Poster Session: Increasing the luminance of primary colors increases the perception of warmth.

There is a long history of linking the perceptions of temperature and color: red (R) and yellow (Y) are considered warm, whereas blue (B) and green (G) are relatively cool. Past studies, however, have not varied the intensity of those colors to determine how the perception of temperature is influenced. To test this, we used four colored lights that were varied over five intensity levels. 20 young healthy subjects with normal color vision were tested. An optical system with a Xenon-arc light source, interference filters (peak l = 470, 516, 572, 652 nm), and a circular neutral density wedge to vary intensity were used. Temperature perception was assessed using an ordinal scale from - 5 (coolest) to +5 (warmest). The order of the colors used and the intensity levels were varied randomly. Considering the average across power levels, B (-1.87) and Y (+1.09) were considered the coolest, whereas G (+2.1) and R (+3.75) were considered the warmest colors. All colors, however, warmed with increasing intensity. A linear regression fit to the averaged data across luminance explained the majority of the variance: B (r2 = 0.78), Y (r2 = 0.93), G (r2 = 0.98) and R (r2 = 0.92). For example, the average rating for B went from -2.3 at the lowest intensity to -1.6 at the highest intensity. Like others, our data show that color is significantly (p<0.001) linked with temperature perception. Increasing the luminance of colors, however, consistently skews the perception toward increased warmth.