Abstract
It has previously been shown that differences in environmental adaptation can alter our perception of colour. For instance, colour discrimination differences have been found for individuals born above and below the Arctic circle (Laeng et al., 2007), and shifts in unique yellow settings have been recorded for individuals adapted to an altered chromatic environment using tinted contact lenses (Neitz, Carroll, Yamauchi, Neitz, & Williams, 2002). In York (UK) the colours of the natural environment change between winter and summer – predominately because the prevalence of green vegetation increases. We investigated whether changes in the chromatic environment between seasons are great enough to impact on specific unique hue settings, by means of adaptation. Sixty-six subjects were tested in two seasons of the year (winter and summer) on a number of measures, including monochromatic wavelength settings of unique green and unique yellow. Spectral measurements of the mean environment taken at fixed locations were also obtained for each season using a spatially integrating photospectrometer. It was found that measurements of unique yellow shifted to shorter wavelengths in summer compared to winter, whereas we found no significant difference in unique green settings. Neitz et al (2002) argued that the shift they found in unique yellow settings following adaptation to tinted lenses demonstrates that colour vision is mediated by a plastic normalisation process; it may be possible that several months of exposure to an altered seasonal environment is enough to induce a comparable shift in unique yellow settings as was produced by the tinted lenses.