Color naming, lens aging, and grue: what the optics of the aging eye can teach us about color language

Abstract

Many languages without separate terms for green and blue are or were spoken in locations receiving above-average exposure to ultraviolet-B (UV-B) radiation. It has been proposed that this correlation is caused by premature lens aging. This conclusion was supported by an experiment in which younger observers used the term "blue" less often when they described simulated paint chips filtered through the equivalent of an older observer's lens-removing much short-wavelength light-than when they described the unfiltered versions of the same paint chips. Some stimuli that were called "blue" without simulated aging were called "green" when filtered. However, in the experiment reported here, we found that the proportion of "blue" color-name responses did not differ between younger subjects and older observers with known ocular media optical densities. Color naming for stimuli that were nominally green, blue-green, or blue was virtually identical for older and younger observers who viewed the same (unfiltered) stimuli. Our results are inconsistent with the lens-brunescence hypothesis.

Fig. 1

Scotopic sensitivity functions (upper panels) and corresponding estimated ocular media optical densities (bottom panels) for a 27-year-old observer (left) and a 73-year-old observer (right). In the upper panels, the solid curves are the scotopic sensitivity function (V′_λ) for the Commission Internationale de l'Eclairage (CIE) standard observer; the dashed curves are scotopic sensitivity functions for the 27-year-old and 73-year-old adjusted for their ocular media optical densities using the model of Pokorny, Smith, and Lutze (1987).

Fig. 2

Experimental results: modal color names for the 40 Value-6 Munsell hues used in the World Color Survey. The color in each box corresponds to the color name given to that stimulus most often. The dark-colored boxes reflect a minimum of 80% agreement among the observers' responses, and the light-colored boxes reflect less than 80% agreement. The letters across the top correspond to the nominal colors of the simulated Munsell chips (R = red, Y = yellow, G = green, B = blue, P = purple). Rows A and B illustrate modal responses in the standard stimulus condition, for the older and younger groups, respectively. Row C shows modal responses from the older group in the simulated-youthening condition. Row D shows modal responses from the younger group in the simulated-aging condition.

Fig. 3

Proportion of “green” and “blue” responses as a function of Munsell hue stimulus. Gray and black curves and symbols denote “green” and “blue” responses, respectively. The upper panel plots data from the standard stimulus conditions for older and younger observers. The lower panel plots data from older observers in the standard stimulus condition (same as upper panel) and younger subjects in the simulated-aging condition. Letters across the bottom correspond to the nominal colors of the simulated Munsell chips (G = green, Y = yellow, B = blue, P = purple).

Fig. 4

Proportion of trials on which each observer used the color name “blue” as a function of ocular media optical density (OD) at 400 nm.