Chapter 4: Hours to Days Before

Welcome to Last Minute Lecture.

This free chapter overview is designed to help students review and understand key concepts.

These summaries supplement not replaced the original textbook and may not be redistributed or resold.

For complete coverage, always consult the official text.

Welcome to the Deep Dive.

We're your shortcut to getting genuinely well informed and doing it fast.

Today we are diving deep into a really fascinating chapter from Robert Spolsky's huge book, Behave, the biology of humans at our best and worst.

Our mission really is to unpack how hormones and stress shape our behavior.

Not just right now, but in the hours, even days leading up to whatever we do, we'll tackle some complex biology, psychology, social science stuff, all without visuals.

Just clear language and hopefully some good analogies to make it stick.

And just to give you a taste upfront, two big surprises.

First, testosterone.

It's really not the simple aggression driver we all assume.

Not at all.

And second, oxytocin, that so -called love hormone.

Turns out it has a kind of darker side, a more, let's say, xenophobic side even.

We'll get into that.

Absolutely.

And what we're doing here, essentially, is looking back in time chronologically.

We're examining how these powerful chemicals inside us, our hormones,

really set the stage for our actions, for our best behaviors and also our worst.

And you'll see, I think, again and again, context is just,

well, it's everything.

It's absolutely critical.

Okay.

Let's jump right into testosterone then and this bum rap it gets.

The common idea is pretty simple, right?

Testosterone equals aggression.

You see links to male aggression across species.

It shows up in brain areas like the amygdala.

It seems pretty straightforward.

It does seem that way on the surface, but science looks deeper.

These subtraction and replacement experiments, like castration in animals, aggression does drop.

Okay.

So it plays a role.

Definitely plays a role.

But this is key.

It doesn't disappear completely.

Some male aggression is just totally independent of testosterone.

And what's really interesting is the more aggressive experience an animal had before losing testosterone, the less its future aggression depends on the hormone.

It shifts more towards learned behavior.

Social learning kicks in.

Ah, okay.

So experience matters a lot.

Hugely.

It's why chemical castration in humans, for instance, it lowers sex drive, sure, but it doesn't reliably stop violent reoffending if the motivation was, say, power or anger, not sex itself.

That's learned.

That makes sense.

So, okay, taking away testosterone doesn't stop aggression entirely.

What about just natural levels?

Do guys with higher T levels just

act more aggressive?

Yeah, that was the old idea.

Early studies found correlations, but Sapolsky points out this classic chicken and egg issue.

Right.

Does the testosterone cause the aggression or does the aggression cause a spike in testosterone?

Exactly.

Turns out aggression itself can boost testosterone.

Most modern research shows that within the normal range, individual T levels don't really predict who's going to be aggressive.

And giving extra testosterone to volunteers usually doesn't make them more aggressive either.

Unless you push it into super physiological levels.

We're talking way beyond natural amounts, like with anabolic steroid abuse.

Even then, the aggression might actually stem from the anxiety and paranoia those doses can cause, not the testosterone directly.

Okay, so it's not this simple on -off switch regression.

What does it actually do then?

What are these subtle effects you mentioned?

Well, there are quite a few.

It tends to decrease empathic mimicry, that unconscious mirroring of others' emotions.

It makes it a bit harder to read people.

It also makes strangers' faces seem less trustworthy,

lights up the amygdala a bit more when looking at them.

But on the flip side, it boosts confidence and optimism.

It lowers fear and anxiety.

This is part of the winner effect, seeing an animal.

Yeah, win a fight, get a testosterone boost, feel more confident, become more likely to win the next fight.

It's a feedback loop.

Okay, sounds good, but I sense a but coming.

There's always a but.

That increased confidence can easily slide into overconfidence, egocentricity, even narcissism.

There was a study where guys given testosterone just ignored their partner's perfectly good input because they were so sure they were right.

It also makes us more impulsive, more prone to risk taking.

It seems to dial down the prefrontal cortex, our brain's sensible breaks, and lets the amygdala, the emotional shortcut, have more say,

leads to, well, Sapolsky calls them dumbass decisions.

Okay.

And it can feel good too.

It tapped into the brain's dopamine reward pathways.

Rats will actually work to get little infusions of testosterone.

Right.

So summing this up, it's not a direct cause, but it changes how we feel, how we perceive things, how likely we are to take risks.

Exactly.

And here's the big takeaway, the unifying idea.

Testosterone's effects are massively context dependent.

It doesn't cause aggression, for example.

It amplifies the power of something else to cause aggression.

Amplifies something else.

Can you give an example?

Sure.

That talipoint monkey study from the 70s.

Middle ranking monkeys got testosterone.

They became more aggressive, yes, but only to the monkeys below them in the hierarchy.

Nope.

It didn't change the social rules.

It just exaggerated the existing patterns.

Same in human studies.

Testosterone boosted brain responses to angry faces, but not neutral or happy ones.

So it enhances reactions to specific triggers.

Precisely.

Or in economic games, it made people more punitive, more likely to retaliate if they were provoked first.

It amplified vengeful reactive aggression, not just general nastiness.

Even at the neuron level, it basically primes amygdala cells to fire faster if they're already being stimulated by some other input.

Okay, this context thing is huge.

It leads to this challenge hypothesis, right?

Yes, John Winfield's idea.

Basically, testosterone rises and impacts aggression only when there's a challenge.

Your baseline level doesn't predict much.

So puberty, mating season.

Those rises don't automatically mean more aggression.

Generally, no.

But when you face a challenge, a dominance contest, a sports match, even watching your team win testosterone goes up, and it seems less about the physical effort and more about the psychology, the status, the dominance.

And after the challenge.

Then the hypothesis suggests testosterone helps drive whatever behaviors are needed to maintain that status you just gained or defended.

Which isn't always aggression.

Which brings us to that flabbergastingly important research.

It's eyes and nigger and fair.

The ultimatum game.

Here's the kicker.

If the way to gain status in the game was by being fair and generous.

Let me guess.

People given testosterone made more generous offers.

Testosterone pushed them to do whatever was needed to look good, to be studly in that specific context.

Wow.

So it really depends on what being studly means in that situation.

Exactly.

And get this, the belief effect.

People who thought they got testosterone, even if they got a placebo, acted less generously.

Just believing the stereotype made them act that way.

Pretty much.

Believing T equals aggression made them aggressive.

Other studies back this up.

Testosterone sometimes promotes pro -social behavior, like reducing cheating when pride is on the line, or increasing public contributions.

So the final word on testosterone isn't bad guy hormone.

It's more like

it makes us try harder to get and keep status using whatever strategy works in that context.

That's a great way to put it.

If our society truly rewarded kindness as high status, testosterone might just make us competitively kind.

The issue isn't the hormone.

It's what we as a society choose to reward.

Okay.

Mine's slightly blown on testosterone.

Let's switch gears to oxytocin and vasopressin.

The cuddle chemicals, the love hormones.

You hinted they're not quite so simple.

Not quite as groovy as Sapolsky says.

Yeah.

Vasopressin is very similar chemically.

They're neuropeptides.

Initially, they seemed frankly a bit boring.

Oxytocin for uterine contractions during birth.

Vasopressin for water balance.

Important, but not exactly brain altering stuff.

But then they found receptors elsewhere.

Everywhere.

All over the brain.

Dopamine pathways, hippocampus, amygdala, frontal cortex.

Suddenly, they weren't just plumbers.

They were major players in emotion, memory, and reward.

And the early findings really pushed this pro -social angle.

Right.

Absolutely.

Oxytocin is crucial for maternal behavior in rats.

You can make a virgin rat act maternally by giving her oxytocin, block it, and a mom might ignore her pups.

Vasopressin plays a similar role for paternal behavior in species where dads help out, like prairie voles.

And both hormones strengthen pair bonds in monogamous species.

Like those prairie voles everyone talks about.

Exactly.

It's not even about having more hormone.

It's about having more receptors in the brain's reward center than nucleus accumbens.

They even engineered other voles species to have more receptors.

And boom, they became more cuddly and attached.

And in humans.

Similar patterns.

Higher oxytocin in new couples predicts affection, how in sync they are, even how long the relationship lasts.

Give couples oxytocin during a conflict discussion, and they tend to communicate more positively.

It even works unconsciously.

Men in stable relationships, given oxytocin, literally kept more physical distance from an attractive female researcher they didn't know.

Protecting the pair bond subconsciously.

Seems like it.

And it's not just human -human.

That gaze between you and your dog boosts oxytocin in both of you.

An ancient bonding hormone adapted for a new kind of relationship.

It also seems to have calming effects.

Yes.

It inhibits parts of the amygdala, reduces fear and anxiety, activates the parasympathetic rest and digest system.

Sapolsky calls it a physiological metaphor for safety.

It also boosts trust.

People given oxytocin rate faces as more trustworthy.

They act more trusting in economic games, but only with human partners.

Interestingly, not computers, it sort of inoculates against the fear of betrayal.

Okay, so far it sounds pretty great.

Bonding, trust, calm.

Where's the catch?

Is it really about universal love or something else?

That's the million dollar question.

Is it pro -sociality in general, or is it more about enhancing social competence, our ability to navigate the social world effectively?

What's the difference?

Well, oxytocin does make us better at social stuff.

It makes people look at eyes more, which helps read emotions.

It boosts activity in brain areas related to understanding others' minds, their theory of mind.

So yes, it can help us connect and understand.

It's even shown some promise in helping individuals with autism spectrum disorders improve social skills like eye contact, but that improved social reading isn't always used for good.

And like testosterone, it's contingent, depends on the person, the situation.

Hugely contingent.

Effects differ by gender, personality, culture, you name it.

Who you are matters.

Okay,

embraced.

Lay the dark side on us.

Right.

So remember how oxytocin calms things down?

Well, it also dramatically increases aggression when a mother defends her pups.

Maternal aggression, it's fierce.

Vasopressin does something similar for paternal males in some species.

And in those economic games, oxytocin didn't just boost trust.

It could also increase envy if you got unlucky and gloating if you got lucky.

Yeah, not so cuddly.

Not at all.

And then Carson DeDrew did these groundbreaking studies.

Oxytocin made people more generous and cooperative, but only with their own teammates, their in -group, their us.

And towards the other team?

So towards them, it actually made people more likely to launch preemptive attacks, to stab them in the back in games like The Prisoner's Dilemma.

It didn't foster universal goodwill.

It fostered in -group favoritism and out -group hostility.

Wow.

So it divides the world into us and them.

The themes that way.

Studies using implicit association tests showed oxytocin exaggerated existing biases against out -groups.

In a version of The Trolley Problem, people given oxytocin were less likely to sacrifice someone with a name from their own group compared to someone perceived as foreign.

So oxytocin isn't the make everyone love everyone hormone.

It's parochial.

It makes us nicer to our people and potentially nastier or more suspicions of other people.

Precisely.

It promotes prosociality towards us and ethnocentrism, even xenophobia, towards them.

The context who are you dealing with is absolutely critical.

Okay, let's shift again.

Female aggression.

You said it's complex.

Very.

You're dealing with ratios of hormones, constantly changing levels.

Estrogen isn't one thing, but many.

It's tricky.

But the first myth to bust is that females are inherently non -aggressive, except maybe protecting babies.

Right.

Researchers like Sarah Blaff or Hardy showed that's just not true.

Female animals, including primates, engage in plenty of aggression, often very strategic, competing for food, status, mates, sometimes even killing rivals' infants.

And you have species like bonobos or spotted hyenas where females are actually dominant and more overtly aggressive than males.

So it's not just about accidental male hormone exposure.

Definitely not.

Female brains didn't just passively receive androgens.

They actively evolved to use them just differently than male brains.

There's a balancing act.

Androgens can promote aggression, but high levels can interfere with reproduction in females.

So evolution seems to have wired female brains to allow androgens to influence aggression circuits without messing up the crucial reproduction and maternal care circuits quite as much.

It's a fine -tuning process.

But it's still not simple.

Like, high androgens equals high aggression in women.

No.

The link isn't that direct at the individual level within the normal range.

Many factors are involved.

What about PMS or PMDD?

That connection to irritability or even aggression seems widely believed.

Okay.

This is sensitive territory.

Extreme claims like Margaret Mead's early anthropological work suggesting it was purely cultural have been largely discredited by biological evidence.

There are real, cyclical biological shifts happening in the brain and body.

PMS and PMDD are essentially extreme disruptive versions of these normal fluctuations.

The underlying biology is real.

However...

The interpretation is cultural.

Exactly.

How symptoms are reported, perceived, and especially whether they're pathologized as a medical disorder, that part is heavily influenced by social constructs.

But does it actually link to increased aggression, generally?

Very little evidence supports that.

Most women don't become aggressive around menses.

Studies looking at female violent crime don't find a strong link to menstrual cycle phase, either.

There are rare, extreme legal cases where PMS was considered, but they are truly exceptional.

Final big topic, stress.

Specifically, stress in the hours or days before we act.

You said it rarely makes things better.

Almost never when it comes to complex decisions.

Let's start with basics.

Homeostasis is the body's happy balance.

A stressor knocks you out of balance.

The stress response fight or flight is the body's attempt to regain balance.

Acutely, it's brilliant.

Epinephrine, glucocorticoids mobilize energy, heart rate goes up, non -essentials get postponed, senses sharpen.

Great if you're dodging a predator.

We're not usually dodging predators.

Our stressors are different.

Deadlines, traffic, arguments.

Exactly.

Psychological stress, anticipation, worry.

We activate the same ancient physiological response, but for reasons it wasn't designed for, and often for much longer periods.

And that's where the problems start.

Chronic stress.

That's the core issue.

Sustained activation is incredibly damaging.

Metabolic syndrome, diabetes, hypertension, impaired tissue growth and repair,

messed up reproductive physiology in both sexes, suppressed immunity.

The list goes on.

We basically make ourselves sick by activating an emergency system too often for too long, purely because of thoughts in our heads.

Okay, but isn't some stress good?

Like a roller coaster or a challenge?

Yes.

There's the concept of the inverted you.

Too little stress, we're bored.

Moderate stress, we're engaged, performing optimally.

Too much or too prolonged, and performance plummets.

We need that sweet spot.

So what does sustained bad stress do to our brains neurobiologically?

A lot.

None of it good for clear thinking.

It makes us unconsciously focus more on angry faces.

It ramps up that quick, dirty sensory pathway straight to the amygdala, bypassing thoughtful processing.

Accuracy in quickly judging emotions goes down.

Amygdala neurons become more excitable, easier to trigger, especially for learning and remembering fearful things.

So we learn to be scared more easily.

Yes, and it creates a nasty feedback loop.

Amygdala triggers stress response.

Stress hormones, glucocorticoids, make amygdala more excitable.

Repeat.

Crucially, sustained stress also makes it harder to unlearn fear, what's called extinction, because it weakens the prefrontal cortex's ability to put the brakes on the amygdala.

The prefrontal cortex, PFC, the judgment center.

How does distress mess with it?

It significantly compromises its function.

Working memory gets disrupted harder to hold information online.

It causes perseveration.

Perseveration.

Sticking with something.

Yeah.

Sticking with a habitual response, even when it's clearly not working.

Under stress, the PFC struggles to override old habits or incorporate new information effectively.

You just keep doing the same dumb thing.

It also messes with risk assessment.

Often, it shifts people from trying to protect what they have towards making riskier bets for bigger potential gains than desperate gambling.

Though there can be gender differences here, too.

Impaired judgment,

can't update strategies, skewed risk perception.

Sounds like a recipe for bad decisions.

Absolutely.

Put that together with the hypersensitive amygdala, you get faster, more reactive aggression.

Stress lowers the threshold for lashing out, especially if you're already prone to it.

That leads to displacement aggression, taking it out on someone else.

Exactly.

The classic example is the baboon who gets stressed by a dominant male, then turns around and bites a subordinate.

We see echoes in human society.

Economic stress correlating with increased domestic violence, even spikes in partner abuse after the local sports team loses unexpectedly.

It's like kicking the cat, but potentially much worse.

Is there a reason we do that?

Does it help?

Potentially.

There's some evidence suggesting that lashing out might activate those dopamine or reward pathways we talked about, which could actually inhibit the stress response itself.

It's grim, but the idea is giving an ulcer helps avoid getting one.

And stress makes us more selfish, too.

It seems to bias us that way.

Studies using moral dilemmas found that stressed individuals gave more self -serving answers, especially on emotionally charged problems.

Less altruism, more egoism, correlating with stress hormone levels.

Empathy also takes a hit.

So less able to feel for others when stressed.

Right.

Mogul's mouse study showed stressed mice were less responsive to the pain of a cage mate unless their stress hormone production was blocked.

You mentioned gender differences.

What about tend and befriend?

Yes.

Shelley Taylor's work highlights that the female stress response often involves nurturing offspring and seeking social support, tending and befriending, potentially driven by stronger oxytocin effects under stress.

It's a counterpoint to the classic male fight or flight.

Though obviously not absolute rules for individuals.

Not at all.

Plenty of exceptions on both sides.

But as broad patterns, they're observable.

And remember, Sapolsky notes the effects of stress -induced impairment are neurobiologically value -free.

Impaired judgment is bad if you're an EMT trying to save a life, maybe less bad if you're a warlord trying to commit genocide, and stress makes you less effective.

Right.

Perspective matters.

Okay, one last quick point.

Alcohol.

Does it just make everyone aggressive?

Big myth.

The research is clear.

Alcohol only reliably increases aggression under specific conditions.

One, in people already predisposed to aggression, maybe due to brain chemistry, genetics, whatever.

And two.

Two, in people who believe alcohol makes them aggressive.

That belief effect again.

It powerfully shows how our expectations and social learning shape even basic biological responses.

It's not a universal aggression potion.

Okay, wow.

That was a lot to unpack.

Let's try to summarize the key takeaways from this whole section on hormones and stress in the hours today's timeframe.

Okay.

First, hormones are versatile, with long -lasting influences.

Testosterone.

Forget the simple aggression link.

It facilitates and amplifies existing tendencies, especially around status, and it's all about the context.

Right.

Context is king.

Absolutely.

Oxytocin and vasopressin.

They do promote bonding and social connection, but it's often a parochial love.

Prosocial towards us, but can increase bias and hostility towards them.

Not the universal love hormone.

Definitely not.

Female aggression.

It's complex.

It's often adaptive.

It's not just about androgens.

There's an intricate balance.

Perimenstrual mood shifts are biological, but calling them a disorder is often a social construct, and the link to actual aggression is weak overall.

And stress.

Sustained chronic stress.

It's bad news for the brain.

It hammers the prefrontal cortex, messing up working memory, impulse control, decision -making.

It over -activates the amygdala, boosting fear learning, reducing empathy.

Overall, it biases us towards reactive aggression and selfishness.

And alcohol doesn't automatically cause aggression.

Nope.

Depends on predisposition and belief.

The big theme weaving through all of this.

Hormones don't issue commands.

They whisper suggestions.

They facilitate.

They amplify.

They modulate what's already there, based entirely on the context, who you are, where you are, and who you're with.

That really changes how you think about these things.

Which leaves us with a final thought, maybe a challenge for you, our listener.

If context is so incredibly powerful in shaping how these hormones influence our behavior,

how could we actually design our social contexts, our societies, to bring out the best in us?

Could we structure things so that achieving status genuinely comes from cooperation, fairness, kindness?

If we did that, could testosterone, ironically, become maybe the most pro -social hormone we have?

Something to think about.

Thank you so much for joining us for this deep dive, and a very warm thank you from the whole Last Minute Lecture team.