Olfactory lateralization: odor intensity but not the hedonic estimation is lateralized.

An earlier study in humans comparing the olfactory sensitivity of both nostrils revealed a small but significant advantage of the right nostril for detection and for olfactory quality discrimination. However lateralization was not evaluated for the perception of odor intensity and hedonic evaluation (pleasantness/unpleasantness). Thus we investigated lateralization of olfactory intensity and hedonic evaluation in right-handed healthy volunteers (n=186) from the HeDoS-F database (Hedonic Database of Smell-Franconia). For olfactory evaluation the Sniffin' Stick Test was employed with the parameters detection, discrimination, identification and extended by analogue hedonic and intensity rating scales. Over all odors subjects rated the perceived intensity significantly higher following stimulation of the right compared to the left nostril. The analysis of the single odors of the Sniffin' Stick Test consistently confirmed higher intensity ratings for the right compared to the left nostril reaching a statistically significant difference for 10 out of 16 odors. In contrast we found no significant differences between the nostrils for the hedonic estimates over all odors. Differences in odor detection, discrimination and identification did not reach a statistically significant level, but for all these parameters the scores of the right nostril were slightly higher compared to the left nostril. For odor identification, however, a statistical tendency was observed. Based on our results we concluded that olfactory intensity estimates represent the most sensitive parameter of olfactory lateralization.