When was the last time you looked a stranger in the face and made a snap judgment about how they behave? If you've graduated kindergarten, you know you're not supposed to. But for centuries, scientists and philosophers believed that physical traits corresponded to personality. Even Aristotle thought there was a connection between the book and its cover.
Today, physiognomy—as the study of facial features linked to personality became known—is considered a pseudoscience, but it was the first application of any science at all to criminology. Some argue that it helped pave the way for the development of forensics and tools like psychological profiling; others point out that attempts to link biology to criminal behavior are often deeply problematic, and have been used to justify discrimination against various ethnic and religious groups.
Controversial though they may be, theories linking biology to criminal behavior have not gone away. From skull shape to body types, here are some of the ways we've tried to use what's on the surface to unearth the monsters underneath.
As a young man in late 18th-century Vienna, physician Franz Josef Gall wondered why his classmates were so good at memorization while he struggled. And why did he surpass them in other areas? After noticing that those who were particularly skilled at memorization had prominent eyes, he spent years searching for a biological explanation for differences in mental characteristics. Eventually, he landed on a theory that aimed to explain all human behavior.
Gall based his theory, soon to be known as phrenology, on the notion that the brain was composed of 27 separate “faculties,” or organs, each responsible for a behavioral trait—benevolence, covetousness, arrogance, and wit, just to name a few. He believed that the size of an organ was correlated to its power and that the skull took its shape from the brain. As such, by examining the shape of the skull one could determine personality. Eventually, Gall's followers introduced the idea that people were born with their faculties in balance and were essentially good, but under- or over- development, diseases of, or damage to any of these faculties could cause an imbalance that would lead to a particular behavior.
Phrenology soon took off in Europe and then in North America. It wasn't long until Gall's acolytes were applying his principles to the study of criminality, examining the skulls of criminals for clues about their personality and publishing books and treatises that showed others how to do the same. For phrenologists, crime was a result of an overgrowth or other anomaly in a particular faculty—say, destructiveness.
By attributing behavior to a brain defect, phrenology broke with existing notions of deviant behavior. Pre-Enlightenment theory had held that such behavior was the result of “evil” or supernatural forces. During the Enlightenment, free will reigned supreme, and criminality was seen as an exercise of that will, the only deterrent for which was severe punishment. Phrenology removed free will from the equation. While those with “normal” faculties could commit crimes based on free will and should be punished accordingly, the habitually criminal were not necessarily responsible for their actions—they behaved the way they did because of mental disorder, one which could be addressed and treated. It's no coincidence that phrenologists were among the most vocal opponents of capital and corporal punishment and major proponents of rehabilitation in the middle of the 19th century.
Phrenology declined in popularity in the second half of the 19th century, although it persisted into the 20th century in some areas. For a brief moment, it was the first and most comprehensive scientific approach we had to criminology.
Sometimes called the “father of criminology,” Italian physician Cesare Lombroso spent much of his career examining the bodies (both dead and alive) of convicted criminals and the mentally ill. The army doctor and professor of psychiatry was struck by both Darwin's theories and the work of Italian evolutionists during the 1860s, and evolution greatly influenced his later work.
Like Gall, Lombroso experienced a “eureka” moment while making a minute examination of a human head—only in his case, it was the skull of the recently deceased thief and arsonist Giuseppe Villella. Villella had a small indentation at the back of his skull; unusual for a human, but common in some primates. Lombroso noticed the trait in a few other crooks, and theorized that criminals were in fact some evolutionary throwback to primitive humans. He began to argue that deviance was inherited in many of these “born delinquents,” and they could be differentiated from the masses by physical characteristics that he claimed resembled our primate ancestors: large jaws, jug ears, high cheekbones, bloodshot eyes, to name a few attributes. Behavioral traits like idleness and non-biological features like tattoos could also be a sign.
Lombroso ran experiments on prisoners, the insane, and even low-lifes he wrangled from Italian alleyways. He took measurements of their bodies and features and tested their blood pressure, pain resistance, and reaction to other stimuli. Over the years, he established a set of features associated with different types of crime. His theory, known as degeneration, laid the foundation for a systematic approach to crime and even punishment. Like the phrenologists, Lombroso and his acolytes argued against capital punishment for those whose degeneration was not particularly advanced but triggered by an environmental factor—they were to be treated rather than locked up.
While wildly popular during his lifetime (he even argued the merits of his theory with Russian novelist Leo Tolstoy while visiting the writer's home), Lombroso's ideas faded from prominence as sociological theories of crime became more popular at the turn of the 20th century. Besides his emphasis on a scientific approach to criminology, his legacy consists of a museum in Turin stocked with the skulls and other ephemera he collected throughout his career ... along with the good doctor's own head, preserved in a jar.
Body type is blamed for a lot these days—a propensity for obesity, jeans that don't fit quite right. But in the early 20th century, an American psychologist named William Sheldon looked a little deeper.
Sheldon examined some 4000 photographs of college students and distilled their bodies into three categories, or somatotypes: endomorphs, mesomorphs, and ectomorphs. Endomorphs were soft, round, and put on fat easily; they were also amiable, relaxed, and extroverted. Mesomorphs were hard, muscular, and broad-chested; they were also assertive, aggressive, and insensitive. Finally, ectomorphs were long, narrow, and fragile-looking; they were also more introverted and anxious. Bodies fell into a spectrum defined by the degree to which they exhibited each of these three traits.
In a study of 200 delinquent youths, Sheldon concluded that mesomorphs had the greatest predisposition for impulsive (and thus perhaps criminal) behavior. While his work was criticized for its methodology, Sheldon did attract more than a few students, some of whom modified his theory to include social pressures; for example, it was possible that society treated people with certain physical characteristics a certain way, thereby encouraging delinquency.
4. XYY SYNDROME
In 1961, a 44-year-old man underwent genetic testing after discovering his child had Down syndrome. The test results surprised his doctor—the man had an extra Y chromosome. Over the following decades, further testing revealed that XYY syndrome, as it became known, was rather common, appearing in men at a rate of 1 in 1000.
In 1965, when a study from a Scottish institution for people with dangerous, violent, or criminal propensities reported a high frequency of XYY syndrome among its population, scientists and the media alike began to wonder if that extra chromosome somehow caused violence and aggression in men. XYY was used as a defense in the trial of a French murderer, and has been brought up in regard to the case of Richard Speck, the student nurse killer of Chicago, though he turned out not to have the extra Y. Books and TV shows featured XYY killers even into the 1990s.
But what does the science say? While men with XYY syndrome tend to be taller, more active, and have a greater chance of having learning or behavioral problems, there's been no evidence showing a decrease in intelligence or a higher propensity for violence or aggression. In fact, most XYY men are unaware of their genetic quirk and blend perfectly well into the rest of the population. While two Dutch studies did show an increase in criminal convictions among XYY men, researchers have posited that this could be explained away based on socioeconomic variables that have also been linked to the chromosome aberrations.
For now, the XYY theory remains just a theory—as well as a convenient plot device.