Progress Daily

Research by Paola Sapienza & Luigi Zingales (”Gender differences in financial risk aversion and career choices are affected by testosterone“) suggests that testosterone levels may explain why men dominate risky financial professions.

The researchers measured the amount of testosterone in the saliva of aspiring bankers (MBA students from the University of Chicago). They also estimated the students’ exposure to the hormone before they were born by measuring the ratios of their index fingers to their ring fingers (a long ring finger indicates high testosterone exposure) and by measuring how accurately they could determine human emotions by observing only people’s eyes, which also correlates with prenatal exposure to testosterone.

The students had to decide between a 50:50 chance of getting $200 or a gradually increasing sure payout, which ranged from $50 up to $120. The point at which a participant decided to switch from the gamble to the sure thing was reckoned a reasonable approximation of his appetite for risk.

Women and men with the same levels of testosterone generally switched at the same time, demonstrating similar risk preferences. Women who had more testosterone were more risk-loving than women with less, while the data for men at the lower end of the spectrum displayed a similar relationship. Curiously, the relationship between testosterone and risk taking was not as strong for men with moderate to high levels.

The correlation was strongest when the salivary measure of testosterone was used.

The researchers then followed the subjects’ progress after they graduated, to see what sort of careers they entered. Men were more likely than women to choose a risky job in finance but the difference was accounted for entirely by their levels of salivary testosterone.

“Risky business, The Economist

Toxoplasma gondii is a parasite that lives in the guts of cats, where it sheds eggs in cat feces that are often eaten by rats. The parasites increase their odds of getting back to cats by changing the infected rats’ brains, making them less scared of cats (and so more likely to be eaten).

A new study by Jaroslav Flegr, Jan Havlíček, et. al, (”Increased incidence of traffic accidents in Toxoplasma-infected military drivers and protective effect RhD molecule revealed by a large-scale prospective cohort study“) found that subjects with high titers of anti-Toxoplasma antibodies had a probability of a traffic accident (17%) more than 6 times higher than Toxoplasma-free subjects.

“The Return of the Puppet Masters,” by Alex Tabarrok

Martin Gibala had a group of college students, who were healthy but not athletes, ride a stationary bike at a sustainable pace for between 90 and 120 minutes. Another set of students grunted through a series of short, strenuous intervals: 20 to 30 seconds of cycling at the highest intensity the riders could stand. After resting for 4 minutes, the students pedaled hard again for another 20 to 30 seconds, repeating the cycle 4-6 times (depending on how much each person could stand), for a total of 2-3 minutes of intense exercise per training session.

Each of the groups exercised 3 times a week. After 2 weeks, both groups showed almost identical increases in their endurance (as measured in a stationary bicycle time trial), even though one group had exercised for 6-9 minutes per week, and the other about 5 hours. Additionally, molecular changes that signal increased fitness (such as increased volume of muscular mitochondria) were evident equally in both groups. The short, intense workouts aided in weight loss, too; the rate of energy expenditure remained higher longer into recovery after brief, high-intensity exercise than after longer, easier workouts. (Other researchers have found that intense, brief sessions of exercise improve cardiac health, even among people with heart disease.)

“Can You Get Fit in Six Minutes a Week?,” by Gretchen Reynolds

According to research by Hasse Walum (”Genetic variation in the vasopressin receptor 1a gene associates with pair-bonding behavior in humans“), men with a particular variant of a gene that influences brain activity (specifically, an allele that regulates the activity of the hormone vasopressin) are less likely to be devoted and loyal husbands.

About 40% of men have one or two copies of the allele. Men with two copies of the allele had a greater risk of marital discord than men with one copy, and men with one copy of the allele were at more risk of such discord than men with no copies.

In a sample of more than 1,000 heterosexual couples, about 15% of the men without the allele reported serious marital discord in the past year, compared with 34% of men with two copies of the allele.

17% of the men without the allele were living with women without being married to them, compared with 32% of men with two alleles.

“Study Links Gene Variant in Men to Marital Discord” by Shankar Vedantam

The volume of the brain’s grey matter, made up of “processor” cells, is heritable and correlates with certain elements of IQ (Nature Neuroscience, DOI: 10.1038/nn758).

The amount of white matter, which provides the connections between these processors, is also heritable (Journal of Neuroscience, vol 26, p 10235).

And a new study suggests that the quality of these connections is also largely genetic, and correlates with IQ.

Paul Thompson scanned the brains of 23 sets of identical twins and the same number of fraternal twins, using HARDI (a type of magnetic resonance imaging).

By comparing brain maps of identical twins, which share the same genes, with fraternal twins, which share about half their genes, the team calculate that myelin integrity is genetically determined in many brain areas important for intelligence.

This includes the corpus callosum, which integrates signals from the left and right sides of the body, and the parietal lobes, responsible for visual and spatial reasoning and logic. Myelin quality in these areas is correlated with scores on tests of abstract reasoning and overall intelligence (The Journal of Neuroscience, vol 29, p 2212).

Myelin integrity is an especially promising target for manipulation, because, unlike the volume of grey matter, it changes throughout life.

Richard Haier said: “If it’s genetic, it’s biochemical, and we have all kinds of ways of influencing biochemistry.” 

“High-speed brains are in the genes,” by Aria Pearson

100 trillion microbes live in the average human, while the human body contains only about 10 trillion cells. The microbes’ total weight is slightly less than that of a liver.

By the end of 2009, the Human Oral Microbiome Project will give names to the 600 or so different microbes that live in the mouth. In the gut, 1,000+ species have been labelled already. The DNA of these bugs has been found to contain 60,000 genes, — twice the number in the human genome.

In the colon, microbes synthesise vitamins for us and provide 10% of our calories by breaking down dietary fibre we cannot process. Gut bacteria can affect how fats are processed, change the likelihood of obesity, alter cholesterol levels and affect chances of developing diabetes — & alter individual reactions to medicines. New data suggest that they might affect brain development, the immune system and allergies.

“Life on Man,” by Alun Anderson

According to research by John Babraj, Niels Vollaard, & James Timmons (”Extremely short duration high intensity training substantially improves insulin action in young sedentary males“), an intense exercise session every couple of days may be the best way to cut the risk of diabetes.

Sixteen young men (age: 21+/-2 y; BMI: 23.7+/-3.1 kg * m-2; VO2peak: 48+/-9 ml * kg-1 * min-1) performed 2 weeks of supervised HIT (high-intensity interval training) comprising of a total of 15 min of exercise (6 sessions; 4-6 x 30-s cycle sprints per session). Aerobic performance (250-kJ self-paced cycling time trial), and glucose, insulin and NEFA responses to a 75-g oral glucose load (oral glucose tolerance test; OGTT) were determined before and after training.

Following 2 weeks of HIT, the area under the plasma glucose, insulin and NEFA concentration-time curves were all reduced (12%, 37%, 26% respectively, all P<0.001). Fasting plasma insulin and glucose concentrations remained unchanged, but there was a trend towards reduced fasting plasma NEFA concentrations post-training (pre: 350 +/- 36 v post: 290 +/- 39 mumol * l-1, P=0.058). Insulin sensitivity as measured by the Cederholm index was improved by 22.5% (P<0.01). Aerobic cycling performance was improved by ~6% (P<0.01).

"Regular sprints boost metabolism,” Physorg

Joel Weinstock has used worms (found in dirt) to both prevent and reverse autoimmune disease in mice.

Immunologists now recognize a four-point response system of helper T cells: Th 1, Th 2, Th 17 and regulatory T cells. Th 1 inhibits Th 2 and Th 17; Th 2 inhibits Th 1 and Th 17; and regulatory T cells inhibit all three.

A lot of inflammatory diseases — multiple sclerosis, Crohn’s disease, ulcerative colitis and asthma — are due to the activity of Th 17. If you infect mice with worms, Th 17 drops dramatically, and the activity of regulatory T cells is augmented.

Children who grow up on farms and are frequently exposed to worms and other organisms from farm animals are much less likely to develop allergies and autoimmune diseases. Weinstock advises: “Children should be allowed to go barefoot in the dirt, play in the dirt, and not have to wash their hands when they come in to eat.” Also: “let kids have two dogs and a cat” (which will expose them to intestinal worms that can promote a healthy immune system).

“Babies Know: A Little Dirt Is Good for You,” by Jane E. Brody

 Researchers (John Coates, Mark Gurnell & Aldo Rustichini) at the University of Cambridge report that men with longer ring fingers, compared to their index fingers, tended to be more successful in the frantic high-frequency trading in the London financial district. (See “Second-to-fourth digit ratio predicts success among high-frequency financial traders.”)

The impact of biology on success was about equal to years of experience at the job.

(The same ring-to-index finger ratio has previously been associated with success in soccer and basketball.)

The length ratio between those two fingers is determined during the development of the fetus and the relatively longer ring finger indicates greater exposure to the male hormone androgen.

(Previous studies have found that such exposure can lead to increased confidence, risk preferences, search persistence, heightened vigilance and quickened reaction times.

In a separate study last year, the researchers researchers studied male financial traders in London, taking saliva samples in the morning and evening. They found that those with higher levels of testosterone in the morning were more likely to make an unusually big profit that day. (Testosterone affects aggression, confidence and risk-taking.)

In the new study, the researchers measured the right hands of 44 male stock traders who were engaged in a type of trade that involved rapid decision-making and quick physical reactions.

Over 20 months those with longer ring fingers compared to their index fingers made 11 times more money than those with the shortest ring fingers. Over the same time the most experienced traders made about 9 times more than the least experienced ones.

Looking only at experienced traders, the long-ring-finger folks earned 5 times more than those with short ring fingers.

“Finger length may predict financial success,” by Randolph E. Schmid

Wen Zhou & Denise Chen speculated that if humans produce and respond to sweat pheromones, then a woman should respond to a guy’s sweat when sexually aroused differently than she does to his normal sweat.

The researchers asked 20 heterosexual guys to put pads in their armpits as they watched pornographic videos and became aroused (verified by electrodes). Later, they collected the sweat they produced when they weren’t aroused. (See “Encoding Human Sexual Chemosensory Cues in the Orbitofrontal and Fusiform Cortices“)

The researchers then recruited 19 women to smell the men’s pads while undergoing (fMRI) brain scans. The sexual sweat, but not the normal sweat, activated the right orbitofrontal cortex and the right fusiform cortex, brain areas that help us recognize emotions and perceive things, respectively. Both regions are in the right hemisphere, which is generally involved in smell, social response, and emotion.

“Women Can Smell a Man’s Intentions,” Melinda Wenner