Differential sensitivity in olfaction.

Abstract

Differential sensitivity in olfaction was measured by means of a modification of the blast injection technic. By introducing controls over the temp., pressure, and volume of the stimulus, and by using an odorous compound with a calculable vapor pressure (phenylethyl alcohol), it was possible to express the stimulus intensity in terms of the number of odorous molecules rather than the less direct measures variously used in the past. Four subjects were tested for discrimination of amt. of odor. In addition, 1 subject was tested in a control series in which amt. of pressure was to be discriminated, the odorous material being removed. The results showed that, on the avg., the. stimulus intensity had to be varied by 15% to make the variation detectable 84% of the time. This degree of sensitivity is considerably lower than any previously reported. The results showed further a number of significant fluctuations in sensitivity of individual subjects from day to day. The distributions of judgments obtained under the 2 conditions of odor-plus-pressure and of pressure alone did not differ significantly, suggesting, but not establishing conclusively, that the subject was responding to pressure rather than odor in the first condition. Several reasons are offered as to why this interpretation is not considered likely but caution is advised in applying the blast injn. technic.