Tuesday, March 29, 2022

The cat parasite Toxoplasma gondii might boost people's sexual attractiveness, possibly thru changes in facial symmetry

Borraz-León JI, Rantala MJ, Krams IA, Cerda-Molina AL, Contreras-Garduño J. 2022. Are Toxoplasma-infected subjects more attractive, symmetrical, or healthier than non-infected ones? Evidence from subjective and objective measurements. PeerJ 10:e13122. Mar 2022. https://doi.org/10.7717/peerj.13122


Background: Parasites are among the main factors that negatively impact the health and reproductive success of organisms. However, if parasites diminish a host’s health and attractiveness to such an extent that finding a mate becomes almost impossible, the parasite would decrease its odds of reproducing and passing to the next generation. There is evidence that Toxoplasma gondii (T. gondii) manipulates phenotypic characteristics of its intermediate hosts to increase its spread. However, whether T. gondii manipulates phenotypic characteristics in humans remains poorly studied. Therefore, the present research had two main aims: (1) To compare traits associated with health and parasite resistance in Toxoplasma-infected and non-infected subjects. (2) To investigate whether other people perceive differences in attractiveness and health between Toxoplasma-infected and non-infected subjects of both sexes.

Methods: For the first aim, Toxoplasma-infected (n = 35) and non-infected subjects (n = 178) were compared for self-perceived attractiveness, number of sexual partners, number of minor ailments, body mass index, mate value, handgrip strength, facial fluctuating asymmetry, and facial width-to-height ratio. For the second aim, an independent group of 205 raters (59 men and 146 women) evaluated the attractiveness and perceived health of facial pictures of Toxoplasma-infected and non-infected subjects.

Results: First, we found that infected men had lower facial fluctuating asymmetry whereas infected women had lower body mass, lower body mass index, a tendency for lower facial fluctuating asymmetry, higher self-perceived attractiveness, and a higher number of sexual partners than non-infected ones. Then, we found that infected men and women were rated as more attractive and healthier than non-infected ones.

Conclusions: Our results suggest that some sexually transmitted parasites, such as T. gondii, may produce changes in the appearance and behavior of the human host, either as a by-product of the infection or as the result of the manipulation of the parasite to increase its spread to new hosts. Taken together, these results lay the foundation for future research on the manipulation of the human host by sexually transmitted pathogens and parasites.


Limitations and future directions

Results showed that boys as young as age 3 generally valued strength more than girls: boys, on average, said it was more important to be strong than girls did, & were more likely to prefer strength-related occupations than girls

Early Gender Differences in Valuing Strength. May Ling D. Halim, Dylan J. Sakamoto, Lyric N. Russo, Kaelyn N. Echave, Miguel A. Portillo & Sachiko Tawa. Archives of Sexual Behavior, Mar 28 2022. https://link.springer.com/article/10.1007/s10508-021-02185-4

Abstract: Being strong is a prominent male stereotype that children learn early in life; however, it is unknown as to when children start to value being strong and when gender differences in valuing strength might emerge. In the current study, we interviewed an ethnically diverse sample of 168 3–5 year-olds (88 girls, 80 boys) to address this gap in the literature. Results showed that boys as young as age 3 generally valued strength more than girls: (1) boys, on average, said it was more important to be strong than girls did, and (2) boys were more likely to prefer strength-related occupations than girls. Boys were also more likely to select boys than girls as the gender who cares more about physical strength. Additionally, with age, both girls and boys demonstrated knowledge of the stereotype that boys care about physical strength, with girls also being less likely to associate being a girl with being strong. Overall, the results suggest that valuing physical strength starts in early childhood, and gender differences in valuing strength are evident at the eve of gender identity development. Possible implications for boys’ later well-being and health are discussed.

Individuals with higher income may exhibit profiles of adult personality development that more closely resemble aspects of a healthy personality

Income moderates changes in big-five personality traits across eighteen years. Vincent YS Oh, Ismaharif Ismail, Eddie MW Tong. European Journal of Personality, March 28, 2022. https://doi.org/10.1177/08902070221078479

Abstract: The role of income in adult personality change remains poorly understood. Using latent growth modeling, we performed exploratory analyses of how longitudinal trajectories of change in personal income and the Big Five personality traits would be related. We examined 4234 participants (2149 Males, 2085 Females; MT1age = 46.42, SDT1age = 13.36, age range at T1: 20–74 years) across three time points spanning 18 years using data from the Midlife in the United States study. Results indicated that starting levels of income moderated changes in four personality traits. Specifically, income moderated the slopes of openness to experience, extraversion, agreeableness, and neuroticism, such that for high-income individuals, openness to experience, extraversion, and agreeableness were less likely to decline and more likely to either increase or remain stable over time, while neuroticism was less likely to increase and more likely to remain stable over time. Conversely, personality traits were weaker predictors of income change as slopes of income were not moderated by starting levels of any of the personality traits. Moreover, changes in income were not correlated with changes in any of the personality traits. The findings suggest that individual differences in income could potentially explain diverging trajectories of personality change.

Keywords: big five, income, personality development, personality change, socioeconomic status

Women are unhappier than men in anxiety, depression, fearfulness, sadness, loneliness, & anger; are also less satisfied with many aspects of their lives such as democracy, the economy, the state of education and health services

The Female Happiness Paradox. David G. Blanchflower & Alex Bryson. NBER Working Paper 29893.  March 2022. https://www.nber.org/papers/w29893

Abstract: Using data across countries and over time we show that women are unhappier than men in unhappiness and negative affect equations, irrespective of the measure used – anxiety, depression, fearfulness, sadness, loneliness, anger – and they have more days with bad mental health and more restless sleep. Women are also less satisfied with many aspects of their lives such as democracy, the economy, the state of education and health services. They are also less happy in the moment in terms of peace and calm, cheerfulness, feeling active, vigorous, fresh and rested. However, prior evidence on gender differences in global wellbeing metrics – happiness and life satisfaction – is less clear cut. Differences vary over time, location, and with model specification and the inclusion of controls especially marital status. We also show that there are significant variations by month in happiness data regarding whether males are happier than females but find little variation by month in unhappiness data. It matters which months are sampled when measuring positive affect but not with negative affect. These monthly data reveal that women’s happiness was more adversely affected by the COVID shock than men’s, but also that women’s happiness rebounded more quickly suggesting resilience. As a result, we now find strong evidence that males have higher levels of both happiness and life satisfaction in recent years even before the onset of pandemic. As in the past they continue to have lower levels of unhappiness. A detailed analysis of several data files, with various metrics, for the UK confirms that men now are happier than women.