Sunday, October 18, 2020

An evolutionary account for why men have to wait between orgasms

Why Women Can Have Multiple Orgasms and Men Cannot. Glenn Geher. Psychology Today, Oct 18, 2020.


I will never forget Gordon Gallup's invited presentation at the 2007 meeting of the NorthEastern Evolutionary Psychology Society. 

This research essentially answers the question as to why the human erection is shaped with the unique characteristics that it has. From an evolutionary perspective, any adaptation that increases the likelihood of an individual being able to achieve reproductive success at a cost of the reproductive success of competitors will be naturally selected. And this explanation accounts for the unique nature of the human erection in a way that matches the data, along with the accompanying evolutionary framework, quite well.  

During the question and answer session, a young male student asked an interesting question. He essentially asked about the possibility of a male pulling out his own seminal fluid. And, in addition, he asked if this clear possibility posed something of a problem for Dr. Gallup's framework.

Dr. Gallup, a seasoned academic, did not hesitate in his response. He first acknowledged that it was a good question. He then paused, looking for the right words, and said essentially this: You may have noticed that after an ejaculation, an erection dissipates quickly. And it becomes uncomfortable for the penis to be touched at that state. I hypothesize that this is an adaptation to reduce the likelihood of the male pulling out any seminal fluid that he, himself, has just released into a female's reproductive tract. 

Highly convincing evidence that mental health factors are associated with obesity; suggestive evidence that a range of cognitive and psychosocial factors are also; associations tend to be small in statistical size

The psychology of obesity: An umbrella review and evidence-based map of the psychological correlates of heavier body weight. Eric Robinson et al. Neuroscience & Biobehavioral Reviews, October 18 2020.

Rolf Degen's take: 


• We reviewed meta-analyses of psychological individual differences and body weight.

• Highly convincing evidence that mental health factors are associated with obesity.

• Suggestive evidence that a range of cognitive and psychosocial factors are also.

• However, associations with obesity tend to be small in statistical size.

• People with obesity vs normal weight are psychologically more similar vs different.

Abstract: Psychological factors may explain why some people develop obesity and others remain a normal weight during their life course. We use an umbrella review approach to build an evidence-based map of the psychological correlates of heavier body weight. Synthesising findings from 42 meta-analyses that have examined associations between psychological factors and heavier body weight, we assessed level of evidence for a range of cognitive, psychosocial and mental health individual difference factors. There is convincing evidence that impaired mental health is associated with heavier body weight and highly suggestive evidence that numerous cognitive factors are associated with heavier body weight. However, the relatively low methodological quality of meta-analyses resulted in lower evidential certainty for most psychosocial factors. Psychological correlates of heavier body weight tended to be small in statistical size and on average, people with obesity were likely to be more psychologically similar than different to people with normal weight. We consider implications for understanding the development of heavier body weight and identifying effective public health interventions to reduce obesity.

Keywords: ObesityBMIindividual differencescognitivemental healthpsychosocialpersonalitydepressionanxietyexecutive functionimpulsivity

Monopoly Myths: Is Concentration Eroding Labor’s Share of National Income?

Monopoly Myths: Is Concentration Eroding Labor’s Share of National Income? Joe Kennedy. ITIF, October 13, 2020.

Pundits and activists have looked at the reduced share of U.S. national income going to workers and have simply asserted that the cause is increased market concentration. This assessment is misplaced.


*  Despite the persistent claims that increased market power has hurt workers, the scholarly evidence is weak, while the macroeconomic data is strong and clear in showing that this is not the principal cause.

*  Labor’s share of income has declined slightly over the past two decades, but not principally because capital’s share of income has increased.

*  Most of the decline is offset by an increase in rental income—what renters pay and what the imputed rent homeowners pay for their house. This increase is due to restricted housing markets, not growing employer power in product or labor markets.

*  Antitrust policy is not causing the drop in labor share, so changing it is not the solution. For issues such as employer collusion over wages or excessive use of noncompete agreements, antitrust authorities already have power to act.

*  Stringent antitrust policy would do little to raise the labor share of income, but it could very well reduce investment and productivity growth. The better way to help workers is with pro-growth, pro-innovation policies that boost productivity.

On Bari Weiss comments about the current situation (Stop Being Shocked, Oct 15 2020)

On Bari Weiss comments about the current situation (Stop Being Shocked, Oct 15 2020,

A friend requests some comments about B W's piece.


I understand this is a call to inaction... And you must think what to vote, and send your vote. Sorry for not being helpful here, I am paralyzed.

Some thoughts, as requested:

1  I'm afraid that Alexandria Ocasio is, I am sorry to be so Manichean and categorical, a bad person... Hates too much, too much of an activist. It is my belief that, if in power, she would have fewer limits than mainstream politicians. That's why this all happens (her pulling out of a Y Rabin event, other things she says, the way she shows support for bad guys).

2 Lots of people lie, not only Alexandria, and this harms Bari Weiss piece.... We are not sure that the Iranian mullahs, murderous and crazy as they are, are genocidal. When we re-ask, they consistently say that what they want is to erase the Zionist entity, the Republic, not the persons. So why Bari Weiss repeatedly claims (& many others do the same too) that the Tehran's mad mullahs wish to kill unarmed civilians en masse?

That said, if the day comes when Israel is successfully invaded and defeated, I have no doubts that there would be mass displacements of population, very similar to what we saw with Germans after WWII (the Czechs, the Poles, etc., sent Germans packing to Germany after the National Socialists lost the war). But we cannot say so easily that the victors would kill the population à la Rwandan. I may be afraid of that, but cannot write so with such carelessness.

All the other is ok to me. Ignorant, hater-in-chief de Blasio; the KIPP charter schools's stupid, cowardly change in their motto, the allusion to "the illusion of meritocracy" (pardon the alliteration). And the first main thesis, stop being shocked, and accept that what it seems strange is clearly wrong (like Alexandria's views), is ok to me.

3  The second main thesis, that we should have friendships with political opponents, is something I ardently support too. But at times this is not generally possible, it is not so widespread. And we are in such a time.

Let me add and example here I lived a few years ago: A girl in the dating forums asked for an Anarchist boyfriend. And she also said that Communists are acceptable too. Well... When the Communists were in power, they exiled, imprisoned and killed mercilessly the Anarchists. But that was decades ago, I didn't live it, and my enemies' enemies are my friends. Then, I can date a Communist.

4  B Weiss piece will change nothing. My sad note is not about that, it is that the author publishes this because she needs money to pay the rent. She knows this has a negligible effect in the opposing side. That's the (falsely) cynical view.

Being positive about the author, her comments of being horrorized by Trump and simultaneously by the "others" remind me of those I love and who opposed at the same time the Nazis and the Communists (my dear gurus Popper, Hayek, many others). They had to emigrate to England, etc., and of course had no influence at all in the big confrontation that ended in conflagration.

Which is my view... I cannot support Alexandria O (or J Biden) and cannot support Trump. I am living in a permanent toothache, and are paralyzed, as I said at the beginning.

5  My summary is: let's love the others, even if we cannot understand why they vote as they do; and be realistic, which now, at this time in history, means  let's be pessimistic.

A smaller proportion of males reported having a best friend (85% vs 98% of females); the quality of these relationships seemed to be a great deal less intimate than was the case for females

Sex Differences in Intimacy Levels in Best Friendships and Romantic Partnerships. Eiluned Pearce, Anna Machin & Robin I. M. Dunbar. Adaptive Human Behavior and Physiology, Oct 18 2020.

Rolf Degen's take:


Objectives Close romantic and friendship relationships are crucial for successful survival and reproduction. Both provide emotional support that can have significant effects on an individual’s health and wellbeing, and through this their longer term survival and fitness. Nonetheless, the factors that create and maintain intimacy in close relationships remain unclear. Nor is it entirely clear what differentiates romantic relationships from friendships in these terms. In this paper, we explore which factors most strongly predict intimacy in these two kinds of relationship, and how these differ between the two sexes.

Results Aside from best friendships being highly gendered in both sexes, the dynamics of these two types of relationships differ between the sexes. The intimacy of female relationships was influenced by similarity (homophily) in many more factors (notably dependability, kindness, mutual support, sense of humour) than was the case for men. Some factors had opposite effects in the two sexes: gift-giving had a negative effect on women’s friendships and a positive effect on men’s, whereas shared histories had the opposite effect.

Conclusion These results confirm and extend previous findings that the dynamics of male and female relationships are very different in ways that may reflect differences in their functions.


Taken together, these results confirm previous findings that homophily is an important criterion for close relationships (Curry and Dunbar 2013; Launay and Dunbar 2015). In particular, similarity in dependability was consistently found to be strongly predictive of higher levels of intimacy. For women, this was the case in both best friendships and romantic partnerships, but for men dependability was included in the best-fit model only for intimacy in best friendships. For romantic partnerships, none of the variables measured showed significant partial relationships in men. Aside from these similarities, however, the results suggest that intimacy in males' friendships is underpinned by very different dynamics than intimacy in females' friendships.

Mirroring previous findings with respect to romantic partners (Buss 1989; Pawlowski and Dunbar 19992001), we found that women seemed to be much more demanding in their selection of romantic partners than men were. The intimacy of women’s relationships were homophilous for at least four traits (financial prospects, outgoingness, dependability and kindness), whereas no traits predicted intimacy for males. Similarly, longterm maintenance of women’s romantic relationships were predicted by relationship duration, gift-giving and supportiveness, but for males there was only one significant predictor (the frequency of face-to-face contact). In contrast, best friend relationships exhibited a very different pattern: their intimacy is predicted by similarity on four traits for both women and men, but the traits are very different (education, humour, dependability and happiness for women versus relationship duration, financial prospects, outgoingness and dependability in men).

Longevity in both women’s and men’s friendships was best predicted by provision of mutual support, but differed in the influence of shared histories (negative in the case of women, positive in the case of men). The traits characterizing women’s friendships seem to have more to do with the closeness of the relationship itself, whereas those characterizing men’s friendships seem to have more to do with engaging in social activities. Interestingly, none of the best-fit models included physical attractiveness or athleticism, indicating that personality and resource factors (such as education and financial potential) may be more important for intimacy levels in these close non-kin relationships than traits that might be assumed to correlate more directly with genetic fitness. This likely reflects the fact that relationships are indirect, rather than direct, means of enhancing fitness. In other words, this is a two-step process: we form close relationships not simply to access a direct fitness reward but in order to create coalitions or alliances that in turn allow us to maximise fitness. One possibility, for example, might be to mitigate the fertility costs of group-living (Mesnick 1997; Wilson and Mesnick 1997; Dunbar 2018a2019; Dunbar and MacCarron 2019).

The fact that outgoingness was a predictor for the intimacy of men’s friendships might be linked to the fact that males tend to prefer social interaction in groups whereas females have a strong preference for one-to-one interactions (Baumeister and Sommer 1997; Benenson & Heath, 2006; Dávid-Barrett et al. 2015; Gabriel and Gardner 1999; Rustin and Foels 2014). In addition to these homophily effects, we also found that mutual support and shared history are important for intimacy, and are therefore key factors underpinning the successful maintenance of close personal relationships. Mutual support had a much stronger influence on intimacy in female participants for both romantic partners and best friends, but only in respect of best friends for men (Fig. 2). In relation to their romantic partners, the degree to which men considered in-person contact an important mechanism for relationship maintenance was the strongest predictor of intimacy, at least when the sample was considered as a whole, irrespective of the sex of the best friend.

Interestingly, the extent to which shared history were considered an important mechanism of relationship maintenance in best friendships had opposite effects on intimacy in men and women. Whereas this relationship was positive in men, in women it was negative (the greater the emphasis on shared history, the lower the level of intimacy). This might, again, reflect the difference between men’s preference for group-based activities (for which shared history is usually an important component) and women’s preference for more intimate dyadic ones (for which shared history might be less important than, for example, conversation and levels of mutual disclosure).

In women, both the importance placed on gift-giving and mutual support as ways of sustaining romantic partnerships were included in the best-fit model, but these variables had opposite effects on intimacy. The greater the importance placed on gift-giving, the lower the intimacy; in contrast, the greater the importance given to mutual support as a mechanism of relationship maintenance, the greater the reported intimacy. Whereas gift-giving is observed cross-culturally as a means of creating and maintaining social network ties (e.g. Wiessner 1983), it may be that this strategy is only appropriate in the more distal layers of the social network where tokens of affiliation are required; in the inner layers, intimacy and emotional closeness may be more important (see Sutcliffe et al. 2012). It is possible that gift-giving is associated with forms of strict reciprocity in relationships that block the development of deeper emotional ties.

The importance of intimacy in same-sex female friendships may explain why similar humour profiles were found to be important for female but not male best friendships: laughter is thought to be important in the creation of social bonds (Dunbar 2017; Dunbar et al. 2012; Manninen et al. 2017). In contrast, similarity in social characteristics (outgoingness and social connections) were deemed more important for intimacy in male best friendships, perhaps reflecting the fact that men tend to prefer interacting in groups rather than one-to-one (Dávid-Barrett et al. 2015). Why this might be so evolutionarily remains to be answered, but one obvious suggestion relates to men’s near-universal role in communal defence in small scale societies and the demand this imposes for being able to cooperate in groups.

These behavioural differences suggest that best friend relationships are viewed very differently by the two sexes, corroborating and extending previous studies which suggest that the two sexes have very different expectations as regards friendships (Hall 20112012; Machin and Dunbar 2013) and very different social styles (Roberts and Dunbar 2015). This strongly suggests that friendships serve rather different functional roles in the two sexes arising from different evolutionary selection pressures. While romantic relationships are, inevitably, equally common in the two sexes (in both cases, 86% of respondents reported having a romantic partner), a smaller proportion of males reported having a best friend (85%, compared to 98% of females). Moreover, whereas only 2% of females had a romantic partner but no best friend, 15% of males were in this situation suggesting that males, but not females, are more likely to have one or the other but not both. Although a significant proportion of males reported having a best friend, the quality of these relationships seemed to be a great deal less intimate than was the case for females (Fig. 2). This reflects earlier findings suggesting that the male social world is built around half a dozen relatively casual relationships, whereas the female social world is built around one or two much more intimate, and hence more fragile, dyadic relationships (Benenson and Christakos 2003; Roberts and Dunbar 2015; Dávid-Barrett et al. 2015).

In both sexes, only a minority of best friends were opposite-sex (15% for females; 22% in males). The gender homophily is itself striking, and probably reflects the fact that social networks are highly assortative for sex (Block and Grund 2014; Mehta and Strough 2009; Roberts et al. 2008; Rose 1985; Dunbar 2021). Even conversations readily segregate by sex once they contain more than four individuals (Dunbar 2016b; Dahmardeh and Dunbar 2017). Although having male best friends may be advantageous to females in terms of protection against the unwanted attentions of other males (Mesnick’s bodyguard hypothesis: Mesnick 1997; Wilson and Mesnick 1997; Dunbar 2010; see also Snyder et al. 2011; Ryder et al. 2016), it may be that male partners are likely to become jealous if their romantic partners show too much interest in male best friends, fearing either mate theft or cuckoldry. This might make cross-sex best friends less functional for paired females. Alternatively, intimate friendships between women may be more beneficial or easier to maintain (if only because of similar conversational styles: Coates 1996; Grainger and Dunbar 2009), while common interests make cooperation more straightforward (de Waal and Luttrell 1986).

These data are, of course, self-report data and represent the views of only one party in a relationship, and so are inevitably subject to the usual distortions this can involve. Nonetheless, in that respect, they do represent the aspirations and expectations of the person concerned, and it is these as much as anything that we are here interested in. While relationships are necessarily two-way processes, it is nonetheless failure of one individual’s expectations to be met in a relationship that is the usual cause of relationship breakdown (Dunbar and Machin 2014). Relationships break down because one party is dissatisfied with the deal they are getting, not because both parties “agree to disagree”. In this sense, these results provide us with direct insights into how individuals view their relationships, irrespective of whether they are right in their views.

Why do animals sometimes kill each other's offspring? Among hyenas, infanticide is a leading source of juvenile mortality; in all observed cases, killers were adult females, frequently higher-ranking than the mothers

Infanticide by females is a leading source of juvenile mortality in a large social carnivore. Ally Kelsey Brown et al. , Oct 17 2020.

Rolf Degen's take:

Abstract: Social animals benefit from their group-mates, so why do they sometimes kill each other's offspring? A major barrier to understanding the evolution of infanticide is a lack of data from natural populations. Especially when perpetrated by females, infanticide remains poorly understood, because the increased mating opportunities that explain infanticide by males do not apply in females. Using 30 years of data from several spotted hyena groups, we show that infanticide is a leading source of juvenile mortality, and we describe the circumstances under which it occurs. In all observed cases, killers were adult females, but victims could be of both sexes. Killers only sometimes consumed the victims. Mothers sometimes cared for their deceased offspring, and sometimes consumed the body. Killers tended to be higher-ranking than the mothers of victims, and killers were sometimes aided by kin. Our results are consistent with theory that infanticide by females reflects competition among matrilines.

Key words: infanticide by females, matrilineal society, thanatology, female-female competition, nepotism 

We attribute our own phone use to positive social motives & overestimate our ability to multitask compared to others; we may fail to recognize the negative consequences of phone use

Barrick, Elyssa M., Diana Tamir, and Alixandra Barasch. 2020. “The Unexpected Social Consequences of Diverting Attention to Our Phones.” PsyArXiv. October 18. doi:10.31234/

Rolf Degen's take:

Abstract: Phone use is everywhere. Previous work has shown that phone use during social experiences has detrimental effects on cognitive processing, well-being, and relationships. In this work, we first replicate this by showing the negative effects of phone use on relationships during both controlled and naturalistic social experiences. In Study 1, participants that were randomly assigned to complete a task with a confederate who used their phone part of the time reported lower feelings of social connection than participants paired with a partner who did not use their phone at all. In Study 2, dyads in a park completed a survey about their experience of the day. Participants reported that increased phone use resulted in lower feelings of social connection, enjoyment, and engagement in the experience. People were keenly aware that phone use in social situations can be harmful. If the negative effects of phone use are so obvious, why do people continue to phub their friends? Studies 3 and 4 demonstrate that people accurately intuit the effects of others’ phone use on experiences, but fail to recognize the effects of their own phone use. Study 4 explains this phubbing blindspot by demonstrating asymmetric positive attributions – people attribute their own phone use to positive social motives, and overestimate their ability to multitask compared to others. These findings suggest that people may fail to recognize the negative consequences of their own phone use by attributing positive motives for phone use to themselves.