DETECTION THRESHOLDS FOR AN OLFACTORY MIXTURE AND ITS 3 CONSTITUENT COMPOUNDS

Single sub-threshold odorants can, according to a few reports, become perceptible in concert. That is, they can exhibit mixture additivity. The present study measured thresholds for mixture of 1-butanol, 2-pent anone, and n-butyl acetate, and for each of these separately. 'Complet e' additivity resulted, in that the threshold concentration of each co mpound in the mixture (measured by gas chromatography) turned out to b e one-third of each component separately. Earlier threshold studies al so claimed complete additivity and even hyper-additivity (synergism); in this regard they, like this study, differ from the more numerous st udies of suprathreshold mixtures, which yield imperfect additivity (hy po-additivity). Mixtures not only enhance sensitivity, but they may al so promote stability; intersubject variability was smaller for the mix ture than for the components. Subjects were 20 young (18-26 years) and 20 elderly (69-91 years) persons, who gave two sets of thresholds on 2 days. Concordant with earlier findings, the elderly's thresholds ave raged higher (similar to 20 times) than the young's, but complete addi tivity nevertheless held, even though they operated over different por tions of the concentration continuum. The study affords a look at inte r-test reliability of thresholds by comparing correlations between sam e and different compounds examined on same and different days.