Monday, April 5, 2021

Contrary to expectations, the suicide rate in the U.S. decreased in 2020, possibly due to a "we are all in the same boat" effect and an increased appreciation for life

Why Did U.S. Suicides Decrease in 2020? Kathryn Gordon. Psychology Today, Apr 5 2021.

Preliminary 2020 data for U.S. mortality causes were published last week*. A startling statistic revealed an estimated 17.7% increase in deaths from 2019 to 2020. Approximately 344, 323 (10.3%) of those lives were lost directly due to COVID-19. While deaths related to heart disease, unintentional injury, diabetes, stroke, and Alzheimer's disease reportedly increased from 2019 to 2020, the number of suicides seemed to decrease by 5.6%. The decline in suicides may feel counterintuitive in the context of the rising U.S. suicide rates in recent years (with the exception of a decrease from 2018 to 2019) and the significant social, economic, and political stresses faced by many people in 2020. 

* The Leading Causes of Death in the US for 2020. Farida B. Ahmad, Robert N. Anderson. JAMA, Mar 31 2021.


“Time Slows Down Whenever You Are Around” for Women but Not for Men

“Time Slows Down Whenever You Are Around” for Women but Not for Men. Joana Arantes et al. Front. Psychol., April 6 2021 |

Abstract: What happens when we unexpectedly see an attractive potential partner? Previous studies in laboratory settings suggest that the visualization of attractive and unattractive photographs influences the perception of time. The major aim of this research is to study time perception and attraction in a realistic social scenario, by investigating if changes in subjective time measured during a speed dating are associated with attraction. The duration of the dates was variable and participants had to estimate the time that passed. Among other measures, participants also rated the potential partners in terms of their physical attractiveness before and after the dates and reported if they would like to exchange contact with them. Results showed that, in a real speed dating situation, when there is a perception of the partner as being physically more attractive, women tend to overestimate the duration of that meeting, whereas men tend to underestimate its duration. Such changes may reflect evolutionary adaptations which make the human cognitive system more responsive in situations related to reproductive fitness.


The main objective of this research was to study time perception and attraction in a realistic social scenario by investigating if changes in subjective time measured during a speed dating session were related with attraction. The duration of the dates was variable and participants had to estimate the time that passed. Participants were asked to rate potential partners in terms of their physical attractiveness before and after the dates and to report if they wanted to exchange contacts with them. Our data suggest, consistently with our hypotheses, that the estimated time of the dates were associated with the physical attractiveness of the potential partners perceived by participants.

More specifically, our results showed that the more females rated a potential partner as physically attractive, the longer they perceived the duration of the date. That goes along with the popular idea that “time slows down whenever you are around” (Swift, 2010). This may be due to a bigger allocation of women’s cognitive resources to process more information of the meeting (Loftus et al., 1987) and of the potential partner they are interested in. More specifically, even though physical attractiveness is important in a potential partner, for women there are other characteristics that may have a higher value, such as good economic prospects (Buss and Barnes, 1986Bech-Sørensen and Pollet, 2016). Therefore, searching for cues of positive traits in a potential mate requires the use of cognitive resources. Besides that, research has shown that when women perceive the partner as attractive, they tend to be more motivated to make a good impression on the partner and pay more attention to the things they say that might influence this impression (Dong and Wyer, 2014). According to Ornstein’s storage size model (Ornstein, 1969Sasaki and Yamada, 2017), when people store more information in memory, they tend to perceive the duration of that interval of time as being longer. Furthermore, women may consider the experience with a partner who they consider physically attractive as positive in an emotional way. This result is also consistent with that study of Kellaris and Kent (1992) in which time did seems to slow downs when participants were exposed to positively valenced music, compared to participants exposed to negatively valenced music. The authors suggested that when people receive positive emotional information they tend to invest more cognitive resources in listening to music. Therefore, they tend to perceive the received stimulus information as larger and remember the event as being longer. Besides that, a study conducted by Zhang et al. (2017) showed a reliable sex differences in temporal distortion with an emotional stimulus. Women, compared to men, tended to overestimate the durations of emotional words.

However, for men, our results showed that time does not seems to slow down whenever someone attractive is around. In fact, the more males rated a female participant as physically attractive, the shorter they perceived the duration of the speed date. This seems to be consistent with the idea that “time flies when you are having fun.” Research has shown that men’s preferences for potential mates are based mostly in physical attractiveness (Lippa, 2007Todd et al., 2007Eastwick et al., 2011). Therefore, when they have a meeting with a potential partner that they perceive as being physically attractive, they do not need to spend much cognitive resources searching for other cues, feeling automatically motivated to be with her. Consequently, they will tend to estimate the time that passed as being shorter. This result also suggests that time perception in males during the dates may be affected by motivation because, according to previous literature, positive approach motivation causes the perception of time to be shorter (Glabe and Poole, 2012). Besides that, the subjective perception of the passage of time seems to be an important component to evaluate the experience of boredom (Danckert and Allman, 2005). So, when males are interested and motivated in the date with a physical attractive potential partner, they tend to estimate the date duration as shorter and, on the other hand, this time underestimation reinforces the perception of an interesting date (Sackett et al., 2010). Underestimation of the duration of the date may prolong approach-motivated behavior (Glabe and Poole, 2012) and this increases the probability of a successful mating. On time, Einstein said “Put your hand on a hot stove for a minute and it seems like an hour. Sit with a pretty girl for an hour, and it seems like a minute.”

According to Trivers’ (1972) theory, the relative parental investment of the sexes in their offspring is the key variable controlling the operation of sexual selection. Sexual intercourse for a male is a small investment, but for a female can produce a 9-month investment, at least. For a female, this investment requires more choosiness in the partner choice. Besides that, prior research showed that females tend to be more selective (Kurzban and Weeden, 2005) and more discriminating (Todd et al., 2007) than males. Therefore, it is expected that females allocate more attention to capturing a greater number of characteristics of the potential partner in addition to physical attractiveness, such as intelligence, personality, earning prospects and other signs suggesting he could be good partner in the future. This process seems to imply an exhaustive evaluation in the first meeting which requires the allocation of a lot of cognitive resources. On the other hand, men are attracted by fewer characteristics of the partner compared to females (Luo and Zhang, 2009). So, males do not use so much energy and resources in cognitive processing of information and focus more energy in having fun with the partners they perceived as being more attractive. Such changes may reflect evolutionary adaptations which make the human cognitive system more responsive in situations related to reproductive fitness.

Williams (2012) suggested that sex differences in timing might be due to the effects of circulating estrogen in adult females versus testosterone in adult males. Besides that, gonadal hormones had been found to influence sexual motivation (Wallen, 2001). In men, testosterone increases interest in a woman, engagement in self-presentation, smiling and making eye contact (Roney et al., 2006Meij et al., 2011Thornhill et al., 2013). Meij et al. (2011) suggested that during encounters with the opposite sex, testosterone may promote the display of affiliative behaviors that increase a man’s mating prospects and during social contact with a potential partner testosterone is linked to the initiation of courtship behaviors. On the other hand, in women, estradiol seems to be a significant positive predictor of sexual desire (Puts et al., 2013Roney and Simmons, 2013).

Estradiol is one of the natural estrogens and has been shown to increase striatal dopamine release, that may modify temporal perception and timing performance in a manner similar to indirect dopamine agonists such as amphetamine and cocaine (Pleil et al., 2011). Estrogen as a dopamine agonist facilitates striatal dopaminergic activity (Sandstrom, 2007), stimulating the dopaminergic transmission and, consequently, producing an overestimation of time intervals (Cheng et al., 2006). Pleil et al. (2011) investigated sex differences in the rapid and acute effects of estradiol on time perception in adult male and female rats. According to the authors, their results are consistent to the idea that there are multiple mechanisms of estrogen’s action in the striatum that modulate dopaminergic activity and are differentially organized by gonadal steroids during early brain development. Additionally, Becker (1999) found that striatal dopaminergic release is affected by estrogen only in females. The striatum is one of the components of the basal ganglia that have been suggested to be a fundamental component of the neural basis of timing (Ivry and Spencer, 2004) and multiple studies, specifically with patients with dopamine system disorders as Parkinson (Leranth et al., 2000Michel et al., 2002), and schizophrenia (Seeman and Lang, 1990Riecher-Rössler and Häifner, 1993Michel et al., 2002) and others, found an interaction between gonadal steroid hormones such as estrogen in basal ganglia mechanisms (Hartesveldt and Joyce, 1986). Therefore, because of the fact that estrogen is a predictor of sexual desire and sexual motivation, this may increase their circulation in women during a speed date with physically attractive partners and, subsequently, increase dopamine release in striatum. Besides that, some studies found that women, on average, have higher presynaptic dopamine synthesis capacity (Laakso et al., 2002) and lower D2 receptor affinity (Pohjalainen et al., 1998) that suggests an increased endogenous dopamine in women’s striatum, comparing to men. So, neural sex differences in dopaminergic circuits in the striatum could explain this sex difference on the influence of physical attractiveness in time perception. It is thus possible that sexual hormones on males have an opposite effect in striatum (Myers et al., 2003).

Our results may diverge from Dong and Wyer (2014) study because sex differences in their study could be masked by lack of cues in the interaction that could influence attraction mechanisms. Specifically, the reduction of non-verbal information may influence the response of females more than males because, according to a vast literature (Mehrabian, 1972Mehrabian and Ksionzky, 1972Zahn, 19731975), females are more sensitive to non-verbal information and males to a verbal information.

Our study also demonstrates that for the decision of exchanging or not contact with the partner, physical attractiveness seems to be an important factor for both sexes because when participants perceived the partners as physically attractive, they tended to exchange contacts with them. In addition, consistent with our second hypothesis, the physical attractiveness of the potential partner perceived by the participant changes according to the interest in exchanging contact with him/her. In other words, interest or not in the meeting with a potential partner and the desire or not to keep in contact in the future influences their perceived physical attractiveness. Particularly, when participants are interested in a potential partner at the end of the date, they perceive their physical attractiveness as being higher compared to the initial evaluation (i.e., before the date). When participants are not attracted to partners at the end of the date, expressing the desire not to exchange contacts with them, they not change their evaluation of the potential partner’s physical attractiveness. These results suggest that there may be an effect of other characteristics of the potential partner in the evaluation of physical attractiveness. This is supported by some laboratory studies that have shown that the evaluated attractiveness of opposite-sex people is influenced by their personality. For example, Lewandowski et al. (2007) found that when a person was presented with positive personality information about the person shown in a photograph, participants rated that person as more physically attractive and when photographs were paired with negative personality information the person depicted was rated as less physically attractive. These results are also consistent with Kniffin and Wilson’s (2004) naturalistic studies that showed that non-physical characteristics such as familiarity, liking, respect, talent, and effort have a great influence on physical attraction judgments.

Limitations and Future Research

First, previous studies found that preferences in mate selection are influenced by the type of desired relationship, short or long-term. Thus, in future research it seems relevant to question participants in the speed dating event about whether they would like to have a short or long-term relationship with the partners they show an interest in exchanging contacts with. Second, this research shows that in a realistic scenario where two people meet each other, changes occur in time perception and it seems plausible to us that other implicit cognitive processes are affected in this context. However, there are no studies about other implicit measures in speed dating events, such as memory or attention, and future research should focus on this theme. Third, in terms of time perception and attractiveness, our data were correlational, so do not provide evidence for a causal influence of physical attractiveness on timing. Our results suggest that the two variables are associated but it would be interesting to understand if there is a causal relation between them. Third, there were 32 (18.50%) exchanges of contact details but only three intimate relationships were formed and lasted at least 6 months. It would be interest to investigate in future studies which variables have contributed to the development of an intimate relationship after the speed-dating. Fifth, participants were relatively young people, which may represent a limitation of the present study. Research has shown that men tend to prefer females at the age at which fertility peaks in order to increase their reproductive success (Conroy-Beam and Buss, 2019). In future research, it seems important to understand if the results of this study are applicable to older ages, in particular in postmenopausal women. If time perception in dating situations is an adaptive mechanism for mating, this bias should no longer occur in post-reproductive, menopausal women (Cyrus et al., 2011). Finally, our results based on stepwise multiple regression analyses showed that the attraction felt toward the partner was the strongest and unique predictor of both men’s and women’s perceptions of date duration. These results support the idea that when individuals are exposed to opposite-sex persons to whom they feel an attraction, their timing system is affected – women tend to overestimate, whereas men tend to underestimate the passage of time. However, it is still important to notice the weak explanatory power of the models, which indicates that there are other contributing factors to time perception that need to be explored in future research.

Sex differences in brain in response to midlife stress linked to fetal stress exposures

Impact of prenatal maternal cytokine exposure on sex differences in brain circuitry regulating stress in offspring 45 years later. Jill M. Goldstein et al. Proceedings of the National Academy of Sciences, April 13, 2021 118 (15) e2014464118.

Significance: Clinical research and animal models have demonstrated a significant connection between maternal stress during pregnancy and sensitivity to stress in offspring, leading to increased susceptibility to neuropsychiatric disorders later in life. In a unique prenatal cohort that was followed for over four decades, we tested associations between pro- and anti-inflammatory markers in maternal prenatal sera and sex differences in neural responses to negative stress in the offspring in early midlife using functional MRI. Men and women exposed in utero to abnormal levels of pro-inflammatory cytokines and to an imbalance of pro- to anti-inflammatory influences showed dysregulation of stress response circuitry 45 y later, with sex-dependent effects.

Abstract: Stress is associated with numerous chronic diseases, beginning in fetal development with in utero exposures (prenatal stress) impacting offspring’s risk for disorders later in life. In previous studies, we demonstrated adverse maternal in utero immune activity on sex differences in offspring neurodevelopment at age seven and adult risk for major depression and psychoses. Here, we hypothesized that in utero exposure to maternal proinflammatory cytokines has sex-dependent effects on specific brain circuitry regulating stress and immune function in the offspring that are retained across the lifespan. Using a unique prenatal cohort, we tested this hypothesis in 80 adult offspring, equally divided by sex, followed from in utero development to midlife. Functional MRI results showed that exposure to proinflammatory cytokines in utero was significantly associated with sex differences in brain activity and connectivity during response to negative stressful stimuli 45 y later. Lower maternal TNF-α levels were significantly associated with higher hypothalamic activity in both sexes and higher functional connectivity between hypothalamus and anterior cingulate only in men. Higher prenatal levels of IL-6 were significantly associated with higher hippocampal activity in women alone. When examined in relation to the anti-inflammatory effects of IL-10, the ratio TNF-α:IL-10 was associated with sex-dependent effects on hippocampal activity and functional connectivity with the hypothalamus. Collectively, results suggested that adverse levels of maternal in utero proinflammatory cytokines and the balance of pro- to anti-inflammatory cytokines impact brain development of offspring in a sexually dimorphic manner that persists across the lifespan.

Keywords: prenatal immune programmingprenatal stressstress circuitrysexfunctional brain imaging

Press release: Sex differences in brain in response to midlife stress linked to fetal stress exposures --- Exposure to inflammatory substances in the womb due to prenatal stress differentially affects stress circuitry function in male and female offspring, which is retained into midlife.

Naïve, unenculturated chimpanzees fail to make and use flaked stone tools

Naïve, unenculturated chimpanzees fail to make and use flaked stone tools. E Bandini et al. European Human Behaviour and Evolution Association, 15th Conference, Mar 2021.


Objective: Despite extensive research on early hominin lithic technology, the mechanisms underlying flake manufacture and use are still debated. To draw phylogenetic inferences on the potential cognitive processes underlying these abilities in early hominins, we examined whether our closest living relatives, chimpanzees (Pan troglodytes), could learn to make and use flakes.

Methods: We provided naïve unenculturated chimpanzees from two independent populations (n=11) with baited puzzle boxes that could only be accessed with cutting tools, stone cores, and hammerstones to test for their ability to spontaneously make and use flakes.

Results: Despite the fact that the chimpanzees demonstrated an understanding of the requirements of the task and were sufficiently motivated, none of the chimpanzees made or used flakes in any of the experimental conditions.

Conclusions: These results differ from previous ape flaking experiments, which found flake manufacture and use in bonobos and one orangutan. However, these earlier studies tested only enculturated apes and provided them with demonstrations. The contrast between these earlier positive findings and our negative findings (despite using a much larger sample size) suggests that enculturation and/or human demonstrations may be necessary for chimpanzees to acquire these abilities. The data obtained here is consistent with the hypothesis that flake manufacture and use might have evolved in the hominin lineage after the split between Homo and Pan 7 million years ago, a  scenario further supported by the apparent absence of flaked stone tools in the archaeological record after this split.

Intent-based morality in Colombian and Spanish children: Punishment & retribution

Intent-based morality in Colombian and Spanish children. RL Arini et al. European Human Behaviour and Evolution Association, 15th Conference, Mar 2021.


Objective: The majority of the developmental literature about the role of outcomes and intentions in moral evaluations has been conducted on English-speaking children and focused on harm and property transgressions. We aimed at investigating this phenomenon in 5- to 11-year-olds from collectivistic Colombia and individualistic Spain (N=123) employing moral scenarios involving disloyalty and unfairness.

Methods: We developed a computer game showing internet players violate moral norms; children took the role of referees and had the opportunity to judge and punish the players for their behaviour.

Results: Regarding judgements of transgression severity, Colombian children judged failed intentional transgressions more severely than accidental transgressions in case of disloyalty, but not yet in case of unfairness. Regarding punishment severity, Spanish children began to punish failed intentional transgressions of both moral domains more severely than accidents around 8 years of age. While punishment severity decreased with increasing age for both unfairness and disloyalty in Spanish children, in Colombian children the downward pattern was observed only for unfairness. Additionally, children anticipated punishment to feel worse than how it actually felt during and after punishment allocation.

Conclusions: According to cultural group selection, it makes evolutionary sense that children’s sensitivity to intentionality develops earlier within the moral domains (loyalty) privileged by their own (collectivistic) cultures. Moreover, selective concerns for one moral domain (loyalty) over another (fairness) may become more pronounced with development because of culture-directed learning processes. The lack of hedonic punishment expectations suggests that retribution is unlikely to be the primary driver of children’s third-party punishment.

Even though inaccurate beliefs lead to costly mistakes, people interpret favorable feedback to be more informative; author casts a new light on the origins of overconfidence & the mechanisms that perpetuate it in the face of feedback

Belief-Based Utility and Signal Interpretation. Marta Kozakiewicz. February 23, 2021.

Rolf Degen's take:

Abstract: People tend to overestimate their abilities and chances of success, even though inaccurate beliefs lead to costly mistakes. How can these beliefs persist in an environment with frequent feedback? I propose a new test of the hypothesis that people interpret favorable feedback to be more informative. Using experimental data, I provide the first causal evidence that the utility from beliefs affects one’s perception of signal informativeness. To establish causality, I adopt a matching estimator approach and construct a counterfactual outcome of a subject who observes the same signal, but the signal is not affecting his belief-based utility. I find a strong and significant effect: subjects interpret favorable signals to be more informative due to changes in belief-based utility. The results cast a new light on the origins of overconfidence and illuminate mechanisms that perpetuate it in the face of feedback.

Keywords: overconfidence, belief formation, learning, experiment

JEL classification: C91, D83

Claims About The Hidden Cost of Religiosity and the Gender Wage Gap

The Hidden Cost of Prayer: Religiosity and the Gender Wage Gap. Traci Sitzmann and Elizabeth M. Campbell. Academy of Management Journal, Oct 27 2020.

Abstract: Religion is a preeminent social institution that meaningfully shapes cultures. Prevailing theory suggests that it is primarily a benevolent force in business, and differences across world religions preclude examining effects that thread across religions. We develop a theoretical account that fundamentally challenges these assumptions by explaining how and why religiosity—regardless of which religion is prominent—differentiates based on gender, widening the gender wage gap. Guided by an integrated review of the religion literature, we specify three dimensions of gender differentiation—social domains, sexuality, and agency—that explain why religiosity widens the gender wage gap. A series of studies tested our theoretical model. Two studies showcased the predictive power of religiosity on the gender wage gap across 140 countries worldwide and the 50 United States via gender-differentiated social domains, sexuality, and agency, explaining 37% of the variance in the wage gap. U.S. longitudinal data indicated the gender wage gap is narrowing significantly faster in secular states. Moreover, experiments allowed for causal inference, revealing that gender-egalitarian interventions blocked the effect of religiosity on the gender wage gap. Finally, theoretical and empirical evidence converge to suggest that religiosity’s effect on the gender wage gap applies across the major world religions.