sensitivity. Compensation for white may reflect long-term gain changes within the cones that equate sensitivity for the local average stimulus in the fovea and periphery. However, adjusting only to the average stimulus cannot correct for all of the effects of a spectral sensitivity change, and predicts differences in colour percepts between the fovea and periphery that were not observed. The similarities in hue percepts at 0 and 8° thus suggest that additional processes help compensate colour appearance to maintain constancy in the near periphery. We model the results of previous studies to show that similar adjustments are implied by age-related changes in lens pigment, and to show that these adjustments are consistent with previous measurements of peripheral colour appearance based on hue cancellation.

Systematic biases in adult color perception persist despite lifelong information sufficient to calibrate them

“…However, perceptual biases are clearly larger than predicted if perception were best calibrated through lifelong learning. Observed bias is also clearly smaller than predicted from bare normalization to white without further recalibration, confirming the findings of a previous study (Webster et al, 2010). There are two perspectives to take for our observed data being halfway between ''no learning'' and ''achievable learning'': emphasizing the ''half-full'' or emphasizing the ''half-empty.''…”

“…The results of the present work departs from those reported in Webster et al (2010), despite the large similarities between the two studies. Webster et al measured perceptual matches to unique and binary hues between central and 88 eccentricity and report no significant deviation from perfect constancy.…”

“…Perceptual nonhomogeneities have been consistently reported for far periphery (.158), but they are more controversial at smaller eccentricities (Parry et al, 2006;Webster, Halen, Meyers, Winkler, & Werner, 2010). Furthermore, spectra generated with computer monitors or monochromatic lights are quite different to spectra reflected from real objects under natural illumination (see Figure 1), and the visual system may have learned to compensate for natural (usually broadband spectra), but not artificial (possibly more narrow band spectra) stimuli.…”

“…The fact that observed distortions are systematically smaller than predicted from normalization to the average stimulation has traditionally been interpreted as evidence for compensatory calibration and taken to support lifelong plasticity (e.g., Webster et al, 2010). This viewpoint, depicted by the red dashed line in Figure 5B, implicitly takes the ''no-learning'' case, depicted by the black line, as the important point of comparison.…”

Macular Pigment: Its Associations with Color Discrimination and Matching

“…Since the MP absorption spectrum ranges from about 400 to 520 nm and peaks at 460 nm 21 , it would seem likely that these pigments influence color vision through selective absorption of short wavelengths, thereby influencing the shortwave sensitive (SWS) cones and the blue-yellow opponent-color channel. However, changes in spectral sensitivity across the fovea, macula and paramacula are accompanied by relatively little change in color appearance, depending on whether corrections are made for macular pigment absorption 27,28 .…”