Natural born killers: brain shape, behaviour and the history of phrenology

Phrenologists believed the shape of the brain offered a clear-cut explanation for behaviour. Hey Paul Studios/Flickr, CC BY-SA

Long before neuroscience, phrenology claimed to have the power to determine who was afflicted with badness and who was suffering from madness.

In the second-last article in our series Biology and Blame, James Bradley details some interesting facts about this pseudo-science.


At 8am on Monday October 24, 1853, Patrick O’Connor and Henry Bradley were hanged together outside the Melbourne Gaol in front of a large crowd.

Bradley and O'Connor were responsible for one of the lesser known, but more spectacular outbreaks of bushranging in the early period of the Gold Rushes, and paid the ultimate penalty for their violent crimes.

Having murdered a man in cold blood, they piratically seized a boat in northern Tasmania, and crossed the Bass Strait, landing somewhere near Western Port. They then stole horses, held up travellers, and shot anyone who got in their way.

No one died, but that was through luck rather than judgement.

A different judgement

A phrenology chart. Heida Maria via Wikimedia Commons

After the execution, medical men descended on the corpses. They paid particular attention to the malefactors’ skulls, and the following day’s The Argus explained how “cerebral physiology” had revealed that both were, in effect, natural born killers.

O’Connor’s skull revealed that:

even if blessed by the controlling influence of a most powerful intellect instead of a very weak one, this would still have been a violent, murderous man.

Bradley’s case was worse:

Here … we have a person with all the passions and appetites of full-grown man, and controlling intellect of an average child — in fact a criminal idiot.

The newspaper concluded that the “pirate bushrangers”, as they had become known, “had not powers of self-control.” They were, in fact, “not so much criminals as state patients.”

“Their destination should have been the asylum not the gallows.”

In other words, they should have been treated rather than punished.

Phrenology’s heart

“Cerebral physiology” was a euphemism for phrenology, a now-discredited pseudo-science. But make no mistake: in its day, phrenology was on the cutting edge of brain science.

During the first half of the 19th century, and arguably beyond, it offered a clear-cut explanation for why people behaved the way they did. And it was hailed by many as an extraordinarily effective explanatory tool.

Two ideas lay at the heart of phrenology’s seductive power. First, different areas of the brain were associated with different mental capacities or faculties. And, as the brain developed, it shaped the skull.

An illustration and definition of ‘phrenology’ from Webster’s Dictionary circa 1900. Quasipalm via Wikimedia Commons

An underdeveloped faculty might result in a depression of the skull then, while an overdeveloped faculty would result in a bump or protuberance.

A skilled (usually medical) observer could detect either.

But what phrenology also offered was the potential to sort the wheat from the chaff — most phrenologists agreed that some criminals were born bad, while others were made bad by life circumstances.

Some scepticism

This was the position of the doyen of British phrenology, George Combe, who, in his The Constitution of Man in Relation to External Objects (1828), wrote that “certain individuals were unfortunate at birth”.

This line was reiterated by Scottish geologist George S. Mackenzie in 1836 when he petitioned the Secretary of State for the Colonies. Spurred by “recent atrocities that have occurred in New South Wales”, Mackenzie argued the selection of convicts to be transported to that colony was too haphazard.

Instead, their “individual history and characters should be inquired into”, and only the redeemable sent. And, of course, the best way to achieve this was by using phrenology, which would be “an engine of unlimited power” in shaping the reform of criminals.

Mackenzie’s petition was accompanied by a plethora of supporting testimonials provided by eminent scientists and medical men.

But the Secretary of State was unmoved by phrenology’s claims. And so too was the legal profession as a whole.

Impact in the colonies

Indeed, the legal profession would soon seek to purge the courts of the insanity plea in favour of whether the criminal, sane or not, knew that he or she was committing a crime.

With this most phrenologists concurred: however underdeveloped a mental organ was, the criminal still possessed the ability to make a moral decision.

But just because phrenology failed to make an impact on the courts, doesn’t mean it had no impact upon penal policy in general. Alexander Maconochie, who, for a short time, was the progressive governor of the Norfolk Island penal colony, was deeply influenced by the discipline.

So too were the medical men who dissected the bodies of executed criminals. Like Bradley and O’Connor’s, dissections involved a minute examination of the internal structures of the brain, combined with a more general analysis of the bumps and depressions of the skull; all as part of the search to establish brain-based criminality.

Phrenology cast an extraordinarily long shadow over the 19th and early 20th centuries. Its public face may have become a tool for mesmerists and other quacks. But the project to locate criminal culpability in the brains and bodies of criminals continued apace.

Criminal tattoos

We see its inheritance in psychiatrist and anthropologist Cesare Lombroso’s 1876 L’Uomo Delinquente (Criminal Man), although by now there was no talk of specific faculties or organs.

Lombroso’s work was deeply influential. ivan losi/Flickr, CC BY-NC-SA

For Lombroso, the criminal was the product of a vitiated nervous system. Both the brains and skulls of criminals demonstrated evidence of atavism; in other words, criminals were evolutionary throwbacks, no less, and their skulls and faces bore the signs of degeneration.

It was for this reason that Lombroso made tattoos a dominant symptom of the pathological criminal (the striking illustrations in L’Uomo Delinquente are an abundant resource for the historian of tattooing). Only a person with a degenerated brain and nervous system would be able to subject him or herself to the pain of the tattooist’s needle!

But this notion of the biologically hard-wired criminal was one view among many. To be sure, it was deeply influential, particularly within the emergent discourse of eugenics. But it also vied with other ideas.

The celebrated French criminologist Alexandre Lacassagne, for instance, had a different take to Lombroso on the matter of tattoos. For him, they were “speaking scars” that talked of the life and culture of the tattooed individual. In the same way, the criminal was made by social circumstances rather than biological inheritance.

Echoes of the past

Neuro-culpability: the modern-day phrenology? Jon Olav Eikenes/Flickr (resized), CC BY-SA

However alien phrenology looks, and however much it appears to modern eyes as a pseudo-science, we would do well to remember that, like contemporary neuroscience, it was once believed to possess the power to determine who was afflicted with badness and who was suffering from madness.

Indeed, this gives us reason to exercise some scepticism about contemporary neuroscience’s claims. The eminent historian of forensic psychiatry Joel Eigen has noted that neuroscience is “the latest but not the final chapter” in the story of identifying the pathological criminal.

Phrenology, which once spoke so loudly about the human condition, has gone the way of all things. Is it possible that the same fate awaits our contemporary understanding of neuro-culpability?

It is not impossible that today’s neuroscience will end up looking like yesterday’s phrenology. And only time will reveal the next instalment of the fraught dialogue between criminology and biological determinism.


This is the sixth article in our series Biology and Blame. Click on the links below to read other pieces:

Part one – Genes made me do it: genetics, responsibility and criminal law

Part two – Irresponsible brains? The role of consciousness in guilt

Part three - Psychiatry’s fight for a place in defining criminal responsibility

Part four – Looking for psychopaths in all the wrong places: fMRI in court

Part five - Why shouldn’t addiction be a defence to low-level crime?

Part seven - Put down the smart drugs – cognitive enhancement is ethically risky business

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