The Anatomy of Violence (37 page)

Figure 7.1
   Scores on
externalizing behavior problems in malnourished and control groups across three time periods

The type of malnutrition the kids had did matter a bit, though.
Iron deficiency was especially important. This ties in with findings from
experimental studies on animals showing that iron is involved in
DNA synthesis, neurotransmitter production and functioning,
¹¹
and white-matter formation in the brain.
¹²
If iron benefits the brain, low iron should be a problem. And it is. Experimental studies that have supplemented children’s diets with iron show improved
cognitive functioning.
¹³
My
angular stomatitis, which reflected a vitamin B
₂
deficiency, would also play a helping hand in poor cognition, because vitamin B
₂
enhances the hematological response to iron.
¹⁴
Consequently,
riboflavin deficiency would reduce iron and further negatively affect cognition. Eat your vitamin-fortified cardboard cornflakes.

It really does seem that poor nutrition, right across the board—across
ages and types of problem behaviors—raises the odds of behavior problems in the growing child. But we get back again to a central, fundamental question. What is the mechanism of action, the way in which nutrition—or rather the lack of it—translates itself into aggressive and antisocial behavior? Back to basics. Back to the brain, and back to cognitive functioning.

Figure 7.2
   Dose-response relationship between
signs of
malnutrition at age three and behavior problems at age seventeen

Jianghong Liu found that the children with poor nutrition at age three also had
lower IQs at that age and eight years later at age eleven. She again found a dose-response relationship, with increasing levels of malnutrition resulting in decreasing scores on IQ. If a child had three indicators of malnutrition, her IQ dropped seventeen points. It’s a significant tumble: imagine being average in your class and dropping to the bottom 11 percent—not because of who you are, but because of what you don’t eat. It did not matter what type of cognitive ability we looked at, malnutrition had an influence on verbal IQ as well as spatial (nonverbal) IQ.

In Mauritius, as in my day at primary school, they take national examinations at age eleven to decide what type of secondary school they will go to. The exams are in English, French, mathematics, and environmental studies. It really decides the rest of these children’s lives.
We looked at their performance on these standardized national examinations, and again we found that poor
nutrition drives down academic scores in a dose-response fashion. The same thing with neuropsychological test functioning at age eleven, and the same thing with reading ability. Poor nutrition sinks school performance and neurocognitive functioning. And yes, we know that poverty and parental education is linked to both IQ and poor nutrition, but controlling for multiple social adversity indicators like these did not alter the relationship. We could not escape the fact that nutrition is in its own right
absolutely critical
for kids to do well in all realms of intellectual life, and has real-life consequences in determining what level of secondary education the kids end up getting.

From nutrition to cognitive functioning and back to behavior problems. We are on our way to a part-answer to the core question of “What is the mechanism of action?” Does poor nutrition make a dent in cognitive functioning? And do dull wits turn kids to vandalism and antisocial activities? It seems that they do.
Liu statistically controlled for the fact that kids with poor nutrition have lower IQ.
¹⁵
This technique makes the good and poor nutrition groups equal on intelligence. When that is done, the group difference in antisocial behavior disappears. This vanishing trick identifies poor cognition as a likely mechanism. Poor nutrition leads to low IQ, and this lowering of cognitive ability leads to antisocial behavior.

And it makes sense. You can imagine how low IQ can lead to school
failure. You likely did well in school, but imagine what it’s like to instead go in every day and get stuck on your reading, get your mind numbed with numbers that don’t add up, while all the time most other kids seem to be doing just fine. Day in, day out, you’re a failure. A failure for weeks, for months, for years.

It’s easy to see how this can result in low self-esteem and a loss of hope. No wonder such kids try to bail out and kick back against the institutional system once they gain the muscle to rebel. Note here that just because poor nutrition acts negatively on the brain to predispose someone to aggression, we are not saying no to social factors altogether. Indeed, poor nutrition is very much an environmental factor. We see here that a negative environment—not getting enough of the right food—results in poor brain and cognitive functioning, which leads some kids down the primrose path to crime and violence. And as we are about to see, it’s something of a slippery slope.

Strange stories abound when it comes to trying to explain violence and other devious behavior. Perhaps one of the strangest circulating at the moment is that it’s all to do with how much fish we eat. This may sound odd, but if we take a close look at the data, what your grandma always told you may be literally true—that fish food is brain food. And if something affects the brain, it’s up for grabs as a causal agent in crime.

We’ll begin with a topic in criminology that does not receive as much attention as it should. Why do countries around the
world differ so much in violence, and what’s the cause of these
differences? There are plenty of ideas, old and new. Differences in unemployment rates do not seem to explain international differences in
homicide and, perhaps surprisingly, neither does urbanization.
¹⁶
A lot of emphasis has been placed on social processes and for good reason, as the correlational data supports it. As we might expect, gross domestic product (GDP) is a strong correlate—the lower the GDP, the higher the violence: a correlation of .68. It really makes sense if we think of
poverty as a cause of crime, because a higher GDP goes along with political development, increased democracy, and better education of the people.

A different social mechanism—
income inequality—endorses this social perspective. As measured by the
Gini index, the higher the income inequality, the higher the homicide rate—a correlation of .57. So the more a country is divided into the haves and the have-nots, the higher the homicide rate.
Denmark, Norway,
Sweden, and Japan all have relative income equality and low homicide, while countries like
Colombia,
Botswana, and South Africa have high inequality and high homicide, with the United States in between on both counts.

Interestingly, psychological beliefs also play a role. Some people prefer money, while others prefer
love. What would your own pick be? We all differ to some degree, and just like individuals, countries as a whole differ from each other in the relative value they place on love, on the one hand, versus social status, good financial prospects, power, and status on the other. In countries where people believe love is more important than money, there is less violence. Perhaps the
Beatles were not far off the mark—all you need is love.

But we need to eat as well as make love. And this is the fishy part. Countries differ an enormous amount in how much fish they eat, just as they differ in their homicide rates.
Joe Hibbeln, a leading fish-oil
expert working at the
National Institute on Alcohol Abuse and Alcoholism in the United States put yearly homicide
rates and
fish
consumption together. He found that they were negatively related—at a correlation level of -.63.
¹⁷
Take a look at
Figure 7.3
. It does look as if something may be going on here. Take Japan. They have very low yearly homicide rates—only one homicide per 100,000 people—and they eat well over their own body weight in fish every year. Then you look at eastern European countries like
Bulgaria. They eat a measly four pounds of fish a year and rack up homicide rates ten times that of Japan. If you pick out the East Asian countries, they almost follow a straight line, with
China at 4.3 homicides/100,000;
Singapore at 3.8;
South Korea at 3.0; and Japan at 1.2. The greater the fish consumption, the lower the homicide rate.

Figure 7.3
   Relationship between seafood consumption and homicide rates across the world

I showed Joe Hibbeln’s provocative data in a talk I gave to the
Criminology Department at the University of Pennsylvania in 2005 when I was being interviewed for a job, and one provocative question posed was, “Wait a bit, where’s America here?” The United States was not on the graph of twenty-six countries. My colleagues-to-be didn’t exactly smell a rat, but felt it was a bit of a slippery story. So they went and looked up the data for the United States for the year in question, and
what did they find?
Fish
consumption right in between the two least-fish-consuming countries, Hungary and
Bulgaria, and with homicide rates way up at 9 per 100,000, right next door to the eastern European countries. The correlation of -.63 was large and just as strong as that between GDP and homicide rates.

Explaining differences in violence across countries in the world is one thing, but such explanations may or may not apply to variations in offending
within
a country. Yet even within countries there is evidence that variation in fish consumption is related to antisocial
behavior. In a very large sample—11,875 pregnant women from Bristol, England—women who ate more fish during pregnancy had offspring who showed significantly higher levels of
prosocial
behavior at age seven.
¹⁸
Put another way, the offspring of mothers who did not eat much fish during pregnancy had more antisocial behavior.

In the United States, a study of 3,581 people from
Chicago, Minneapolis, and Birmingham, Alabama, showed that those who hardly ever ate fish had higher levels of hostility than those eating fish at least once a week.
¹⁹
There are also more behavior problems and temper tantrums in boys with lower total fatty-acid concentrations as measured from blood.
²⁰
The same is true of aggressive
cocaine addicts.
²¹
Even
dogs with low levels of omega-3 have been shown to be more aggressive.
²²
Giving your dog omega-3 may do more than give it a sleek, shiny coat.

Let’s just suppose for a minute that this is a causal relationship, that bolting down boatloads of sushi and salmon somehow stops you from blowing your fuse. How on earth could this be possible from a scientific standpoint?

There is a reasonable answer based on experimental
studies that
manipulate the amount of omega-3 that rats have in their diet.
²³
Recall from previous chapters that violent offenders have brain structural and functional impairments as well as neurochemical deficiencies. Fish is inevitably rich in fish oil. Fish oil, in turn, is rich in omega-3—a polyunsaturated long-chain fatty acid. Omega-3 has two important components—DHA (
docosahexaenoic acid) and EPA (
eicosapentaenoic acid). What does DHA do? It is known to play a key role in neuronal structure and function. Making up 6 percent of the dry cerebral cortex, it influences the functioning of the blood-brain barrier that regulates what gets into your brain from your bloodstream. It enhances synaptic functioning, facilitating communication between brain cells. It makes up 30 percent of the membrane of your brain cell and regulates the
activity of membrane enzymes. It protects the neuron from cell death. It increases the size of the cell.

DHA also stimulates neurite outgrowth. There is more intricate dendritic branching in the
neurons of animals fed a diet rich in omega-3 compared with those fed a normal diet. Dendrites of the cell receive signals from other
brain cells, so this dendritic branching translates to more connectedness between cells. The axon that transmits the electrical signal to other cells is longer and has a better sheath to conduct the electrical impulse. DHA regulates
serotonin and
dopamine neurotransmitters, and we saw in
chapter 2
that offenders have abnormalities in those neurotransmitters. We also know that DHA is involved in regulating gene expression,
²⁴
so in theory it can help turn on genes that protect against
violence—or turn off genes that increase the probability of violence.