ODOR HEDONICS - CONNECTION WITH EMOTIONAL RESPONSE ESTIMATED BY AUTONOMIC PARAMETERS

The aim of this paper is to analyse the relationship between self-repo rt hedonic evaluations and the physiological expression of emotion in response to odorants. We try to solve the following questions: (1) Is it possible to find any experimental evidence that the sense of smell is linked with emotion? (2) What kind of odorants can be distinguished by autonomic analysis? (3) Is there a link between hedonics and auton omic information? The effects of odorants on the emotional process wer e estimated, in terms of autonomic nervous system (ANS) activity. Fift een subjects inhaled five odorants as olfactory stimuli: lavender (LAV ), ethyl acetoacetate (EAA), camphor (CAM), acetic acid (AA) and butyr ic acid (BA). After inhaling the odorant, subjects were requested to f ill out an 11-point hedonic scale to rate its pleasantness versus unpl easantness. ANS parameters were as follows: two electrodermal response s, skin potential (SP) and resistance (SR); two thermovascular paramet ers, skin blood flow (SBF) and skin temperature (ST); and two cardiore spiratory parameters: instantaneous respiratory frequency (IRF) and in stantaneous heart rate (IHR). Simultaneous recording of six parameters showed that specific autonomic patterns were associated with each odo rant. An analysis of variance made it possible to differentiate among the five odorants. Two-by-two odorant comparisons for autonomic respon ses using Tukey's HSD multiple comparison test only permitted differen tiation between pleasant odorants (LAV and EAA) and unpleasant (AA and BA) ones, but camphor was differentiated from both pleasant and unple asant odorants. Each odorant elicited responses in the different param eters, yet subjects responded through their preferential channels; an average of two channels was used by each subject. These results when c ompared with those obtained with other senses (visual and auditory), d id not evidence the postulated preferential link between olfaction and emotion. A strong link between hedonics and ANS response could be dem onstrated when considering each subject and mainly through his/her pre ferential channel(s); conversely a weak correlation (SR duration excep ted) was obtained between inter-subjects' hedonic evaluation. It seems that for a given population the autonomic response reflect the odor v alence only through some parameters related to the main preferential c hannel(s) and thus the global autonomic pattern has to be considered.