By the 1980s, the onset of puberty, if not actual menstruation, had gone into free fall–a change so sudden and pronounced that something more than normal evolution must have been at work. In a landmark 1997 study of 17,000 [US] girls, more than 10% of white girls and an astonishing 37.8% of black girls were showing early breast development by age 8. (…)

Later studies, one in 1998 and another in 2010, included Hispanics and produced similar results. On average, 2 out of every 10 white girls, 3 out of 10 Latinas and 4 out of 10 black girls are showing breast development by age 8.

Obesity, a well-established puberty accelerant, is high on the list of suspects.

{ Time via Overcoming Bias | Continue reading }

photo { Mustafah Abdulaziz }

Rather than being fixed over our lifespan, a person’s IQ can show both significant increases and decreases during their teenage years, new results suggest.

Reported in Nature today, the results reveal that verbal and non-verbal ability, as measured by IQ (Intelligence Quotient) tests, fluctuated over a period of three to four years during adolescence. They also showed that these changes correspond to specific structural changes in brain regions associated with speech and movement.

{ Cosmos | Continue reading }

{ Women defy biology to avoid giving birth on Halloween | full story }

It’s one of the worst-kept secrets of family life that all parents have a preferred son or daughter, and the rules for acknowledging it are the same everywhere: The favored kids recognize their status and keep quiet about it. (…) The unfavored kids howl about it like wounded cats. And on pain of death, the parents deny it all. (…)

65% of mothers and 70% of fathers exhibited a preference for one child, usually the older one. (…) “The most likely candidate for the mother’s favorite was the firstborn son, and for the father, it was the last-born daughter. ” (…)

Firstborns have a 3-point IQ advantage over later siblings. (…)

Not all experts agree on just what the impact of favoritism is, but as a rule, their advice to parents is simple: If you absolutely must have a favorite (and you must), keep it to yourself.

{ Time | Overcoming Bias | Continue reading }

In December 2010, two independent laboratories have demonstrated that a full genome-wide analysis of the fetus could be performed from a sample of maternal blood, making fetal diagnostic testing possible in the future for any known genetic condition. The convergence of cffDNA (cell-free fetal DNA) testing with low cost genomic sequencing will enable prospective parents to have relatively inexpensive access to a wide range of genetic information about their fetus from as early as seven weeks gestation.

This article examines a range of ethical, legal and social implications associated with introducing NIPD (non-invasive prenatal diagnosis) into prenatal practice.

{ SSRN | Continue reading }

Moody. Impulsive. Maddening. Why do teenagers act the way they do? Viewed through the eyes of evolution, their most exasperating traits may be the key to success as adults.

The first full series of scans of the developing adolescent brain showed that our brains undergo a massive reorganization between our 12th and 25th years. The brain doesn’t actually grow very much during this period. It has already reached 90 percent of its full size by the time a person is six, and a thickening skull accounts for most head growth afterward. But as we move through adolescence, the brain undergoes extensive remodeling, resembling a network and wiring upgrade. (…)

This process of maturation, once thought to be largely finished by elementary school, continues throughout adolescence. Imaging work done since the 1990s shows that these physical changes move in a slow wave from the brain’s rear to its front, from areas close to the brain stem that look after older and more behaviorally basic functions, such as vision, movement, and fundamental processing, to the evolutionarily newer and more complicated thinking areas up front. The corpus callosum, which connects the brain’s left and right hemispheres and carries traffic essential to many advanced brain functions, steadily thickens. Stronger links also develop between the hippocampus, a sort of memory directory, and frontal areas that set goals and weigh different agendas; as a result, we get better at integrating memory and experience into our decisions. At the same time, the frontal areas develop greater speed and richer connections, allowing us to generate and weigh far more variables and agendas than before.

When this development proceeds normally, we get better at balancing impulse, desire, goals, self-interest, rules, ethics, and even altruism, generating behavior that is more complex and, sometimes at least, more sensible. But at times, and especially at first, the brain does this work clumsily. It’s hard to get all those new cogs to mesh.

{ National Geographic | Continue reading }

painting { Gustav Klimt, Bildnis Helene Klimt, 1898 }

Lisa and Louise Burns, the actresses who played the Grady daughters, are identical twins; however, the characters in the book and film script are merely sisters, not twins.

{ Wikipedia }

Stuart Ullman: My predecessor in this job left a man named Charles Grady as the Winter caretaker. And he came up here with his wife and two little girls, I think were eight and ten. And he had a good employment record, good references, and from what I’ve been told he seemed like a completely normal individual. But at some point during the winter, he must have suffered some kind of a complete mental breakdown. He ran amuck and killed his family with an axe. Stacked them neatly in one of the rooms in the West wing and then he, he put both barrels of a shot gun in his mouth.

{ Quotes from The Shining, 1980 }

Diane Arbus, Identical Twins, Roselle, New Jersey, 1967. The Grady Twins are a reference to Diane Arbus’s photo. Stanley Kubrick was a friend of the photographer.

{ The Shining: A Rough Guide By Stuart Gray }

Mothers who inherited either one or two copies of a particular form of the dopamine D2 receptor gene, dubbed DRD2, cited sharp rises in spanking, yelling and other aggressive parenting methods for six to seven months after the onset of the economic recession in December 2007, sociologist Dohoon Lee of New York University reported August 22 at the American Sociological Association’s annual meeting.

Hard-line child-rearing approaches then declined for a few months and remained stable until a second drop to pre-recession levels started around June 2009, the research showed.

Mothers who didn’t inherit the gene variant displayed no upsurge in aggressive parenting styles after the recession started, Lee and his colleagues found.

{ ScienceNews | Continue reading }

images { 1 | 2 }

It’s email, it’s the Internet, it’s video games, then when texting comes along, it’s texting, and when social networking comes along, it’s social networking. So whatever the flavor of the month in terms of new technologies are, there’s research that comes out very quickly that shows how it causes our children to be asocial, distracted, bad in school, to have learning disorders, a whole litany of things.

And then the Pew Foundation and MacArthur Foundation started saying, about three or four years ago: “Wait, let’s not assume these things are hurting our kids. Let’s just look at how our kids are using media and stop with testing that’s set up from a pejorative or harmful point of view.” (…)

The phenomenon of attention blindness is real — when we pay attention to one thing, it means we’re not paying attention to something else. When we’re multitasking, what we’re actually really doing is what Linda Stone calls “continuous partial attention.” We’re not actually simultaneously paying equal attention to two things: One of the things that we’re doing is probably being done automatically, and we’re sort of cruising through that, and we’re paying more attention to the other thing. Or we’re moving back and forth between them. But any moment when there is a major new form of technology, people think it’s going to overwhelm the brain. In the 1930s there was legislation introduced to prevent Motorola from putting radios in dashboards, because it was thought that people couldn’t possibly cope with driving and listening to the radio. (…)

We used to think that as we get older we develop more neural pathways, but the opposite is actually the case. You and I have about 40 percent less neurons than a newborn infant does. (…) They are learning to process that kind of information faster. That which we experience shapes our pathways, so they’re going to be far less stressed by a certain kind of multitasking that you are or than I am, or people who may not have grown up with that.

{ Interview with Cathy N. Davidson | Salon | Continue reading }

illustration { Geneviève Gauckler }

If you live on a country road you can say hello to each of the occasional persons who passes by: but obviously you can’t do this on Fifth Avenue.

As a measure of social involvemcnt for instance, we are now studying thc rcsponse to a lost child in big city and small town. A child of nine asks people to help him call his home. The graduate students report a strong difference between city and town dwellers: in the city, many more people refused to extend help to the nine-year-old. I like thc problem because there is no more meaningful measure of the quality of a culture than the manner in which it treats its children.

{ Conversation with Stanley Milgram, Psychology Today, 1974 | Continue reading | PDF }

photo { Helen Levitt, New York, c. 1940 }

Boys are maturing physically earlier than ever before. The age of sexual maturity has been decreasing by about 2.5 months each decade at least since the middle of the 18th century. Joshua Goldstein, director of the Max Planck Institute for Demographic Research, has used mortality data to prove this trend, which until now was difficult to decipher. What had already been established for girls now seems to also be true for boys: the time period during which young people are sexually mature but socially not yet considered adults is expanding.

{ MPG | Continue reading }

This was in Japan, so the major breakfast staples were white rice and white bread. (…)

The kids who had rice for breakfast showed higher grey matter volumes than those who had bread. The authors of the study related this to cognitive performance, and said that the rice group had higher IQ scores and POI scores compared to the bread group. (…)

I’ve got a few issues with this paper.

{ Scientopia | Continue reading }

photo { Thatcher Keats }

We don’t name babies to honor people any more. (…)


The 2008 election saw the historic election of America’s first black president. As you might expect, this event was commemorated in names. Approximately 60 more babies were named Barack or Obama than the year before. How big a deal was that? Well, it means hero naming for the new president accounted for .00001 percent of babies born, or one in every 71,000. Neither Barack nor Obama ranked among America’s top 2,000 names for boys. In other words, the effect was so trivially small that you would never notice it unless you went searching for it. Recent presidents with more familiar names, like Clinton, fared even worse on the name charts.



Now roll back the clock to the presidential election of 1896. Democrat William Jennings Bryan inspired a dramatic jump in the names Jennings and Bryan. Those jumps accounted for one in every 2,400 babies born  — an effect 30 times bigger than Obama’s. It was enough to rank both names in the top 300 for the year. And in case your American history is a little shaky: Bryan lost the election.


{ The Baby Name Wizard | Continue reading }

photo { Mustafah Abdulaziz }

It is well recognized that there are consistent differences in the psychological characteristics of boys and girls; for example, boys engage in more ‘rough and tumble’ play than girls do.

Studies also show that children who become gay or lesbian adults differ in such traits from those who become heterosexual – so-called gender nonconformity. Research which follows these children to adulthood shows that between 50 to 80 per cent of gender nonconforming boys become gay, and about one third of such girls become lesbian. (…)

The team followed a group of 4,000 British women who were one of a pair of twins. They were asked questions about their sexual attractions and behavior, and a series of follow up questions about their gender nonconformity. In line with previous research, the team found modest genetic influences on sexual orientation (25 per cent) and childhood gender nonconformity (31 per cent).

{ EurekAlert | Continue reading }

images { 1 | 2 }

Whines, cries, and motherese have important features in common: they are all well-suited for getting the attention of listeners, and they share salient acoustic characteristics – those of increased pitch, varied pitch contours, and slowed production, though the production speed of cries varies. Motherese is the child-directed speech parents use towards infants and young children to sooth, attract attention, encourage particular behaviors, and prohibit the child from dangerous acts. Infant cries are the sole means of communication for infants for the first few months, and a primary means in the later months. Cries signal that the infant needs care, be it feeding, changing, protection, or physical contact. Whines enter into a child’s vocal repertoire with the onset of language, typically peaking between 2.5 and 4 years of age. This sound is perceived as more annoying even than infant cries.

These three attachment vocalizations – whines, cries, and motherese – each have a particular effect on the listener; to bring the attachment partner nearer. (…)

Participants, regardless of gender or parental status, were more distracted by whines than machine noise or motherese as measured by proportion scores. In absolute numbers, participants were most distracted by whines, followed by infant cries and motherese.

{ Whines, cries, and motherese: Their relative power to distract | Journal of Social, Evolutionary, and Cultural Psychology | Continue reading }

photo { Tod Seelie }

{ More than half of the women in a recently published survey reported that near the end of their pregnancies, they took it upon themselves to try to induce labor, mostly by walking, having sex, eating spicy food or stimulating their nipples. | Ohio State University | Continue reading }

photo { Mark Borthwick }

The normal human ratio is around 105 boys for every 100 girls, a natural evolutionary ratio that takes into account the fact that more boys tend to die before reaching adulthood. But in China today, the ratio is 121 boys for every 100 girls; in India the ratio is 112 boys for every 100 girls. (…)

In her thorough and compelling new book, Unnatural Selection, Hvistendahl explains why these trends will have far-reaching effects. She argues that the sex imbalance could prove devastating to social stability across the developing world, sparking crime, human trafficking, and - if history is any guide - even war.

{ The National | Continue reading }

photo { Sally Mann }

Why we remember some scenes from early childhood and forget others has long intrigued scientists—as well as parents striving to create happy memories for their kids. One of the biggest mysteries: why most people can’t seem to recall anything before age 3 or 4.

Now, researchers in Canada have demonstrated that some young children can remember events from even before age 2—but those memories are fragile, with many vanishing by about age 10, according to a study in the journal Child Development this month.

{ WSJ | Continue reading }

photo { Garry Winogrand, Albuquerque, New Mexico, 1957 }

Who is harder to raise, sons or daughters? I’ve asked by a show of hands and with iClickers, over the years, and the room of 750 is almost unanimous: daughters are harder to raise. (…)

So then I show them this.

It is a graph of maternal longevity based on the number of sons or daughters they have. This data was based on a historical population from Finland from 1640-1870 using church records (Helle et al 2002). As you can see, the more sons mothers bear, the shorter their lifespans.

{ Context and Variation | Continue reading }