Individual differences in the perceived intensity and quality of specific odors following self- and cross-adaptation

Adaptation techniques have traditionally been employed in sensory physiology and psychology to characterize afferent pathways and to dissect the quantitative and, to a lesser degree, the qualitative aspects of perception. We continue to explore the individual differences in olfactory capabilities among subjects initially classified by their ability to detect and identify the diastereoisomeric ketone, cis-4-(4'-t-butylcyclohexyl)-4-methyl-2-pentanone (pemenone) which shares with 5 alpha-androst-16-en-3-one (androstenone) a pronounced urine-sweaty odor. Our previous studies of these and other compounds for which specific anosmias were said to exist revealed significant relationships between intensity scores and a corresponding clustering of the odor quality descriptors used to characterize these materials by subjects judged to be specifically anosmic for the urinous note. Here, we attempt to dissect the web of interactions which give rise to individual differences in perceived odor quality by evaluating the effects of self- and cross-adaptation on the intensity and quality reports elicited by pemenone, androstenone and four other odors in 18 human subjects including both pemenone-osmic and non-osmic (n = 6) individuals. Intensity and quality ratings for the six compounds were obtained before and after an adaptation sequence in which subjects sniffed a test odorant, pemenone or the diluent. For each odorant, intensity ratings under the different adapting conditions were compared by ANOVA. Self-adaptation was universal but cross-adaptation by pemenone was only found in the intensity ratings of androstenone. The intensity ratings of isovaleric acid, which shares the urinous note with pemenone and androstenone, were unaffected by pemenone adaptation. Most of the subjects judged to be osmic still reported a urinous odor quality for androstenone and isovaleric acid following pemenone adaptation. Except for shifts to the no-odor category, adaptation did not significantly alter the odor quality reports of osmic or non-osmic individuals. This suggests that the odor quality reports engendered by these substances are multidimensional and that compounds which share the same odor quality label may interact with different perceptual channels.