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

Relationship between odour performance and personality traits

Katedra filosofie a dějin přírodních vědDepartment of Philosophy and History of SciencePřírodovědecká fakultaFaculty of Scienc

16-androstenes Anosmia in Men

16-androstenes Anosmia in Men 16-androstens are compounds of steroid character which are secreted to the skin as part of apocrine glands secrets and they participate in creating body odor. It was found that androstenes influence affective state and psychophysiological reactions. The effect of androstenes can be also found on subliminal level. However, it has not yet been tested whether individuals with specific anosmia could also be influenced this way. Specific anosmia is described as an individual's incapability of conscious detection of particular odor while the detection of other compounds remains unaffected. The aim of the thesis is to test whether specifically anosmic individuals can be influenced by compounds to which they are anosmic to. This hypothesis is based on research of sensitization. Previous research indicates that olfactory perception may be of larger plasticity than thought. The theoretical part focuses on critical analysis of androstenes and research on specific anosmia. This field contains topics such as influence of chemical structure on androstenes perception, genetic influences, sensitization, functions of androstenes in interpersonal interactions and research on brain imagining. The experimental part focused on measuring subjective ratings of mood and psychophysiological..

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

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

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