The researchers also found that men require a slightly longer wavelength to see the same hue as women; an object that women experience as orange will look slightly more yellowish to men, while green will look more blue-green to men.

This last part doesn’t confer an advantage on either sex, but it does demonstrate, Abramov says, that “the nervous system that deals with color cannot be wired in the exact same way in males as in females.” He believes the answer lies in testosterone and other androgens.

{ Smithsonian | Continue reading }

photo { Nicholas Nixon }

Explicit communication involves the deliberate, conscious choosing of words and signals to convey a specific message to a recipient or target audience. […] Much of human communication is also implicit, and occurs subconsciously without overt individual attention. Examples include nonverbal communication and subconscious facial expressions, which have been argued to contribute significantly to human communication and understanding. […] Additionally, recent studies conducted by evolutionary psychologists and biologists have revealed that other animals, including humans, may also communicate information implicitly via the production and detection of chemical olfactory cues. Of specific interest to evolutionary psychologists has been the investigation of human chemical cues indicating female reproductive status. These subliminally perceived chemical cues (odors) are often referred to as pheromones.

For two decades, psychologists studying ovulation have successfully employed a series of “T-shirt studies” supporting the hypothesis that men can detect when a woman is most fertile based on olfactory detection of ovulatory cues. However, it is not known whether the ability to detect female fertility is primarily a function of biological sex, sexual orientation, or a combination of both.

Using methodologies from previous T-shirt studies, we asked women not using hormonal contraceptives to wear a T-shirt for three consecutive nights during their follicular (ovulatory) and luteal (non-ovulatory) phases. Male and female participants of differing sexual orientations then rated the T-shirts based on intensity, pleasantness, and sexiness.

Heterosexual males were the only group to rate the follicular T-shirts as more pleasant and sexy than the luteal T-shirts. Near-significant trends also indicated that heterosexual men and non-heterosexual women consistently ranked the T-shirts, regardless of menstrual stage, to be more intense, pleasant, and sexy than did non-heterosexual men and heterosexual women.

{ Journal of Social, Evolutionary, and Cultural Psychology | PDF }

Problem #1: Inability to Focus

“The average office worker changes windows [on her computer] 37 times an hour,” Headspace’s head of research Nick Begley says in a meditation tutorial. According to Begley, when your mind changes gears that rapidly, part of your brain is still engaged in the previous task and you don’t have all of the attention and resources necessary to concentrate on the current task. […]

Problem #2: Stress

When people get stressed, there is a part of the brain called the amygdala that fires up the “fight or flight” part of the nervous system that helps you make quick, impulsive decisions. “It signals to our hormonal system to secrete adrenaline and cortisol and increases our heart rate, respiration, and blood pressure, so we can escape this immediate physical danger,” says Begley. The problem arises when there is no immediate physical danger–when, say, you’ve forgotten to hit “save” on an important document and your computer crashes, or you arrive unprepared for an important business meeting. […]

The Solution

Refreshing your brain is easier than you think. Here’s the first and only step: Do nothing. […] 10 minutes each day to quiet your mind. Practice observing thoughts and anxieties without passing judgment–simply experience them.

{ Inc. | Continue reading }

photo { Philip Lorca Dicorcia }

The more alcoholic drinks people consume, the more attractive they perceive themselves to be. […]

First, women with high levels of estrogen feel prettier, and second, smoking causes a lowered presence of estrogen in your body. So if you’re a female smoker and want to feel more attractive, boost your estrogen levels and stop smoking. Additionally this hormone helps maintain your female features and is vital to your body’s fertility.

{ United Academics | Continue reading }

photo { Bill Brandt }

Over the second half of the 20th century, the average age for girls to begin breast development has dropped by a year or more in the industrialized world. And the age of first menstruation, generally around 12, has advanced by a matter of months. Hispanic and black girls may be experiencing an age shift much more pronounced. […]

“If you basically say that the onset of puberty has a bell-shaped distribution, it seems to many of us the whole curve is shifting to the left,” says Paul Kaplowitz, chief of the division of endocrinology and diabetes at Children’s National Medical Center in Washington, D.C. More girls, he says, are starting puberty before age 8, putting them at “the lower end of the new normal range.”

Researchers are now turning their attention to what could be driving the trend. Many scientists suspect that younger puberty is a consequence of an epidemic of childhood obesity, citing studies that find development closely tied to the accumulation of body fat. But there are other possibilities, including the presence of environmental chemicals that can mimic the biological properties of estrogen, and psychological and social stressors that might alter the hormonal makeup of a young body.

{ ScienceNews | Continue reading }

Ovulation, Female Competition, and Product Choice: Hormonal Influences on Consumer Behavior

Recent research shows that women experience nonconscious shifts across different phases of the monthly ovulatory cycle. For example, women at peak fertility (near ovulation) are attracted to different kinds of men and show increased desire to attend social gatherings. Building on the evolutionary logic behind such effects, we examined how, why, and when hormonal fluctuations associated with ovulation influenced women’s product choices. In three experiments, we show that at peak fertility women nonconsciously choose products that enhance appearance (e.g., choosing sexy rather than more conservative clothing). This hormonally regulated effect appears to be driven by a desire to outdo attractive rival women. Consequently, minimizing the salience of attractive women who are potential rivals sup- presses the ovulatory effect on product choice. This research provides some of the first evidence of how, why, and when consumer behavior is influenced by hormonal factors.

Ovulation Leads Women to Perceive Sexy Cads as Good Dads

Why do some women pursue relationships with men who are attractive, dominant, and charming but who do not want to be in relationships—the prototypical sexy cad? Previous research shows that women have an increased desire for such men when they are ovulating, but it is unclear why ovulating women would think it is wise to pursue men who may be unfaithful and could desert them. […] Ovulating women perceive that sexy cads would be good fathers to their own children but not to the children of other women.

{ Improbable Research | Links to PDFs }

Researchers have discovered that a form of oxytocin — the hormone responsible for making humans fall in love — has a similar effect on fish, suggesting it is a key regulator of social behavior that has evolved and endured since ancient times.

{ EurekAlert | Continue reading }

art { Francisco Castro }

Castration had a huge effect on the lifespans of Korean men, according to an analysis of hundreds of years of eunuch “family” records.

They lived up to 19 years longer than uncastrated men from the same social class and even outlived members of the royal family.

The researchers believe the findings show male hormones shorten life expectancy.

{ BBC | Continue reading }

When Wallace Craig dissected the feeding behavior of doves, his experimental animal of choice, he discovered the existence of two distinct phases - an appetitive and a consummatory phase. He defined appetite as “a state of agitation”, which continues until food is presented, whereupon phase 2 begins. That’s the phase you and I call eating. It’s followed by a third phase of relative rest, which Craig called the state of satisfaction. You are forgiven if you now ask “what science nugget could possibly be hidden in this platitude.” But the best-hidden gems are often those, which are in plain sight. […]

When Craig published his paper in 1917 he described the behaviors of his doves as instinctive. In other words, being driven by some innate processes which require no conscious decision making nor any degree of intellect. Today we know a lot more about those “innate processes”, particularly that they are the result of a complex conversation between neurons and hormones playing out in the recesses of the animal brain. Not only do we know the chains of command running from brain centre to periphery we also know the hormones (at least some of them) by names, such as Neuropeptide Y (NPY) or Leptin. You don’t need to remember them. What you need to remember is that “instinctive” has matured from a black box stage to the stage of neurohormonal mechanisms, which can be tested quantitatively in the lab with experimental animals. […]

NPY is the most potent “orexigenic” peptide currently known. That’s science speak for appetite stimulating peptide. Now you also know what it means when I tell you that leptin’s effect is just the opposite, that is, anorexigenic, or appetite suppressant. Inject NPY into the right places of a rat’s brain and it will turn into a voracious eater. Give obese rats leptin, and they slim down.

{ Chronic Health | Continue reading }

The ‘body clock’ or circadian rhythms controls things like alertness, sleep patterns, appetite and hormones, and travelling across time zones or working nights can disturb it. […]

The researchers found that two nuclear receptors (receptors that sense hormones), called REV-ERB-α and REV-ERB-β, control the circadian expression of core circadian clock and lipid homeostatic gene networks. Not getting enough sleep puts you at increased risk of obesity, diabetes and related metabolic disorders.

{ Genome Engineering | Continue reading }

Research that I have done over the past decade suggests that a chemical messenger called oxytocin accounts for why some people give freely of themselves and others are coldhearted louts, why some people cheat and steal and others you can trust with your life, why some husbands are more faithful than others, and why women tend to be nicer and more generous than men. In our blood and in the brain, oxytocin appears to be the chemical elixir that creates bonds of trust not just in our intimate relationships but also in our business dealings, in politics and in society at large.

Known primarily as a female reproductive hormone, oxytocin controls contractions during labor, which is where many women encounter it as Pitocin, the synthetic version that doctors inject in expectant mothers to induce delivery. Oxytocin is also responsible for the calm, focused attention that mothers lavish on their babies while breast-feeding. And it is abundant, too, on wedding nights (we hope) because it helps to create the warm glow that both women and men feel during sex, a massage or even a hug.

Since 2001, my colleagues and I have conducted a number of experiments showing that when someone’s level of oxytocin goes up, he or she responds more generously and caringly, even with complete strangers. (…)

In our studies, we found that a small percentage of subjects never shared any money; analysis of their blood indicated that their oxytocin receptors were malfunctioning.

{ Paul J. Zak/WSJ | Continue reading }

polaroid { Robert Whitman }

Women differ from men in circulating levels of certain hormones, and some of those hormones change across the menstrual cycle. Estradiol, progesterone, the lutenizing hormone, and the follicle-stimulating hormone all change over the menstrual cycle. (…)

We find that naturally cycling women bid significantly higher than men and earn significantly lower profits than men except during the midcycle when fecundity is highest. We suggest an evolutionary hypothesis according to which women are predisposed by hormones to generally behave more riskily during their fecund phase of their menstrual cycle in order to increase the probability of conception, quality of offspring, and genetic variety. We also find that women on hormonal contraceptives bid significantly higher and earn substantially lower profits than men. This may be due to progestins contained in hormonal contraceptives or a selection effect.

{ University of California | PDF }

related { The Impact of Female Sex Hormones on Competitiveness }

photos { Raymond Meeks }

The study, reported in The Journal of Neuroscience [2007], provides the first direct evidence that humans, like rats, moths and butterflies, secrete a scent that affects the physiology of the opposite sex. (…)

He found that the chemical androstadienone — a compound found in male sweat and an additive in perfumes and colognes — changed mood, sexual arousal, physiological arousal and brain activation in women.

Yet, contrary to perfume company advertisements, there is no hard evidence that humans respond to the smell of androstadienone or any other chemical in a subliminal or instinctual way similar to the way many mammals and even insects respond to pheromones, Wyart said. Though some humans exhibit a small patch inside their nose resembling the vomeronasal organ in rats that detects pheromones, it appears to be vestigial, with no nerve connection to the brain.

“Many people argue that human pheromones don’t exist, because humans don’t exhibit stereotyped behavior. Nonetheless, this male chemical signal, androstadienone, does cause hormonal as well as physiological and psychological changes in women.” (…)

Sweat has been the main focus of research on human pheromones, and in fact, male underarm sweat has been shown to improve women’s moods and affect their secretion of luteinizing hormone, which is normally involved in stimulating ovulation.

Other studies have shown that when female sweat is applied to the upper lip of other women, these women respond by shifting their menstrual cycles toward synchrony with the cycle of the woman from whom the sweat was obtained.

{ ScienceDaily | Continue reading }