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1/15/2006 12:03:00 AM

Scents are more intense when emotions are in motion

In the words of Irving Berlin, "The sun never shines so bright, nor do things seem to go so right, when we're in love. " Our emotions also affect the intensity of scents, a Rice University psychologist has found.

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Lyricists have written about it, and psychologists continue to study it: the notion that our moods influence how we perceive the world around us. When it comes to our sense of smell, however, the relationship between a person's perception and state of mind is not as straightforward, according to Denise Chen, an assistant professor of psychology at Rice.

"A happy mood state does not make ordinary smells more pleasant or bad smells more tolerable,"Chen says.   "However, the intensity of smells are perceived differently depending on whether a person is feeling emotional or not. "

For example, smells seem stronger when a man is feeling emotional, be it happiness, sadness, or hostility.

In a paper published in the journal Chemical Senses , Chen reports on the first study of the effect of emotion on olfaction in men and women. Funded by the National Institutes of Health, the research was co-authored by Pamela Dalton of the Monell Chemical Senses Center in Philadelphia, Pennsylvania.

In their study, participants watched a series of videos, which were selected with the intention of eliciting emotions of happiness, sadness, hostility or a neutral mood.   Following each video, they completed a short questionnaire on how the segment made them feel.   They were told that at any point during the experiment a smell would be introduced into their room.   The smells were a pleasant citrus scent, an unpleasant fecal odor, or a neutral odor consisting of a very low concentration of rubbing alcohol.   Every time participants smelled an odor, they were instructed to press a bell, rate its strength, and describe what it smelled like.

"We measured how quickly the subjects responded to each smell, and how pleasant and intense they found it to be,"Chen explains.

Based on prior studies, Chen and Dalton had expected women's sense of scent to be more influenced by emotion. While there are no differences between men and women regarding their overall sensitivity to smell, women generally are better able than men to discriminate, identify and name smells.

"A number of prior studies showed that women are more emotional and better at detecting emotional signals,"Chen says. "We were surprised to discover that, under certain conditions, men are influenced more strongly by their emotional state than women. "

In addition to the effect of emotion, Chen and Dalton were also interested in how personalities influenced a person's sense of smell. Their subjects were pre-screened for specific personality characteristics, including neuroticism or moodiness versus stability, and anxiety versus calmness.

Prior studies found that anxious and moody people are more likely to attend to negative information. However, when it comes to smells, Chen and Dalton report that these individuals had heightened sensitivities to both positive and negative odors over neutral smells. Anxious women perceived pleasant or unpleasant smells stronger than the neutral smell, while calm women perceived them equally strong.   Moody men responded to positive or negative odors faster than the neutral smell, while stable men responded to them equally fast.

Chen believes that studies on how emotion and personality influence sensory perceptions not only have inherent scientific importance, but may also have clinical implications for the understanding of the causes of the "sick building"and multiple chemical syndromes.  

"The behavioral study of human olfaction is still at a beginning stage,"Chen says.   "Results like these form an integral part of a multi-pronged approach to the understanding of human olfaction that is being carried out here and elsewhere. "

Chen's research interests include human olfaction, emotion and cognition, with a special focus on the interplay between psycho-social and biological factors in human behavior.   She earned undergraduate and graduate degrees from the University of Chicago and her Ph.D. from Rutgers University.

For more information on this research, contact Chen at xdchen@rice.edu or B.J. Almond in the Office of News and Media Relations at balmond@rice.edu .