senescent changes in color discrimination -To the interface design for elderly users-

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In this research, senescent changes in color discrimination on human observers were investigated with psychophysical method. Thresholds in wavelength discrimination increased with age. This increment was statistically significant. This indicates that even the illuminance on the retina is constant by individual adjustment of luminance, ability of color discrimination reduces with age. This measurement is also performed in United States to figure out the effect of different races like difference of the color of pupil, but there is no actual difference between races.Experimental results were analyzed by color discrimination model. The analysis shows that sensitivities reduce with age not only on chromatic discrimination mediated by yellow-blue chromatic opponent mechanism (S-cones), as already known, but also on chromatic discrimination mediated by red-green chromatic opponent mechanism (L- and M-cones). Increment of noise ratio against signal causes the relatively-large reduction of sens … More itivity on chromatic discrimination mediated by S-cone but this noise increment itself is little on chromatic discrimination mediated by L- and M-cones. Age-related change in discrimination mediated by S-cone can be described by the change of a noise parameter in the model. However, in order to describe the age-related change in discrimination mediated by L- and M-cones, it is required that not only the noise parameters, but also two parameters ; ratio of L- and M-cones on the retina and signal ratio between red-green chromatic opponent channel and luminance channel. Thus, it is difficult to predict the change of sensitivity with age because these two parameters are different between observers but regardless of age.Color appearance is relatively stable with age even the ocular media density increases because of signal amplification. However, as the result of signal amplification, biological noise like self-firing is also amplified and causes the increment of signal/noise ration. Thus, in the case that chromatic signal is relatively small, sensitivity of chromatic discrimination decreases with age even the retinal illuminance is adjusted to the constant. It causes the problem that elderly people loose the ability of color discrimination with almost no subjective symptom. To the interface design for elderly users, it is better to avoid the color coordination which require the color discrimination around white because of small chromatic signals. Instead, we should use the color coordination which make the chromatic signal used for discrimination, like red, green, yellow and blue, would be enough strong. Less