Measuring the Psychological Effects of Fragrances on Subjects

Odors are important. When in danger, skunks release a malodorant spray meant to avert the attack of a predator. The bad odor is associated with three sulfur-containing molecules, (E)-2-butene-1-thiol, 3-methyl-1-butanethiol, and 2-quinolinemethanethiol, as well as with acetate thioesters of these three. The human nose is very sensitive to these molecules and can detect them when they are at concentrations as low as 11.3 parts per billion.

Although not as sensitive as the dog’s nose, the human nose is quite sensitive. It has been reported to be able to detect ethylbutyrate (used as flavor enhancer with orange, cherry, pineapple, mango etc) at 1 part per billion, and 1-p-Menthene-8-thiol (aka Grapefruit mercaptan) at 0.02 parts per trillion.

Molecules that are detected by the olfactory system are called olfactory signals. Fragrances are olfactory signals, as are the smell of baked bread, freshly cut grass, horse manure and the like. Not all olfactory signals are recognized by humans because of their odor—some are odorless. In any case, olfactory signals bind to receptors in the human olfactory system and can have remarkable effects. For instance, Roberts and coworkers point out that “Genes in the Major Histocompatibility Complex (MHC) influence individual odors and females often prefer the odor of MHC-dissimilar males. Women using oral hormonal contraceptive, on the other hand, seem to prefer males with similar MHC.”¹ This can lead to catastrophic results in a couple when the decision is taken to procreate and the female partner stops using the oral contraceptive.

Effects of Olfactory Signals

When we smell something, we might find the odor pleasing, repugnant, invigorating, calming, tantalizing or even sexually stimulating. In short, odor can affect our mood. The interesting thing is that scientists propose methods to quantitatively assess the effect of something on one’s mood. In the 1970s, McNair, Lorr and Doppleman designed a method (Profile of Mood States or POMS) to assess six mood states: Anxiety, Anger, Vigor, Fatigue, Depression and Confusion. These states are detected by a questionnaire of 65 self-report questions. Participants answered by stating in what degree every question relates to them or not. According to the answers, the “intensity” of one’s mood is assessed.

The Effect on Mood
To measure the effects of olfactory signals on mood it is necessary to gather a cohort of volunteers according to rigorous inclusion and exclusion criteria. The cohort should be reasonably large—100 panelists or more—and a schedule is established for the panelists to join the evaluation center. When the panelists arrive for the first meeting, they are allowed to rest for a specific duration of time. They are then given the questionnaire and they answer the questions. After that, they are given a vial containing the fragrance or the olfactory signals to be tested, or a negative control; e.g., the solvent of the fragrance. They are allowed to smell the fragrance for a specified duration of time. After that, they are given the questionnaire and they answer the questions.

A few days later, the panelists return to the center for a second meeting, rest for a specified time and answer the questions of the questionnaire. They are then given the olfactory signal to smell (if in the previous meeting they were given the control) or the control (if in the previous meeting they had been given the olfactory signal) and answer the questionnaire. For each mood—anxiety, anger, vigor, fatigue, depression and confusion—the results are reported as the number of panelists having a defined “intensity” plotted versus the intensity of the mood.

One expects three plots to be identical (the two relative to the answers provided after arriving at the evaluation center and the one relative to the smelling of the control). When these three plots are remarkably different, the experimenter might need to reconsider the protocols of the assessment or consider possible environmental variables such as traffic or even changes in the fertility status of female panelists that might have occurred between the first and the second meeting.

An olfactory signal can be considered to affect the mood when it provokes the swinging of the mood profile for a sufficiently large fraction of the cohort so that the result is at least statistically significant.

Anecdotal Experience

Individual variability can play a major role when it comes to large cohorts of human beings. For this reason, results of epidemiological studies are too often only partially conclusive. When I was working in Long Island, my attention was called to the effects of olfactory signals. I started a study on their effects on panels composed by more than 100 women, using both fragrances and non-odorant signals according to the protocols described in this column. This was before I learned that the president of the company where I worked was not a fan of the marketing concept of pheromones and olfactory signals in general. As a result, the project was abandoned and the results were never published. I am, therefore, not at liberty to disclose what fragrances and olfactory signals were used. I can only confirm that in these studies, the smelling of some olfactory signals provoked a measurable and remarkable swing in the mood of a vast majority of panelists, by decreasing confusion, anxiety and depression.

And I will never forget how the sniffing of a few drops of one of those olfactory “things” applied on the wrist of an aggressive lawyer helped bring serenity into a difficult meeting! 

References

1. Roberts SC et al (2008) MHC-correlated odor preferences in humans and the use of oral contraceptives. Proc. Biol. Sci. 275 : 2715-2722

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Paolo Giacomoni, PhD
Insight Analysis Consulting
paologiac@gmail.com
516-769-6904
 
Paolo Giacomoni acts as an independent consultant to the skin care industry. He served as Executive Director of Research at Estée Lauder and was Head of the Department of Biology with L’Oréal. He has built a record of achievements through research on DNA damage and metabolic impairment induced by UV radiation as well as on the positive effects of vitamins and antioxidants. He has authored more than 100 peer-reviewed publications and has more than 20 patents. He is presently Head of R&D with L.RAPHAEL—The science of beauty—Geneva, Switzerland.