Your Evolved Brain Is at the Mercy of Your Reptilian Impulses—and Vice Versa

You have three types of brain inside your brain. And they're all fighting for dominance.

ROBERT SAPOLSKY: What’s the best way to think about the brain? It’s insanely complicated. Everything connects to everything. A gazillion little subregions. 

Amid all that complexity there’s a broadly sort of simplifying way to sort of think about aspects of brain function when it comes to behavior. And this was an idea put forth by this guy Paul MacLean, a grand poohbah on the field, conceptually of thinking of the brain as coming in three functional layers.
The triune brain—and again this is highly schematic—the brain really doesn’t come in three layers, but one could think of the first most, the bottom most, the most ancient as being what’s often termed the “reptilian brain,” where basically the parts in there, we’ve got the same wiring as in a lizard, as in any ancient creature. It’s been there forever—ancient, ancient wiring at the base of the brain, most inside. And what does that region do? All the regulatory stuff. Your body temperature changes, it senses it and causes you to sweat or shiver. It’s monitoring your blood glucose levels. It’s like releasing hormones that are essential to sort of everyday shop keeping. It’s just keeping regulatory stuff in balance.

Sitting on top of that is conceptually what could be termed the limbic system, the emotional part of the brain. And this is very much a mammalian specialty. Lizards are not well known for their emotional lives. Part of the brain having to do with fear, arousal, anxieties, sexual longings, all those sorts of things – very mammalian. You’re off there in the grasslands butting heads with somebody else with antlers, and its your limbic system that’s heavily involved in that. 

Then sitting on the top is the layer three, the cortex. The cortex, spanking new, most recently evolved part of the brain. Everybody’s got a little bit of cortex but it’s not until you get to primates that you’ve got tons, and then apes, and then us. So functionally it’s very easy to think of this simplistic flow of commands. Layer two, the limbic system, can make layer one, the reptilian brain, activate. When is that? Your heart beats faster not because of a regulatory reptilian thing—Ooh, you’ve been caught in something painful but oh, an emotional state. You’re a wildebeest and they’re some scary menacing wildebeest threatening you and that emotional state causes your limbic system to activate the reptilian brain and your heart beats faster. You have a stress response. Not because a regulatory change happened in your body but for an emotional reason.

Then it’s very easy to think of, layered on top, this cortical area commanding your second layer, your limbic system to have an emotional response rather than something emotional: Here’s a threatening beast right in front of you. Something emotional. You see a movie that’s emotionally upsetting. See a movie. These are not real characters. They’re pixels and it’s your cortex that’s turning that abstract cognitive state into an emotional response. 

Likewise your cortex, layer three, could influence events down in layer one. You see something upsetting, you think about - you think about mortality, “One of these days my heart is going to stop beating,” and your heart’s going to beat faster. You’re not bleeding and hypotensive. You’re not in some—nothing in the reptilian brain could make sense of this. A purely cognitive state: “Ooh, on the other side of the planet there are people undergoing some traumatic event and I feel upset about it,” and your reptilian brain responds. 

So it’s very easy given that to think of a “three talks to two talks to one” sort of scenario. 

Just as readily though, one talks to two talks to three. What would be a case of that? 

What’s your reptilian brain talking to your cortex? Remarkable finding: When we’re hungry we make harsher moral judgments about people’s transgressions. We’re less charitable. We cheat more in economic games. Our cortex assessing the effects of prosociality, antisociality and altruism and its evolution. 

And part of what it’s doing in deciding how it feels about somebody else’s plight is if your stomach is gurgling, if you’re hungry, if you’re in pain that affects very cortical judgment-type areas. 

Layer one, this ancient reptilian brain that should have nothing to do with how your cortex works, having tons to do with it. Or layer two influencing layer three, your limbic system, your emotional state influencing your abstract cognitive processes. What’s the most obvious example of it? When we’re under stress. When we’re in an emotionally aroused state. We make stupid impulsive decisions that seem brilliant at the time. Affective emotional limbic layer two influencing how your cortical cortex goes about its abstractions. It’s not that abstract. It’s embedded in the biology of all these layers. 

So this interaction between these layers it seems this very mechanical process, potentially even an unconscious one. How do we consciously have, say, our cortex regulate an emotion, a limbic two layer? Simple. Think about the most arousing, wonderful thing that ever happened to you umpteen decades ago, and your cortex is evoking a memory that’s got your limbic system humming along in some excited state. Or think about—think cortically, or pull out the memories of—some traumatic event and your limbic system is responding. 

How about reptilian level? Easy to make it get into an agitated state. Sit there and think about, think  something incredibly upsetting. Think about some memory that was truly disturbing. Think about mortality. Think about global warming. And your heart speeds up. Layer three in a very conscious way has mobilized layer one. A lot harder is the inverse: You’re sitting there and you suffer from high blood pressure and either they could marinate you in antihypertensive drugs for the rest of your life or an alternative approach, a biofeedback approach is sit there and think about the happiest day of your life. Think about being in an open field that’s beautiful. Think about your favorite vacation. Think about, think about. And if it’s the right “thinking about,” suddenly your heart slows down. Suddenly your blood pressure goes down. Ah, the core of biofeedback is figuring out what sort of conscious states you can evoke that will affect your reptilian brain in a direction that’s good for your health. And all you do then is learn how to get better and better in some stressed hypertensive circumstance. What conscious act of thinking can I mobilize here at this point that will cause changes in how my big toe’s blood flow is working? And a case like that, that is very conscious regulation of more autonomic, more ancient parts of your brain.

 

You have three brains—the triune, the limbic, and the cortex—and they're all fighting for dominance as you go about your life. The so-called lizard brain (the triune) is perhaps the one we tend to think of as instinctual and gives us our basic instincts like, for example, staying alive or not touching fire. The limbic brain controls our emotions like fear and desire, while our cortex gives us the knowledge that makes us human. Basically, the three brains talk to one another and vie for rank in certain situations... it's sort of like Three's Company except with brain systems. For instance: you're reminded of something sad by your cortex and it triggers your limbic system, or you get cut off in traffic your lizard brain can trigger the cortex and the limbic. It is a pretty fascinating subject, and Robert Saplosky waxes poetic about the three distinct "characters" that live up inside your head.


Robert Sapolsky's most recent book is Behave: The Biology of Humans at Our Best and Worst.

7 most notorious and excessive Roman Emperors

These Roman Emperors were infamous for their debauchery and cruelty.

1876. Painted by Henryk Siemiradzki.
Politics & Current Affairs
  • Roman Emperors were known for their excesses and violent behavior.
  • From Caligula to Elagabalus, the emperors exercised total power in the service of their often-strange desires.
  • Most of these emperors met violent ends themselves.

We rightfully complain about many of our politicians and leaders today, but historically speaking, humanity has seen much worse. Arguably no set of rulers has been as debauched, ingenious in their cruelty, and prone to excess as the Roman Emperors.

While this list is certainly not exhaustive, here are seven Roman rulers who were perhaps the worst of the worst in what was one of the largest empires that ever existed, lasting for over a thousand years.

1. Caligula

Officially known as Gaius (Gaius Caesar Augustus Germanicus), Caligula was the third Roman Emperor, ruling from 37 to 41 AD. He acquired the nickname "Caligula" (meaning "little [soldier's] boot") from his father's soldiers during a campaign.

While recognized for some positive measures in the early days of his rule, he became famous throughout the ages as an absolutely insane emperor, who killed anyone when it pleased him, spent exorbitantly, was obsessed with perverse sex, and proclaimed himself to be a living god.

Caligula gives his horse Incitatus a drink during a banquet. Credit: An engraving by Persichini from a drawing by Pinelli, from "The History of the Roman Emperors" from Augustus to Constantine, by Jean Baptiste Louis Crevier. 1836.

Among his litany of misdeeds, according to the accounts of Caligula's contemporaries Philo of Alexandria and Seneca the Younger, he slept with whomever he wanted, brazenly taking other men's wives (even on their wedding nights) and publicly talking about it.

He also had an insatiable blood thirst, killing for mere amusement. Once, as reports historian Suetonius, when the bridge across the sea at Puteoli was being blessed, he had a number of spectators who were there to inspect it thrown off into the water. When some tried to cling to the ships' rudders, Caligula had them dislodged with hooks and oars so they would drown. On another occasion, he got so bored that he had his guards throw a whole section of the audience into the arena during the intermission so they would be eaten by wild beasts. He also allegedly executed two consuls who forgot his birthday.

Suetonius relayed further atrocities of the mad emperor's character, writing that Caligula "frequently had trials by torture held in his presence while he was eating or otherwise enjoying himself; and kept an expert headsman in readiness to decapitate the prisoners brought in from gaol." One particular form of torture associated with Caligula involved having people sawed in half.

He caused mass starvation and purposefully wasted money and resources, like making his troops stage fake battles just for theater. If that wasn't enough, he turned his palace into a brothel and was accused of incest with his sisters, Agrippina the Younger, Drusilla, and Livilla, whom he also prostituted to other men. Perhaps most famously, he was planning to appoint his favorite horse Incitatus a consul and went as far as making the horse into a priest.

In early 41 AD, Caligula was assassinated by a conspiracy of Praetorian Guard officers, senators, and other members of the court.

2. Nero

Fully named Nero Claudius Caesar, Nero ruled from 54 to 68 AD and was arguably an even worse madman than his uncle Caligula. He had his step-brother Britannicus killed, his wife Octavia executed, and his mother Agrippina stabbed and murdered. He personally kicked to death his lover Poppeaea while she was pregnant with his child — a horrific action the Roman historian Tacitus depicted as "a casual outburst of rage."

He spent exorbitantly and built a 100-foot-tall bronze statue of himself called the Colossus Neronis.

He is also remembered for being strangely obsessed with music. He sang and played the lyre, although it's not likely he really fiddled as Rome burned in what is a popular myth about this crazed tyrant. As misplaced retribution for the fire which burned down a sizable portion of Rome in the year 64, he executed scores of early Christians, some of them outfitted in animal skins and brutalized by dogs, with others burned at the stake.

He died by suicide.

Roman Emperor Nero in the burning ruins of Rome. July 64 AD.Credit: From an original painting by S.J. Ferris. (Photo by Kean Collection / Getty Images)

3. Commodus

Like some of his counterparts, Commodus (a.k.a. Lucius Aelius Aurelius Commodus) thought he was a god — in his case, a reincarnation of the Greek demigod Hercules. Ruling from 176 to 192 AD, he was also known for his debauched ways and strange stunts that seemed designed to affirm his divine status. Numerous statues around the empire showed him as Hercules, a warrior who fought both men and beasts. He fought hundreds of exotic animals in an arena like a gladiator, confusing and terrifying his subjects. Once, he killed 100 lions in a single day.

Emperor Commodus (Joaquin Phoenix) questions the loyalty of his sister Lucilla (Connie Nielsen) In Dreamworks Pictures' and Universal Pictures' Oscar-winning drama "Gladiator," directed by Ridley Scott.Credit: Photo By Getty Images

The burning desire to kill living creatures as a gladiator for the New Year's Day celebrations in 193 AD brought about his demise. After Commodus shot hundreds of animals with arrows and javelins every morning as part of the Plebeian Games leading up to New Year's, his fitness coach (aptly named Narcissus), choked the emperor to death in his bath.

4. Elagabalus

Officially named Marcus Aurelius Antoninus II, Elagabalus's nickname comes from his priesthood in the cult of the Syrian god Elagabal. Ruling as emperor from 218 to 222 AD, he was so devoted to the cult, which he tried to spread in Rome, that he had himself circumcised to prove his dedication. He further offended the religious sensitivities of his compatriots by essentially replacing the main Roman god Jupiter with Elagabal as the chief deity. In another nod to his convictions, he installed on Palatine Hill a cone-like fetish made of black stone as a symbol of the Syrian sun god Sol Invictus Elagabalus.

His sexual proclivities were also not well received at the time. He was likely transgender (wearing makeup and wigs), had five marriages, and was quite open about his male lovers. According to the Roman historian (and the emperor's contemporary) Cassius Dio, Elagabalus prostituted himself in brothels and taverns and was one of the first historical figures on record to be looking for sex reassignment surgery.

He was eventually murdered in 222 in an assassination plot engineered by his own grandmother Julia Maesa.

5. Vitellius

Emperor for just eight months, from April 19th to December 20th of the year 69 AD, Vitellius made some key administrative contributions to the empire but is ultimately remembered as a cruel glutton. He was described by Suetonius as overly fond of eating and drinking, to the point where he would eat at banquets four times a day while sending out the Roman navy to get him rare foods. He also had little social grace, inviting himself over to the houses of different noblemen to eat at their banquets, too.

Vitellius dragged through the streets of Rome.Credit: Georges Rochegrosse. 1883.

He was also quite vicious and reportedly either had his own mother starved to death or approved a poison with which she committed suicide.

Vitellius was ultimately murdered in brutal fashion by supporters of the rival emperor Vespasian, who dragged him through Rome's streets, then likely beheaded him and threw his body into the Tiber river. "Yet I was once your emperor," were supposedly his last words, wrote historian Cassius Dio.

6. Caracalla

Marcus Aurelius Antoninus I ruled Rome from 211 to 217 AD on his own (while previously co-ruling with his father Septimius Severus from 198). "Caracalla"' was his nickname, referencing a hooded coat from Gaul that he brought into Roman fashion.

He started off his rise to individual power by murdering his younger brother Geta, who was named co-heir by their father. Caracalla's bloodthirsty tyranny didn't stop there. He wiped out Geta's supporters and was known to execute any opponents to his or Roman rule. For instance, he slaughtered up to 20,000 citizens of Alexandria after a local theatrical satire dared to mock him.

Geta Dying in His Mother's Arms.Credit: Jacques Pajou (1766-1828)

One of the positive outcomes of his rule was the Edict of Caracalla, which gave Roman citizenship to all free men in the empire. He was also known for building gigantic baths.

Like others on this list, Caracalla met a brutal end, being assassinated by army officers, including the Praetorian prefect Opellius Macrinus, who installed himself as the next emperor.

7. Tiberius

As the second emperor, Tiberius (ruling from 42 BC to 16 AD) is known for a number of accomplishments, especially his military exploits. He was one of the Roman Empire's most successful generals, conquering Pannonia, Dalmatia, Raetia, and parts of Germania.

He was also remembered by his contemporaries as a rather sullen, perverse, and angry man. In the chapter on his life from The Lives of the Twelve Caesars by the historian Suetonius, Tiberius is said to have been disliked from an early age for his personality by even his family. Suetonius wrote that his mother Antonia often called him "an abortion of a man, that had been only begun, but never finished, by nature."

"Orgy of the Times of Tiberius on Capri".Painting by Henryk Siemiradzki. 1881.

Suetonius also paints a damning picture of Tiberius after he retreated from public life to the island of Capri. His years on the island would put Jeffrey Epstein to shame. A horrendous pedophile, Tiberius had a reputation for "depravities that one can hardly bear to tell or be told, let alone believe," Suetonius wrote, describing how "in Capri's woods and groves he arranged a number of nooks of venery where boys and girls got up as Pans and nymphs solicited outside bowers and grottoes: people openly called this 'the old goat's garden,' punning on the island's name."

There's much, much more — far too salacious and, frankly, disgusting to repeat here. For the intrepid or morbidly curious reader, here's a link for more information.

After he died, Tiberius was fittingly succeeded in emperorship by his grandnephew and adopted grandson Caligula.

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A 19th-century surveying mistake kept lumberjacks away from what is now Minnesota's largest patch of old-growth trees.

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