Article

The Relation of Toxoplasma Infection and Sexual Attraction to Fear, Danger, Pain, and Submissiveness

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Abstract

Behavioral patterns, including sexual behavioral patterns, are usually understood as biological adaptations increasing the fitness of their carriers. Many parasites, so-called manipulators, are known to induce changes in the behavior of their hosts to increase their own fitness. Such changes are also induced by a parasite of cats, Toxoplasma gondii. The most remarkable change is the fatal attraction phenomenon, the switch of infected mice’s and rat’s native fear of the smell of cats toward an attraction to this smell. The stimuli that activate fear-related circuits in healthy rodents start to also activate sex-related circuits in the infected animals. An analogy of the fatal attraction phenomenon has also been observed in infected humans. Therefore, we tried to test a hypothesis that sexual arousal by fear-, violence-, and danger-related stimuli occurs more frequently in Toxoplasma-infected subjects. A cross-sectional cohort study performed on 36,564 subjects (5,087 Toxoplasma free and 741 Toxoplasma infected) showed that infected and noninfected subjects differ in their sexual behavior, fantasies, and preferences when age, health, and the size of the place where they spent childhood were controlled (F(24, 3719) ¼ 2.800, p < .0001). In agreement with our a priori hypothesis, infected subjects are more often aroused by their own fear, danger, and sexual submission although they practice more conventional sexual activities than Toxoplasma-free subjects. We suggest that the later changes can be related to a decrease in the personality trait of novelty seeking in infected subjects, which is potentially a side effect of increased concentration of dopamine in their brain.

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... If this is true, then the sadomasochistic preference could occur in higher frequencies in Toxoplasma-infected subjects. To test this hypothesis, we searched for a positive association between sadism-and masochism-related preferences among the population of 36,564 subjects (5,087 Toxoplasma-free and 741 Toxoplasma-infected) using a Facebook-based snowball method [10]. The question regarding toxoplasmosis status of subjects was mixed among 700 other questions, and the subjects were not informed that the study concerned the effects of toxoplasmosis. ...
... Both women and men were less aroused by Sexual dominance and sadism and both practiced any kind of sadomasochistic sex less often than their Toxoplasma-free peers (all p < 0.0005). Other factors correlated with toxoplasmosis, e.g., zoophilia and homosexual sex (not the homosexual orientation), had no direct relation to BDSM or fear [10]. Generally, infected subjects expressed relatively high attraction to nonconventional sexual practices, especially certain BDSM-related practices, but they also reported to perform such activities less often than the Toxoplasma-free subjects. ...
... Therefore, it is difficult to detect these effects using simple univariate statistical techniques, for example, by studying the effect of the infection on sexual preference, without controlling for the effect of the infection on sexual activity and sexual desire. For example, Toxoplasma-infected subjects scored higher than their Toxoplasma-free peers in the factor Arousal by submission and masochism when the other sex-related variables were controlled in the process of factor analysis [10]. However, they scored lower when asked how much they are aroused by being humiliated, or by suffering pain, 2 traits that positively load the factor Arousal by submission and masochism see the Fig. 1. ...
Article
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The parasite Toxoplasma needs to get from its intermediate hosts, e.g. rodents, to its definitive hosts, cats, by predation. To increase the probability of this occurrence, Toxoplasma manipulates the behavior of its hosts, for example, by the demethylation of promoters of certain genes in the host's amygdala. After this modification, the stimuli that normally activate fear-related circuits, e.g. the smell of a cat, or smell of leopards in chimpanzee, start to additionally co-activate sexual arousal-related circuits in the infected rodents. In humans, the increased attraction to masochistic sexual practices was recently observed in a study performed on 36,564 subjects. Here I show that lower rather than higher attraction to sexual masochism and submissiveness among infected subjects is detected if simple univariate tests instead of multivariate tests are applied to the same data. I show and discuss that when analyzing multiple effects of complex stimuli on complex biological systems we need to use multivariate techniques and very large data sets. We must also accept the fact that any single factor usually explains only a small fraction of variability in the focal variable.
... The data was originally collected for the purpose of another study (11). The subjects were invited to participate in the study using a Facebook-based snowball method (12) by advertisements published in various papers and electronic media, as well as TV and radio broadcasting. ...
... The electronic survey consisted of 5 already published questionnaires studying various facets of human sexuality (11). The survey also contained an anamnestic questionnaire collecting various socioeconomic, demographic, health related, epidemiologic, and psychological data and three projective psychological tests. ...
Article
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Infection by the parasite Toxoplasma, which affects about 33% of world population, is associated with an increased risk of several mental health disorders, the most strongly with schizophrenia. It is unknown whether schizophrenia is associated with this infection the most strongly, or whether this association has just been the most intensively studied for historical reasons. We used the data from 6,367 subjects tested for toxoplasmosis who took part in an internet survey to search for associations of these infections with 24 mental health disorders and evidence of otherwise impaired mental health. The typical symptom associated with toxoplasmosis was anxiety, and the typical toxoplasmosis-associated disorders were autism (OR = 4.78), schizophrenia (OR = 3.33), attention deficit hyperactivity disorder (OR = 2.50), obsessive compulsive disorder (OR = 1.86), antisocial personality disorder (OR = 1.63), learning disabilities (OR = 1.59), and anxiety disorder (OR = 1.48). Toxoplasmosis could play a substantial role in the etiopathogenesis of mental health disorders and its association with schizophrenia is the second strongest association, after autism.
... The results of dimension 5 which concentrated on loss of interest in sex, showed that all the questions were with no relationship with the latent T. gondii (p >0.05). A recent study confirmed the reality of specific differences in desires, sexual behavior, and preferences between Toxoplasma-free and Toxoplasma-infected subjects (Flegr & Kuba 2016). Minor propensities for performance nonconventional sexual practices in the infected persons could be associated to their health status reduction . ...
... Minor propensities for performance nonconventional sexual practices in the infected persons could be associated to their health status reduction . However, these negative related were found even when controlled the covariates healthrelated (Flegr & Kuba 2016). Some authors supposed that, in infected women decreased of personality factor could be responsible for the observed negative associations between toxoplasmosis and performing nonconventional sexual activities (Flegr et al., 2003;Novotná et al., 2005& Skallová et al., 2005 In the current study, the results of last dimension questionnaire which deals with loss of interest in sex, have showed that all the questions were negatively responded indicated that no relation with the latent T. gondii infection (p >0.05) and this result coincident with the previous publications. ...
... Subjects. The internet questionnaire was promoted and distributed as a 'study that tests certain evolutionary psychological and parasitological hypotheses and contains many questions related to sexual life' (for details see Ref. 106 ). Participants were informed about the general aims of the study on the first page of the questionnaire. ...
... The online survey consisted of several questionnaires aimed at collecting various socioeconomic, demographic, health-related, sexual life-and reproduction-related, psychological, behavioural, and epidemiologic data. The survey also contained the Sexual Preferences and Behaviours Inventory 2015 (SPBI-2015) 106 and Revised Sociosexual Orientation Inventory (SOI-R) 107 . All in all, the survey consisted of about 700 questions and the mean time needed for completion was about 101 min (median 96 min). ...
Article
Full-text available
Factors which indicate lower life expectancy also induce switching to a faster life strategy, that is, a higher investment in current reproduction at the expense of future reproduction and body maintenance. We tested a hypothesis according to which impairment of individual health serves as a signal for switching to a faster life strategy using online-gathered data from 32,911 subjects. Worse health was associated with lower age at menarche and earlier initiation of sexual life in women and higher sexual desire and earlier reproduction in both sexes. Individuals with worse health also exhibited lower sexual activity, lower number of sexual partners, and lower total number of children. These results suggest that impaired health shifts individuals towards a faster life strategy but also has a negative (physiological) effect on behaviours related to sexual life. Signs of a faster life strategy were also found in Rh-negative men in good health, indicating that even just genetic predisposition to worse health could serve as a signal for switching to a faster life strategy. We suggest that improved public health in developed countries and the resulting shift to a slower life strategy could be the ultimate cause of the phenomenon of demographic transition.
... The results of dimension 5 which concentrated on loss of interest in sex, showed that all the questions were with no relationship with the latent T. gondii (p >0.05). A recent study confirmed the reality of specific differences in desires, sexual behavior, and preferences between Toxoplasma-free and Toxoplasma-infected subjects (Flegr & Kuba 2016). Minor propensities for performance nonconventional sexual practices in the infected persons could be associated to their health status reduction . ...
... Minor propensities for performance nonconventional sexual practices in the infected persons could be associated to their health status reduction . However, these negative related were found even when controlled the covariates healthrelated (Flegr & Kuba 2016). Some authors supposed that, in infected women decreased of personality factor could be responsible for the observed negative associations between toxoplasmosis and performing nonconventional sexual activities (Flegr et al., 2003;Novotná et al., 2005& Skallová et al., 2005 In the current study, the results of last dimension questionnaire which deals with loss of interest in sex, have showed that all the questions were negatively responded indicated that no relation with the latent T. gondii infection (p >0.05) and this result coincident with the previous publications. ...
... Miscellaneous human diseases that correlated with chronic T. gondii infection, including Alzheimer's 10,11 schizophrenia 12-14 Parkinson 15-18 depression 19 epilepsy 20 . Its induce behavioral changes in human [21][22][23] and rodents 24 , also a significant association between T. gondii infection and suicide attempts was reported 25 . Many studies correlated these symptoms with alterations in hormones concentrations in host, that include sex hormones 21,[26][27][28][29] and neurotransmitters hormones 23,30 . ...
... Its induce behavioral changes in human [21][22][23] and rodents 24 , also a significant association between T. gondii infection and suicide attempts was reported 25 . Many studies correlated these symptoms with alterations in hormones concentrations in host, that include sex hormones 21,[26][27][28][29] and neurotransmitters hormones 23,30 . One factor that pay to the vague changes and neurological disorder in human and animal is modulate of neurotransmitters levels during chronic toxoplasmosis such as dopamine 31 . ...
Article
Full-text available
Latent Toxoplasma gondii infection has been considered asymptomatic for many years, but results of recent studies have associated it with various neuropsychiatric problems, including Alzheimer's, Schizophrenia, Parkinson, Depression, Epilepsy. These chronic disease occur as a result of changes in the levels of hormones and neurotransmitters caused by parasitic infection in the host brain. A total of 45 blood samples of donors (33 men and 12 women) from AL-Najaf province, Iraq were tested for IgG anti-Toxoplasma antibodies by Elisa method and the results as follows 17 seropositive(12 male and 5 female) and 28 seronegative (21 male and 7 female). All samples were subjected to Elisa test to determine levels of three of neurotransmitters (Dopamine, Adrenaline, and Noradrenaline) in serum. The result show significantly (t test) higher serum levels of Adrenaline in patients with latent toxoplasmosis compared to controls (p<0.05). Both Dopamine and Noradrenaline hormones serum levels in patients showed a slight increase compared with control group, but statistically insignificant (p>0.05). Our findings suggest that chronic infection by T. gondii causes a change in some neurotransmitters and may be explained by the occurrence of certain neurological diseases in the incidence of latent toxoplasmosis.
... Miscellaneous human diseases that correlated with chronic T. gondii infection, including Alzheimer's 10,11 schizophrenia 12-14 Parkinson 15-18 depression 19 epilepsy 20 . Its induce behavioral changes in human [21][22][23] and rodents 24 , also a significant association between T. gondii infection and suicide attempts was reported 25 . Many studies correlated these symptoms with alterations in hormones concentrations in host, that include sex hormones 21,[26][27][28][29] and neurotransmitters hormones 23,30 . ...
... Its induce behavioral changes in human [21][22][23] and rodents 24 , also a significant association between T. gondii infection and suicide attempts was reported 25 . Many studies correlated these symptoms with alterations in hormones concentrations in host, that include sex hormones 21,[26][27][28][29] and neurotransmitters hormones 23,30 . One factor that pay to the vague changes and neurological disorder in human and animal is modulate of neurotransmitters levels during chronic toxoplasmosis such as dopamine 31 . ...
Article
Full-text available
Latent Toxoplasma gondii infection has been considered asymptomatic for many years, but results of recent studies have associated it with various neuropsychiatric problems, including Alzheimer's, Schizophrenia, Parkinson, Depression, Epilepsy. These chronic disease occur as a result of changes in the levels of hormones and neurotransmitters caused by parasitic infection in the host brain. A total of 45 blood samples of donors (33 men and 12 women) from AL-Najaf province, Iraq were tested for IgG anti-Toxoplasma antibodies by Elisa method and the results as follows 17 seropositive(12 male and 5 female) and 28 seronegative (21 male and 7 female). All samples were subjected to Elisa test to determine levels of three of neurotransmitters (Dopamine, Adrenaline, and Noradrenaline) in serum. The result show significantly (t test) higher serum levels of Adrenaline in patients with latent toxoplasmosis compared to controls (p<0.05). Both Dopamine and Noradrenaline hormones serum levels in patients showed a slight increase compared with control group, but statistically insignificant (p>0.05). Our findings suggest that chronic infection by T. gondii causes a change in some neurotransmitters and may be explained by the occurrence of certain neurological diseases in the incidence of latent toxoplasmosis.
... represents a behavioural syndrome consisting of reduced innate fear, increased sexual attractiveness and greater delay aversion; all hallmarks of a 'carpe diem' animal personality" (Tan et al., 2015, p. 5). As of now there is only one study that has tested the parasite's impact on sexual and/or mating behavior of humans (Flegr & Kuba, 2016). Although this is just speculation, toxoplasmosis could influence the quality of relationships between men and women in workplaces or the prevalence of sexual harassment in firms (as infected men have higher testosterone levels and infected women tend to exhibit more warmth). ...
Article
Full-text available
The article reviews recent literature on the effects of host manipulation by the parasite Toxoplasma gondii (prevalent in about a third of the world’s population) on perception, cognition, and behavior of humans, and on the changes in their physical appearance and personality characteristics. I argue that the mind-affecting parasite paradigm offers many research opportunities for management sciences, especially for organizational psychology and neuroscience. The article summarizes the parasite’s physiological mechanisms of affecting the host; highlights important behavioral effects of the infection in humans; and speculates on the possible impacts on skills and careers of employees and managers, organizational dynamics, intercultural management, and gender work roles. The conclusion shows limitations of the presented speculations and possible directions for future research on Toxoplasma’s effect on organizational dynamics.
... The link to the English version was distributed across social media (e.g., Facebook, Twitter), which included mostly individuals from North America, the UK, and other English-speakers from other parts of the world, as well as to psychology students and staff at the University of Stirling in Scotland. The link for the Czech version was distributed to participants using a Facebook-based snowball method (Flegr and Kuba, 2016). The link to the Spanish version was distributed to staff and students at El Bosque University and the University of La Sabana in Colombia, several of whom also posted it on social media. ...
Article
Full-text available
The emotion of disgust plays a key role in the behavioral immune system, a set of disease-avoidance processes constituting a frontline defense against pathogenic threats. In the context of growing research interest in disgust, as well as recognition of its role in several psychiatric disorders, there is need for an improved understanding of behavioral triggers of disgust and for adequate techniques to both induce disgust in experimental settings and to measure individual variability in disgust sensitivity. In this study, we sought to address these issues using a multi-stage, bottom-up approach that aimed first to determine the most widespread and effective elicitors of disgust across several cultures. Based on exploratory factor analysis of these triggers, revealing four main components of pathogen-related disgust, we then generated a novel visual stimulus set of 20 images depicting scenes of highly salient pathogen risk, along with paired control images that are visually comparable but lack the disgust trigger. We present a series of validation analyses comparing our new stimulus set (the Culpepper Disgust Image Set, C-DIS) with the most commonly used pre-existing set, a series of 7 images devised by Curtis et al. (2004). Disgust scores from participants who rated the two image sets were positively correlated, indicating cross-test concordance, but results also showed that our pathogen-salient images elicited higher levels of disgust and our control images elicited lower levels of disgust. These findings suggest that the novel image set is a useful and effective tool for use in future research, both in terms of priming disgust and for measuring individual differences in disgust sensitivity.
... On the other hand, many studies in the world and Iraq in particular, have shown that toxoplasmosis causes a recurrent abortion among pregnant women (4). With the progress of research in the fields of molecular biology it has been found that this parasite, which is transmitted through sexual contact causes serious complications (5). Recent studies conducted in the field of molecular biology has proven the transmission of the parasite through sexual contact leads to a new field of research about the parasite to infect the reproductive organs and causes proliferative device occurs great damage that cannot be cured (6). ...
Article
Full-text available
Seminal fluid and blood samples were collated from sixty 20-60 years aged and attended Teba Center for Children and ICSI/ in Babylon Province during the period from 1 st June 2016 to 1 st February 2017. The same number of samples were also taken from 60 age matched apparently healthy individuals to act as a control group. Anti IgG levels were measured in the sera of both groups to detect the presence of Toxoplasma infection, while seminal fluid samples were examined to detect infertility. Toxoplasma gondii genotype was applied by using nested PCR to detect SAG2 gene. Gene sequencing technique infection was performed for detection occurrence of mutation in the mitochondria of the sperm. Results confirmed that the age group (20-40years) was significantly more prone P<0.05 to infective with T. gondii where the percentage of seropositivty was 65% (39 patients) while it was 35% (21 individuals) in the apparently healthy control group. Concerning the residence, there was a highly significant difference (P < 0.006) where the percentage of seropositivty was 68% in idiveduals living in rural areas while it was 32% among those living in the urban areas. Genotyping showed that presence in two strains of Toxoplasma which has been found in males infected with Toxoplasmosis. Type I was found in 10 persons (17%) while type II was found in 50 persons (83%) and the difference between two strains was significant (P<0.05). Oligospermia has recorded the highest number of positive cases among patients (92%; 55 cases), in comparison with negative cases (8%; 5 cases), Asthenospermia showed significant P<0.05 decrease (35%; 21 cases) in comparison with negative (65%; 39 cases). Mutation occurs with Oligospermia of both of types I and II of T. gondii strains in 2 cases only, which was found on DN2 gene with a highly significant P<0.01 difference of positive cases (3%; 2 cases), and negative cases (97%; 58 cases). The mutation in single-nucleotide polymorphisms SNP G4580A site, showed that G was converted to A that was recognized at nt 4580 in the ND2 region. This evolution was experiential in oligozoospermic samples (code 010830). This SNP is a synonymous substitution that occurred in the third position of methionine codon, changing the codon from ATG to ATA. ، ‫رسن‬ ‫عبود‬ ‫فرحان‬ 2 ‫و‬ ‫محسن‬ ‫صبر‬ ‫سلوى‬ 3 1 ‫و‬ 2 ‫الوسطى‬ ‫التقنية‬ ‫الجامعة‬-‫والطبية‬ ‫الصحية‬ ‫التقنيات‬ ‫كلية‬-‫المرضية‬ ‫التحليالت‬ ‫تقنيات‬ ‫قسم‬ 3 ‫الوسطى‬ ‫التقنية‬ ‫الجامعة‬-‫الطبي‬ ‫التقني‬ ‫المعهد‬-‫بغداد‬ ‫الخالصة‬ ‫المقوسات‬ ‫بداء‬ ‫والمصابين‬ ‫العقم‬ ‫يعانون‬ ‫كانوا‬ ‫الذين‬ ‫المرضى‬ ‫الرجال‬ ‫من‬ ‫ستين‬ ‫من‬ ‫جمعها‬ ‫تم‬ ‫والدم‬ ‫المنوي‬ ‫السائل‬ ‫عينات‬ ‫بين‬ ‫ما‬ ‫أعمارهم‬ ‫تتراوح‬ ‫والذين‬ 20-60 ‫من‬ ‫الفترة‬ ‫خالل‬ ‫بابل‬ / ‫المجهري‬ ‫والحقن‬ ‫لألطفال‬ ‫طيبة‬ ‫مركز‬ ‫من‬ ‫أخذت‬ ‫والتي‬ ‫سنة‬ 1 ‫حزيران‬ 2016 ‫شهر‬ ‫إلى‬ 1 ‫األول‬ ‫تشرين‬ 2017. ‫من‬ ‫أيضا‬ ‫العينات‬ ‫العدد‬ ‫نفس‬ ‫أخذ‬ ‫تم‬ 60 ‫األصحاء‬ ‫األفراد‬ ‫من‬ ‫عينات‬ ‫فحص‬ ‫تم‬ ‫حين‬ ‫في‬ ،‫الكونيدية‬ ‫بالمقوسة‬ ‫إصاباتهم‬ ‫عن‬ ‫للتحري‬ ‫المجموعتين‬ ‫كال‬ ‫مصول‬ ‫فحص‬ ‫تم‬ .‫سيطرة‬ ‫كمجموعة‬ ‫ت‬ ‫باستخدام‬ ‫الكونيدية‬ ‫للمقوسة‬ ‫الجيني‬ ‫التنيمط‬ ‫تطبيق‬ ‫تم‬ ‫وكذلك‬ .‫العقم‬ ‫حدوث‬ ‫عن‬ ‫للتحري‬ ‫المنوي‬ ‫السائل‬ ‫البلمرة‬ ‫فاعل‬ ‫المتداخل‬ nPCR ‫جين‬ ‫عن‬ ‫للكشف‬ SAG2 ‫الجيني‬ ‫التتابع‬ ‫في‬ ‫طفرة‬ ‫حدوث‬ ‫عن‬ ‫للكشف‬ ‫الجيني‬ ‫التتابع‬ ‫تقنية‬ ‫إجراء‬ ُ ‫وأيضا‬. (‫العمرية‬ ‫الفئة‬ ‫أن‬ ‫النتائج‬ ‫وأكدت‬ .‫المنوية‬ ‫الحيوانات‬ ‫لميتوكوندريا‬ 20-40 ‫معنوي‬ ‫بشكل‬ ‫لألصابة‬ ً ‫أستعدادا‬ ‫أكثر‬ ‫كانت‬) P <0.05 ‫المدروسة‬ ‫المجموعة‬ ‫بين‬ ‫الكونيدية‬ ‫للمقوسة‬ ‫النوعية‬ ‫للألضداد‬ ‫المصلية‬ ‫لاليجابية‬ ‫المئوية‬ ‫النسبة‬ ‫بلغت‬ ‫حيث‬ 65 ٪ ‫السيطرة‬ ‫مجموعة‬ ‫بلغت‬ ‫حين‬ ‫في‬ 35 ‫الريف‬ ‫سكان‬ ‫بين‬ ‫عالي‬ ‫معنوي‬ ‫فرق‬ ‫هناك‬ ‫وكان‬ ،٪ 68 ‫والحضر‬ ٪ 32 ،٪ P < 0.006) ‫جدا‬ ‫عالي‬ ‫معنوي‬ ‫فرق‬ ‫هناك‬ ‫كان‬ ‫كما‬ .‫لإلقامة‬ ‫وفقا‬) P < 0.001 ‫الث‬ ‫النوع‬ ‫بين‬ ‫اني‬ 50 (83٪ ‫وفقط‬ ،) 10 (17٪) ،‫األول‬ ‫النوع‬ ‫من‬ P = 0.001 ‫النطاف‬ ‫قلة‬ ‫سجلت‬ ‫وقد‬. ‫الكونيدية‬ ‫المقوسة‬ ‫لسالالت‬ .
... The truck man may have had a cat bite, but justice prevailed for him because of microbial forensics. Similarly, the parasite Toxoplasma gondii may arouse sexual masochism and submission [83,84]. Microbes can change toxicology results, point to causes of death and match suspects to the scene of a crime [85]. ...
Article
Full-text available
Modernization has thrown humanity and other forms of life on our planet into a ditch of problems. Poverty, climate change, injustice and environmental degradation are a few of the shared global problems. The United Nations Sustainable Development Goals (SDGs) are the blueprint to achieve a better and more sustainable future for all. The SDGs are well structured to address the global challenges we face including poverty, inequalities, hunger, climate change, environmental degradation, peace and justice. Five years into the implementation, the SDGs have been driven mainly by international donors and ‘professional’ international development organizations. The world is left with 10 years to achieve these ambitious goals and targets. Various reviews show that little has been achieved overall, and the SDGs will not be a reality if a new strategy is not in place to bring inclusion. Microbiology, the scientific discipline of microbes, their effects and practical uses has insightful influence on our day-to-day living. We present how microbiology and microbiologists could increase the scorecard and accelerate these global goals. Microbiology has a direct link to achieving SDGs addressing food security, health and wellbeing, clean energy, environmental degradation and climate change. A non-classical growing relationship exists between microbiology and other SDGs such as peace, justice, gender equality, decent work and economic growth. The pledge of ‘Leave No One Behind’ will fast track progress and microbiology is in a better position to make this work.
... The Czech and Slovak populations contain about 16% of Rh-negative subjects. The frequency of such subjects, however, was much higher (about 23%) among the participants of the present study and even higher (25%) among participants of other internet studies, for example among the participants of our previous study about the sexual behavior of the Czech population [27]. It can be speculated that a fraction of subjects intentionally or unintentionally misreports their Rh phenotype. ...
Article
Full-text available
Background Since its discovery in the 1930s, the effects of Rh phenotype on human health and wellbeing, with the exception of the effects of Rh-negativity of a mother on the risk of hemolytic anemia of Rh-positive children, has only rarely been studied. In the last few years, however, several studies have shown that Rh-negative subjects have worse health and performance in certain tests than their Rh-positive peers. Nothing is known about the effect of Rh phenotype on the quality of life of subjects as measured by a standard instrument. Methods We hereby analyzed the data of 1768 male (24% Rh-negative) and 3759 female participants (23% Rh-negative) of an anonymous internet study using the partial Kendall test with the age and the population of the hometown of subjects controlled. Results The results showed that the Rh-negative women, but not men, scored worse in wellbeing measured with the WHO-BREFF. The Rh-negative men scored worse in mental health-related variables and in their reported economic situation and the Rh-negative women scored better in physical health-related variables. Both the Rh-negative men and women reported higher sexual activity than their Rh-positive peers. Conclusions The effects of the Rh phenotype were significant after the correction for multiple tests. However, they were usually weaker and less numerous than those of smoking, consuming alcohol, and high body mass index, which were used as a sort of internal control.
... The methods and description of the electronic survey "Sexual Preferences and Behaviors Inventory 2015" are described in detail elsewhere. 15 In brief, data were collected between January 2015 and March 2018 via an online questionnaire distributed by Qualtrics (www.qualtrics.com). Participants were recruited via advertisements placed at a Facebook page and in the media. ...
Article
Full-text available
Introduction: A limited number of scientific studies explore the frequency with which various sexual positions are used in human populations and the potential of particular sexual position to facilitate female coital orgasm. Aim: The aim of this study was to provide data about the prevalence and frequency of various sexual positions, their rated pleasurability, and their association with female coital orgasm consistency (COC). Methods: A sample of Czech heterosexual population (11,225 men/9,813 women) were presented with a list of 13 sexual positions in black-and-white silhouettes. For each position, they indicated frequency and pleasurability. COC was assessed as the proportion of penile-vaginal intercourse with a current partner which led to orgasm. Main outcome measure: Participants reported the frequency of use of sexual positions and rated their pleasurability. Using ordinal logistic regression, association between the COC and frequency of use of coital positions was tested. Results: In both men and women, the most commonly used sexual positions were face to face/male above, face to face/female above, and kneeling/rear entry. Nonetheless, there emerged some gender differences in the rating of pleasurability of various positions (all P < .001). We found that a higher proportion of female coital orgasms are positively associated with the frequency of use of face to face/female above (odds ratio [OR] = 1.005, P < .001) and sitting/face-to-face positions (OR = 1.003, P < .001) and negatively associated with the frequency of kneeling/rear entry position (OR = 0.996, P < .001). Conclusions: Our findings suggest that there are no gender differences in the frequency of use of sexual positions, but their rated pleasurability differs between men and women, and higher frequency of use of face-to-face positions with female above increases the likelihood of achieving coital orgasm during penile-vaginal intercourse. Most results, however, were of small effect sizes, and more research is needed to further explore this issue. Krejčová L, Kuba R, Flegr J, et al. Kamasutra in Practice: The Use of Sexual Positions in the Czech Population and Their Association With Female Coital Orgasm Potential. Sex Med 2020;8:767-776.
... The data was originally collected for the purpose of another study (Flegr and Kuba, 2016). The subjects were invited to participate in the study using a Facebook-based snowball method (Kankova et al., 2015) by advertisements published in various papers and electronic media, as well as TV and radio broadcasting. ...
Preprint
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Infection by the parasite Toxoplasma , which affects about 33% of world population, is associated with increased risk of several mental health disorders, the most strongly with schizophrenia. It is unknown whether toxoplasmosis really plays a substantial role in the etiopathogenesis of these disorders and whether schizophrenia is associated with this infection the most strongly, or whether this association has just been the most intensively studied for historical reasons. We used the data from 3,440 and 7,800 subjects tested for toxoplasmosis and borreliosis, respectively, who took part in an internet survey, for searching in the associations of these infections with 22 mental health disorders and other indices of impaired mental health. The typical symptom associated with toxoplasmosis was anxiety, and the typical toxoplasmosis-associated disorders were autism (OR=4.86), schizophrenia (OR=3.34), attention deficit hyperactivity disorder (OR=3.02), Asperger syndrome (OR=2.49), antisocial personality disorder (OR=1.81), OCD (OR=1.69), and anxiety disorder (OR=1.57). Borreliosis was associated only with symptoms of depression and with major depression (OR=1.65). The negative effects of borreliosis were detectable only in the Toxoplasma -infected subjects. Toxoplasmosis could play a substantial role in the etiopathogenesis of mental health disorders and its association with schizophrenia is the second strongest association, after autism.
... Niebuhr and colleagues (2008) found a significant positive association between T. gondii antibodies and diagnosis of schizophrenia among military personnel. Interestingly T. gondii infection has been shown to be related to a number of risk-taking behaviors ranging from dangerous driving, suicide attempts, and risky sexual pursuits (Flegr & Kuba, 2016;Sutterland et al., 2019). It may that T. gondii-induced neuronal changes that can cause an escalation in risk-taking behavior may be related to an increased risk of developing schizophrenia. ...
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Schizophrenia is a severe mental illness that has devastating consequences for those who suffer from the disorder. The epidemiology of schizophrenia indicates that it occurs relatively often, in many different contexts, and in conjunction with other disorders, decreasing quality of life and causing premature death. There has been an enormous amount of research into the causes of schizophrenia and there is now have a much better understanding of the genetic, environmental, and psychological factors that contribute to the disease. While there are numerous ways to understand and conceptualize schizophrenia, a unified picture of the neurobiology, changes in brain structure, cognitive and social-cognitive impairments related to the disorder has yet to emerge. Convulsive therapies and psychosurgery were used unsuccessfully, indiscriminately and without scientific validation in the past to treat schizophrenia. Medical advances including advanced imaging technology have now provided the ability to perform specifically focused neuromodulation and psychosurgery in severe and treatment resistant cases of schizophrenia. While still at a preliminary stage, these approaches have the potential to yield effective treatments in the future. For the last 70 years antipsychotic medication has become the prevailing treatment for schizophrenia. However, many people suffering from the disorder have trouble with side-effects and adhering to a regimen of antipsychotic medication. Newer pharmacological agents are being developed and include not only novel antipsychotic drugs, but anti-inflammatory and immunomodulating agents as well. These new agents, used either alone or in combination, have the potential to improve outcomes for people suffering from schizophrenia. Nevertheless, conclusively better pharmacotherapies will likely not arise until there is better understanding of the pathophysiology underlying schizophrenia. After the development of antipsychotic medication, psychotherapeutic methods for treating schizophrenia fell out of favor, but there is currently some reversal of this trend. The use of newer psychotherapies and modified forms of older therapeutic treatments are not only targeting the symptoms of schizophrenia but are also now focusing on recovery from the disorder. These newer approaches as well as efforts at preventing schizophrenia show promise in reducing the suffering caused by this disease.
... changes to sexual behavior (Flegr and Kuba 2016;Flegr and Markoš 2014). Of all life forms, fungi seem to be the champions of behavioral manipulation. ...
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Many pathogens, especially fungi, have evolved the capacity to manipulate host behavior, usually to improve their chances of spreading to other hosts. Such manipulation is difficult to observe in long-lived hosts, like humans. First, much time may separate cause from effect in the case of an infection that develops over a human life span. Second, the host-pathogen relationship may initially be commensal: the host becomes a vector for infection of other humans, and in exchange the pathogen remains discreet and does as little harm as possible. Commensalism breaks down with increasing age because the host is no longer a useful vector, being less socially active and at higher risk of death. Certain neurodegenerative diseases may therefore be the terminal stage of a longer-lasting relationship in which the host helps the pathogen infect other hosts, largely via sexual relations. Strains from the Candida genus are particularly suspect. Such pathogens seem to have co-evolved not only with their host population but also with the local social environment. Different social environments may have thus favored different pathogenic strategies for manipulation of human behavior.
... Furthermore, these receptors are among the best described G protein-coupled receptors (Cotecchia et al. 2012). Multiple studies have reported a relationship between these behavioral changes and alterations in the concentration of neurotransmitters (Jaroslav Flegr and Kuba 2016;Skallova et al. 2006). According to the evidence, it was shown that urinary epinephrine excretion during a cognitive challenge in ADHD subjects was at least 40% lower than that reported for the control group (Pliszka et al. 1994). ...
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The most common form of the disease caused by Toxoplasma gondii (T. gondii) is latent toxoplasmosis due to the formation of tissue cysts in various organs, such as the brain. Latent toxoplasmosis is probably a risk factor in the development of some neuropsychiatric disorders. Behavioral changes after infection are caused by the host immune response, manipulation by the parasite, central nervous system (CNS) inflammation, as well as changes in hormonal and neuromodulator relationships. The present review focused on the exact mechanisms of T. gondii effect on the alteration of behavior and neurotransmitter levels, their catabolites and metabolites, as well as the interaction between immune responses and this parasite in the etiopathogenesis of psychiatric disorders. The dysfunction of neurotransmitters in the neural transmission is associated with several neuropsychiatric disorders. However, further intensive studies are required to determine the effect of this parasite on altering the level of neurotransmitters and the role of neurotransmitters in the etiology of host behavioral changes.
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Toxoplasmosis is a parasitic disease widespread in the temperate zone. The definitive hosts of Toxoplasma gondii, which causes the disease, are cats. All warm-blooded vertebrates, including humans, can be intermediate hosts. A person is usually infected by ingesting oocysts, e.g. by consuming along with vegetables some contaminated soil, by drinking contaminated water, or by ingesting tissue cysts contained, for instance, in poorly cooked meat. Less common is congenital transmission or transmission via organ transplant from an infected donor. Recently, it has been suggested that toxoplasmosis could also be transmitted sexually from infected men to uninfected women. In this article, we discuss and present evidence for an alternative hypothesis, which suggests that toxoplasmosis could be transmitted by oral sex (via fellatio) from an infected man to an uninfected person (male or female), especially if the uninfected individual swallows the infected ejaculate. This hypothesis finds support in the following facts and findings: (1) Toxoplasma has been found in male ejaculate. (2) In several animal species, presence of the parasite in the seminal fluid of infected males can lead to infection of uninfected females during mating. (3) A higher prevalence of toxoplasmosis has been reported in both homosexuals and promiscuous individuals, i.e. in populations which practice a broader spectrum of sexual activities, including oral sex. (4) In heterosexual couples, a partner’s infection seems to be a risk factor for infection in women but not in men. (5) A higher prevalence of toxoplasmosis in females compared to males has been observed in adolescents aged 10 to 14, where oral sex, including fellatio, is highly prevalent among those who have not yet engaged in penetrative intercourse. (6) On a theoretical level, one could expect that when an uninfected person swallows ejaculate containing Toxoplasma tissue cysts, this results in a similar infection pattern to ingestion of Toxoplasma-contaminated undercooked meat. (7) Approximately two-thirds of Toxoplasma infections in pregnant women cannot be explained by any of the known risk factors. (8) In both women and men who report practicing fellatio with men, there is a higher prevalence of toxoplasmosis than in corresponding controls. If our hypothesis is correct, an effective public health campaign with emphasis on early sexual education about the risks of unprotected oral sex will be necessary, especially in pregnant women and HIV-positive people. This route of toxoplasmosis transmission could be experimentally verified by force-feeding laboratory mice with the ejaculate of infected men.
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Toxoplasmosis affects about one third of human population worldwide. It has a wide range of effects on the health, immunity, behaviour, and both prenatal and postnatal outcomes of infected hosts, including humans. Among these effects, stage of infection-specific shifts in secondary sex ratio were described about ten years ago both in humans and in artificially infected mice. In both women and female mice, in the early stage of infection the probability of giving birth of sons significantly increases, up to 260 sons to every 100 daughters. In the late stages of infection, the probability of giving birth to sons markedly decreases to as low as 78 to every 100 daughters. An ecological correlation study shows that the effect of latent toxoplasmosis on human population biology and demography can be large. In fact, the effect of prevalence of toxoplasmosis on a nationwide sex ratio was the third strongest effect from the effects of 15 factors included in the analysis. It has been suggested that toxoplasmosis-associated concentration of steroid hormones or glucose may be the proximal cause in the sex ratio shift. A more parsimonious explanation of the upward secondary sex ratio shift is found in a lower stringency of quality control of embryos, whose side-effect is increased survival rate of the more immunogenic male embryos in immunosuppressed infected females. The most parsimonious explanation of the downward secondary sex ratio shift relies on the Trivers–Willard hypothesis, which predicts an adaptive shift to more daughters in females with impaired health or lower socioeconomic status.
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A recent study performed on 1.3 million patients showed a strong association between being bitten by a cat and probability of being diagnosed with depression. Authors suggested that infection with cat parasite Toxoplasma could be the reason for this association. A cross sectional internet study on a non-clinical population of 5,535 subjects was undertaken. The subjects that reported having been bitten by a dog and a cat or scratched by a cat have higher Beck depression score. They were more likely to have visited psychiatrists, psychotherapists and neurologists in past two years, to have been previously diagnosed with depression (but not with bipolar disorder). Multivariate analysis of models with cat biting, cat scratching, toxoplasmosis, the number of cats at home, and the age of subjects as independent variables showed that only cat scratching had positive effect on depression (p = 0.004). Cat biting and toxoplasmosis had no effect on the depression, and the number of cats at home had a negative effect on depression (p = 0.021). Absence of association between toxoplasmosis and depression and five times stronger association of depression with cat scratching than with cat biting suggests that the pathogen responsible for mood disorders in animals-injured subjects is probably not the protozoon Toxoplasma gondii but another organism; possibly the agent of cat-scratched disease – the bacteria Bartonella henselae.
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A man whose romantic partner is sexually unfaithful is at risk of sperm competition and cuckoldry—unwitting investment in offspring to whom he is genetically unrelated. Men, therefore, may have evolved mechanisms to solve the adaptive problems of sperm competition and cuckoldry. The current research investigates another potential anti-cuckoldry tactic: reducing in-pair copulation duration, thereby more quickly placing his sperm into competition. We hypothesize that in-pair copulation duration will be negatively correlated with female infidelity (Hypothesis 1). We further hypothesize that in-pair copulation duration will be negatively correlated with sexual coercion (Hypothesis 2). Results of Study 1 (men’s reports, n = 410) indicate that both men’s perceptions of female infidelity and men’s sexual coercion predict shorter in-pair copulation duration. Results of Study 2 (women’s reports, n = 455) did not provide statistical support for the study hypotheses. The current research provides an initial investigation of men’s adjustment of copulatory duration, and suggests that men reduce in-pair copulation duration, and ejaculate more quickly at the couple’s most recent copulation, in response to greater risk of sperm competition and in the context of sexual coercion.
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Objectives: We theorize that sexual arousal by dominance and submission may be connected to a reproduction strategy respecting a reached social dominance rank (a common reproduction strategy in socially living mammals), while the preference for "bondage" may be derived from an opportunistic strategy when being unable to compete for hierarchic rank (an alternative reproductive strategy that co-occurs frequently with the above-named main strategy). The answers to questions dealing with hierarchy in character should correlate exclusively with sexual arousal connected to any kind of expression of a hierarchy, but not with bondage. Design and settings: The data were obtained from young adults (157 males and 183 females aged 18-20, with mean 18.4 years) via questionnaires. Results: Seven out of eight questions dealing with hierarchy correlated with sexual arousal by dominance and submission in men (Spearman's r=0.169-0.313; p<0.05 - p<0.001), two questions correlated with sexual arousal by dominance and submission in women (Spearman's r=0.32-0.166, p<0.001, p<0.05). THE MAIN FINDINGS: The questions dealing with hierarchy correlated with sexual arousal by dominance and submission while no answers correlated with bondage, neither in men nor in women. Conclusion: The preference for sexual arousal by dominance and submission may be connected to strategy respecting rank, while the preference for "bondage" may be derived from an opportunistic strategy that may be essential for possible partner problems solution. From the evolutionary biology point of view, these patterns of sadomasochistic sex appear as adaptive rather than as pathology.
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Objectives: Toxoplasma gondii, the protozoan parasite infecting about 30% population worldwide, is suspected to be the etiological agent of certain form of schizophrenia disease. Toxoplasma is known to change levels of certain neurotransmitters, cytokines and several hormones in both infected animals and humans. A common feature of toxoplasmosis and schizophrenia is a disorder of immune system. Methods: Here we studied the levels of five neuro- and immunomodulatory steroids, selected hormones and lipids in sera of 173 schizophrenia patients. Results: Toxoplasma infected schizophrenia patients expressed only insignificantly lower concentration of neuro- and immunomodulatory DHEA metabolites. Infected women had higher concentration of glucose while infected men had higher concentration of cholesterol and LDL cholesterol. No significant effect of human cytomegalovirus infection on the concentration of the above parameters was observed. The difference in the concentration of DHEA metabolites faded with the decrease of the concentration of anti-Toxoplasma IgG antibodies (i.e. with the duration of Toxoplasma infection) while the difference in the concentration of cholesterol and LDL-cholesterol increased with the decrease of the concentration of anti-Toxoplasma IgG antibodies. The prevalence of toxoplasmosis in male (53.2%) but not female (29.8%) schizophrenia patients was unusually high in comparison with prevalence of toxoplasmosis in a general population. Conclusion: Our results provided an explanation for seemingly decreasing prevalence of toxoplasmosis in schizophrenia patients observed in current studies (increased concerns about the rights of patients resulting in absence of non-cooperative Toxoplasma-positive patients in the study population) and suggest possible explanation for reported positive correlation between prevalence of toxoplasmosis and incidence of cardiovascular diseases (accelerated atherosclerotic development due to increased level of cholesterol and LDL in Toxoplasma infected humans).
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Existing evidence suggests that the psychological design of romantic jealousy differs for men and women: Men are more likely than women to report greater upset in response to a partner's sexual than emotional infidelity, whereas women are more likely than men to report greater upset in response to a partner's emotional than sexual infidelity. However, the observed sex difference can be explained after the fact by both an evolutionary analysis of past reproductive costs and a social constructionist analysis of social and gender role training. Attempting to disentangle these competing perspectives, researchers have measured participants' upset in response to a sibling's or a child's partner's infidelities. In contrast to what a socialization perspective would predict, participants' sex did not seem to affect their responses; the key variable was the sex of the sibling or the child, in line with a heuristic application of the evolutionary perspective. The present study attempted not only to test these competing hypotheses but also to extend previous work by involving participants with a gay or lesbian sibling and examining whether participants' responses are triggered by their sibling's or sibling's partner's sex. In line with an evolutionary perspective, participants' sex did not assert an effect on their responses. The key variable seemed to be the sex of the sibling (rather than the sex of the sibling's partner), with participants reporting greater levels of upset in response to the sexual than emotional infidelity of a gay brother's partner and to the emotional than sexual infidelity of a lesbian sister's partner. The ensuing discussion offers suggestions for future work on sex-specific triggers of jealousy.
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Several studies have investigated the association between infection with Toxoplasma gondii (Nicolle et Manceaux, 1908), pregnancy and fertility, but the results of studies focused on the fertility are rather ambiguous. Here we report results of four new cross-sectional studies. The studies were performed in the General University Hospital, Prague (study A with n = 1 165, and study C with n = 317), in private clinics of the Centre of Reproductive Medicine, Prague (study B with n = 1 016), and in a population of Czech and Slovak volunteers from the Facebook page 'Guinea Pigs' willing to participate in various basic science studies (study D with n = 524). In studies A and B, the clinical records were used to assess the fertility problems, whereas in studies C and D, the women were asked to rate their fertility problems using a six-point scale. Pregnant T. gondii-infected women were older than T. gondii-free women (study A: 33.1 vs 31.2, P < 0.001; study B: 30.6 vs 29.6, P = 0.012) and more often used assisted reproductive technology to conceive (study A: 17.2% vs 12.4%, P = 0.041; study B: 13.4% vs 9.2%, P = 0.317). Pregnant T. gondii-infected primiparous women were older than T. gondii-free primiparas (study A: 31.1 vs 29.5, P < 0.001; study B: 29.7 vs 28.9, P = 0.064) and more often used assisted reproductive technology to conceive (study A: 24.7% vs 14.4%, P = 0.010; study B: 15.9% vs 15.5%, P = 0.888). T. gondii-infected women reported to take a longer time to conceive than T. gondii-free women (P = 0.015). They also claimed to have more fertility problems than T. gondii-free women (P < 0.0001). Our results suggest that 'asymptomatic' latent toxoplasmosis could be a more serious source of fertility problems and health-associated burden than more severe but far rarer congenital toxoplasmosis.
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Male homosexual preference (MHP) has long been of interest to scholars studying the evolution of human sexuality. Indeed, MHP is partially heritable, induces a reproductive cost and is common. MHP has thus been considered a Darwinian paradox. Several questions arise when MHP is considered in an evolutionary context. At what point did MHP appear in the human evolutionary history? Is MHP present in all human groups? How has MHP evolved, given that MHP is a reproductively costly trait? These questions were addressed here, using data from the anthropological and archaeological literature. Our detailed analysis of the available data challenges the common view of MHP being a "virtually universal" trait present in humans since prehistory. The conditions under which it is possible to affirm that MHP was present in past societies are discussed. Furthermore, using anthropological reports, the presence or absence of MHP was documented for 107 societies, allowing us to conclude that evidence of the absence of MHP is available for some societies. A recent evolutionary hypothesis has argued that social stratification together with hypergyny (the hypergyny hypothesis) are necessary conditions for the evolution of MHP. Here, the link between the level of stratification and the probability of observing MHP was tested using an unprecedented large dataset. Furthermore, the test was performed for the first time by controlling for the phylogenetic non-independence between societies. A positive relationship was observed between the level of social stratification and the probability of observing MHP, supporting the hypergyny hypothesis.
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Equality between partners is considering a feature of the functional partnerships in westernized societies. However, the evolutionary consequences of how in-pair hierarchy influences reproduction are less known. Attraction of some high-ranking women towards low-ranking men represents a puzzle. Young urban adults (120 men, 171 women) filled out a questionnaire focused on their sexual preference for higher or lower ranking partners, their future in-pair hierarchy, and hierarchy between their parents. Human pairs with a hierarchic disparity between partners conceive more offspring than pairs of equally-ranking individuals, who, in turn, conceive more offspring than pairs of two dominating partners. Importantly, the higher reproductive success of hierarchically disparate pairs holds, regardless of which sex, male or female, is the dominant one. In addition, the subjects preferring hierarchy disparity in partnerships were with greater probability sexually aroused by such disparity, suggesting that both the partnership preference and the triggers of sexual arousal may reflect a mating strategy. These results challenge the frequently held belief in within-pair equality as a trademark of functional partnerships. It rather appears that existence of some disparity improves within-pair cohesion, facilitating both cooperation between partners and improving the pairs' ability to face societal challenges. The parallel existence of submissivity-dominance hierarchies within human sexes allows for the parallel existence of alternative reproductive strategies, and may form a background for the diversity of mating systems observed in human societies. Arousal of overemphasized dominance/submissiveness may explain sadomasochistic sex, still little understood from the evolutionary psychology point of view.
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Background: About 30% of people on Earth have latent toxoplasmosis. Infected subjects do not express any clinical symptoms, however, they carry dormant stages of parasite Toxoplasma for the rest of their life. This form of toxoplasmosis is mostly considered harmless, however, recent studies showed its specific effects on physiology, behaviour and its associations with various diseases, including psychiatric disorders such as schizophrenia. Individuals who suffer from schizophrenia have about 2.7 times higher prevalence of Toxoplasma-seropositivity than controls, which suggests that some traits characteristic of schizophrenic patients, including the sex difference in schizophrenia onset, decrease of grey matter density in specific brain areas and modification of prepulse inhibition of startle reaction could in fact be caused by toxoplasmosis for those patients who are Toxoplasma-seropositive. Methodology/principal findings: We measured the effect of prepulse inhibition/facilitation of the startle reaction on reaction times. The students, 170 women and 66 men, were asked to react as quickly as possible to a startling acoustic signal by pressing a computer mouse button. Some of the startling signals were without the prepulse, some were 20 msec. preceded by a short (20 msec.) prepulse signal of lower intensity. Toxoplasma-seropositive subjects had longer reaction times than the controls. Acoustic prepulse shorted the reaction times in all subjects. This effect of prepulse on reaction times was stronger in male subjects and increased with the duration of infection, suggesting that it represented a cumulative effect of latent toxoplasmosis, rather than a fading out after effect of past acute toxoplasmosis. Conclusions: Different sensitivity of Toxoplasma-seropositive and Toxoplasma-seronegative subjects on effect of prepulses on reaction times (the toxoplasmosis-prepulse interaction) suggested, but of course did not prove, that the alternations of prepulse inhibition of startle reaction observed in schizophrenia patients probably joined the list of schizophrenia symptoms that are in fact caused by latent toxoplasmosis.
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Background: Toxoplasmosis is becoming a global health hazard as it infects 30-50% of the world human population. Clinically, the life-long presence of the parasite in tissues of a majority of infected individuals is usually considered asymptomatic. However, a number of studies show that this 'asymptomatic infection' may also lead to development of other human pathologies. Aims of the study: The purpose of the study was to collect available geoepidemiological data on seroprevalence of toxoplasmosis and search for its relationship with mortality and disability rates in different countries. Methods and findings: Prevalence data published between 1995-2008 for women in child-bearing age were collected for 88 countries (29 European). The association between prevalence of toxoplasmosis and specific disease burden estimated with age-standardized Disability Adjusted Life Year (DALY) or with mortality, was calculated using General Linear Method with Gross Domestic Product per capita (GDP), geolatitude and humidity as covariates, and also using nonparametric partial Kendall correlation test with GDP as a covariate. The prevalence of toxoplasmosis correlated with specific disease burden in particular countries explaining 23% of variability in disease burden in Europe. The analyses revealed that for example, DALY of 23 of 128 analyzed diseases and disease categories on the WHO list showed correlations (18 positive, 5 negative) with prevalence of toxoplasmosis and another 12 diseases showed positive trends (p<0.1). For several obtained significant correlations between the seroprevalence of toxoplasmosis and specific diseases/clinical entities, possible pathophysiological, biochemical and molecular explanations are presented. Conclusions: The seroprevalence of toxoplasmosis correlated with various disease burden. Statistical associations does not necessarily mean causality. The precautionary principle suggests however that possible role of toxoplasmosis as a triggering factor responsible for development of several clinical entities deserves much more attention and financial support both in everyday medical practice and future clinical research.
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In this second article of a two‐part series, data from three separate studies are presented supporting the reliability, discriminant, and construct validity of the Attraction to Sexual Aggression (ASA) scale. Higher scores on this scale were associated with attitudes supporting aggression against women, affective reactions to media portrayals of forced sex, physiological and self‐reported sexual arousal, hostility toward women, dominance motives, and antisocial personality characteristics. Based on data with low sexual aggressors, higher ASA scores were associated with greater similarity (on relevant dimensions) to high sexual aggressors, suggesting that ASA may help identify potentially sexually aggressive men at “risk” for future sexual coercion. However, caution in the use of such identification is urged. Finally, it is concluded that although the data support the usefulness of earlier work with self‐reported likelihood measures, the use of ASA is an improvement in this line of research. Directions for future development of this scale and research are also discussed.
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Although research has made progress in elucidating the benefits exchanged within same- and opposite-sex friendships formed between heterosexual men and women, it is less clear why straight women and gay men form close relationships with one another. The current experiments begin to address this question by exploring a potential benefit hypothesized to be uniquely available to straight women and gay men in the context of these friendships: trustworthy mating advice. Experiment 1 revealed that straight women perceive mating-relevant advice from a gay man to be more trustworthy than similar advice offered by a straight man or woman. Experiment 2 demonstrated that gay men perceive mating advice offered by a straight woman to be more trustworthy than advice offered by a lesbian woman or another gay man. Overall, the results provide initial experimental evidence that relationships between gay men and straight women may be characterized by a mutual exchange of mating-relevant benefits in the absence of sexual interest or competition.
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The parasitic protozoan Toxoplasma gondii infects about one-third of the population of developed countries. The life-long presence of dormant stages of this parasite in the brain and muscular tissues of infected humans is usually considered asymptomatic from the clinical point of view. In the past 20 years, research performed mostly on military personnel, university students, pregnant women and blood donors has shown that this 'asymptomatic' disease has a large influence on various aspects of human life. Toxoplasma-infected subjects differ from uninfected controls in the personality profile estimated with two versions of Cattell's 16PF, Cloninger's TCI and Big Five questionnaires. Most of these differences increase with the length of time since the onset of infection, suggesting that Toxoplasma influences human personality rather than human personality influencing the probability of infection. Toxoplasmosis increases the reaction time of infected subjects, which can explain the increased probability of traffic accidents in infected subjects reported in three retrospective and one very large prospective case-control study. Latent toxoplasmosis is associated with immunosuppression, which might explain the increased probability of giving birth to a boy in Toxoplasma-infected women and also the extremely high prevalence of toxoplasmosis in mothers of children with Down syndrome. Toxoplasma-infected male students are about 3 cm taller than Toxoplasma-free subjects and their faces are rated by women as more masculine and dominant. These differences may be caused by an increased concentration of testosterone. Toxoplasma also appears to be involved in the initiation of more severe forms of schizophrenia. At least 40 studies confirmed an increased prevalence of toxoplasmosis among schizophrenic patients. Toxoplasma-infected schizophrenic patients differ from Toxoplasma-free schizophrenic patients by brain anatomy and by a higher intensity of the positive symptoms of the disease. Finally, five independent studies performed in blood donors, pregnant women and military personnel showed that RhD blood group positivity, especially in RhD heterozygotes, protects infected subjects against various effects of latent toxoplasmosis, such as the prolongation of reaction times, an increased risk of traffic accidents and excessive pregnancy weight gain. The modern human is not a natural host of Toxoplasma. Therefore, it can only be speculated which of the observed effects of latent toxoplasmosis are the result of the manipulation activity of the Toxoplasma aimed to increase the probability of its transmission from a natural intermediate to the definitive host by predation, and which are just side effects of chronic infection.
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A scale designed to measure attraction to sexual aggression is described, based on earlier work assessing self‐reported likelihood of committing rape. This scale's associations with measures of theoretically relevant attitudes, perceptions, and behavioral inclinations are examined in comparison with briefer measures, and with a number of other scales measuring attraction to various types of sexual interactions. These include conventional sex (e.g., heterosexual intercourse), homosexuality, bondage, unconventional sex (e.g., group sex), and deviant sex (e.g., pedophilia). Data supporting the longer and shorter versions of the attraction to sexual aggression scale are presented, showing internal consistency, test‐retest reliability, and discriminant and construct validity. As well, a number of issues raised by critiques of research in this area are addressed empirically.
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Seven experts on personality measurement here discuss the viability of public-domain personality measures, focusing on the International Personality Item Pool (IPIP) as a prototype. Since its inception in 1996, the use of items and scales from the IPIP has increased dramatically. Items from the IPIP have been translated from English into more than 25 other languages. Currently over 80 publications using IPIP scales are listed at the IPIP Web site (http://ipip.ori.org), and the rate of IPIP-related publications has been increasing rapidly. The growing popularity of the IPIP can be attributed to five factors: (1) It is cost free; (2) its items can be obtained instantaneously via the Internet; (3) it includes over 2000 items, all easily available for inspection; (4) scoring keys for IPIP scales are provided; and (5) its items can be presented in any order, interspersed with other items, reworded, translated into other languages, and administered on the World Wide Web without asking permission of anyone. The unrestricted availability of the IPIP raises concerns about possible misuse by unqualified persons, and the freedom of researchers to use the IPIP in idiosyncratic ways raises the possibility of fragmentation rather than scientific unification in personality research.
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Background: 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 "fatal attraction phenomenon," the conversion of innate fear of cat odour into attraction to cat odour in infected rodents. While most behavioural effects of toxoplasmosis were confirmed also in humans, neither the fatal attraction phenomenon nor any toxoplasmosis-associated changes in olfactory functions have been searched for in them. Principal findings: Thirty-four Toxoplasma-infected and 134 noninfected students rated the odour of urine samples from cat, horse, tiger, brown hyena and dog for intensity and pleasantness. The raters were blind to their infection status and identity of the samples. No signs of changed sensitivity of olfaction were observed. However, we found a strong, gender dependent effect of toxoplasmosis on the pleasantness attributed to cat urine odour (p = 0.0025). Infected men rated this odour as more pleasant than did the noninfected men, while infected women rated the same odour as less pleasant than did noninfected women. Toxoplasmosis did not affect how subjects rated the pleasantness of any other animal species' urine odour; however, a non-significant trend in the same directions was observed for hyena urine. Conclusions: The absence of the effects of toxoplasmosis on the odour pleasantness score attributed to large cats would suggest that the amino acid felinine could be responsible for the fatal attraction phenomenon. Our results also raise the possibility that the odour-specific threshold deficits observed in schizophrenia patients could be caused by increased prevalence of Toxoplasma-infected subjects in this population rather than by schizophrenia itself. The trend observed with the hyena urine sample suggests that this carnivore, and other representatives of the Feliformia suborder, should be studied for their possible role as definitive hosts in the life cycle of Toxoplasma.
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Abstract. Scientists have long puzzled over how homosexual orientation has evolved, given the assumed low relative fitness of homosexual individuals compared to heterosexual individuals. A number of theoretical models for the evolution of homosexuality have been postulated including balance polymorphism, "Fertile females", hypervariability of DNA sequences, kin selection, and "parental manipulation". In this paper, I propose a new group-selection model for the evolution of homosexuality which offers two advantages over existing models: (1) its non-assumption of genetic determinism, and (2) its lack of dependency on an inefficient altruism relation and family dynamics theory.
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Popular statistical software packages do not have the proper procedures for determining the number of components in factor and principal components analyses. Parallel analysis and Velicer’s minimum average partial (MAP) test are validated procedures, recommended widely by statisticians. However, many researchers continue to use alternative, simpler, but flawed procedures, such as the eigenvaluesgreater-than-one rule. Use of the proper procedures might be increased if these procedures could be conducted within familiar software environments. This paper describes brief and efficient programs for using SPSS and SAS to conduct parallel analyses and the MAP test.
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Ten male dogs were distributed into three experimental groups for infection with Toxoplasma gondii: GI - three dogs inoculated with 2.0x10(5) P strais oocysts, GII - three dogs infected with 1.0x10(6) RH strain tachyzoites, and GIII - four controls dogs. Several clinical parameters were evaluated. IFAT was performed to detect anti-T. gondii antibodies. Presence of the parasite in semen was evaluated by PCR and bioassay techniques. Tissue parasitism was examined using bioassays and immunohistochemistry in testicle and epididymis fragments collected after orchiectomy. In semen samples collected from these two groups, the presence of T. gondii was verified by bioassays and PCR. T. gondii was detected by immunohistochemistry in tissues (testicle and epididymis fragments) of all six experimentally infected dogs. The T. gondii-positive seminal samples were used in the artificial insemination (AI) of four female dogs free of toxoplasmic infection. Seven days after AI, all of the female dogs presented serologic conversion (IFAT). Fetal reabsorption occurred in two of the dogs, while the others sustained full-term gestation. Several T. gondii cysts were detected in the brains of four offspring. These results suggest that T. gondii can be sexually transmitted in domestic dogs.
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Toxoplasma gondii's importance for humans refers mainly to primary infection during pregnancy, resulting in abortion/stillbirth or congenital toxoplasmosis. The authors sought to evaluate the current global status of T. gondii seroprevalence and its correlations with risk factors, environmental and socioeconomic parameters. Literature published during the last decade on toxoplasmosis seroprevalence, in women who were pregnant or of childbearing age, was retrieved. A total of 99 studies were eligible; a further 36 studies offered seroprevalence data from regions/countries for which no data on pregnancy/childbearing age were available. Foci of high prevalence exist in Latin America, parts of Eastern/Central Europe, the Middle East, parts of south-east Asia and Africa. Regional seroprevalence variations relate to individual subpopulations' religious and socioeconomic practices. A trend towards lower seroprevalence is observed in many European countries and the United States of America (USA). There is no obvious climate-related gradient, excluding North and Latin America. Immigration has affected local prevalence in certain countries. We further sought to recognise specific risk factors related to seropositivity; however, such risk factors are not reported systematically. Population awareness may affect recognition of said risks. Global toxoplasmosis seroprevalence is continuingly evolving, subject to regional socioeconomic parameters and population habits. Awareness of these seroprevalence trends, particularly in the case of women of childbearing age, may allow proper public health policies to be enforced, targeting in particular seronegative women of childbearing age in high seroprevalence areas.
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Using both correlational and experimental evidence, the relationship between parasite load and host activity was assessed in brown rats, Rattus norvegicus. Two hypotheses were tested--(1) that parasites with indirect life-cycles, involving transmission between a prey and its predator, will alter the activity of the intermediate host so as to increase its susceptibility to predation by the definitive host and (2) that activity levels in parasitized rats would be increased rather than decreased. Four groups of rats (n = 140) were examined. One group (n = 50) were wild brown rats trapped from 3 UK farmsteads, with naturally occurring parasites. The others were purpose-bred wild/laboratory hybrid rats with experimentally induced parasitic infections of either (n = 15) adult-acquired or (n = 15) congenitally-acquired Toxoplasma gondii (an indirect life-cycle parasite), or (n = 15) Syphacia muris (a direct life-cycle parasite). Uninfected hybrid rats ( n = 45), matched for sex, age and weight, served as controls. Rats were housed individually in outdoor cages, and their activities were recorded on video-tapes for 6 non-consecutive 10 h nights. Exercise wheels were also available for the hybrid rats. Out of 6 parasite species detected in the wild rats, T. gondii was the only one which required predation by a definitive host to complete its life-cycle, and was also the only parasite to be associated with higher activity levels in infected than uninfected rats. Hybrid rats infected with T. gondii were also more active than those uninfected, whereas there were no differences in activity levels between S. muris infected and uninfected rats. This study shows that the indirect life-cycle parasite T. gondii can influence the activity of its intermediate host the rat. I suggest that this may facilitate its transmission to the cat definitive host.
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Homosexuality is increasingly recognized as having a genetic component. Why then does it persist, when common sense suggests that it should result in fewer offspring? Monozygotic-twin studies permit a rough estimate of the importance of genetics (70%) in the development of male homosexuality, and the proportion of homosexuals remains constant: Fisher's Theorem then tells us there is an advantage to the heterozygote, which we find need be no greater than 2%. Behavior and sperm competition suggest what this advantage might be.
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Sexual narcissism, an egocentric pattern of sexual behavior, has recently been described in the literature and has been discovered to be associated with cluster B type personality disorders. Although the research seems to have validated sexual narcissism as a characteristic of borderline and histrionic personality disorders, it is yet to be tested with narcissistic personalities. In an effort to further explore this relationship as well as the validity of sexual narcissism, this study systematically compared a sample (ages 24-33 years) of males with narcissistic personality disorder with an adequately matched sample of males without personality disorders. As compared to the control group, narcissistic men were found to have significantly lower self-esteem, more negative attitudes toward sex, greater egocentric patterns of sexual behavior, more conservative or traditional gender-role orientation, and greater sexual preoccupation. Despite these findings, there were no significant differences between the groups on sexual depression and the narcissistic men evidenced significantly higher sexual esteem. Implications for these findings are discussed.
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Many parasites induce characteristic changes in behavior of their hosts. In humans latent toxoplasmosis is associated with changes in personality profiles. It has been already shown that a decrease in superego strength is correlated with duration of toxoplasmosis in men. Here we studied changes in personality profiles with Cattell's 16 PF questionnaire in Toxoplasma-infected women. The changes were measured as differences in personality factors between Toxoplasma-infected subjects and uninfected controls of the same age. The low-rate changes were studied in 230 women diagnosed with acute toxoplasmosis during past 14 years. The results showed the correlation between duration of toxoplasmosis and level of factors G (high superego strength) and Q3 (high strength of self sentiment). The high-rate changes were estimated by measuring the correlation between level of Toxoplasma-antibody titers (which rapidly decline after the end of acute phase of toxoplasmosis) and personality factors in an experimental set of 55 young mothers with latent toxoplasmosis. Again, certain factors, namely A (affectothymia), F (surgence), G (high superego strength), H (parmia), and L (protension), correlated with the length of the infection. We suggest that the parasite induced the changes in the personality profiles of the women because of our observation of an increasingly different personality profile over time between women with latent infection and controls. The same evidence questions the view that women with a particular personality profile are more prone to acquisition of T. gondii infection.
Popular statistical software packages do not have the proper procedures for determining the number of components in factor and principal components analyses. Parallel analysis and Velicer's minimum average partial (MAP) test are validated procedures, recommended widely by statisticians. However, many researchers continue to use alternative, simpler, but flawed procedures, such as the eigenvalues-greater-than-one rule. Use of the proper procedures might be increased if these procedures could be conducted within familiar software environments. This paper describes brief and efficient programs for using SPSS and SAS to conduct parallel analyses and the MAP test.
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Toxoplasmosis is one of the more common parasitic zoonoses world-wide. Its causative agent, Toxoplasma gondii, is a facultatively heteroxenous, polyxenous protozoon that has developed several potential routes of transmission within and between different host species. If first contracted during pregnancy, T. gondii may be transmitted vertically by tachyzoites that are passed to the foetus via the placenta. Horizontal transmission of T. gondii may involve three life-cycle stages, i.e. ingesting infectious oocysts from the environment or ingesting tissue cysts or tachyzoites which are contained in meat or primary offal (viscera) of many different animals. Transmission may also occur via tachyzoites contained in blood products, tissue transplants, or unpasteurised milk. However, it is not known which of these routes is more important epidemiologically. In the past, the consumption of raw or undercooked meat, in particular of pigs and sheep, has been regarded as a major route of transmission to humans. However, recent studies showed that the prevalence of T. gondii in meat-producing animals decreased considerably over the past 20 years in areas with intensive farm management. For example, in several countries of the European Union prevalences of T. gondii in fattening pigs are now <1%. Considering these data it is unlikely that pork is still a major source of infection for humans in these countries. However, it is likely that the major routes of transmission are different in human populations with differences in culture and eating habits. In the Americas, recent outbreaks of acute toxoplasmosis in humans have been associated with oocyst contamination of the environment. Therefore, future epidemiological studies on T. gondii infections should consider the role of oocysts as potential sources of infection for humans, and methods to monitor these are currently being developed. This review presents recent epidemiological data on T. gondii, hypotheses on the major routes of transmission to humans in different populations, and preventive measures that may reduce the risk of contracting a primary infection during pregnancy.
Article
The existence of homosexuality in humans poses a problem for evolutionary theory. Exclusive male homosexuality has a catastrophic effect on reproduction and yet inherited factors appear to contribute to it. Previous attempts to resolve this conundrum are inconsistent with aspects of evolutionary theory. Additional limitations are as follows. Until recently, accounts of homosexuality have paid little attention to the probable existence of adaptive bisexuality in ancestral populations, from which further variations in sexual orientation may have evolved. Secondly, previous explanations have concentrated on the ancestral environment of two to three million years ago as the determinant of modern sexuality, when more recent influences are likely to have had considerable impact. I argue in favour of a longitudinal rather than cross-sectional model of the ancestral environment. Thirdly, they have often ignored the possibility of variable phenotypic expression, whereby those individuals with a genetic propensity for homosexuality exhibit different and adaptive qualities on most other occasions. It has been demonstrated in previous studies that homosexual men have superior linguistic skills compared to heterosexual men. This may be the result of an adaptive feminising effect on the male brain and apply to many practising heterosexuals. Other adaptations to the recent ancestral environment may include enhanced empathy, fine motor skills and impulse control. By drawing together these contributing factors an evolutionary basis for homosexuality can be demonstrated.
Article
Toxoplasma gondii, a parasitic protozoan, infects about 30-60% of people worldwide. The latent toxoplasmosis, i.e. life-long presence of cysts in the brain and muscular tissues, has no effect on human health. However, infected subjects score worse in psychomotor performance tests and have different personality profiles than Toxoplasma-negative subjects. The mechanism of this effect is unknown; however, it is supposed that presence of parasites' cysts in the brain induces an increase of the concentration of dopamine. Here we search for the existence of differences in personality profile between Toxoplasma-positive and Toxoplasma-negative subjects by testing 857 military conscripts using a modern psychobiological questionnaire, namely with Cloninger's Temperament and Character Inventory (TCI). ANCOVA showed that Toxoplasma-positive subjects had lower Novelty seeking (NS) scores (P=0.035) and lower scores for three of its four subscales, namely Impulsiveness (P=0.049), Extravagance (P=0.056) and Disorderliness (P=0.006) than the Toxoplasma-negative subjects. Differences between Toxoplasma-negative and positive subjects in NS was inversely correlated with duration of toxoplasmosis estimated on the basis of concentration anti-Toxoplasma antibodies (P=0.031). Unexpectedly, the infected subjects had also lower IQ (P(2)=0.003) and lower probability of achieving a higher education (P(2)<0.0000). Decrease of NS suggests that the increase of dopamine in brain of infected subjects can represent a missing link between toxoplasmosis and schizophrenia.