Biological Psychology Links

Tiny worm-like creatures that have no males and reproduce by cloning can escape disease by drying up and floating away on the breeze, researchers have found. The rotifers reproduce by laying eggs, but without males, the eggs hatch without being fertilized, a process called parthenogenetic cloning. The offspring are exact genetic clones of their mothers. "Generally, when organisms lose males and start reproducing asexually, they go extinct relatively quickly afterwards," Chris Wilson, a doctoral student in neurobiology at Cornell University, told CBC Radio's As It Happens. Rotifers, though, have diversified into 450 different species and have survived for 30 million years reproducing only by parthenogenesis. This type of asexual reproduction is seen in nematode worms, and in some species of insects, crustaceans, reptiles and sharks. But reproduction exclusively by cloning is rare. Cloning is efficient because it essentially doubles the reproductive output of a species by eliminating the need for two parents. However, since the offspring are genetically identical to their mothers, a parasite or virus can wipe out a large population if it is genetically susceptible to it. Scientists think sex allows a species to swap and recombine genetic material in new ways and avoid such diseases. © CBC 2010

By RANDOLPH E. SCHMID WASHINGTON – Little girls may learn to fear math from the women who are their earliest teachers. Despite gains in recent years, women still trail men in some areas of math achievement, and the question of why has provoked controversy. Now, a study of first- and second-graders suggests what may be part of the answer: Female elementary school teachers who are concerned about their own math skills could be passing that along to the little girls they teach. Young students tend to model themselves after adults of the same sex, and having a female teacher who is anxious about math may reinforce the stereotype that boys are better at math than girls, explained Sian L. Beilock, an associate professor in psychology at the University of Chicago. Beilock and colleagues studied 52 boys and 65 girls who in classes taught by 17 different teachers. Ninety percent of U.S. elementary school teachers are women, as were all of those in this study. Student math ability was not related to teacher math anxiety at the start of the school year, the researchers report in Tuesday's edition of Proceedings of the National Academy of Sciences. But by the end of the year, the more anxious teachers were about their own math skills, the more likely their female students — but not the boys — were to agree that "boys are good at math and girls are good at reading." © 2010 The Associated Press

By Craig H. Kinsley and R. Adam Franssen What turns a young female concerned mainly about herself into a good mother who will make sure her offspring survive in an otherwise hostile world? The bodily changes of childbearing are obvious, but as we are discovering, the changes in the brain are no less dramatic. The maternal brain is a formidable object, a singular entity forged by hormones, neurochemicals, and exposure to the ravening demands and irresistible cuteness of offspring. During pregnancy, the female brain is effectively revving up for the difficult tasks that await. A mother-to-be may most notice her cravings for ice cream and pickles, but inside her head, a transformation is afoot in fundamental functions ranging from attention to memory. As an intriguing new paper demonstrates, even her sensitivity to others' emotions increases. Before we describe the new paper, let us contemplate the maternal brain in all of its wet majesty. Among its remarkable changes are those that allow the mother to focus on her infant in the persistent attempt to puzzle out the child’s needs and wants. As any parent knows, the infant is inscrutable – indeed, the child remains so for much of the parent’s life – and intuition is the mother’s best friend. The parent tests hypotheses: Is the baby hungry? Tired? A sensitized brain facilitates these “experiments.” In humans, rodents and other animals, we find data showing that the mother’s interest in, and motivation toward young increases dramatically as pregnancy nears term, and still further immediately following birth. © 2010 Scientific American

By Ann Gibbons The Y chromosome has long been thought of as a stagnant part of the genome, where genes are slowly decaying in males of all species. But the first comprehensive comparison of the Y chromosome in two species--specifically, humans and chimpanzees--shows that in fact, it is a hot spot of evolution. "It's really exciting; it's totally well-documented; it's really dramatic," says population geneticist Andrew Clark of Cornell University. As is well-known, humans and chimps share 98% of their DNA. But more than 30% of the DNA differs between chimps and humans in the region of the Y chromosome that determines sex. This suggests that the Y chromosome has undergone "extraordinary" remodeling in both species in the 6 million years or so since they split from a common ancestor, says geneticist David Page of the Howard Hughes Medical Institute in Chevy Chase, Maryland, and director of the Whitehead Institute of the Massachusetts Institute of Technology in Cambridge. For almost a century, researchers have thought that the Y chromosome, with far fewer genes than the X, was decaying. Both sex chromosomes evolved from an ordinary pair of chromosomes more than 200 million years ago (Science, 29 October, 1999, p. 964). But since then, the Y has steadily lost genes as well as its ability to recombine and swap genes with the X chromosome. This suggested that the Y has long been an isolated chromosome with little left to lose--just a couple of hundred genes, at most, whose job is to produce sperm and determine the sex of offspring. As a result, researchers predicted that the Y chromosome should be nearly identical in humans and chimpanzees, like the rest of the genome. © 2010 American Association for the Advancement of Science.

by Bob Holmes Sometimes it pays to give underlings a treat. Dominant male chacma baboons allow lower-ranking males to mate with their females as a way to protect the dominant male's own offspring in their absence. That's the conclusion reached by Louise Barrett of the University of Lethbridge in Alberta, Canada, who studied 11 years of observations from a baboon troop in De Hoop Nature Reserve, South Africa. Chacma baboons have a despotic social structure in which a single alpha male can almost completely monopolise mating opportunities by guarding females during their oestrus periods. Yet Barrett found that subordinate males in the De Hoop troop fathered 23 of 64 offspring during that time. Closer analysis showed that this was not because the alpha male was too tired, too busy, or too inexperienced to guard the females. Instead, he appeared to be willingly ceding copulations to subordinate males Spare dads The alpha male's apparent generosity may be a strategy for protecting his young after he is no longer around. When an alpha male dies or wanders off, new alpha males – usually from an outside group – move in, and tend to try to kill infants from the previous regime. Having "spare dads" in the troop may help ensure that these infants receive protection, says Barrett. © Copyright Reed Business Information Ltd

By Cristen Conger Caffeine has a stronger effect on boys than on girls, finds a new study that zeros in on the drug's health impacts on adolescents. More kids are consuming more and more caffeinated drinks, but the stimulant's effects on their growing bodies are still largely unknown. The study, which was published in Behavioural Pharmacology, looked at how consuming caffeinated beverages affected children between 12 and 17 years old. It found that boys would work significantly longer at a computer game to win a caffeinated soda than girls would. The study also controlled for factors including regular caffeine consumption, thirst and boredom. Jennifer R. Temple, lead researcher and neurobiologist at University of Buffalo, said she expected caffeinated drinks to work most strongly on those in the study who routinely consumed the most caffeine, regardless of sex. Instead, the results revealed a relationship between gender and the desire for caffeinated soda. "We aren't sure (why boys responded more), but we speculate that it could have to do with circulating hormones and their effect on the metabolism of caffeine," Temple said. © 2009 Discovery Communications, LLC.

by Linda Geddes PARENTS hoping to shield their children from sex stereotypes by giving them gender-neutral toys may be fighting a losing battle, especially if their offspring are boys. It seems that hormones released both before birth and well into the first few months of life may dictate the type of toys and play that boys are drawn to. By the age of 3, boys and girls show differences in their play preferences. Boys are more strongly drawn to balls, vehicles and construction toys than girls and tend to prefer playing with larger groups, whereas girls are more likely to prefer play with a few individuals. To what extent these differences are biologically programmed rather than a result of social pressure is hotly debated. Recent research hints that exposure to differing levels of hormones in the uterus might sway the preferences that both boys and girls have for "boy-like" toys later on. No one had looked at whether the surges in testosterone and oestrogen that boys and girls experience in the early months of life also affect behaviour. "We tend to think of early development as a time when hormones aren't having effects," says Gerianne Alexander of Texas A&M University in College Station and colleagues. To investigate the effects of these hormone surges on behaviour, Alexander and her colleagues used eye-tracking software to measure levels of interest in animations of a ball versus a doll and a group of figures versus an individual figure, in 21 boys and 20 girls aged 3 to 4 months. The researchers measured levels of oestrogen in the girls' saliva and testosterone in the boys' and compared the lengths of their index and middle fingers - a guide to prenatal testosterone exposure. © Copyright Reed Business Information Ltd.

The female cane toad can pump herself up to mega-size to throw off smaller males striving to mate with her, Australian biologists reported on Wednesday. The unusual tactic suggests that female anurans, as frogs and toads are called, may have far more power to select their sex partner than thought, according to their study, appearing in the British journal Biology Letters. Female cane toads (Bufo marinus) are typically choosier than males when it comes to reproduction. They discriminate among potential mates by approaching the toad with the best call. But, as they head to a rendezvous with the hunk with the mightiest ribbit, they also have to run the gauntlet of excited rival males. An unwanted suitor will seek to climb on the female's back, grasping her tightly in the armpit or groin, waiting until she starts laying her eggs in order to fertilize them. This is where the pneumatic trick comes in, say the scientists, led by Benjamin Phillips of the University of Sydney. By inflating sacs in her body, the female is able to loosen the grip and the luckless male slides off her body, defeated. © 2009 Discovery Communications, LLC.

By Emily Laut When it came to insect penises, Charles Darwin had it right. The famed naturalist suspected that insect genitalia, which are frequently festooned with bizarre combinations of hooks, spines, and knobs, essentially functioned like peacock tails. That is, they helped males beat out their rivals for females. Now, researchers have confirmed this hypothesis by zapping fly penises with a laser. Darwin's hypothesis relies on something called preinsemination sexual selection. Basically, the idea holds that the male with the most effective strategy for getting a female to mate with him--attractive plumage, for instance--is most likely to pass on his genes to the next generation. But since then, studies in various insects have suggested that sexual selection can happen during or even after mating. Researchers noticed, for example, that certain flies engage in courtship displays only after copulation has begun, perhaps as a way to get the female to favor a male's sperm over that of his competitors. (Female flies typically mate with multiple males over a short time period.) They also reasoned that the complicated penis ornaments might help sweep away other males' sperm during mating. But there was no direct way to test this. Enter laser beams. Evolutionary ecologist Michal Polak of the University of Cincinnati in Ohio and entomologist Arash Rashed now of the University of California, Berkeley, modified a laser commonly used to cut very small things, like the nerve cells of nematodes, so that it could zap off the hooks on fruit fly penises. "We can cut the tiniest of structures with the highest of precision," says Polak, all without harming the fly. © 2010 American Association for the Advancement of Science.

A Canadian-led study has found that men's minds and bodies are more in sync than women's when it comes to sexual arousal. The analysis of previous research on human sexuality found that men's feelings of arousal tend to match their physiological responses, while women's mind and body responses were more often inconsistent. Psychology professor Meredith Chivers of Queen's University led the study, which included researchers from the Royal Ottawa Health Care Group, the University of Lethbridge, the University of Amsterdam and the Ontario Institute for Studies in Education at the University of Toronto. "We wanted to discover how closely people's subjective experience of sexual arousal mirrors their physiological genital response — and whether this differs between men and women," Chivers said in a statement. The researchers analyzed the results from 134 previous studies, conducted between 1967 and 2007, collectively involving more than 2,500 women and 1,900 men. Participants in the studies were asked how aroused they felt while watching or listening to sexually explicit content, and sometimes after the exposure to the sexual stimulus. The researchers then compared these descriptions of the participants' feelings with their physiological responses: changes in erection for men and in genital blood flow in women. © CBC 2010

Mosquitoes can impress potential mates by harmonizing the high-pitched whine of their tiny wings. Now, scientists have discovered how this musical matchmaking helps the insects to pick their perfect partner. Research on one of the main malaria carriers in Africa, Anopheles gambiae, shows that the insects use subtle differences in tone to distinguish between forms of mosquito that appear to be physically identical. The preference for harmony is so strong that it seems to be causing two forms of mosquito living in the same region to become separate species. This strict mating policy may be a key factor in maintaining the genetic diversity that makes the insect so adaptable to different environments, and could point to other ways to disrupt mosquito reproduction in malaria-ridden countries. A. gambiae is actually a complex of seven species that are physically indistinguishable but with slightly different behavioural traits. In Burkina Faso, one of these species includes two forms — Mopti (M) and Savannah (S) — and additional forms exist in other parts of Africa. The sheer diversity of the mosquito has puzzled scientists. "People studying this mosquito have wondered how it manages to speciate so quickly," says sensory physiologist Gabriella Gibson at the University of Greenwich, UK. Also unclear is how two forms that swarm together can avoid mating with one another, thereby preventing their genetic diversity from being diluted. © 2010 Nature Publishing Group,

by Geoffrey Miller PEOPLE have radically diverse responses to the very idea of conspicuous consumption. Some folks consider it blindingly obvious that most economic behaviour is driven by status seeking, social signalling and sexual solicitation. These include most Marxists, marketers, working-class fundamentalists and divorced women. Other folks consider this an outrageously cynical view, and argue that most consumption is for individual pleasure ("utility") and family prosperity ("security"). Those folks include most capitalists, economists, upper-class fundamentalists, and soon-to-be-divorced men. Such differences of opinion can rarely be resolved by trading examples or anecdotes, or arguing from first principles. It more often helps to apply some psychology. With this in mind, some colleagues and I devised a series of experiments inspired by "costly signalling theory" - the idea that animals, including humans, use costly, intricate and hard-to-fake signals to flaunt their biological fitness to potential mates and social partners. Our goal was to see how thinking about mating influences people's decisions about spending and giving (Journal of Personality and Social Psychology, vol 93, p 85). In the first experiment the team, led by Vladas Griskevicius from Arizona State University in Tempe and Josh Tybur from the University of New Mexico in Albuquerque, invited college students to the lab in small groups. Each was randomly assigned to one of two conditions: "mating" or "non-mating". The mating subjects looked at three photographs of people of the opposite-sex on a computer screen, picked which one they thought most desirable, and spent a few minutes writing about an ideal first date with that person. The non-mating subjects looked at a street scene photograph and spent the same amount of time writing about the ideal weather for walking around and looking at the buildings it featured. © Copyright Reed Business Information Ltd

by Boonsri Dickinson Four years ago, when Lawrence Summers suggested that the scarcity of prominent female scientists and engineers was in part because there are fewer women on the extremes of the range of innate math ability—fewer geniuses and fewer duds—he stirred up a lot of misguided arguments about gender differences in the brain. Although the former president of Harvard University and current director of the National Economic Council may have been right on a few details, he was wrong on his major point. Men’s and women’s brains are different, but those distinctions are much smaller than we typically think, and few of them are innate. Rather, the slight asymmetries present at birth, shaped and molded by interests, predilections, and the cues of parents and teachers, grow into more significant gender gaps in adulthood. This divergence is an example of plasticity, the brain’s marvelous ability to adapt and change. “Most differences in behavior develop through experience,” says neuroscientist Lise Eliot of Rosalind Franklin University of Medicine and Science in Chicago. “Nature sets the ball rolling, biasing boys and girls toward different interests, but the gaps themselves are largely due to learning and plasticity.” In her new book, Pink Brain Blue Brain: How Small Differences Grow Into Troublesome Gaps and What We Can Do About It, Eliot dispels many myths about male and female brain development. “In parenting literature, there’s a lot of stuff that’s made up,” she says. When the toddler son of peaceniks pines for a toy army truck, she argues, he is expressing an inborn tendency toward active, physical play that has been shaped by social influences, not by the effects of a “gun gene” on the Y chromosome. Until about 1 year of age, boys and girls are equally drawn to dolls; it is only later, when boys become more active, that they strongly prefer balls and cars. Parents also play a role in shaping their children’s interests, often in ways that they may not be fully aware of.

JoNel Aleccia For every woman who has ever obsessed that her chin was too long or that her eyes were set too close together, scientists appear to have a new message: You might be right. Researchers at the University of California, San Diego, claim they’ve discovered the ideal alignment of female facial features, a pair of measurements that explain why one woman is perceived as attractive and the other, well, isn’t. It all has to do with the horizontal distance between the eyes and the vertical distance between the eyes and the mouth, says Pamela M. Pallett, a researcher who believes she has identified new “golden ratios” for facial beauty. Story continues below ↓advertisement | your ad here That may be bad news for gals who don’t conform, but the upside, says Pallett, is that even if your face isn’t perfectly proportioned, a strategic haircut can help. “Everybody can achieve these golden ratios,” said Pallett. “For most people, it might be just as simple as pulling your hair back, or having it hang down in front of your ears. If they have bangs, that can affect the length you perceive of the face.” Faces were judged as most attractive when the distance between the eyes was 46 percent of the face’s width and when the distance from eyes to mouth was 36 percent of the face’s length, according to the study published in the most recent issue of the journal Vision Research. © 2009 msnbc.com

A gene associated with a rare form of progressive deafness in males has been identified by an international team of researchers funded by the National Institute on Deafness and Other Communication Disorders. The gene, PRPS1, appears to be crucial in inner ear development and maintenance. The findings are published in the December 17 early online issue of the American Journal of Human Genetics. The gene is associated with DFN2, a progressive form of deafness that primarily affects males. Boys with DFN2 begin to lose their hearing in both ears roughly between the ages of 5 and 15, and over the course of several decades will experience hearing loss that can range from severe to profound. Their mothers, who carry the defective PRPS1 gene, may experience hearing loss as well, but much later in life and in a milder form. Families with DFN2 have been identified in the United States, Great Britain, and China. The NIDCD-funded researchers led by Xue Zhong Liu, M.D., Ph.D., of the University of Miami Miller School of Medicine, discovered that the PRPS1 gene encodes the enzyme phosphoribosylpyrophosphate (PRPP) synthetase 1, which produces and regulates PRPP (phospho-ribosylpyrophosphate), and appears to play a key role in inner ear development and maintenance. The four mutations identified in the PRPS1 gene cause a decrease in the production of the PRPP synthetase 1 protein that results in defects in sensory cells (called hair cells) in the inner ear, and eventually leads to progressive deafness.

By Melissa Lee Phillips Sometimes a difference between the sexes is not based on sex at all. Women have a finer sense of touch than men do, but a new study shows that this is simply because their fingertips tend to be smaller. Neuroscientist Daniel Goldreich of McMaster University in Hamilton, Canada, and his colleagues first became curious about the sex difference while studying differences between blind and sighted people. They found that blind people are better than those with normal vision at distinguishing fine textures but that, within each group, women are better than men. The researchers thought that the discrepancy might be the result of brain differences between men and women, but they first wanted to see if something simpler could explain it. So they tested 50 women and 50 men on a simple task: Each person touched a small, grooved surface and tried to identify the orientation of the grooves. As the grooves got closer together, it became more difficult to determine their direction. As expected, women performed better at this task than men did, but when the scientists looked at the results by finger size, they found that the sex difference disappeared: On average, men and women with the same size fingertips perform at the same level, the team reports in the 16 December issue of The Journal of Neuroscience. (Finger size does not explain all individual variability, however; there are differences between people with the same size fingers, perhaps as a result of differences in the mechanical properties of skin or in how each person's brain processes the information.) © 2009 American Association for the Advancement of Science.

BY Prachi Patel No woman has yet won one of the three top mathematics awards–the Fields, the Abel, or the Wolf. It’s part of what’s often called the math gender gap, which in the United States starts early—at least twice as many boys as girls score in the 99th percentile on state-level math assessment tests. Five years ago, then Harvard president Lawrence Summers’s suggestion that women lack an ”intrinsic aptitude” for math and science drew a firestorm of protest, but he was drawing on a century-old hypothesis that males exhibit greater variability in many features, math included. By such reasoning, it is possible for girls to be as good as boys in math on average but to be less well represented in the upper (and lower) echelons. This, Summers said, is one reason there are fewer women in tenured science and engineering positions at top universities and research institutions. ”I would like nothing better than to be proved wrong,” he added. A recent study published in the Proceedings of the National Academy of Sciences might make him happy. In it, psychologists Janet Hyde and Janet Mertz, from the University of Wisconsin–Madison, used data from math aptitude tests to show that among top math performers, the gender gap doesn’t exist in some ethnic groups and in some countries. The researchers conclude that culture is the main reason more men excel at the highest math levels in most countries.

By Helen Fields It's hard out there for a sexy female fruit fly. All she wants is a nice meal and a little sperm to fertilize her eggs, but male fruit flies harass her so much, according to a new study, that she lays fewer eggs than normal. And that, researchers say, could be bad for the evolution of the entire species. When it comes to choosing a mating partner, females are usually the more picky sex. Female peacocks like the boys with the most colorful feathers, for example, and female deer go for big antlers. In the fruit fly world, however, males are the choosy ones. They prefer fatter females--they dance around them and constantly try to mate with them--probably because these females lay more eggs. Evolutionary biologist Tristan Long of the University of California, Santa Barbara, and colleagues wondered if all of this attention was bad for the females. The team sorted female fruit flies by knocking them out with carbon dioxide and sifting them through a series of sieves, each with holes a little smaller than the level above. In some experiments, males were given a choice between large-bodied females and randomly chosen females of all sizes; in others, they chose between small-bodied females and randomly chosen females. In still others, males were put in vials with all large females or all small females. When placed in vials with females of various sizes, the guys swarmed the largest females. "The males will court, they'll put their wings out and dance around, and they'll interfere with female foraging" by chasing them around while they're trying to eat, says Long. Eventually, the females gave in and mated many more times with the aggressive males than they needed to. (One time provides plenty of sperm.) "She's not mating because she needs sperm; she's probably mating because she's being worn down by this ongoing courtship," says Long. © 2009 American Association for the Advancement of Science.

by Kate Douglas NOT long ago, the news was full of reports about two male Humboldt penguins at a zoo in Germany that adopted an egg, hatched it and reared the chick together. It seems like every time you turn around, the media spotlight has fallen on another example of same-sex liaisons in the animal kingdom. In the past few years, the ubiquity of such behaviour has become apparent. This summer evolutionary biologists Marlene Zuk and Nathan Bailey from the University of California, Riverside, published a paper on the subject that included examples from dozens of species ranging from dung flies and woodpeckers to bison and macaques. That is just the beginning of the story. The burning question is why same-sex behaviour would evolve at all when it runs counter to evolutionary principles. But does it? In fact there are many good reasons for same-sex sexual behaviour. What's more, Zuk and Bailey suggest that in a species where it is common, it is an important driving force in evolution. Although terms such as homosexual, gay and transgender are commonly used by the mass media, and even by some ethologists, Bailey and Zuk believe you shouldn't extend these descriptors of human sexuality to animals. "It's not simply that they are burdened with the weight of social, moral and political implications, which can obscure objective scientific study," says Bailey. "The problem is that while we can observe the sexual behaviour of animals, we often have little inkling about what motivates it." Besides, as far as we know animals do not form sexual self-identities in the way humans do, he adds. That is why he and Zuk prefer to use the more objective term "same-sex sexual behaviour", which they define as behaviours found in two animals of the same sex that you would find in opposite-sex pairs during courtship, copulation or parenting. © Copyright Reed Business Information Ltd.

Alison Abbott The popular idea that testosterone always makes people more aggressive has been debunked by researchers. A team based in Switzerland has shown that the hormone can make people behave more fairly in an effort to defend their social status. Ernst Fehr, an experimental economist at the University of Zurich, and his colleagues used the 'ultimatum bargaining' game to test how testosterone would affect behaviour in a group of 121 women. Counter-intuitively, women who were given testosterone bargained more fairly. But the idea that testosterone causes aggression in humans, as it clearly does in rodents, is so firmly ingrained in the human psyche that women who believed they had been given testosterone — whether or not they had — bargained much less fairly. Women, not men, were tested because they have less variable 'baseline' blood testosterone levels. The study is published in Nature1. "It is a folk hypothesis that testosterone causes aggression," says Fehr. "But human society is more complex than this." Fair play Several studies in humans have shown positive correlations between high blood testosterone levels and confrontational behaviour. But it has been hard to determine experimentally whether the aggression is caused by testosterone or is instead a consequence of a challenge to a person's social status. The ultimatum game makes it possible to distinguish between these possibilities. © 2009 Nature Publishing Group

Chapter 12. Sex: Evolutionary, Hormonal, and Neural Bases