50 REAL Differences Between Men & Women

Brain scans, controlled studies, evolutionary psychology, and anthropology demonstrate that men and women are not the same! We are physically & mentally different. We input, process and deliver information differently. We evolved with different priorities, and we are marinated in different combinations of hormones. This leads to a misaligned interpretation of reality...which creates conflict, not only in our love lives, but in our family lives, and the lives of our children. The following is a list of 50 of these differences...perhaps if we're aware of them, we can interact with more empathy, and better logic.

1. Men & women don't see in the same way

From the very start of light hitting the retina, to the information arriving in the cerebral cortex, this process is different in males and females.

For example:

-The male retina is thicker

• It has more M cells (magnocellular)

• M cells are larger and are distributed across the retina

• M cells are responsible for tracking the movement of objects

-The female retina is thinner

• It has more P cells (parvocellular)

• P cells are smaller & concentrated around the center of the retina

• P cells are responsible for identifying objects & analyzing texture and color

(has been documented in other mammals)

(Sax, Leonard. “Why Gender Matters” 23)Wright, Robert. "The Moral Animal" Robert. "The Moral Animal"

1. Female babies like faces, male babies like moving objects

This isn't surprising, since - as we just learned - males and females see differently.

Over 100 infants were studied on the day of their birth. They were given a choice between looking at a young woman's face or a dangling mobile. The researchers were not told the sex of the babies while they recorded their eye movement. The boys were twice as likely to prefer gazing at the mobile and the girls were more likely to look at the face. (Sax, Leonard. “Why Gender Matters” 19)

• In the first few months of life, a baby girl's eye contact and mutual facial gazing will increase by over 400% while the boys will show significantly less improvement. (Brizendine. “The Female Brain” 15)

1. Boys and girls like to draw different things

• Most girls prefer drawing people, animals, and plants, arranged symmetrically & facing the viewer

• They're more likely to use lots of color and the colors they use tend to be warm

• Boys mostly draw action scenes with dynamic movement

• It's not common for them to use more than 6 colours, and the colours they do use tend to be cool

(Sax, Leonard. “Why Gender Matters” 25) (Brizendine. “The Male Brain” 20)

If you're finding yourself thinking "Ok who cares? Kids draw different stuff" keep in mind that most early grade teachers are female, with a feminine bias. They favour girls’ drawings to be the correct type of art, which can put boys off art forever. And it goes beyond boys doing poorly in art class. I always see headlines like "boy suspended from school for drawing a gun." I think if teachers were aware of these hardwired differences then they would stop raising concerns about male students depicting “violent” scenes. We should look back to the old proverb “boys will be boys,” take a deep breath, and relax.

1. Females hear better than males

-In the brain centres for language and hearing, women have 11% more neurons than men (Brizendine. “The Female Brain” 5)

• Females not only hear better, but can discern between a broader range of emotional tones in the human voice. This is probably because BABIES! Women evolved to be nurturers, so hearing & interpreting their infant's cries is kind of an important skill.

• And it's a skill we're born with: a study of infants on the day of their birth showed that girls will respond more to the cries of another baby than boys. (Brizendine. “The Female Brain” 17)

Hey! Soft spoken female teachers! Before you label a boy with attention deficit, try moving him to the front of the class. He probably can't hear you!

1. Music affects us differently

Premature baby girls who received music therapy had fewer complications, grew faster and were able to be discharged earlier than the ones that did not. There was no effect on premature baby boys. (Sax, Leonard. “Why Gender Matters” 16)

1. Males will automatically block out certain sounds

-A study of adults in the Netherlands monitored the brain activity of 17 to 25 year old males and females as they processed white noise and music.

• the females had an intense response to both sounds.

• the males responded to the music but deactivated to the white noise, as if they didn't even hear it.

-This may be because during male fetal brain development, testosterone impacts the formation of the auditory system, making it block out unwanted noise and repetitious acoustic stimuli. (Brizendine. “The Male Brain” 41)

This is a big issue in most male/female relationships. A girl will say something and the guy won't hear her. She will repeat herself, several times, which makes his brain register her voice as "unwanted repetitious acoustic stimuli" ...and before you know it, it devolves to "he never listens" and "she's always nagging." And a lot of us will get stuck in a feedback loop of behaviour, creating a fascinating ‘chicken or the egg scenario’...does my mom say the same thing 500 hundred times because my dad doesn't hear her, or does my dad tune her out because she repeats herself?

1. Females can verbally express their emotions better than males

The key word here is can, as in, have the ability to. This is not, as some will have you believe, a difference caused by societal gender norms: This is a legitimate brain difference.

-MRI’s were used to examine how emotion is processed in the brains of girls & boys from the ages of 7 through to 17.

-They found that in children, negative emotions were localized in the primitive area of the brain, the amygdala. This part of the brain has few direct connections to the language & reasoning centre in the cerebral cortex, which is why it's difficult for most kids to verbally express how they feel.

-Then in adolescence, a large portion of the brain activity associated with negative emotion moves up from the amygdala to the cerebral cortex...but this change only happens in girls.

-A study from Germany duplicated this finding, and went on to conclude that both positive and negative emotions are processed differently in males and females post puberty.

Judging by this, it's no surprise that men rarely want to "talk about it." Men are wired to avoid contact with others when they are going through a rough time & even report thinking women would want to do the same. So before you get mad at your boyfriend for his silence, remember that it's literally difficult for him to verbalize his feelings. (Brizendine. “The Female Brain” 126) (Sax, Leonard. “Why Gender Matters” 29)

1. Boys naturally use movement to think

Boys and girls of grade school age were studied to see how long it took them to solve conceptual math problems.

-The boys solved the problems faster than the girls.

• The researchers noted that when asked to explain how they got the answer, most of the boys gave an explanation without using any words; they wiggled, acted and gestured their process! Words were a barrier.

-So over the following few weeks the researchers taught the girls to explain their answers with movement and then retested everyone.

• The girls were now able to solve the math problems as quickly as the boys.

-It seems that the male and female brains have access to the same circuitry but use differently circuitry by default. (Brizendine. “The Male Brain” 26-27)

1. Groups of boys play differently than groups of girls

Boys:

larger play groups

they focus on the game itself

rough n' tumble

very competitive

confrontational

establish dominance & test hierarchies

claim territory and monopolize toys

show off their physical strength

struggle for social rank

and are more likely to use threats

Girls:

focus on relationship building

take turns 20 times more often than boys do

more likely to make collaborative proposals (like starting their sentences with let's)

their pretend play is usually about caregiving and relationships

(Brizendine. “The Male Brain” 18-23) (Brizendine. “The Female Brain” 22-24) (Harris, Judith Rich. “The Nurture Assumption” 214)

These differences also ring true in our close relatives. For example, long tailed male macaque are six times more likely to engage in rough and tumble play than female macaque , who prefer baby-sitting baby monkeys. (Sax, Leonard. “Why Gender Matters” 61)

By the time boys are in first grade they get a dopamine rush when they display their power, and some studies have indicated that unanimously agreed upon hierarchies will form in nursery school, and stay stable for at least 6 months. And the boys at the top are not necessarily the biggest; they're the boys who are least likely to back down during a conflict. (Brizendine. “The Male Brain” 22-24)

Even males castrated shortly after birth and raised as females still tend to be the dominant ones in the group. (Harris, Judith Rich. “The Nurture Assumption” 222)

You know what's the most interesting thing about group play? That when given the option, boys and girls naturally segregate. This only changes when there's not enough kids, then boys and girls all play together. Could it be that kids prefer playing with those similar to themselves? (Documented in the west as well as in hunter gatherer societies)

1. Boys and Girls play with different toys

A team at Concordia University studied almost 100 one and a half year olds and their preference for toys. The girls had a preference for dolls, and the boys had a strong preference for trucks.

Many would argue this is socialized gender behaviour...but an important thing to note about one and a half year olds is that they have trouble assigning themselves and others the correct gender. In fact, the boys, because they develop slightly slower than girls, did a poorer job in gender assignment than the girls.

If we assume that playing with sex specific toys is a social construct, then it would make sense for the girls, who have a better understanding of gender, to have a stronger preference for girly toys. But what they found was the opposite. I'll repeat the results; the girls had a preference for dolls, and the boys had an even stronger preference for trucks. These results were duplicated in 9 month olds, who had an even poorer understanding of gender. (Sax, Leonard. “Why Gender Matters” 27)

Even with direct intervention from parents & teachers, who encourage gender-neutral (translation: gender opposite) play, girls will choose dolls over trucks as soon as they are given the choice. Without choice, girls will play with their trucks as though they were dolls and boys will use their dolls as if they were swords or hammers. Kids are so goddamn sexist! (Harris, Judith Rich. “The Nurture Assumption” 204 & 210)

In reality, all mammals are sexist. Male monkeys prefer to play with toy cars and female monkeys prefer to play with dolls. Young male rats engage in much more rough-and-tumble play than young female rats. Study any mammal; their young play differently depending on their sex. (Sax, Leonard. “Why Gender Matters” 28)

1. Boys are more likely to take risks

Researchers in Missouri studied the responses of kids that rode a stationary bicycle while watching a hyper-realistic simulation. When confronted with a hazard, the boys were much slower to break than the girls. If it was real, many of the boys would have been seriously injured.

The boys also reported feeling excited during a simulated collision, while the girls reported feeling fearful.

(Sax, Leonard. “Why Gender Matters” 43) (Higher risk taking in males has also been observed in primates) (Sax, Leonard. “Why Gender Matters” 44)

1. Females are easier to startle

This was demonstrated in a ‘scary stimuli study’ that measured fear through electrical conductivity in the skin. (Brizendine. “The Female Brain” 123)

1. Women also exhibit a stronger emotional response to the anticipation of pain

("Sex Differences in Brain Response to Anticipated and Experienced Visceral Pain in Healthy Subjects." American Journal of Physiology)

(Brizendine. “The Female Brain” 132)

1. Males are More Likely to Overestimate Their Ability

When a professor looked at male and female students that graduated from the same University with the same business degree, he found that the starting salaries of the men were an average of $4000 more. How incredibly sexist...if it was the whole story.

It turned out that only 7% of the females had asked for more money compared to 57% of the males. So the actual result of this study is: if you're confident enough to ask for a higher starting salary, regardless of your gender, you are more likely to get it than if you don't ask. (Sax, Leonard. “Why Gender Matters” 46)

But it's not all dandy for the boys. Overestimation of ability also leads to things like drowning.

1. Males are more likely to die from an accident than females

As mentioned...men are more likely to take risks and overestimate their ability. Psychologists at Boston University figure that this is probably why almost all drowning victims are male. (Sax, Leonard. “Why Gender Matters” 43)

-Boys are way more likely to do dangerous things (especially if other boys are around).

-They're way less likely to listen to the warnings of their parents.

-And way less likely to tell anyone if they had an accident.

US data shows that boys are more likely than girls to be seriously hurt or killed in accidents like the misuse of a firearm or a head injury from riding a bike. (Sax, Leonard. “Why Gender Matters” 41-42)

And this goes even deeper. Let's say the same amount of women and men were to get head injuries...the damage would still be worse in men.

Research at Children's Hospital in Pittsburgh Pennsylvania discovered that there's a difference in the way brain cells die after injury in males & females. Once brain injury occurs, levels of glutathione, (a molecule that helps brain cells survive oxygen deprivation) remain stable in females, yet drops up to 80% in males, resulting in greater brain cell death. (Brizendine. “The Female Brain” 174)

This could also be a vital contributing factor to the difference in the overall longevity of men and women.

1. Men are more likely to perceive a neutral face as unfriendly

During puberty, vasopressin (influences defend your turf behaviour, works with testosterone, and has a stronger effect in men) influences a boy's brain to perceive neutral faces as unfriendly. Researchers in Maine gave teenagers a single dose of vasopressin and found that the girls were more likely to rate neutral faces as friendly, while the teen boys rated neutral faces as unfriendly or hostile. (Brizendine. “The Male Brain” 39)

1. Males are more likely to exhibit aggression physically while females are more likely to exhibit aggression verbally

This difference has been well documented in almost all other mammals. (Harris, Judith Rich. “The Nurture Assumption” 222) We used to blame it on testosterone, but we now know it's because we've evolved to process anger differently.

• A male's aggression pathways are more directly connected to brain areas for physical action.

• A female's aggression pathways are closer linked to verbal functions. (Brizendine, “The Female Brain” 42)

• Males have a larger amygdala which is the centre for aggression.

• Females have a larger and faster maturing prefrontal cortex which is responsible for inhibiting aggression (Brizendine. “The Female Brain” 102 & 129) (Campbell, and Stockley. "The Evolutionary Psychology of Women's Aggression.")

• Males have a more active right amygdala which is linked to taking action & negative emotions.

• Females have a more active left amygdala which responsible for mental reaction rather than physical reaction.

(Lanteaume, L.; Khalfa, S.; Régis, J.; Marquis, P.; Chauvel, P.; Bartolomei, F. (2006). "Emotion Induction After Direct Intracerebral Stimulations of Human Amygdala")

-Some men have what is called auto-catalytic anger, which means it becomes self reinforcing, it inhibits their fear and actually produces sensations of pleasure. (Brizendine. “The Male Brain” 105)

-Although a woman is slower to act out of anger physically, her verbal response is difficult to stop once it gets going. (Brizendine. “The Female Brain” 131)

These brain differences exist because they've helped our survival.

• Females are generally smaller than males so being violent towards someone stronger than you is a good way to put an end to your genetic legacy.

• Females are often vulnerable because of pregnancy and infants; their survival is contingent on being part of a social group. Because females have to band together for protection, fighting other females can be just as risky to their life.

• Another reason females have evolved with brain circuitry that helps prevent physical outbursts is to decrease the likelihood of harming their own children (Brizendine. “The Female Brain” 42 & 130)

(Harris, Judith Rich. “The Nurture Assumption” 220)

• A male’s survival is linked to his rank, dominance and power, and these things, even today, can be attained by physical confrontation.

But aggression isn't necessarily bad. Males are also the valiant defenders of their tribe, their land and their family; these things all need physical acts of violence.

If you’re still unconvinced, look to the modern jungle: high school. Boys fight with fists, girls fight with gossip.

1. Women use both sides of the brain to respond to emotional experiences while men use just one

A study from Stanford University found that when a female was shown an emotional image, 9 different areas of her brain lit up, while only 2 lit up in the men. (Brizendine. “The Female Brain” 127)

On average, women retain stronger memories for emotional events than men. (Hamann, Stephan. "Sex Differences in the Responses of the Human Amygdala.")

1. Women read subtle emotion better than men

-Women recognize signs of sadness in a face 90% of the time, while men do only 40% of the time.

-This may be why women evolved to cry 4 times more easily than men; it's a visual display of sadness that will be obvious to any male. (Brizendine. “The Female Brain” 119)

-A Stanford study may even have shown that little girls recognize faked facial expressions (specifically fear) better than little boys.

(Mumme, Donna L., Anne Fernald, and Carla Herrera. "Infants' Responses to Facial and Vocal Emotional Signals in a Social Referencing Paradigm.")

In terms of evolution, it make sense for females to be better at reading facial cues so that they can recognize the physical needs of non-verbal BABIES.

A male's brain circuits use more testosterone and vasopressin while the female brain uses more estrogen and oxytocin. If you give a man just a single dose of oxytocin, it will improve his ability to empathize and read subtle facial expressions. (Brizendine. “The Male Brain” 101)

1. Males and females are not empathetic in the same way

We have two emotional systems: the mirror neuron system (MNS) and the temporal-parietal junction system (TPJ). The MNS is responsible for emotional empathy; it helps one feel what the other person is feeling. The TPJ is responsible for cognitive empathy; it actually helps one distance themselves from the person's emotions, focusing instead on analytically solving the problem. Both sexes start their empathy process in the MNS, but the male brain quickly switches over to the TPJ. (Brizendine. “The Male Brain” 97)

We see this clash all the time. A woman will tell her man about a problem, looking for emotional support, but he, if unable to actually solve her problem, won't see the value of having a lengthy conversation about it.

The male's mirror-neuron systems is also more fragile, and can be stunted by pacifier use. (“Male and Female Differences in Nonconscious Mimicry: A Systematic Review.” Journal of European Psychology Students)

The most interesting study that indicates that women are more emotionally empathetic was conducted at the Institute of Neurology in London. They tested couples; first the women were given a range of electric shocks. Then their partners were hooked up to the same treatment. It was indicated to the women when and what kind of shock was being administered to their partner, and even though the females couldn't see or hear their loved one, the same pain areas of their brains that had activated when they themselves were shocked, lit up as they learned their partners were being subjected to the same treatment. Researchers were unable to duplicate this result with males.

1. Men Thrive in Conflict, Women Avoid it

• Females are more concerned with social approval and preserving relationships than males. (Brizendine. “The Female Brain” 21)

• Men tend to get a positive chemical boost from conflict and competition, while in women, conflict is more likely to elicit negative chemical reactions, creating stress, fear & sadness. (Brizendine. “The Female Brain” 40)

• If a woman feels one of her close relationships is in danger, she may experience a change in her serotonin, dopamine and norepinephrine levels, which creates a negative brain reaction on a similar spectrum to a small seizure. (Brizendine. “The Female Brain” 130)

• Females have more circuits dedicated to monitoring the closeness of their relationships than males. (Brizendine. “The Female Brain” 41)

Now don't misunderstand me...this is not because girls are better human beings than boys or something, this is an incredibly powerful survival tactic. It's even seen in other primates, like baboons. A female baboon with the most social connectivity will also have the most number of surviving young. As I already mentioned, in nature, females are more vulnerable, so their survival depends on social ties. (Brizendine. “The Female Brain” 42)

1. Males are aroused under stress while females are turned off

Men get an extra sexual kick when stress levels are high. In fact, they will bond better with a female in a stressful or aggressive environment.

By contrast, a female is more likely to reject a male's advances in a stressful environment. Cortisol blocks the reception of oxytocin in female brains, shutting down a woman's desire for physical touch. And if a woman does have sex under stress, she won’t be able to reach orgasm while her amygdala is active, which is the centre for anxiety, aggression, fear. (The female orgasm actually increases her chances of pregnancy). (Brizendine. “The Female Brain” 72- 77)

From an evolutionary perspective, this makes perfect sense. If a female is stressed, it's often a reaction to an unstable environment, in which becoming pregnant is a terrible idea. But for a male, a dangerous environment is an incentive to procreate with as many females as possible, in order to increase the odds of his genetic survival during tumultuous times.

1. Men and women use different parts of the brain during sexual arousal

Women:

• the ventromedial hypothalamus and cerebral cortex

Sexual experience in women is more connected with the rest of what's going on in her mind and the world around her.

(Sax, Leonard. “Why Gender Matters” 122)

Men:

• the hypothalamus, specifically medial preoptic area, and the amygdala (the centre for anxiety, aggression, fear)

The medial preoptic area guides the performance of sexuality while the amygdala creates the motivation for sex.

1. This is probably why men are also much more likely than women to conflate violence with sexuality. (Sapolsky, Robert. “Human Sexual Behavior I” 36:00)

1. Men are easier to sexually arouse than women

The center of sexual performance anxiety (the anterior cingulate cortex), is smaller in men than in women, and as mentioned, if the woman's amygdala is active, she'll have a hard time getting aroused. (Wright, Robert. "The Moral Animal" 129)

1. Men are more motivated by sex than women

-Males have double the brain space and processing power devoted to sex. (Brizendine. “The Female Brain” 5)

-This change starts as early as 8 weeks after conception, once testosterone cooks the fetus, enlarging the hypothalamus. A second massive surge of testosterone hits at puberty, strengthening the brain connections responsible for smell & touch.

-Teen boys typically have three times more sex drive than girls of the same age, a difference that often persists through life. (Brizendine. “The Female Brain” 89)

• A woman's sexual interest decreases in the last two weeks of her menstrual cycle, when progesterone is high. This obviously does not happen to men...unless progesterone is administered. They do this with sex offenders to reduce their impulses. (Brizendine. “The Female Brain” 90-92)

• One study scanned the brains of men and women observing a neutral scene of a male and female having a conversation. The male's sexual areas immediately lit up; the female's did not. (Brizendine. “The Female Brain” 5)

1. A man's sexual fantasies are almost purely visual, while a woman’s often include romance (Wright, Robert. "The Moral Animal" 129)

1. Our orgasms affect us differently

• In females the oxytocin and dopamine released after an orgasm make her want to cuddle and talk. But in males it's released into their hypothalamus, which triggers the brain’s sleep centre…

• And the back arching response during orgasm is strictly a female phenomenon. (Sapolsky, Robert. “Human Sexual Behavior I” 36:00)

1. The bed nucleus of the striate terminals (where the amygdala begins its descent into the hypothalamus) holds a neurotransmitter that's twice the size in males than females

What's interesting is that when transexuals were studied post-mortem, the size of their neurotransmitter coincided with the gender they identified with. This was true for those who went through hormone therapy and those who did not. (Sapolsky, Robert. “The neurobiology of sexual orientation & identification”)

1. Men are attracted to youth & beauty. Women are attracted to status.

David Buss studied over 10,000 individuals from 37 different cultures and found that there are universal preferences from both sexes when it comes to choosing one's mate, preferences that haven't changed since we became a species.

Men want:

• symmetrical

• young

• healthy-looking

• and fertile

A man's visual cortex is pre-wired to notice hourglass figures (Brizendine. “The Male Brain” 52) and it takes the male brain only one fifth of a second to classify a woman as hot or not. (Brizendine. “The Male Brain” 68)

Women want:

• symmetrical

-generous

-trustworthy

• about 3 years older

• 4 inches taller

• high status

• an investment in her and their offspring

• security

• resources or the potential for resources

This is even true for females that are completely financially secure. (Brizendine. “The Female Brain” 63) (Wright, Robert. "The Moral Animal" 60-61, 65)

1. Men want high pitched voices, women want deep voices

In a study of an African hunter-gatherer tribe called the Hosta, men rated women with deep voices as better foragers but said they were more sexually attracted to the women with the highest pitched voices. The women rated the men with the deepest voices to be the best hunters and protectors but were turned off by men with high pitched voices. (Brizendine. “The Male Brain” 55)

1. Men pursue, women are pursued

The coyness of females and the sexual boldness of males seems to be universal. Even in tribal cultures, untouched by western principles, men do the wooing. The evolutionary reason for this is simple...eggs are expensive, sperm is cheap. A woman is limited to how many offspring she can have because pregnancy is a costly and time consuming investment, while a man is only limited by the amount of women he can sleep with.

Note: in species where parental investment is more evenly distributed, we see wooing behaviour in females. For example: male pipefish are responsible for incubating the eggs, so their female counterparts will seek out and court males.

1. When a man is in love, dopamine mixes with testosterone and vasopressin. If you're, female it gets mixed with estrogen and oxytocin (Brizendine. “The Male Brain” 63)

1. Contrary to popular belief, it's men that fall in love at first sight

A woman's brain is setup to be more cautious when it comes to potential mates; brain imagining studies reveal that when a woman is in love, there's more activity in areas that process intuition, attention, & memory, while men in love show more activity in high-level visual processing areas. (Brizendine. “The Female Brain” 65)

A female needs to carefully assess a man's “survival and replication value,” which takes time. This is why pick up artists like to surround themselves with pretty girls. The strategy is called preselection; it signals the other females to believe that the male has already been vetted and approved. (Lovedrop, and Mystery. Revelation. 1-4)

A man on the other hand knows almost immediately if he would have offspring with a girl based on her visual appearance. This is why we have a beauty industry; it's not driven by patriarchy...it's driven by a natural urge to want to attract high value mates.

1. Men are more comfortable lying to the opposite sex

When measuring the vocal strain of men and women telling lies to each other, the men showed significantly less strain. This also allowed them to lie more convincingly. (Brizendine. “The Male Brain” 62)

1. High self-esteem makes teen girls less promiscuous, but it makes teen boys more promiscuous

(Wright, Robert. "The Moral Animal" 85)

1. A man is more likely to sleep with a stranger than a woman

Many studies confirm this. For example: in an experiment on college campuses, three quarters of men approached by an unknown woman agreed to have sex with her. When the reverse was done, 0 women agreed to the casual sex. (Wright, Robert. "The Moral Animal" 34)

1. When it comes to casual sex, women care about intelligence, men don't

In a study where men and women were asked about the minimal level of intelligence they would accept in someone they were dating, the general response for both was average. Then they asked what the minimal level of intelligence for someone they would have sexual relations with...the women said above average, while the men said below average.

1. Men have a stronger reaction to sexual infidelity, while women have a stronger reaction to emotional infidelity

Men will react with visible distress to the idea of their mate physically cheating on them. This distress lessens if the cheating is emotional. For women, the opposite effect has been documented. This makes perfect sense. Think about it...if a woman seeks a man who will invest his time and resources in her and their offspring, the bigger threat lies in her mate becoming emotionally attached to another woman because it means he may abandon her. A one night stand isn't exactly a threat to her stability. For a man, the risk of his mate having a child from another man is the threat. Investing in a child that is not actually his does not fare well for his genetic success...

1. A man's fertility depends on who is around him

A man's sperm count will increase when he is away from his mate. (Wright, Robert. "The Moral Animal" 72) It will also rapidly replenish if he is having sex with multiple partners. But if the sex is with the same woman, his sperm count will deplete with each copulation. A woman's egg count stays the same from birth, and no, she will not keep ovulating if the prevalence of young dapper lads increases around her.

1. Females are slower at spatial task than males

When mentally rotating abstract three dimensional shapes, females will get the right answer as often as males, but will take them much longer.(Brizendine. “The Female Brain” 5) This difference is documented in both kids and adults and is likely because the special movement area in the male brain runs on autopilot but in the female brain it's on standby, waiting to be turned on. (Brizendine. “The Male Brain” 27)

1. Women navigate using landmarks, men navigate using cardinals and distance

This difference emerges as early as 5 years old (Sax, Leonard. “Why Gender Matters” 26), and is probably due to the fact that we use completely different areas of the brain for navigation. Women use the cerebral cortex (also used for understanding and interacting), while men use the hippocampus (an area of the brain that is pre-wired for spatial navigation). (Sax, Leonard. “Why Gender Matters” 101)

1. We’re on different schedules

Around the age of 12, testosterone receptors reset the boys’ clock cells (in the suprachiasmatic nucleus). This makes him stay up and wake up about an hour later than girls his age. (Brizendine. “The Male Brain” 36)

1. Men are more consistent than women

Men go through several hormonal changes during their life. In the womb, throughout adolescence, during puberty (20x testosterone increase from 9-15), when fathering a child, and as they age, but a woman's hormonal shifts and changes are much more frequent and severe.

Women are constantly under the influence of their monthly hormonal shifts, and they are more severe than we would like to believe. At the start of a woman's cycle she will experience a 25% growth of connections in the hippocampus. Estrogen will stimulate brain function, making girls socially relaxed and sharp.

Then, during ovulation, progesterone reverses the actions of estrogen and destroys the new connections. During the last two weeks of the cycle, progesterone causes her brain to be sedated, irritable, and unfocused. Then progesterone collapses, leaving the female brain sensitive, sentimental, stressed and even hostile. (Brizendine. “The Female Brain” 45)

This can make a female act very different from week to week. It can augment or amputate parts of her personality. It can leave her swinging between interpretations of the world. For example when her estrogen peaks right before ovulation she may feel incredible verbal intimacy and sex drive, but when androgen peaks she may be more prone to aggressive outbursts. (Brizendine. “The Female Brain” 47)

Another thing...a woman's hormones may bottom out right before her period and then not replenish fast enough which prevents a much needed serotonin boost, leaving the brain irritated. This is otherwise known as PMS and it happens to 10% of women. (Brizendine. “The Female Brain” 47) (note the severe cases of this)

1. A woman's brain is more 'flexible' than a man's

At a very special point in her life, a woman will experience a major restructuring of her brain. Her stress circuits will become suppressed, her cortex will increase in size, and the rest of the brain will experience shrinkage! She won't lose any brain cells, but her pathways will change, and new networks will form until her brain is back to normal size. When does this happen? When babies! This change starts during pregnancy, completing the new and improved mommy brain about six months after delivery. (Brizendine. “The Female Brain” 100)

1. We react to crying babies differently

• Mother's show greater activation in some brain regions than fathers when they hear the crying of their baby. (Raeburn, Paul. “Do Fathers Matter?” 42)

• Mothers show activity in brain areas related to pain and emotion when they hear the cries of their newborn, while fathers show similar activity in the cortex. This activity ceases for fathers between 2 to 4 weeks after the infant's birth, and then reignites in new ways at 3 - 4 months. (Raeburn, Paul. “Do Fathers Matter?” 133)

• When a male hears the cries of a baby, his brain is likely to remain in default mode, while a woman's brain will often turn its focus to the crying. (Women's, Men's Brains Respond Differently to Hungry Infant's Cries. National Institutes of Health)

1. Mothers and fathers don't interact with their kids in the same way

We truly do complement each other.

Mothers create stability, comfort, nurture, encourage, reinforce, and coddle.

Fathers destabilize, rough-house, challenge, tease, and stimulate through unpredictability.

Obviously none of those are mutually exclusive, but you get the point.

Researchers at the University of Toronto found that mothers sing the correct version of classic lullabies while fathers mix it up with their own verses, creating unpredictable songs. (Brizendine. “The Male Brain” 88)

Fathers tend to give their children direct orders while mothers use shorter sentences and vocal tone matching, often having no need for directness because they're so emotionally in tune with their children. (Brizendine. “The Male Brain” 90)

Mothers get an oxytocin boost after expressing affectionate contact with their infants. Fathers get the boost after engaging in exploratory play. (Raeburn, Paul. “Do Fathers Matter?” 174)

So you can think of it like a yin and yang: mother offers stability and security while the father is there to challenge the child, prepping them for the unpredictability of the real world. A perfect example of this dichotomy is a study of 1 year olds at their swimming class. It was observed that fathers were more likely to stand behind their children so that the children face the water while mothers stood in front of the children and made eye contact. (Raeburn, Paul. “Do Fathers Matter?” 149)

1. Our friendships are different

Remember how we talked about females evolving to rely on social bonds for survival because of their smaller size? To this day, most women have many friendships which together act like an extensive emotional support network. A man's friendships are quite different; they revolve around common interests, activities, competition and work. Actually a man's significant other is often the only person outside of his immediate family that can offer him emotional support.

Now pair that with men being less likely to seek help and you get males being at a much higher risk for suicide than females, with single males being the most likely demographic to take their own life. (Sax, Leonard. “Why Gender Matters” 131)

1. In a “warm touch” study, researchers found that while both husbands and wives got a boost in oxytocin and a reduction in cortisol, only the husband got a beneficial reduction in blood pressure (Brizendine. “The Male Brain” 126)

Our culture jokes that men die first to escape their nagging wives. Oh yeah...jokes on you society... married men live 1.7 years longer than single men!

(Brizendine. “The Male Brain” 120)

1. Men's and women's brains age differently

Men lose more of the cortex & lose it faster than women. (Brizendine. “The Female Brain” 154) Also, the volume of grey matter in the brain decreases faster with age in men, which may contribute to the development of neuropsychiatric disorders such as Parkinson's. (Male Brain Ages Faster: The Age and Gender Dependence of Subcortical Volumes)

These are not hard rules, but they are an important insight into how we function and what motivates us. They show that your sex comes with a blueprint which heavily influences our behaviour and how we view the world.

Feel free to review my sources, as I'm sure this list isn't perfect. But that's why I made the list so extensive (I cut it down from 100 differences), there's too many to discount an innate, biological difference between the sexes.

Process

I'm aware that some of these books do have a "pop science" flare. I'm aware that they probably have biases. I'm aware that they may have dated information. This is why I read several books (and articles), by several authors, from different years of publication. This is why I checked their cited research against other studies before including in them this project and why I pinned the books against each other. I here are just two examples:

In "The Female Brain," Brizendine describes studies that show how a mother's stress affects unborn girls. She concludes that unborn boys seemed to not be affected. But in "Do Fathers Matter," Raeburn speaks of more recent epigenetic studies that show how sperm from a stressed father will produce offspring whose behaviour has been impacted by this stress. I omitted the sex difference. This research was not available when Brizendine wrote her book.

In "The Male Brain," Brizendine writes about the length of man's vasopressin receptors correlating with a his propensity to monogamy. She playfully calls it the 'monogamy gene.' Neither of her books have an equivalent for women. Raeburn's more recent book, “Do Fathers Matter?” mentions a female monogamy gene.

Bibliography

Brizendine. The Female Brain. New York: Morgan Road, 2006. Print.

Brizendine. The Male Brain. New York: Broadway, 2010. Print.

Campbell, and Stockley. "The Evolutionary Psychology of Women's Aggression." The Royalsociety Publishing. N.p., 28 Oct. 2013. Web. 5 June 2016. http://rstb.royalsocietypublishing.org/content/368/1631/20130078.

Harris, Judith Rich. The Nurture Assumption: Why Children Turn Out the Way They Do, Revised and Updated. 2nd ed. New York: Free, 1998. Print.

Hamann, Stephan (2005). "Sex Differences in the Responses of the Human Amygdala". Neuroscience 11 (4): 288–93. doi:10.1177/1073858404271981.PMID 16061516.

Human Sexual Behavior I. Perf. Robert Sapolsky. Stanford, 11 Feb. 2011. Web. https://www.youtube.com/watch?v=LOY3QH_jOtE.

"Journal of European Psychology Students." Male and Female Differences in Nonconscious Mimicry: A Systematic Review. N.p., 22 Apr. 2012. Web. 18 July 2016. http://jeps.efpsa.org/articles/10.5334/jeps.de/.

Lovedrop, and Mystery. Revelation. Los Angeles, CA: Venusian Arts, 2008. Print.

Male Brain Ages Faster: The Age and Gender Dependence of Subcortical Volumes. N.p., 16 Nov. 2015. Web. 18 July 2016. http://link.springer.com/article/10.1007/s11682-015-9468-3.

Mumme, Donna L., Anne Fernald, and Carla Herrera. "Infants' Responses to Facial and Vocal Emotional Signals in a Social Referencing Paradigm."Child Development 67.6 (1996): 3219. Web.

Raeburn, Paul. Do Fathers Matter?: What Science Is Telling Us About the Parent We've Overlooked. N.p.: Scientific America, 2015. Print.

Sax, Leonard. Why Gender Matters: What Parents and Teachers Need to Know about the Emerging Science of Sex Differences. New York: Doubleday, 2005. Print.

"Sex Differences in Brain Response to Anticipated and Experienced Visceral Pain in Healthy Subjects." American Journal of Physiology - Gastrointestinal and Liver Physiology. American Physiological Society, 15 Apr. 2013. Web. 18 July 2016. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3625873/.

Wright, Robert. The Moral Animal: Why We Are, the Way We Are: The New Science of Evolutionary Psychology. New York: Pantheon, 1994. Print.

"Women's, Men's Brains Respond Differently to Hungry Infant's Cries | National Institutes of Health (NIH)." U.S National Library of Medicine. U.S. National Library of Medicine, 6 May 2013. Web. 18 July 2016. https://www.nih.gov/news-events/news-releases/womens-mens-brains-respond-differently-hungry-infants-cries.