Fatal Attraction Phenomenon in Humans – Cat Odour Attractiveness Increased for Toxoplasma-Infected Men While Decreased for Infected Women

Latent toxoplasmosis, a lifelong infection with the protozoan Toxoplasma gondii, has cumulative effects on the behaviour of hosts, including humans. The most impressive effect of toxoplasmosis is the so-called “fatal attraction phenomenon,” the conversion of innate fear of odour of the definitive host, the cat, into attraction to cat odour in rodents infected with Toxoplasma. While most behavioural effects of Toxoplasma infection were confirmed also in humans, neither the fatal attraction phenomenon nor any toxoplasmosis-induced changes in olfactory functions have been searched for in them. Our study performed on 34 Toxoplasma-infected and 134 noninfected students showed that the infected men rated odour of cat urine as more pleasant than did the noninfected men, while infected women rated the same odour as less pleasant than did noninfected women. No significant effect of toxoplasmosis on the urine odour pleasantness was found for horse, tiger, brown hyena and dog. The possible absence of the effects of toxoplasmosis on the urine odour pleasantness score attributed to tiger would suggest that the amino acid felinine, which is absent in urine of large cats, could be responsible for the fatal attraction phenomenon

Psychology of Fragrance Use: Perception of Individual Odor and Perfume Blends Reveals a Mechanism for Idiosyncratic Effects on Fragrance Choice

Cross-culturally, fragrances are used to modulate body odor, but the psychology of fragrance choice has been largely overlooked. The prevalent view is that fragrances mask an individual's body odor and improve its pleasantness. In two experiments, we found positive effects of perfume on body odor perception. Importantly, however, this was modulated by significant interactions with individual odor donors. Fragrances thus appear to interact with body odor, creating an individually-specific odor mixture. In a third experiment, the odor mixture of an individual's body odor and their preferred perfume was perceived as more pleasant than a blend of the same body odor with a randomly-allocated perfume, even when there was no difference in pleasantness between the perfumes. This indicates that fragrance use extends beyond simple masking effects and that people choose perfumes that interact well with their own odor. Our results provide an explanation for the highly individual nature of perfume choice

Human body odour individuality Methods of body odour sampling

Department of Philosophy and History of ScienceKatedra filosofie a dějin přírodních vědPřírodovědecká fakultaFaculty of Scienc

Human body odour individuality Methods of body odour sampling

Department of Philosophy and History of ScienceKatedra filosofie a dějin přírodních vědPřírodovědecká fakultaFaculty of Scienc

Differences in the urine odour pleasantness scores attributed to various species of animals.

<p>The empty circles and triangles denote mean Z-scores for women and men, respectively; the vertical bars denote 0.95 confidence intervals. The odour of samples with more positive Z-scores was scored as more pleasant (in comparison with other urine samples). The means were controlled for intensity of the odour attributed by particular rater, i.e. they were computed for mean intensity of the odour. A and B are the high and low concentration samples, respectively (see the <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0001389#s2" target="_blank">Methods</a> section).</p

Differences in attributed pleasantness and intensity of the smell of urine of different animals.

<p>The samples labeled “A“ and “B” represent the high dose and low dose samples, respectively. The effects size are described with η², significant effects (p<0.01) and trends (p<0.1] computed with GLM test are denoted with asterisk and printed in bold, respectively.</p

The cat urine odour pleasantness.

<p>The figure shows odour pleasantness scores attributed to the cat urine sample by <i>Toxoplasma</i>-infected and <i>Toxoplasma</i>-free male and female students. The circles and squares denote mean Z-scores for women and men, respectively; the vertical bars denote 0.95 confidence intervals. The odour of samples with more positive Z-scores was scored as more pleasant (in comparison with other urine samples). In contrast to results presented in <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0001389#pntd-0001389-t001" target="_blank">Tab. 1</a>, here the means were controlled for intensity of the odour attributed by particular rater, i.e. they were computed for mean intensity of the odour.</p

Results of ANOVA models for odor attractiveness, pleasantness and intensity in Study 1, 2 and 3.

<p>Table shows values of test statistics (F), significance levels (p) and variance explained (η²) for factor donors identity (ID), odor condition (Perfume) and their interaction.</p

Ratings of perfumed and non-perfumed body odors in Study 1.

<p>Z-scored mean ratings (± SEM) of attractiveness, pleasantness and intensity in individual odor donors and for all donors together in non-perfume (empty bars) and perfume (shaded bars) conditions.</p