Thursday, December 27, 2018

Rise of the West, part II



Paysage à Saint-Joachim (1903), Clarence Gagnon. A hundred years ago genetic evolution came to a halt throughout the West, yet cultural evolution continued to forge ahead ... at an accelerating speed.



My last post covered the reasons why liberal regimes have historically prevailed over conservative ones. In short, liberalism delivers the goods. By reducing the importance of kinship, it has given the market a freer rein to mobilize labor and capital for production of goods and services. More wealth is created—not only in peacetime but also, and just as critically, in wartime. Because liberal regimes are not tied to a single ethnocultural community, they can recruit from a broader pool of people and, if need be, relocate production of arms and ammunition to territories far from enemy attack.

In this post I wish to discuss the contradictions of liberalism. By "contradiction" I mean an inherent problem that will worsen even in the absence of organized opposition. Here, I will focus on one problem: liberal regimes tend to erode their own cultural and genetic foundations, thus undermining the cause of their success.



End and reversal of gene-culture coevolution

Liberalism emerged in northwest Europe. This was where conditions were most conducive to dissolving the bonds of kinship and creating communities of atomized individuals who produce and consume for a market. Northwest Europeans were most likely to embark on this evolutionary trajectory because of their tendency toward late marriage, their high proportion of adults who live alone, their weaker kinship ties and, conversely, their greater individualism. This is the Western European Marriage Pattern, and it seems to go far back in time. The market economy began to take shape at a later date, possibly with the expansion of North Sea trade during early medieval times and certainly with the take-off of the North Sea trading area in the mid-1300s (Note 1).

Thus began a process of gene-culture coevolution:  people pushed the limits of their phenotype to exploit the possibilities of the market economy; selection then brought the mean genotype into line with the new phenotype. The cycle then continued anew, with the mean phenotype always one step ahead of the mean genotype.

This gene-culture coevolution has interested several researchers. Gregory Clark has linked the demographic expansion of the English middle class to specific behavioral changes in the English population: increasing future time orientation; greater acceptance of the State monopoly on violence and consequently less willingness to use violence to settle personal disputes; and, more generally, a shift toward bourgeois values of thrift, reserve, self-control, and foresight. Heiner Rindermann has presented the evidence for a steady rise in mean IQ in Western Europe during the late medieval and early modern era. Henry Harpending and myself have investigated genetic pacification during the same timeframe in English society. Finally, hbd*chick has written about individualism in relation to the Western European Marriage Pattern (Note 2).

This process of gene-culture coevolution came to a halt in the late 19th century. Cottage industries gave way to large firms that invested in housing and other services for their workers, and this corporate paternalism eventually became the model for the welfare state, first in Germany and then elsewhere in the West. Working people could now settle down and have families, whereas previously they had largely been a lumpenproletariat of single men and women. Meanwhile, middle-class fertility began to decline, partly because of the rising cost of maintaining a middle-class lifestyle and partly because of sociocultural changes (increasing acceptance and availability of contraception, feminism, etc.).

This reversal of class differences in fertility seems to have reversed the gene-culture coevolution of the late medieval and early modern era. The evidence is still incomplete, but a consistent pattern is emerging:

1. Mean reaction time has risen in Great Britain by 13 points since Victorian times (Woodley et al. 2013). This finding may be an artefact of better sampling of the general population over time (hbd*chick 2013a). A Swedish study, however, has confirmed this lengthening of reaction time, particularly in cohorts born since the 1970s (Madison 2014; Madison et al. 2016).

2. The genetic basis of intelligence has fallen in Iceland since the cohort born in 1910. This is shown by a progressive decrease in the "polygenic score" of alleles associated with high educational attainment (Kong et al. 2017).

3. The Flynn effect is slowing throughout the West (Flynn 2007, p. 143). In Scandinavia, mean IQ peaked during the late 1990s and has since declined (Teasdale and Owen 2005). A review of this literature has shown recent declines in mean IQ in England, Denmark, Finland, and Austria and a leveling off in Norway and Australia (Rindermann 2018). The Flynn effect does not, in itself, seem to be a real increase in intelligence. Rather, it is simply a greater familiarity by people with the process of doing tests and, as such, has masked an underlying decline in real intelligence. Now that the Flynn effect has exhausted itself, we are seeing this underlying decline.


Causes?

Some of this decline may be due to class differences in fertility, especially during the early to mid-20th century. Today, with widespread use of contraception and abortion by all social classes, this factor is much less operational (Jayman 2012). Recently, two economists, Bernt Bratsberg and Ole Rogeberg, have found that the reversal of the Flynn effect in Norway is largely explained by "within-family variation." So this decline is not due to the poor outbreeding the rich or to immigrants outbreeding natives. 

It doesn't follow, however, as Bratsberg and Rogeberg argue, that a genetic cause is excluded. In Norway, as elsewhere, siblings are increasingly half-siblings. This is not a minor factor. Bratsberg and Rogeberg charted their country's IQ decline by looking at pairs of brothers; their data came from the military conscript register, and only men are subject to conscription. To produce a pair of brothers, a woman has to have three children on average. Among Norwegian women with three children, 36.2% have had them by two or more men (Thomson et al. 2014). Furthermore, because half-siblings tend to be born farther apart than full-siblings, they have contributed more to changes in mean IQ over time. 

If the genetic basis of intelligence has been declining between older and younger half-siblings, two things must be happening:

- Divorced mothers are, on average, having their second children by lower-IQ men;

- Such men have been contributing more than other men to succeeding generations of Norwegians, at least during the last forty years.

Lappegård et al. (2011) found that multi-partner fatherhood is most common among Norwegian men with the lowest level of education. Furthermore, multi-partner fertility has increased over time among such men. Thomson et al. (2014) have similarly observed that education is negatively associated with childbearing across partnerships in Australia, United States, Norway, and Sweden. These differentials increased from the 1970s to the 2000s.

Unfortunately, we cannot easily measure the impact of multi-partner fatherhood on the IQ of the next generation. How can we compare the first father’s children with the second father’s children when Norwegian statistics do not identify a child's biological father? Only the "registered father" is identified. Once a man has adopted the earlier children of his spouse, he becomes their father for all statistical purposes.


Uncoupling of gene-culture coevolution

There has thus been an uncoupling of gene-culture co-evolution. Genetic evolution is leveling off throughout the West and even reversing in some countries. Meanwhile, cultural evolution has been forging ahead. The mean phenotype is no longer one step ahead of the mean genotype. It's several steps ahead.

A century ago the market economy was important, but a lot of economic activity still took place within the family, especially in rural areas. In the late 1980s I interviewed elderly French Canadians in a small rural community, and I was struck by how little the market economy mattered in their youth. At that time none of them had bank accounts. Few even had wallets. Coins and bills were kept at home in a small wooden box for special occasions, like the yearly trip to Quebec City. The rest of the time these people grew their own food and made their own clothes and furniture. Farms did produce food for local markets, but this surplus was of secondary importance and could just as often be bartered with neighbors or donated to the priest. Farm families were also large and typically brought together many people from three or four generations. 

By the 1980s things had changed considerably. Many of my interviewees were living in circumstances of extreme social isolation, with only occasional visits from family or friends. Even among middle-aged members of the community there were many who lived alone, either because of divorce or because of relationships that had never gone anywhere. This is a major cultural change, and it has occurred in the absence of any underlying changes to the way people think and feel.

Whenever I raise this point I'm usually told we're nonetheless better off today, not only materially but also in terms of enjoying varied and more interesting lives. That argument made sense back in the 1980s—in the wake of a long economic boom that had doubled incomes, increased life expectancy, and improved our lives through labor-saving devices, new forms of home entertainment, and stimulating interactions with a broader range of people.

Today, that argument seems less convincing. Median income has stagnated since the 1970s and may even be decreasing if we adjust for monetization of activities, like child care, that were previously nonmonetized. Life expectancy too has leveled off and is now declining in the U.S. because of rising suicide rates among people who live alone. Finally, cultural diversity is having the perverse effect of reducing intellectual diversity. More and more topics are considered off-limits in public discourse and, increasingly, in private conversation. 

Liberalism is no longer delivering the goods—not only material goods but also the goods of long-term relationships and rewarding social interaction.

To be cont'd


Notes

1. Markets, of course, go much farther back in time, farther than the earliest historical records. For most of that time, however, they were secondary to kinship. People organized their lives primarily in terms of blood ties or the ties of procreation between husband and wife. The main unit of economic activity was the family. Markets were not only of secondary importance but also highly localized in space and time. In short, there were markets but no market economy.

2. Hbd*chick has accused me of plagiarizing her work on the Hajnal Line and the Western European Marriage Pattern. The truth is that I became interested in that subject much earlier— during the early 1990s in an exchange of letters with Kevin MacDonald in the pages of Ethology and Sociobiology. Afterwards, I intended to write a follow-up that would prove two points: 1) the Western European Marriage Pattern predates Christianity; and 2) this cultural environment has selected for certain psychological traits. Over the years I gathered material, but I didn't feel I had enough for a publishable article. I finally wrote up several blog posts on the subject in 2011 and eventually a full article in 2017. Meanwhile, hbd*chick had published her first post on the Hajnal Line in 2011. I did read that post but she seemed to be taking the same position that Kevin MacDonald had taken, i.e., that the WEMP was created by the Catholic Church and that outbreeding was key to emergence of the Western mindset. Later, in a 2012 post, she began to see the WEMP as a template for gene-culture coevolution. At that point I had the impression she was drawing on my material, either directly from my articles and blog posts or indirectly through various bloggers.

So did I "discover" this idea? No, of course not. Neither I nor hbd*chick was the first to write about the Hajnal Line or the WEMP. More importantly, neither of us was the first to link the WEMP to Western European individualism and mercantilism. I would award that title to Wally Seccombe in his 1992 book A Millennium of Family Change. Feudalism to Capitalism in Northwestern Europe. In the end, few ideas are truly original. It's no coincidence that both of us began writing about that subject around the same time. Other people were writing on related topics, and those people were influencing both me and her. I'm thinking here about authors like Gregory Clark and blogs like Jayman and Those Who Can See. I didn't read it at the time, but in January 2011 Kevin MacDonald wrote a book review that discussed the Hajnal Line and European individualism:

The nuclear family, freed from extended kinship obligations, is the basis of Western social organization. It is unique relative to other culture areas. This pattern is particularly noticeable in the Northwest of Europe rather than the Pontic steppe region. As one goes from the Northwest of Europe to the Southeast, there is an increase in joint family structure, with brothers living together with parents, grandparents and children. Family historian John Hajnal discovered the "Hajnal line" that separates Western Europe from Eastern Europe, the former characterized by nuclear family structure, relatively late marriage and large numbers of unmarried in economically difficult times, the latter by joint family structure and relatively early and universal marriage.

Finally, while preparing my 2017 article, I wanted to cite hbd*chick as someone with an alternate point of view, but I couldn't find anything published under her real name. There were only pseudonymous posts from her blog. To cite her in my manuscript would require inserting citations like (hbd*chick 2014). The reviewers would immediately notice, and the chances of rejection would increase accordingly. This point should be obvious.


References

Bratsberg, B., and O. Rogeberg. (2018). Flynn effect and its reversal are both environmentally caused. Proceedings of the National Academy of Sciences June 2018, DOI: 10.1073/pnas.1718793115

Clark, G. (2007). A Farewell to Alms. A Brief Economic History of the World. Princeton University Press: Princeton and Oxford.

Clark, G. (2009a). The indicted and the wealthy: surnames, reproductive success, genetic selection and social class in pre-industrial England.

Clark, G. (2009b). The domestication of man: The social implications of Darwin. ArtefaCTos 2: 64-80. 

Flynn, J.R. (2007). What is Intelligence? Beyond the Flynn Effect. Cambridge University Press.

Frost, P. (2017). The Hajnal line and gene-culture coevolution in northwest Europe. Advances in Anthropology 7: 154-174.

Frost, P. (2011a). From markets to market economy. Evo and Proud. March 4

Frost, P. (2011b). Bringing reproductive maturity into line with the age of marriage. Evo and Proud. October 29

Frost, P. (2011c). The Western European Marriage Pattern. Evo and Proud. November 12 http://evoandproud.blogspot.ca/2011/11/western-european-marriage-pattern.html

Frost, P. (1991). "Mechanisms of sexual egalitarianism in Western Europe": Comment. Ethology & Sociobiology 12(5), 335-336. 

Frost, P. and H. Harpending. (2015b). Western Europe, state formation, and genetic pacification. Evolutionary Psychology 13: 230-243.

Greer, T. (2013a). The Rise of the West: Asking the Right Questions. July 7. The Scholar's Stage

Greer, T. (2013b). Another look at the 'Rise of the West' - but with better numbers. November 20. The Scholar's Stage

Hbd*chick (2013a). A response to a response to two critical commentaries on woodley, te nijenhuis & murphy. May 27

Hbd*chick (2014b). Big summary post on the Hajnal Line. October 3

Hbd*chick (2013c). Going Dutch. November 29

Hbd*chick (2012). Behind the Hajnal Line. January 16

Hbd*chick (2011a). The Hajnal Line. June 30

JayMan (2012). It's not the cads, it's the tramps. JayMan's Blog. December 28

Kong, A., M.L. Frigge, G. Thorleifsson, H. Stefansson, A.I. Young, F. Zink, G.A. Jonsdottir, A. Okbay, P. Sulem, G. Masson, D.F. Gudbjartsson, A. Helgason, G. Bjornsdottir, U. Thorsteinsdottir, and K. Stefansson. (2017). Selection against variants in the genome associated with educational attainment. Proceedings of the National Academy of Sciences 114(5): E727-E732.

Lappegård, T., Rønsen, M., & Skrede, K. (2011). Fatherhood and fertility. Fathering 9: 103-120.

MacDonald, K. (2011). Going against the Tide: Ricardo Duchesne's Intellectual Defence of the West. The Occidental Quarterly 11(3): 1-22.

Madison, G. (2014). Increasing simple reaction times demonstrate decreasing genetic intelligence in Scotland and Sweden, London Conference on Intelligence, Psychological comments, April 25
#LCI14 Conference proceedings

Madison, G., M.A. Woodley of Menie, and J. Sänger. (2016). Secular Slowing of Auditory Simple Reaction Time in Sweden (1959-1985). Frontiers in Human Neuroscience, August 18

Rindermann, H. (2018). Cognitive Capitalism. Human Capital and the Wellbeing of Nations. Cambridge University Press.

Seccombe, W. (1992). A Millennium of Family Change. Feudalism to Capitalism in Northwestern Europe. London: Verso.

Teasdale, T.W., and D.R. Owen. (2005). A long-term rise and recent decline in intelligence test performance: The Flynn Effect in reverse. Personality and Individual Differences 39(4): 837-843.

Thomson, E., T. Lappegård, M. Carlson, A. Evans, and E. Gray (2014). Childbearing across partnerships in Australia, the United States, Norway, and Sweden. Demography 51(2): 485-508

Woodley, M.A., J. Nijenhuis, and R. Murphy. (2013). Were the Victorians cleverer than us? The decline in general intelligence estimated from a meta-analysis of the slowing of simple reaction time. Intelligence 41: 843-850. 
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Monday, December 17, 2018

Rise of the West



Soldats sénégalais au camp de Mailly (1917) by Félix Vallotton. During WWI, France recruited half a million Africans to fight in Europe.



When did "the West" begin? Usually historians look back to the 17th century, when the maritime nations of northwest Europe—Great Britain, France, and Holland—overtook Spain and Portugal in colonizing the Americas, Africa, and Asia. One can look farther back. Greer (2013a, 2013b) pinpoints the 14th century as the time when the North Sea economies began to diverge from the rest of the world:

[...] the two exceptions are Netherlands and Great Britain. These North Sea economies experienced sustained GDP per capita growth for six straight centuries. The North Sea begins to diverge from the rest of Europe long before the 'West' begins its more famous split from 'the rest.'

[...] we can pin point the beginning of this 'little divergence' with greater detail. In 1348 Holland's GDP per capita was $876. England's was $777. In less than 60 years time Holland's jumps to $1,245 and England's to 1090. The North Sea's revolutionary divergence started at this time. (Greer 2013b; see also Hbd *chick 2013)

This process began before the European conquest of the Americas, the invention of printing, the creation of modern finance institutions, the Atlantic slave trade, or the Protestant Reformation. None of these can be proper explanations for this "little divergence." (Greer 2013a)

One can look even farther back to the 7th century, when North Sea trade began an expansion that would later eclipse Mediterranean trade (Callmer 2002, also see Barrett et al. 2004).


Coevolution with the market economy

There is reason to believe that northwest Europeans were pre-adapted to the market economy. They were not the first to create markets, but they were the first to replace kinship with the market as the main way of organizing social and economic life. Already in the fourteenth century, their kinship ties were weaker than those of other human populations, as attested by marriage data going back to before the Black Death and in some cases to the seventh century (Frost 2017). The data reveal a characteristic pattern:

- men and women marry relatively late

- many people never marry

- children usually leave the nuclear family to form new households

- households often have non-kin members

This behavioral pattern was associated with a psychological one:

- weaker kinship and stronger individualism;

- framing of social rules in terms of moral universalism and moral absolutism, as opposed to kinship-based morality (nepotism, amoral familialism);

- greater tendency to use internal controls on behavior (guilt proneness, empathy) than external controls (public shaming, community surveillance, etc.)

This is the mindset that enabled northwest Europeans to exploit the possibilities of the market economy. Because they could more easily move toward individualism and social atomization, they could go farther in reorganizing social relationships along market-oriented lines. They could thus mobilize capital, labor, and raw resources more efficiently, thereby gaining more wealth and, ultimately, more military power.

This new cultural environment in turn led to further behavioral and psychological changes. Northwest Europeans have adapted to it just as humans elsewhere have adapted to their own cultural environments, through gene-culture coevolution:

1.      People adapt to the new environment by pushing their envelope of phenotypic plasticity.

2.      Natural selection then favors those individuals whose genotype more closely matches the new phenotype.

3.      Over time, the mean genotype of the population moves closer and closer to the new phenotype.

Northwest Europeans adapted to the market economy, especially those who formed the nascent middle class of merchants, yeomen, and petty traders. Over time, this class enjoyed higher fertility and became demographically more important, as shown by Clark (2007, 2009a, 2009b) in his study of medieval and post-medieval England: the lower classes had negative population growth and were steadily replaced, generation after generation, by downwardly mobile individuals from the middle class. By the early 19th century most English people were either middle-class or impoverished descendants of the middle class.

This demographic change was associated with behavioral and psychological changes to the average English person. Time orientation became shifted toward the future, as seen by increased willingness to save money and defer gratification. There was also a long-term decline in personal violence, with male homicide falling steadily from 1150 to 1800 and, parallel to this, a decline in blood sports and other violent though legal practices (cock fighting, bear and bull baiting, public executions). This change can largely be attributed to the State's monopoly on violence and the consequent removal of violence-prone individuals through court-ordered or extrajudicial executions. Between 1500 and 1750, court-ordered executions removed 0.5 to 1.0% of all men of each generation, with perhaps just as many dying at the scene of the crime or in prison while awaiting trial (Clark 2007; Frost and Harpending 2015).

Similarly, Rindermann (2018) has argued that mean IQ steadily rose in Western Europe during late medieval and post-medieval times. More people were able to reach higher stages of mental development. Previously, the average person could learn language and social norms well enough, but their ability to reason was hindered by cognitive egocentrism, anthropomorphism, finalism, and animism (Rindermann 2018, p. 49). From the sixteenth century onward, more and more people could better understand probability, cause and effect, and the perspective of another person, whether real or hypothetical. This improvement preceded universal education and improvements in nutrition and sanitation (Rindermann 2018, pp. 86-87).


Ideology of the market economy: the rise of liberalism

Finally, the emergence of the middle class was associated with ideological change: the rise of liberalism and its belief in the supremacy of the individual. John Locke (1632-1704) is considered to be the "father of liberalism," but belief in the individual as the ultimate moral arbiter was already evident in Protestant and pre-Protestant thinkers going back to John Wycliffe (1320s-1384) and earlier. These are all elaborations and refinements of the same mindset.

Liberalism has been dominant in Britain and its main overseas offshoot, the United States, since the 18th century. There is some difference between right-liberals and left-liberals, but both see the individual as the fundamental unit of society and both seek to maximize personal autonomy at the expense of kinship-based forms of social organization, i.e., the nuclear family, the extended family, the kin group, the community, and the ethnie. Right-liberals are willing to tolerate these older forms and let them gradually self-liquidate, whereas left-liberals want to use the power of the State to liquidate them. Some left-liberals say they simply want to redefine these older forms of sociality to make them voluntary and open to everyone. Redefine, however, means eliminate. If you make a community truly "open" it will eventually become little more than a motel: a place where people share space, where they may or may not know each other, and where very few if any are linked by longstanding ties—certainly not ties of kinship.

For a long time, liberalism was merely dominant in Britain and the U.S. The market economy coexisted with kinship as the proper way to organize social and economic life. The latter form of sociality was even dominant in some groups and regions, such as the Celtic fringe, Catholic communities, the American “Bible Belt,” and rural or semi-rural areas in general. Today, those subcultures are largely gone. Opposition to liberalism is for the most part limited, ironically, to individuals who act on their own. 


Success of the liberal model, in peace and in war

How did liberalism become so dominant, even hegemonic? In a word, it delivered the goods. Liberal regimes were better able to mobilize labor, capital, and raw resources over long distances and across different communities. Conservative regimes were less flexible and, by their very nature, tied to a single ethnocultural community. Liberals pushed and pushed for more individualism and social atomization, thereby reaping the benefits of access to an ever larger market economy.

The benefits included not only more wealth but also more military power. During the American Civil War, the North benefitted not only from a greater capacity to produce arms and ammunition but also from a more extensive railway system and a larger pool of recruits, including young migrants of diverse origins—one in four members of the Union army was an immigrant (Doyle 2015). 

During the First World War, Britain and France could likewise draw on not only their own manpower but also that of their colonies and elsewhere. France recruited half a million African soldiers to fight in Europe, and Britain over a million Indian troops to fight in Europe, the Middle East, and East Africa (Koller 2014; Wikipedia 2018b). An additional 300,000 laborers were brought to Europe and the Middle East for non-combat roles from China, Egypt, India, and South Africa (Wikipedia 2018a). In contrast, the Central Powers had to rely almost entirely on their own human resources. The Allied powers thus turned a European civil war into a truly global conflict.

The same imbalance developed during the Second World War. The Allies could produce arms and ammunition in greater quantities and far from enemy attack in North America, India, and South Africa, while recruiting large numbers of soldiers overseas. More than a million African soldiers fought for Britain and France, their contribution being particularly critical to the Burma campaign, the Italian campaign, and the invasion of southern France (Krinninger and Mwanamilongo 2015; Wikipedia 2018c). Meanwhile, India provided over 2.5 million soldiers, who fought in North Africa, Europe, and Asia (Wikipedia 2018d). India also produced armaments and resources for the war effort, notably coal, iron ore, and steel.

Liberalism thus succeeded not so much in the battle of ideas as on the actual battlefield. 


To be cont'd

References

Barrett, J.H., Locker, A.M. and Roberts, C.M. (2004). Dark Age Economics revisited: The English fish bone evidence AD 600-1600. Antiquity 78 (301): 618-636.

Callmer, J. (2002). North-European trading centres and the early medieval craftsman. Craftsmen at Åhus, North-Eastern Scania, Sweden ca. AD 750-850+, UppSkrastudier 6 (Acta Archaeologica Lundensia Ser. in 8, no. 39), 133-158.

Clark, G. (2007). A Farewell to Alms. A Brief Economic History of the World. Princeton University Press: Princeton and Oxford.

Clark, G. (2009a). The indicted and the wealthy: surnames, reproductive success, genetic selection and social class in pre-industrial England.

Clark, G. (2009b). The domestication of man: The social implications of Darwin. ArtefaCTos 2: 64-80. 

Doyle, D.H. (2015). The Civil War Was Won by Immigrant Soldiers, June 29, Time

Frost, P. (2017). The Hajnal line and gene-culture coevolution in northwest Europe. Advances in Anthropology 7: 154-174.

Frost, P. and H. Harpending. (2015b). Western Europe, state formation, and genetic pacification. Evolutionary Psychology 13: 230-243.

Greer, T. (2013a). The Rise of the West: Asking the Right Questions. July 7, The Scholar's Stage

Greer, T. (2013b). Another look at the 'Rise of the West' - but with better numbers. November 20, The Scholar's Stage

Hbd *chick (2013). Going Dutch, November 29

Koller, C. (2014). Colonial military participation in Europe. International Encyclopedia of the First World War. 

Krinninger, T., and Mwanamilongo, S. (2015). Africa in World War II: the forgotten veterans. July 5, DW

Rindermann, H. (2018). Cognitive Capitalism. Human Capital and the Wellbeing of Nations. Cambridge University Press.

Wikipedia (2018a). Chinese Labour Corps.

Wikipedia (2018b). Indian Army during World War I

Wikipedia (2018c). Débarquement de Provence

Wikipedia (2018d). Indian army during World War II
https://en.wikipedia.org/wiki/Indian_Army_during_World_War_II
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Sunday, December 9, 2018

Inuit and vitamin D



Inuit mothers (Wikicommons - Ansgar Walk) - Inuit have low levels of vitamin D. Does this mean they're not getting enough? Or have their bodies adapted to an environment where it cannot easily be made in the skin or obtained from the diet?



Inuit people have "insufficient" vitamin D, even among those who eat a traditional diet and live a traditional lifestyle. There are consequently moves afoot to remedy this insufficiency by providing vitamin D supplements. In my opinion, this is a response to a largely nonexistent problem and will probably have adverse consequences.

My arguments are explained in an article I have just published in Inuit Studies. Here is the abstract:


Inuit have vitamin D blood levels that generally fall within the range of insufficiency, even when they live on a traditional diet of fish and game meat. Without this vitamin, bones soften and become deformed, a condition called rickets in children and osteomalacia in adults. Until recent times, however, this condition was much rarer among Inuit than among non-Inuit, even when the latter included people living near Inuit communities under similar conditions of climate and housing. This rarity was attributed to extended breastfeeding and a high-meat/low-cereal diet. The situation subsequently reversed, with Inuit becoming more at risk of developing rickets, first in Labrador during the 1920s and later elsewhere. To reduce this excess risk, researchers have recommended vitamin D supplementation, arguing that breast milk has too little vitamin D and that even a traditional diet cannot provide the recommended daily intake. We should ask, however, whether the problem is definitional. Inuit may have lower levels of vitamin D because they need less, having adapted culturally and physiologically to an environment where this vitamin is less easily synthesized in the skin. These adaptations include a diet that enhances calcium bioavailability (by means of ß-casein in breast milk, certain unknown substances in meat, and absence of phytic acid), as well as genetic changes that enable vitamin D to be used more efficiently. Although Inuit are today more at risk of developing rickets than are non-Inuit, this excess risk is nonetheless small and seems to have a dietary cause-namely, early weaning and abandonment of a high-meat/low-cereal diet.


Please feel free to offer comments or criticisms.


Reference

Frost, P. (2018). To supplement or not to supplement: are Inuit getting enough vitamin D? Études Inuit Studies 40(2): 271-291.
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Sunday, December 2, 2018

More unintended consequences




Fond memories, by Raimundo de Madrazo y Garreta (1841-1920). The hormonal state of pregnancy causes women to have a lower capacity for multitasking and remembering future activities. What happens when oral contraceptives maintain this hormonal state for years and years?



In my last post I reviewed the literature on oral contraceptives and behavior. Women invest more in sexual attractiveness near the time of ovulation, putting on more makeup and sending out other visual, behavioral, and olfactory cues. Oral contraceptives seem to suppress this desire to be attractive.

Parallel to these attitudinal and behavioral changes over the menstrual cycle, we also find cyclical changes to certain brain regions:

[...] a large sample of 55 women was scanned three times along their menstrual cycle in concisely defined time windows of hormonal changes. Accordingly this is the first study using a large enough sample size to assess menstrual cycle dependent changes in human brain structure with sufficient power. Results confirm a significant estradiol-dependent pre-ovulatory increase in gray matter volumes of the bilateral hippocampus, but also show a significant, progesterone-dependent increase in gray matter volumes of the right basal ganglia after ovulation. No other areas were affect by hormonal changes along the menstrual cycle. These hormone driven menstrual cycle changes in human brain structure are small, but may be the underlying cause of menstrual cycle dependent changes in cognition and emotion. (Pletzer et al. 2018).

The same research team earlier reported differences in brain structure between oral contraceptive (OC) users and non-users. OC users were closer to men in their brain structure:

Men had larger hippocampi, parahippocampal and fusiform gyri, amygdalae and basal ganglia than women. Women showed larger gray matter volumes in the prefrontal cortex, pre- and postcentral gyri. These sex-dependent effects were modulated by menstrual cycle phases and hormonal contraceptives. We found larger volumes in the right fusiform/parahippocampal gyrus during early follicular compared to mid-luteal cycle phase. Women using hormonal contraceptives showed significantly larger prefrontal cortices, pre- and postcentral gyri, parahippocampal and fusiform gyri and temporal regions, compared to women not using contraceptives. (Pletzer et al. 2010).

This study was criticized because it made no distinction between progestin-only OCs and combined progestin/estradiol OCs. The results were quite different when another research team repeated this study with participants who used only the second type of pill. OC users now had less, not more, brain volume, particularly in certain regions of the cerebral cortex: 

In 90 women, (44 OC users, 46 naturally-cycling women), we compared the cortical thickness of brain regions that participate in the salience network and the default mode network, as well as the volume of subcortical regions in these networks. We found that OC use was associated with significantly lower cortical thickness measurements in the lateral orbitofrontal cortex and the posterior cingulate cortex. These regions are believed to be important for responding to rewards and evaluating internal states/incoming stimuli, respectively. (Petersen et al. 2015 - h/t to Wanda!)

These differing results may reflect the different types of OCs in use. Because progestin, like progesterone, has anti-estrogenic effects, long-term use would tend to masculinize a woman's brain; there is consequently more gray matter in the parahippocampal and fusiform gyri, which are likewise bigger in men than in women. In contrast, when women prevent conception by taking a mix of progestin and estradiol, which more closely mimics the hormonal state of pregnancy, certain regions of their cerebral cortex will tend to atrophy.

Momnesia?

This atrophy may have an evolutionary cause. Keep in mind that a pregnant woman has to cope with a different pattern of cognitive demands: 

Pregnant women often have difficulty with multi-tasking and remembering future activities; however, they show improvement in memory for faces and recognition of emotional changes, particularly in men. They tend to have an increased sensitivity to odors, many of which are perceived as unpleasant. Perceptions of taste alter throughout pregnancy, with cravings for sweet foods in the second trimester and for salt in the third; sour tends to be preferred throughout the pregnancy. (Stadtlander 2013)

In general, the overall cognitive load is lower during pregnancy, so it makes sense that a pregnant woman’s body would allocate more resources to her developing child and fewer to her brain. The brain is, after all, the costliest organ of the human body, and it can probably cope with being a lower priority over the short term. Problems develop only if the hormonal state of pregnancy is artificially maintained for years and years.


References

Petersen, N., A. Touroutoglou, J.M. Andreano, and L. Cahill. (2015).Oral contraceptive pill use is associated with localized decreases in cortical thickness. Human Brain Mapping 36(7): 2644-2654. 

Pletzer, B., T. Harris, and E. Hidalgo-Lopez. (2018). Subcortical structural changes along the menstrual cycle: beyond the hippocampus. Scientific Reports 8: 16042 https://dx.doi.org/10.1038%2Fs41598-018-34247-4

Pletzer, B., M. Kronbichler, M. Aichhorn, J. Bergmann, G. Ladurner, and H.H. Kerschbaum. (2010). Menstrual cycle and hormonal contraceptive use modulate human brain structure. Brain Research 1348: 55-62.

Stadtlander, L. (2013).  Memory and perceptual changes during pregnancy. International Journal of Childbirth Education 28(2): 49-53.




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Sunday, November 25, 2018

Unintended consequences


Oral contraceptives suppress not only ovulation but also concurrent behavioral and attitudinal changes, including the desire to look more attractive. Has "the pill" changed our culture?



The oral contraceptive pill prevents pregnancy by suppressing ovulation—in short, by fooling a woman's body into thinking it is already pregnant. In addition to medical side effects, "the pill" also seems to modify behavior and attitude, often subtly. Whereas women are more likely to initiate sexual behavior at ovulation, this effect is suppressed in women on the pill (Adams et al. 1978). The latter also prefer men whose faces are less masculine (Little et al. 2002) and lighter-skinned (Frost 1994).

Among non-pill-users, ovulation coincides with greater use of cosmetics and increased time spent putting on cosmetics (Guéguen 2012). This behavioral effect seems to be likewise suppressed by pill use:

We photographed a sample of women (N = 36) who self-reported whether or not they use the contraceptive pill, as well as their cosmetic habits. A separate sample of participants (N = 143) rated how much makeup these target women appeared to be wearing. We found that women not using the contraceptive pill (i.e., naturally cycling women) reported spending more time applying cosmetics for an outing than did women who use the contraceptive pill. We also found that the faces of these naturally cycling women were rated as wearing more cosmetics than the faces of the women using the contraceptive pill. (Batres et al. 2018)

These findings are consistent with the results of a study on professional lap dancers. The participants made $335 in tips per 5 hour shift during ovulation, but only $260 per shift during the luteal phase and $185 per shift during menstruation. Lap dancers on contraceptive pills showed no change in earnings over the menstrual cycle (Miller et al. 2007). It's unclear what sort of visual or behavioral cues were suppressed by pill use:

[...] our study did not identify the precise proximal mechanisms that influence tip earnings. These might include the previously documented shifts in body scent, facial attractiveness, soft-tissue body symmetry, waist-to-hip ratio, and verbal creativity and fluency—or they might include shifts in other phenotypic cues that have not yet been studied. We can, however, exclude some possible mediators based on previous exotic dancer research. Tip earnings are unlikely to be influenced by cycle shifts in stage-dance moves, clothing, or initial conversational content because these cues just do not vary much for professional dancers (Miller et al. 2007)

Do women naturally have a more attractive physical appearance at ovulation?


Discussion

The past half-century has seen a trend toward androgyny among women. This trend is usually attributed to feminism and pop culture, but perhaps the latter have in turn been influenced by something else.

Today, "the pill" is used by approximately 100 million women worldwide, particularly in developed countries. Has this widespread use played a role in changing our cultural and ideological environment? 

I'm not suggesting that women look less feminine today simply because more of them are on the pill and thus are hormonally altered. Rather, if a larger proportion of women are in that kind of hormonal state, it will be easier for anti-feminine fashions and ideologies to achieve a critical mass and take off among all women, including those not on the pill.


References

Adams, D.B., A.R. Gold, and A.D. Burt. (1978). Rise in female-initiated sexual activity at ovulation and its suppression by oral contraceptives. New England Journal of Medicine 299: 1145-1150.

Batres, C., A. Porcheron, G. Kaminski, S. Courrèges, F. Morizot, and R. Russell. (2018). Evidence that the hormonal contraceptive pill is associated with cosmetic habits? Frontiers in Psychology 9: 1459
https://doi.org/10.3389/fpsyg.2018.01459

Frost, P. (1994b). Preference for darker faces in photographs at different phases of the menstrual cycle: Preliminary assessment of evidence for a hormonal relationship. Perceptual and Motor Skills 79(1): 507-14.
https://doi.org/10.2466/pms.1994.79.1.507.

Guéguen, N. (2012). Makeup and menstrual cycle: near ovulation, women use more cosmetics. The Psychological Record 62: 541-548. 

Little, A.C., B.C. Jones, I.S. Penton-Voak, D.M. Burt, and D.I. Perrett. (2002). Partnership status and the temporal context of relationships influence human female preferences for sexual dimorphism in male face shape. Proceedings of the Royal Society B. 269: 1095-1100. 

Miller, G., J.M. Tybur, and B.D. Jordan. (2007). Ovulatory cycle effects on tip earnings by lap dancers: economic evidence for human estrus? Evolution and Human Behavior 28: 375-381. https://doi.org/10.1016/j.evolhumbehav.2007.06.002
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Sunday, November 18, 2018

Looking through a lens



The Babylonian goddess Ishtar (Louvre). The cult of feminine whiteness reached its height in a zone stretching from the Mediterranean through the Middle East and into South and East Asia



Skin color differentiates between the sexes at puberty, with complexions becoming paler in girls and ruddier and browner in boys. The cause seems to be hormonal. This is most convincingly shown by recent studies on digit ratio in men and women before and after puberty and by earlier studies on normal, castrated, and ovariectomized subjects (Edwards and Duntley 1939; Edwards and Duntley 1949; Edwards et al. 1941; Manning et al. 2004; Sitek et al. 2018).

How noticeable is this sex difference? If we take the best controlled studies, where this sexual differentiation is measured at the upper inner arm, we find that boys and girls differ after puberty by about one and a half percentage points of skin reflectance (Kalla 1983; Mesa 1983). By comparison, northern Europeans and West Africans differ by 25 to 30 percentage points (Robins 1991, Tables 7.1, 7.2).

Keep in mind that these measurements are from the upper inner arm and that measurements from other body sites show a much larger sex difference. On the buttocks and the breasts, skin reflectance differs by 6 to 15 percentage points between men and women (Edwards et al. 1939; Garn et al. 1956). The literature has always ascribed this finding to differences in dress and, hence, to differences in sun exposure, yet female skin is lighter at these sites not only because it has less melanin but also because it has less blood in its outer layers, a fact hard to reconcile with a simple tanning effect. 

There is reason to believe that women are lighter-skinned where their subcutaneous fat layer is thicker, possibly because body fat contains an enzyme (aromatase) that converts an androgen (androstenedione) into an estrogen (estrone), thus feminizing the skin (Siiteri and MacDonald 1973). Indeed, lightness of skin color correlates with thickness of subcutaneous fat in adult women (Mazess 1967).


Visual processing of this sex difference in the human mind

Whatever its actual magnitude, we seem innately predisposed to notice this small difference in skin color, particularly for face recognition. Research is ongoing, but there is a growing consensus that "color is not merely an accessory of faces, but is rather a complex and crucial feature in facial processing. [...] Further, recent work has revealed consistent patterns of connected face and color selective cortical areas, possibly reflecting a shared overlap of visual processing between faces and color" (Thorstenson 2018).

Faces are recognized by means of many neurons, some of which specialize in recognizing male faces, others in recognizing female faces, and others in recognizing both indifferently (Baudouin and Brochard 2011; Bestelmeyer et al. 2008; Jacquet and Rhodes 2008; Little et al. 2005). To recognize gender, one of the key visual criteria is skin color (Bruce and Langton 1994; Hill, Bruce, and Akamatsu 1995; Russell and Sinha 2007; Russell et al. 2006; Tarr et al. 2001; Tarr, Rossion, and Doerschner 2002). In particular, these neurons use two aspects of facial color: hue (degree of brownness and ruddiness) and luminosity (degree of contrast between lightness of facial skin versus darkness of lip/eye area). Hue is the fast channel for gender identification. If the face is too far away or the lighting too dim, this mental mechanism will switch to the slower but more accurate channel of luminosity (Dupuis-Roy et al. 2009; Nestor and Tarr 2008a; Nestor and Tarr 2008b; Tarr et al. 2001; Tarr, Rossion, and Doerschner 2002). 

It has been shown that an observer can identify the gender of a face even if the image is blurred and differs only in color (Tarr et al. 2001). Indeed, facial color seems especially crucial if face shape is not clearly visible (Yip and Sinha 2002).

Even when not observing a human face we unconsciously associate darkness with men and lightness with women. This was shown in a series of experiments with Dutch, Portuguese, and Turkish participants. In the first one, personal names were gender-recognized faster when male names were presented in black and female names in white than when the combinations were reversed. In the second experiment, very briefly appearing black and white blobs had to be classified by gender; the former were classified predominantly as male and the latter as female. Finally, in an eye-tracking experiment, observation was longer and fixation more frequent when a black or dark object was associated with a male character and a white or light object with a female character (Semin et al. 2018). Similar results come from a word-association test with Navajo participants: the color black was perceived as more potent and masculine and the color white as more active and feminine (Osgood 1960, p. 165).

We therefore perceive skin color, and especially facial color, through the lens of a mental mechanism that initially arose for gender recognition. This may explain not only why lighter skin is subconsciously perceived as feminine but also why women have sought to accentuate this relative pallor in a wide range of cultures and time periods, most often by avoiding the sun and wearing protective clothing (Frost 2010, pp. 120-123). To the same end, and often independently in different geographic regions, powders have been created from white clay, lime, chalk, or gypsum for the purpose of lightening women’s facial color or increasing its contrast with lip/eye color (Russell 2003; Russell 2009; Russell 2010).

This cult of feminine whiteness reached its height in a zone stretching from the Mediterranean through the Middle East and into South and East Asia. Here, the sex difference in skin color could develop to its fullest, without being constrained by the ceiling of very light pigmentation or the floor of very dark pigmentation. Here too were invented the first cosmetics for women, including powders to lighten skin artificially, and accessories to keep skin untanned (parasols, long gloves, conical or wide-brimmed hats). Finally, here too were created the first works of prose, poetry, and visual art, often on the theme of female beauty, including feminine whiteness. The collective imagination thus became populated with women much fairer than their real-life counterparts.


The advent of the tanned look and the end of feminine whiteness

This cult of feminine whiteness came to an end in the Western world when women embraced the tanned look in the early 20th century. This look began as a side effect of heliotherapy, i.e., the use of sun baths and sun lamps to treat rickets, tuberculosis of the skin, and other cutaneous diseases. By 1929 it had become a fashion, to the surprise of observers like this New York Times journalist: "Idealists would like to believe that the people, investigating the medical doctrine and accepting it as sober fact, went deliberately forth to get what was good for them, and took to sun baths with an avidity they had never shown for spinach, sleep, or orthopedic shoes" (Segrave 2005, p. 35). The new fad had become especially popular with women and, as such, entered into the boyish look of the 1920s: bobbed hair, large shoulders, small bust, narrow hips, and long legs. The intent was to evoke the image of a boy on the brink of puberty, as shown by the French name of this fashion trend: la garçonne.

While the first nudist movements were organizing, la garçonne freely exhibited her athletic body and enjoyed the benefits of heliotherapy. The 1920s made tanning fashionable. Translucent skin and pale complexions were relegated to the theatre prop room of fin de siècle romanticism. Thus disappeared an element of gender differentiation. The contrast of flesh colors, brown and copper for the man, white, pink, and ivory for the woman, had been a constant since Ancient Egypt in literary and pictorial representations. (Bard 1998, p. 41)

The tanned look tapped into an erotic response that had previously been marginalized and stigmatized. In Victorian era novels, the "dark lady" appears as an "impetuous," "ardent," and "passionate" object of short-lived romances (Carpenter 1936, p. 254). Similarly, in French novels of the same era "[t]he love incarnated by brown women appears as the conceptual equivalent of a devouring femininity, thus making them similar to the mythical figure of Lilith" (Atzenhoffer 2011, p. 6). This motif goes back at least to the Middle Ages in various European cultures and points to an alternate mode of eroticism:

[...] dark girls [...] are inevitably imagined as sexually more available than their fairer sisters, with whom they are implicitly or explicitly contrasted. In addition, the change of a girl's complexion, such as being burned by the sun, is to be understood as symbolic of her having crossed a sexual threshold without the benefit of marriage. (Vasvari 1999)

European folklore has sayings along the lines of "the darker the berry, the sweeter the juice," such as the following from a Venetian folk-poem:

"My lady mother always told me that I should never be enamoured of white roses," says a sententious young man; "she told me that I should love the little mulberries, which are sweeter than honey." "Cara mora," mora, or mulberry, meaning brunette, is an ordinary caressing term. (Martinengo-Cesaresco 1886, p. 95)

This is consistent with the idea that women evolved lighter skin not as a means to stimulate male sexual arousal but rather as a means to modify such arousal by reducing aggressiveness in the male observer and inducing feelings of care. Women are thus lighter-skinned for the same reason that they have less body hair, a higher pitch of voice, and a more babyish face. These are all key aspects of Konrad Lorenz's Kindchenschema (Lorenz 1971, pp. 154-164). Another ethologist, Richard Russell, was the first to use this concept to explain women's lighter skin:

I believe the sexual differences in skin color resulted from female whiteness being selected for because it is opposite the threat coloration, although the selection pressures may have been rather mild. Light skin seems to be more paedomorphic, since individuals of all races tend to darken with age. Even in the gorilla, the most heavily pigmented of the hominoids, the young are born with very little pigment. [...] Thus, a lighter colored individual may present a less threatening, more juvenile image. (Guthrie 1970)

This explanation is supported by a two-part study where each male participant was first shown pictures of women and asked to rate their attractiveness. Women with lighter skin were not rated more attractive than those with darker skin. In the second part, eye movements were tracked, and it was found that women with lighter skin were viewed for a longer time. The longer duration could indicate a slower rise and fall in sexual arousal (Garza et al. 2016). Women's lighter skin may thus lengthen and pacify male sexual arousal via a Kindchenschema effect.


Conclusion

Today, skin color is seen as a mark of ethnic identity, yet this is not the sole meaning it has had for humans. For most of history and prehistory it was seen as a mark of male or female identity.

This older meaning has received much less interest, even in academia. It is perhaps no coincidence that scholarly interest has come disproportionately from non-Westerners. In contrast, Western academics, and Americans in particular, generally view the psychological meaning of skin color as a legacy of slavery.


References

Atzenhoffer, R. (2011). Les hommes préfèrent les blondes. Les lectrices aussi. Effet de psychologie, horizons idéologiques et valeurs morales des héroïnes dans l'œuvre romanesque de H. Courths-Mahler. Colloque national (CNRIUT), Villeneuve d'Ascq, 8-10 juin 2009, 

Bard, C. (1998). Les garçonnes. Modes et fantasmes des Années folles. Paris: Flammarion.

Baudouin, J.-Y., and R. Brochard. (2011). Gender-based prototype formation in face recognition. Journal of Experimental Psychology: Learning, Memory, and Cognition 37(4): 888-898. 

Bestelmeyer, P.E.G., B.C. Jones, L.M. DeBruine, A.C. Little, D.I. Perrett, A. Schneider, L.L.M. Welling, C.A. Conway. (2008). Sex-contingent face aftereffects depend on perceptual category rather than structural encoding. Cognition 107(1): 353-365.

Bruce, V., and S. Langton. (1994). The use of pigmentation and shading information in recognising the sex and identities of faces. Perception 23(7): 803-822.

Carpenter, F. I. (1936). Puritans preferred blondes. The heroines of Melville and Hawthorne. New England Quarterly 9(2): 253-272.

Dupuis-Roy, N., I. Fortin, D. Fiset, and F. Gosselin. (2009). Uncovering gender discrimination cues in a realistic setting. Journal of Vision 9(2): 10, 1-8.

Edwards, E.A., and S.Q. Duntley. (1939). The pigments and color of living human skin. American Journal of Anatomy 65(1): 1-33.

Edwards, E.A., and S.Q. Duntley. (1949). Cutaneous vascular changes in women in reference to the menstrual cycle and ovariectomy. American Journal of Obstetrics & Gynecology 57(3): 501-509.

Edwards, E.A., J.B. Hamilton, S.Q. Duntley, and G. Hubert. (1941). Cutaneous vascular and pigmentary changes in castrate and eunuchoid men. Endocrinology 28(1): 119-128. https://doi.org/10.1210/endo-28-1-119  

Frost, P. (2010). Femmes claires, hommes foncés. Les racines oubliées du colorisme. Quebec City: Les Presses de l'Université Laval, 202 p.

Garn, S.M., S. Selby, and M.R. Crawford. (1956). Skin reflectance studies in children and adults. American Journal of Physical Anthropology 14:101-117.

Garza, R., R.R. Heredia, and A.B. Cieslicka. (2016). Male and female perception of physical attractiveness. An eye movement study. Evolutionary Psychology 14(1): 1-16. https://doi.org/10.1177/1474704916631614 .

Guthrie, R.D. (1970). Evolution of human threat display organs. In T. Dobzhansky, M.K. Hecht, and W.C. Steere (Eds.) Evolutionary Biology 4: 257-302. New York: Appleton-Century Crofts.

Jaquet, E., and G. Rhodes. (2008). Face aftereffects indicate dissociable, but not distinct, coding of male and female faces. Journal of Experimental Psychology: Human Perception and Performance 34(1): 101-112. 

Kalla, A.K. (1973). Ageing and sex differences in human skin pigmentation. Zeitschrift für Morphologie und Anthropologie 65(1): 29-33.

Hill, H., V. Bruce, and S. Akamatsu. (1995). Perceiving the sex and race of faces: The role of shape and colour. Proceedings of the Royal Society B: Biological Sciences 261(1362): 367-373.

Little, A.C., L.M. DeBruine, and B.C. Jones. (2005). Sex-contingent face after-effects suggest distinct neural populations code male and female faces. Proceedings of the Royal Society of London, Series B 272(1578): 2283-2287.

Lorenz, K. (1971). Studies in Animal and Human Behaviour, vol. 2. London: Methuen & Co.

Manning, J.T., P.E. Bundred, and F.M. Mather. (2004). Second to fourth digit ratio, sexual selection, and skin colour. Evolution and Human Behavior 25: 38-50.

Martinengo-Cesaresco, E. (1886). Essays in the Study of Folk-Songs. London: J.M. Dent & Sons.

Mazess, R.B. (1967). Skin color in Bahamian Negroes. Human Biology 39:145-154.

Mesa, M.S. (1983). Analyse de la variabilité de la pigmentation de la peau durant la croissance. Bulletin et mémoires de la Société d'Anthropologie de Paris, t. 10 série 13: 49-60.

Nestor, A., and M.J. Tarr. (2008a). The segmental structure of faces and its use in gender recognition. Journal of Vision 8(7): 7, 1-12, http://journalofvision.org/8/7/7/, https://doi.org/10.1167/8.7.7.

Nestor, A., and M.J. Tarr. (2008b). Gender recognition of human faces using color. Psychological Science 19(12): 1242-1246.

Osgood, C.E. (1960). The cross-cultural generality of visual-verbal synesthetic tendencies. Behavioral Science 5(2): 146-169.

Russell, R. (2003). Sex, beauty, and the relative luminance of facial features. Perception 32(9): 1093-1107.

Russell, R. (2009). A sex difference in facial pigmentation and its exaggeration by cosmetics. Perception 38(8): 1211-1219.

Russell, R. (2010). Why cosmetics work. In R. Adams, N. Ambady, K. Nakayama, and S. Shimojo (Eds.) The science of social vision (pp. 186-203). New York: Oxford.

Russell, R. and P. Sinha. (2007). Real-world face recognition: The importance of surface reflectance properties. Perception 36(9): 1368-1374.

Russell, R., P. Sinha, I. Biederman, and M. Nederhouser. (2006). Is pigmentation important for face recognition? Evidence from contrast negation. Perception 35:749-759.

Segrave, K. (2005). Suntanning in 20th Century America. Jefferson (North Carolina): McFarland & Company.

Semin, G.R., T. Palma, C. Acaturk, and A. Dziuba. (2018). Gender is not simply a matter of black and white, or is it? Philosophical Transactions of The Royal Society B Biological Sciences 373(1752):20170126

Siiteri, P.K., and P.C. MacDonald. (1973).Role of extraglandular estrogen in human endocrinology, in S.R. Geiger (ed.). Handbook of Physiology, vol. 2, part 1. Washington, D.C.: American Physiology Society, Section 7, pp. 615-629.

Sitek, A., S. Koziel, A. Kasielska-Trojan, and B. Antoszewski. (2018). Do skin and hair pigmentation in prepubertal and early pubertal stages correlate with 2D:4D? American Journal of Human Biology, early view 

Tarr, M.J., D. Kersten, Y. Cheng, and B. Rossion. (2001). It's Pat! Sexing faces using only red and green. Journal of Vision 1(3): 337, 337a.

Tarr, M. J., B. Rossion, and K. Doerschner. (2002). Men are from Mars, women are from Venus: Behavioral and neural correlates of face sexing using color. Journal of Vision 2(7): 598, 598a,

Thorstenson, C.A. (2018). The social psychophysics of human face color: Review and recommendations. Social Cognition 36(2): 247-273 

Vasvari, L.O. (1999). A comparative approach to European folk poetry and the erotic wedding motif. CLCWeb. Comparative Literature and Culture 1(4)

Yip, A.W., and P. Sinha. (2002). Contribution of color to face recognition. Perception 31(8): 995-1003.
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