Color affects perceived odor intensity

In Experiment 1, some odorous solutions (e.g., strawberry) were rated as smelling stronger when colored (e.g., red) than when colorless. Experiment 2 showed this effect to be due to a perceptual change rather than a response to experimental demand characteristics. Experiment 3 showed that the color-induced increase in odor intensity is not due to subjects' preexperimental experience with particular color-odor combinations, because the increase occurred with novel ones. We conclude that color induces a weak olfactory percept that combines with odorant-induced percepts. The effect may be due to conditioning or may be the result of residual intersensory neural connections left over from infancy.