6533b855fe1ef96bd12b044e

RESEARCH PRODUCT

Behavioral and physiological bases of relaxing and stimulating effects of odors and music

subject

description

This doctoral thesis examines the psychological and physiological mechanisms as well as the factors involved in the relaxing and stimulating effect (emotional activation) of pleasant odors, building on research work from the music domain. In Studies 1a and 1b, we observed that the modulation of the activation induced by odors influenced temporal information processing by speeding-up or slowing-down the rate of the internal clock pacemaker, similarly to what was previously reported using musicalstimuli. Moreover, prior verbalsuggestion attributing incongruent activation properties to the odors eliminated these effects, highlighting the importance of a priori expectancies on olfactory-induced emotions. In addition, Study 1c showed that odors did not impact the estimation of above-second durations, which then led us to consider attentional processes when analyzing olfactory activation effects. Study 2 was based on the fact that tempo is regarded as the main musical factor in the modulation of activation, indirectly reflecting the rate of the internal clock pacemaker. We observed that out of two musical excerpts only varying on tempo, participants preferred the slowest one in the presence of a relaxing odor (strawberry), and the fastest one in the presence of a stimulating odor (lemon), while odors were presented within the room at a subliminal level. In Study 3, we evidenced physiological relaxing effects of music (slow classical orchestral excerpts) and odor (lavender) on the Autonomous Nervous System following a cognitive stress. However, these effects were mediated through distinct neurophysiological mechanisms since music acted via the Parasympathetic Nervous System (as reflected by an influence on high frequency component of heart rate variability) whereas the odor operated via the sympathetic Nervous System (as reflected by an influence on electrodermal activity). Strikingly, when music and odor were conjointly presented, no relaxing effect was observed. Finally, in Study 4, we examined whether the variations of the concentration of olfactory stimuli impacted activation judgments using two separate unipolar scales. We observed that some odors could be perceived as both relaxing and stimulating for a same intensity, or that the predominant emotion could switch as a function of increasing intensity. Overall, these results stress the need to reevaluate the relevance of relying on bipolar scales to estimate the perception of relaxing and stimulating activation properties of odors. To conclude, we propose that psychological and neurophysiological mechanisms involved in the activation effects of odors should gain to be envisioned within a theoretical framework of emotions which does not oppose relaxing and stimulating properties. Top-down processes should also be considered, such as participant expectancies as well as the specificity of semantic representation of emotionalstimulations, especially between sensory modalities.