Olfaction and the common chemical sense: some psychophysical contrasts.

Three experiments explored the olfactory and the common chemical attributes of sensations produced by various concentrations of n-butyl alcohol. These two attributes combine in an almost-linear fashion to produce the overall perceived intensity of the stimulus. Common chemical intensity makes only a small contribution to overall magnitude at low concentrations, but its proportional contribution increases with concentration. In like manner, speed of response (i.e., reciprocal of reaction time) to the common chemical attribute increases more rapidly than that to odor. Nevertheless, odor always makes its appearance sooner than the common chemical attribute, even when the two attributes are matched in perceived magnitude. Repeated inhalations cause odor intensity to decrease slightly but cause common chemical intensity to increase dramatically. The results obtained from the normal subjects studied here agree with those obtained from subjects with unilateral destruction of the trigeminal nerve.