The chemistry between us

The followings are what I find interesting in the book.

Sizes of certain brain regions are associated with behaviours.

Transgenders may have different brain structures and circuitries. There are very preliminary anatomical evidence (size associations) to support this notion. A lot more works needs to be done to have firm conclusion. Corollaries of these findings are that we may just be different and are at different points on a normal curve.

Ovulatory cycles influence behaviour.

Menstrual cycles changes levels of various female hormones. Ovulation is the only time that a woman can become pregnant, and her brain knows this. So these hormonal shifts don’t just affect a woman’s physiology; they work in her brain to influence behaviour toward maximising the egg’s chance of being fertilised so it won’t go to reproductive waste. We often deny this influence. For example, when women are asked if they feel any more sexual desire near ovulation, many say no. But when they are asked at around the time of ovulation to count the number of times they have had sex or initiated sex within the past few days, they list more episodes than they do at low fertility points in their cycles. At ovulation, they enjoy porn movie more than at other times of the month. They tend to avoid their own fathers, consume fewer calories, and spend less money on food than on clothing and sexy shoes.

This highlights a well-known weakness of survey research, information participants volunteered is not necessarily true; especially, if it is embarrassing. Researchers may need to corroborate participants answers with other forms of information directly or indirectly related to the questions.

Not only does ovulatory cycle affect female but also male behaviours. Very fun research article was discussed in the book. I imagine the researchers had a great time conducting this research project. The article was “Ovulatory cycle effects on tip earning by lap-dancers: economic evidence of human estrus.” The premise was that men place value on obtaining wealth and displaying it when they are around attractive women, a male customer wants to act the big shot for his dancer. So he’ll suspend disbelief (that the dancers will not have sex with him) and handover tip money. It was found that strippers made, on average, $90 more when they were in estrus compare to anestrus. The effect was substantial. Anestrus state (menstruation) cut dancers’ earning in almost half. The difference can’t be attributed to dancer variations (eg. attractiveness, fashion choices etc.) as a research was done over two months. By linking dancer preference to money, rather than to customer’s statement, researchers bypassed unreliable statements about people state of mind. Researcher could show this preference was real and unconscious. Talk is cheap; if a guy open his wallet, he means business.

Oxytocin nasal spray changes preference.

Women with high level of oxytocin regard male faces as more attractive than when they are at normal level.

On reward

The study looked into inter-temporal choice. Essentially, it’s a choice between small immediate benefit and significantly large benefit weeks later.  The most rational choice would be to delay gratification and get a bigger payout. Subjects who had dopamine replacement medication chose the smaller-sooner payout much more often than when these very same people were given a placebo. Dopamine is associated with reward centre in the brain. Another group of researchers replaced dopamine medication with pictures of pretty women in bikinis or lingerie, Baywatch-style video, women’s bras versus neutral imagery of lovely landscapes. The findings were similar to the previous study. So when reward centre is triggered, impulsive behaviours become more likely. People’s decisions, therefore, can be influenced by medication and sexual thoughts as both triggered reward circuits.

Reward teaches us that eating a meal feels good enough that it’s worth hunting a game or growing wheat. One thing humans quickly learned was that we didn’t have to kill antelope in order to reap the pleasure. We’ve become very good at quickly, powerfully, and efficiently hijacking the circuits made to induce us into eating or sex. That is alcohols (at the low end of the scale) and all kind of drugs (at the high end) that directly tickle reward circuits. The search for more reward with less work is very much a central theme of the human story. This is why drugs can be addictive at emotional level.

Reward system and love

We enjoy the pleasures of relationship, and then, over time, those pleasures fade and compulsion takes over. It’s quite similar to when a person at first has the high feeling in a relationship. Everything is nice and cool. Then after a while, nature makes sure you still want to stay with a partner. This system makes you feel sick as soon as you leave the mate; it’s the same system that got triggered when the addicts stop taking drugs (withdrawal symptoms). This compulsion applies to relationship between adults and also between adults and their children. Drug addiction and love are parallel when we look at brain circuitries and signal pathways.

On cheating

Culture is a reflection of our brains, often a reflection of conflicts within them. Social bonding is certainly in conflict with sexual desire. We’ve instituted marriage and the enforced consequences of wrecking a marriage. These steps are society’s way of trying to exploit our capacity for reason by adding costs to infidelity, and so constrain our desire for extra-pair sex. We want monogamy for those we love, but not necessarily for ourselves.

Through out the book the authors have shown that variation at the neurobiological level can make big differences in behaviour. Another way of putting it is that these variations moderate our individual capacities to fight with ourselves over our urges. Many find the idea that chemicals contribute heavily to what we usually think of as morality, deeply unsettling, even offensive. But nature is neither moral nor immoral. It just is. Evolutionary biology was used frequently in the book to explain why certain things happened.  This is the same approach Jared Diamond employed in his books.