A2 Psychology at Spalding Grammar School

"He's not right in the head" is a common remark made about someone who behaves abnormally and it's often assumed by tabloid newspapers that criminals are "sick". Some biopsychologists argue that special structures inside the brain control our social behaviour - giving us empathy for other people, a sense of conscience and a concern for the consequences of our actions. People without these brain structures might be heartless and impulsive with no sense of right and wrong. This is taking the NATURE side of the nature/nurture debate and the DISPOSITIONAL side of the dispositions vs situations debate.

The strange case of PHINEAS GAGE (John M. Harlow, 1848) is early evidence that moral decisions might be based on the biology of the brain. Phineas Gage was a railroad worker whose brain was damaged when an iron bar was driven through his skull during a gunpowder accident. The tamping iron went in point first under his left cheek bone and completely out through the top of his head, landing about 25 to 30 yards behind him. Gage survived the accident with his intellect undamaged, but his personality was transformed. Before the accident he had been a most efficient foreman with a well-balanced mind. He was now aggressive and obscene, showing no respect for workmates, with little patience for tasks or ability to  plan for the future. His friends declared that he was "no longer Gage” and allegedly he became an aimless drifter. After Gage's death, his skull was preserved and a few years ago it was re-examined by a team of neurobiologists. They concluded that Gage had sustained damage to a part of the brain called the prefrontal cortex. Studies of similar patients confirm that the prefrontal cortex (in particular a region known as the orbitofrontal cortex) plays an important role in moral decision-making.

Visit this website about Phineas Gage, with pictures of his skull and information about his brain injuries. Or check out this animated video on YouTube.

More sophisticated research is carried out today by Professor Adrian Raine at the University of Southern California. Raine uses a brain-scanning technique called POSITRON EMISSION TOMOGRAPHY (PET for short). This involves giving the participant an injection of slightly radioactive glucose. The glucose dissolves in the blood but the radioactive blood then travels to the brain and gathers in parts of the brain that are the busiest. If the participant then carries out a task or solves a puzzle, the PET scanner shows which areas of the brain are being used. A computer can turn this information into a 3-D animation. 

Raine, Buchsbaum & LaCasse (1997) carried out a famous study on brain dysfunction in criminals using PET scans. The experimental group were 41 people (39 males, 2 females) who had been charged with murder but were pleading Not Guilty by Reason of Insanity (NGRI). Some of them were pleading this because they had schizophrenia, others had personality disorders or head injuries. Raine et al. put together a control group who were the same age/sex as the NGRIs, including 6 schizophrenics to match the NGRI schizophrenics, but the control group had no previous criminal record. Everyone was given a PET scan while doing a task that required basic concentration. Raine et al. looked for differences between the NGRIs and the control group; what they found was interesting.

First, the researchers looked at scans of the CEREBRAL CORTEX. This is the outermost layer of the brain that and it is what separates human brains from most other animals. It is made up of four different areas called LOBES. When looking at the NGRIs, Raine found much less activity going on in the prefrontal cortex and the parietal cortex, slightly more activity going on in the occipital cortex while the temporal cortex was about the same.

Neuroscience For Kids has a short web page explaining the lobes of the brain and what they do.

Next the researchers looked at the subcortical areas - the "insides" of the brain that are similar to the brain structures found in other animals. Among the NGRIs there was less activity going on in the corpus callosum. This is the bridge of nerve fibres connecting the two hemispheres of the brain that you learned about in AS when studying Sperry. Raine also found that the activity in the two hemispheres of the NGRIs' brains was not evenly balanced. The NGRIs had more activity on the right side of the amygdala and hippocampus and less on the left. You learned about the hippocampus last year when studying Maguire et al. but the amygdala is an organ that regulates sleep and appetite and controls emotion and fear.

Raine concludes that there is a link between brain structure and violent behaviour. If the amygdala is malfunctioning, then people will have powerful mood swings and won't experience fear. A faulty hippocampus might prevent people from learning from their mistakes and less activity in the corpus callosum ties in with having difficulty planning ahead. The prefrontal cortex (the part of the brain that was damaged for Phineas Gage) deals with rational thought and moral judgement.

However, Adrian Raine argues against drawing too many conclusions from this research. This study might explain why some people have a PREDISPOSITION towards violence, but not all crimes are violent; in fact, not all murders are violent.  The evidence does not tell us that the criminals had no choice or free will about their crimes. We don't even know where these brain differences came from: it's possible the trauma of the crime and imprisonment caused the brain to change in this way, rather than vice versa.

Mark Holah's website has a terrific summary of the Raine et al. study in much more detail than this.

Inside every living thing are sets of instructions called GENES. Genes are the building blocks of DNA and they tell bodies how to grow and develop. Genes affect whether you have have brown eyes or blue and influence things like your height, build and possibly your intelligence and personality. Scientists have been researching genes since the 19th century monk Gregor Mendel discovered how genes were passed on in pea plants. However, we're still a long way from identifying what every single gene does, particularly since most genes work in complicated combinations with other genes. We don't even know how many genes there are in humans; estimates range from 20,000 to 150,000.

Could there be a gene for criminality? First, it's important to clear up what this means. Criminality is a social construct - what's criminal in one society or at one time might be perfectly acceptable somewhere else. Our genes don't know anything about "laws" so you can't have a gene that makes you want to break any particular law. However, genes certainly can give people PREDISPOSITIONS. Predisposition is a natural built-in tendency creatures have to behave or develop a certain way. For example, human babies have a predisposition to walk and talk and learn to do these things with very little encouragement; however, they can still end up not doing these things if they are paralysed, deaf or neglected. Genes might give some people a predisposition to take risks, not think about consequences, be aggressive or behave selfishly. Even that doesn't mean they have to become criminals. They could become contestants on reality TV shows instead.

One of the most effective type of research into the genetic basis for crime is the TWIN STUDY which can show how crime runs in families. Twin studies are particularly revealing if the twins have been raised apart - in which case shared biology is the only thing they have in common. Unfortunately for researchers there are two types of twins. Monozygotic (MZ) twins are the interesting ones because they are physically identical and come from the same fertilised egg; this means they have exactly the same genes. Dizygotic (DZ) twins come from different eggs fertilised at the same time; they may look similar but are no more alike genetically than any normal pair of brothers and sisters. Obviously, MZ twins are the ones that tell us most about the influence of genes.

Karl Christiansen (1977) did an important twin study in Denmark, looking at 3586 twin pairs born between 1881 and 1910. Denmark is an unusual country because it has for a long time kept detailed records about people's criminal records and mental health and allows researchers to look at this data rather than keeping it confidential. Christiansen studied the CONCORDANCE RATE which is the degree to which both twins share the same behaviour. For example, both twins have criminal convictions then that is concordance. The concordance rate for the MZ twins was 52% but for DZ twins concordance dropped to 22%. This is a powerful argument for genes influencing criminal behaviour, since with the DZ twins who were not genetically identical, it was much less likely that if one turned to crime then the other would too.

This study has its flaws. For one thing, it's reductionist and doesn't look at other factors like whether the twins were brought up together and what influences they had from family and friends. Also, it may be invalid because tests for MZ twins were not as accurate in the 1970s as they are today; some twins can look very similar but still not be genetically identical. Finally, the concordance was only strong for property crime (theft, burglary) and not for other sorts.

If genes do influence people to become criminals, then how exactly do they do it? One clue about this mechanism comes from recent research into SEROTONIN. Serotonin is a hormone that operates in the brain. It's a particular type of hormone called a neurotransmitter which means it is responsible for helping nerve impulses travel from one part of the brain to another. Neurotransmitters shape a lot of our moods and serotonin is the "happy hormone" that regulates our mood and sleep patterns, keeps us sexually healthy and fights off depression. The antidepressant drug Prozac works by targeting the amount of serotonin in the brain.

Researchers like J. Dee Higley (2000) link serotonin (or 5-HT) to impulsive violent behaviour. Serotonin acts as a "brake" on a lot of our impulses and people with high levels of serotonin show more restraint and think things through. People with low levels of serotonin "act first and think later". Being impulsive isn't always bad - in fact, for some jobs like soldiers it can be an advantage - but it does explain some sorts of crime, particularly assaults, drug use and crimes of opportunity.

Higley has worked for the past 15 years with a colony of about 5,000 free-ranging rhesus monkeys that live on a South Carolina island. He measures serotonin by taking a little cerebrospinal fluid (CSF) from the monkeys. Those with low 5-HIAA have more scars and wounds. Although other monkeys in the colony are just as likely to be aggressive, the low-5-HIAA monkeys tend to escalate an incident out of control. Even when the low-5-HIAA monkeys aren't having tantrums, they are daredevils. Typical monkeys move throughout the island by way of the treetops. The low 5-HIAA monkeys are not deterred by a gap between trees; they just spontaneously leap from one to the next. This ethological approach suggests low serotonin levels are responsible for impulsive, risk-taking behaviour.

Results with the monkeys might be generalised to human behavior. Higley's colleague Dr Markku Linnoila et al. (1989) studied 1043 arsonists in New York prisons and psychiatric hospitals and found that those who committed the crime impulsively had low serotonin. Those who did it for money had normal levels of 5-HIAA. They also studied 36 prisoners who had committed impulsive, violent crimes. They found a strong negative correlation - that the more times they had acted aggressively throughout their lives, the lower the level of 5-HIAA they had. The conclusion is that a mutated gene can cause the brain to produce too little serotonin, but it needs a stressor before it will do this. The most common stressors are violent family upbringing or excessive alcohol consumption.

The biological psychology presented so far explains crime by pointing to individuals who are extremely fearless, impulsive and risk-taking. The other biological feature of crime is that it's largely carried out by men. Males offenders outnumber female offenders in the UK by more than 4 to 1.

The table shows the crime figures for England & Wales in 2002. If you want to know more, visit the National Statistics website.

Most criminologists prefer to look to social psychology for answers to this. UPBRINGING must play a large part: parents encourage boys to be aggressive, daring and rule-breaking by the way they treat them and the activities they direct them into (aggressive sports, pretending to be cowboys, toy guns) whereas girls are socialised into being quiet, conforming and rules-abiding. This process continues in later life, when men have lifestyles and jobs that allow them to travel freely and work unsupervised - in other words, they have lots of opportunity for crime. Women, by contrast, are normally closely supervised, by managers, family and boyfriends. This is also explained by Travis Hirschi's Social Bonds Theory - women have more social bonds than men, since they care for families.

Biopsychologists have a different explanation which is based on EVOLUTIONARY BIOLOGY. This is the idea that biological traits are passed on through a species and that traits which have "survival value" will become common because creatures which inherit those traits will have more children than creatures which don't. Could male risk-taking and impulsiveness have "survival value"? To answer this, DEMOGRAPHERS who study population trends split causes of death into external causes (like accidents or murders) and internal causes (disease and illness). External causes are the ones affected by risk and young males are far more likely to die from external causes than internal ones. Young men are much more likely to drive at speed and experiment with drugs but much less likely to seek medical help compared to young women. Males are much more likely to take risks when they think that females or other males will see them. Evolutionists say this is because males "win" a female mate by taking risks. In the past, risk-taking males reproduced successfully and passed on their risk-taking genes. What happened to the cautious, risk-averse males? They're all extinct.

Margo Wilson & Martin Daly (2001) carried out a CORRELATIONAL study looking at homicide rates and life expectancy in Chicago. Chicago is an unusual American city because it is divided into 77 distinct community areas or neighbourhoods (eg Oakland, Englewood, Washington Heights). These areas have fairly clear-cut boundaries and their own social and economic characteristics. The researchers took their data from a recent population census and compared it to police and school records on crime, delinquency and truancy. They focused on the communities that had low average life expectancies for males (54-77 years).

The results showed that life expectancy was a good predictor of neighbourhood homicide rates. This is a NEGATIVE CORRELATION: the lower the life expectancy, the higher the homicide rate. The Correlational Coefficient was -0.88, which is very strong. Daly & Wilson suggest that young men in these neighbourhoods have a "short time horizon" - they want instant gratification rather than delayed pleasure, they expect to live short lives and discount the future, meaning that they take risks for short-term rewards.

Another finding was a negative correlation between truancy from school and life expectancy (-0.5 for primary schools, -0.3 for high schools). This could also be explained by a "short time horizon": the boys see little point in working hard at school because they do not imagine a long future for themselves while their parents don't force them to attend because they also operate on a short time horizon. The payoff is that young males who skip school and break rules will have more potential mates, which compensates them for dying younger.

This evolutionary explanation ties in with Merton's Strain Theory, since it is the people at the bottom of the heap in society who have the most to gain through taking risks (innovating) and who stand to gain least by conforming.

These findings can be generalised to other countries and cultures, according to Betsy Mason writing in the New Scientist (2002). A CROSS-CULTURAL STUDY looked at death rates in 20 countries, including the USA, Ireland, Australia, Russia, Singapore and El Salvador. They found that men in every age group had a shorter life expectancy than women. This gap seems to be widening. The researchers have several explanations, including the evolutionary one that males take more risks, but adding two other factors:

1. Technological advances mean that men now have faster cars and more deadly weapons at their disposal; and
2. Medical advances mean that fewer women now die in childbirth, which used to be the biggest killer of young women in the past.

Need evidence for male risk-taking around the world? See this guy from Bangladesh with 22 bricks on his head.

1. Looking at any problem from a purely biological viewpoint is going to be reductionist. This doesn't have to be a bad thing. Biological reductionism can be very useful in the study of crime: it can suggest ways of screening for potential criminals (eg using PET scans) and might lead to medical "cures" for certain crimes. On the other hand biological reductionism ignores some key factors, like the criminal's motives, the social situation and upbringing. Biology only identifies certain tendencies or predispositions (like risk-taking), but lots of law-abiding people have these predispositions too. 
2. It's very hard to manipulate biological variables and even if you could, it would probably be unethical (imagine removing someone's prefrontal cortex, just to see what would happen to them).  This means biopsychologists usually have to study naturally-occurring variables, either in a natural experiment or using correlations. The problem is that natural experiments and correlations don't tell us much about cause-and-effect, just that two variables are related somehow. To find out about the causes of crime, we have to look at other approaches besides the biological approach.
3. Biological measures are based on scientific technology and produce very detailed quantitative data. For example, brain scans and hormone samples are a very objective and accurate way of investigating psychology. However, a lot of this technology is still in development, the data can be hard to interpret and the samples are easily tainted. For example, PET scanning is very sensitive to outside interference while genetic samples are easily ruined if they are exposed to anyone else's DNA.
4. The conclusions drawn from biological research can fly in the face of common sense or even be quite offensive. Some studies are too determinist, suggesting that some people are controlled by their brain dysfunctions, hormones or genes and have no control over their own behaviour. This lets criminals "off the hook". Research can also lead to prejudice and discrimination. There are ethical problems with allowing parents to terminate births that might have criminal genes or informing someone engaged to be married that their partner has criminal brain functioning.