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10 Theories About How Biology Creates A Criminal

by Nathan Willey
fact checked by Jamie Frater

Some researchers theorize that criminal biology is different, with the tendency to break the law encoded in the offender’s DNA. To say that someone is “born bad” is a gross overstatement, but scientists have suggested that some people are genetically at risk of becoming offenders.

10 Some People May Be Unable To Reform


Researchers have been studying the anterior cingulate cortex in the brains of prisoners to predict if and how long it will be until they commit another crime. Before being released on parole or probation, 96 male prisoners were given MRI scans in which their impulsive behavior was tested. They watched a screen and were given less than one second to press a button when an “X” appeared but not when a “K” appeared. “X” appeared the majority of the time, so they had to exhibit self-control to stop themselves from pressing the button when “K” appeared.

The result was that criminals often pressed the button when “K” appeared, implying that they were more impulsive than the average person. The part of their brain responsible for controlling impulsive behavior may have been deficient. After three years, the study found that criminals with the least amount of activity in their anterior cingulate cortex were more likely to commit a crime during that time. The level of brain activity also correlated to the amount of time before the criminal became a reoffender.

Although the researchers found that the activity in this area of the brain correlated with recidivism, they could not determine why this happened. Impulsiveness could be the reason, but the anterior cingulate cortex could also be calculating how likely the prisoners were to make an error when pressing the button. Scientists cautioned against drawing any conclusions from this type of statistical analysis.

9 Some People Could Be Born Criminals


In the late 1960s, the WHO started a project to closely follow about 1,800 children on Mauritius, an island in the Indian Ocean. Researchers have been using that data to predict whether a child will grow up to be a criminal.

Their research showed that children from Mauritius with slower heart rates and reduced skin responses when annoyed by loud tones or challenging questions tended to have criminal records when they got older. Fifteen-year-olds with this pattern tended to have criminal records by age 29. Three-year-olds who displayed the pattern were usually more aggressive than other children five years later. When sets of twins were tested, identical twins showed more similar traits than nonidentical ones. This suggests that genetics played a stronger role than environmental factors because each set of twins was raised in the same household.

According to the theory, criminals are insensitive to fear. A loud noise raises the heart rate and puts the body in a state of alert, which is what the skin sensors pick up. But children who were not alarmed also didn’t react to punishment when they misbehaved. In the same way, they didn’t react to distress in other people. The theory is that the pattern builds as they age, resulting in criminal behavior. However, the researchers caution that environment is a significant factor in whether a child becomes a criminal.

8 A Lot Of Crime Was Caused By Lead


Exposure to lead during pregnancy may cause infants to have reduced head sizes, headaches, lower IQs, and aggressive or dysfunctional behavior. It also reduces the gray matter in the brain responsible for activities like impulse control and thinking.

Scientists calculated the amounts of lead in the environment for different years and compared that to the rates of violent crime during those years. They concluded that a higher amount of lead corresponded to a rise in violent crime two decades later. Still, correlation does not imply causation, so more research was needed.

Researchers tried to determine if the removal of lead from US gasoline in the 1970s could be linked to crime in the 1990s. Gathering lead data from each state, they plotted crime rates in each area. In those states with early or sharp declines in lead, there was a corresponding drop in violent crime 20 years later and vice versa.

The lead causation theory has its supporters, with some claiming that 90 percent of the crime rate in the 20th century can be traced to lead. However, others are skeptical, citing a lack of evidence. Supporters argue that there can never be direct evidence because no one is going to purposely poison children with lead.

7 The Warrior Gene


Researchers suggest that some people are hardwired to commit violent crime. After taking blood samples from violent prisoners in Finland, the researchers found that repeat offenders had the genetic variants CDH13 and MAOA. They nicknamed it the “warrior gene.”

MAOA metabolizes dopamine. If MAOA activity is decreased, the use of alcohol or drugs might induce a larger dopamine burst and spark aggressive behavior. CDH13 helps the development of neuronal connections in the brain and is an important factor in ADHD. Having both variations supposedly makes someone 13 times more likely to commit a violent crime.

MAOA is located on the X chromosome, which could explain why most mass murderers are men. Women have two copies of the gene, so if one carries the variant, another normal gene could offset the effect. However, men have only one copy of the X chromosome, so they suffer the full effects of the variant if they have it.

That is not to say that having either variant definitely makes someone a violent criminal. Researcher Jim Fallon found that he had the gene but did not have a history of violence. Environmental factors are also important, and MAOA is associated with higher rates of crime when the individual experienced childhood adversity.

6 Psychopathy May Be Evolutionary


Psychopaths have different biology than normal humans, with some researchers arguing that psychopathy is evolutionary rather than a mental disorder. In tests, people with more psychopathic tendencies were less likely to harm their families. In an evolutionary sense, this meant that psychopaths acted to protect their own gene pool at the expense of others.

The theory has many critics, but there are other factors suggesting that psychopathy is evolutionary. One anthropological hypothesis looked at the Kung Bushmen and the Mundurucu villagers. The Kung live in the harsh desert environment of South Africa where working together is essential for the tribe’s collective survival. There, reproductive success is dependent on how well one works with the tribe. Any psychopathic traits would be a hindrance to the survival of one’s genes.

The Mundurucu live in the Amazon basin, where women do most of the farming while men compete for social status. It’s a culture where meat can be traded for sex, and reproductive success depends on where a man sits in the social hierarchy. This requires fearlessness, good verbal skills, and a lack of empathy—all traits of a psychopath. In that environment, psychopathy would be an advantage by evolutionary standards. Still, ideas like these do not completely discount the emergence of psychopathy as a mental disorder or a deliberate, behavioral choice. The prevailing theory is still that it is not an adaptive trait.

5 The Criminal Brain As A Legal Defense


The number of criminals using their brain scans to lighten their sentences has skyrocketed in recent years. Between 2007 and 2011, the number of cases in which judges mentioned neuroscientific evidence increased from 112 to 1,500. Researchers derived these numbers from court records. However, many cases were settled out of court and the database was incomplete, so the total number was likely to be even higher. Of course, this may not mean that neuroscience is affecting the outcome of more court cases, just that judges are discussing it more.

In one case, a Virginia teacher was caught viewing child pornography and then convicted of child molestation. But the night before he went to jail, a brain tumor was discovered to have been causing his pedophiliac tendencies. Even without tumors, brains scans show that criminals’ brains sometimes do function differently.

In one case, a woman murdered her sister, set fire to the corpse, and then attempted to murder her parents. She had her sentence reduced from life to 20 years because there was an abnormality in the region of her brain that regulates impulsivity and aggression. Neuroscience is often used in the courtroom to lighten sentences. But whether blaming criminal behavior on a person’s brain should affect legal outcomes is a matter of fierce debate.

4 Using Brain Implants To Prevent Crime


Photo credit: Chuck Kennedy

As in A Clockwork Orange, the idea of creating brain implants to make criminals upstanding members of society has been suggested. After all, we already use implants in our body to modify a number of other things. Some devices can even change our moods. The White House has already funded a $3 billion BRAIN Initiative, $70 million of which went to cranial implant research. Having a cranial implant that prevents crime is moving out of science fiction toward reality.

A criminal could opt out of a death sentence by volunteering to have an implant that would control his temper or violent actions. Potentially, even a person’s negative thoughts could be suppressed, although that’s obviously a frightening concept. But if the alternative is death row, some people might be willing to take that step to preserve their lives and the lives of any potential victims.

It’s been argued that some criminals are already having their identities altered with drugs that treat their criminal impulses like a mental disease. If medicine is already using brain implants to treat conditions like deafness and Alzheimer’s, why not also treat crime as a disease that can be cured?

3 Fighting Crime With Health And Fitness


A mother drinking or smoking while pregnant can double or triple the odds of her baby becoming a violent offender later in life. Lead exposure may also influence adult behavior. Poor nutrition at age three has been shown to cause more aggressive and antisocial behavior in the teenage years. With so many studies linking a child’s environment to violent crime later in life, some are questioning if we can manipulate biology to prevent it.

Scientists are studying the effects of “biological intervention” to combat crime later in life. It doesn’t have to involve medication. Studies have shown that better nutrition, more exercise, and cognitive stimulation from ages three to five reduces crime at age 23 by 35 percent. When nurses visit poor mothers and provide advice to reduce smoking and alcohol consumption, juvenile delinquency is cut in half 15 years later.

Adults can be affected by nutrition, too. Studies in England and the Netherlands showed that supplementing the diets of young prisoners with omega-3, which is critical for proper brain structure and function, has reduced the incidence of serious crimes by 35 percent. Studies like these suggest that reducing the likelihood of a child developing into an adult criminal may be as easy as providing good nutrition and avoiding toxins.

2 A Matter Of The Heart


Studies have shown that teens with a low resting heart rate may be at risk of becoming violent offenders when they become adults. In Sweden, military service was mandatory until 2009. Among other tests, every young man had his heart rate measured when he was about 18. Researchers analyzed this data and divided the men into five groups based on their heart rate.

Surprisingly, those men with resting heart rates of no more than 60 beats per minute were 39 percent more likely to be convicted of a violent crime over the next few decades than the men with the highest heart rates of 83 or more beats per minute. Those violent crimes included murder, assault, and arson. The group with the lowest resting heart rates was also 25 percent more likely to commit nonviolent crimes like drug use and 39 percent more likely to be injured by an assault or in an accident.

To explain this, researchers have suggested that a person with a low resting heart rate may have unusually low levels of psychological arousal, meaning that they feel less awake and alert. This may lead them to seek stimulating experiences like risky behaviors and crime. It may also mean that they have less of a reaction to mildly stressful experiences like getting your heart rate checked, which would mean that they are more fearless and prone to taking risks.

1 It’s Not All Genetic


While a person’s biology may influence whether he becomes a criminal, it’s not all about a person’s genes. As we mentioned earlier, scientist Jim Fallon was researching the minds of serial killers and psychopaths when he discovered that his brain scan was like that of a psychopathic serial killer. Assuming Fallon wasn’t secretly murdering dozens of people, this type of finding suggests that genetic factors may only predispose a person to violence and psychopathic tendencies.

When he realized that he had the mind of a killer, Fallon continued the experiment to check for other factors that are consistent with criminal behavior. His hypothesis was that killers often experience abuse or violence in their childhoods. For example, Ted Bundy was raised by his grandparents and originally thought that his mother was his sister. Once the truth was revealed, his cousin tormented him with that fact. His grandfather was also prone to violence.

However, Fallon had grown up in a loving, caring household, which he thinks made all the difference. He’s a prime example of how neither biology nor environmental factors can solely determine a person’s fate.

Nathan keeps a Japan blog where he writes about the sights, expat life, and finds Japanese culture in everyday items. You can also find him on Facebook and Twitter.

fact checked by Jamie Frater