We Are Our Brains (26 page)

Throughout history, many metaphors have been used to describe consciousness of surroundings, like the “Cartesian theater,” “the film in your head,” and “a TV screen.” But they are all based on the dualist notion that there's a little man in your head watching the images.
It is a curious idea, not least because it raises the question of what is in the head of the little man. Another little man? No, we just have an amazing network of neurons.

John Eccles, who in 1963 won the Nobel Prize for his research into synaptic transmission, simply could not accept the idea that the neural network was responsible for consciousness. Instead he devised a theory (philosophical rather than neurobiological) that the neural units of the cortex were linked to mental units called “psychons.” He believed that these psychons acted on the cortex in “willed” actions and thought and that their common activity gave rise to consciousness as an integrated mental process. No one actually knows what a psychon is. That makes it untestable as a theory and therefore, from a scientific point of view, an unacceptable hypothesis. It is, moreover, entirely redundant. All recent research suggests that the joint activity of enormous numbers of neurons in communication with a number of brain areas provides the foundation for consciousness.

Consciousness can be seen as an emergent characteristic generated by the joint functioning of specific areas of the huge network of neurons in our heads. Brain cells and areas have their own separate functions, but their functional links with one another jointly endow them with a new, “emergent” function. There are many examples of emergent characteristics. For instance, we know hydrogen and oxygen as gases. But when these molecules bind, a substance with entirely different characteristics emerges, namely water. The question of what exactly is needed from a neurobiological point of view to enable this new characteristic, consciousness, to emerge from neural activity is something that preoccupies many brain researchers. The Amsterdam neuroscientist Victor Lamme is looking for an explanation in the functioning of neurons. His theory is that for consciousness to exist, neurons in the prefrontal and parietal cortices have to relay information back to the cerebral cortex. One of the routes involved is via the thalamus. This recurrent processing extends from the purely sensory to the motor areas. Lamme believes that the selective attention crucial to our consciousness emerges because only
a few of the objects that we perceive undergo recurrent processing. So we report on the stimuli on which our attention is focused while being unaware of the rest. There's no reason to assume that basic mechanisms like recurrent processing and attention aren't common to all animals, albeit to varying degrees. The philosopher Daniel Dennett seeks to explain consciousness as a purely bodily, chemical phenomenon, a view I share. However, he also believes that humans have a different
kind
of consciousness than animals because of the far-reaching impact of our linguistic development. I think it's more logical to assume that animals have a different
degree
of consciousness. And although there are differences between species in this regard—a magpie's ability to recognize itself in a mirror is far removed from a dog's ability to distinguish the smell of its own urine from that of another dog—animals can be said to possess rudimentary self-consciousness. In humans, consciousness doesn't depend on language, by the way. People whose language areas have been disabled after a stroke are still fully conscious of their surroundings and of themselves. By nodding or shaking their heads they can make considered decisions, even if they can no longer verbalize them.

The importance of being conscious of your surroundings and of yourself is primarily expressed in social interaction, which involves observing and constantly interpreting your situation compared to others and learning from the mistakes that you make in this process. And that brings us back to Charles Darwin and Frans de Waal, who pointed out the enormous evolutionary importance of individuals being able to function well in the complex social interaction of the group (see
chapter 20
).

Humankind is an aggressive species, just like chimpanzees. It's not for nothing that we share ancestors. In the 1960s and 1970s there was a universal belief in social engineering. Give everyone a good environment in which to live, and aggression and crime would disappear overnight. Anyone who thought differently was publicly reviled. Now that it's once again permissible to consider the biological background to our behavior, we can also look at the question of why one person is more aggressive than another and why some are more likely than others to commit crimes.

Boys are more aggressive than girls. That's something that's determined before birth. The peak in testosterone that male fetuses produce halfway through pregnancy makes them more aggressive for the rest of their lives. Girls with adrenal gland abnormalities that cause them to produce too much testosterone before birth are also much more aggressive later. And hormone-like medicines taken during pregnancy can raise the aggression levels of both boys and girls.

Some children are, however, markedly more aggressive than others, and they are more likely to commit crimes: 72 percent of young offenders in Dutch prisons have been sentenced for crimes of aggression. A strikingly high incidence of psychiatric disorders was found among this group—as high as 90 percent in the case of adolescent males. Besides antisocial behavior, there is a strong link between delinquency and addictive substance abuse, psychoses, and ADHD. Genetic factors are also influential, as has been shown from studies of twins. Tiny variations in the DNA (polymorphisms) of the gene for proteins that break down chemical messengers in the brain can lead to more aggression, alcoholism, or violent suicides. A reduction in the activity of the chemical messenger serotonin is linked to greater aggression, impulsiveness, and antisocial behavior. Some Chinese men have been found to carry a tiny variation in a gene involved in processing serotonin that is linked to extremely violent crime, antisocial personality disorders, and addiction to alcohol and other substances. Another variation of the same protein increases the likelihood of borderline personality disorder, which can also be marked by impulsiveness and aggression. So our genetic background can contribute significantly to our aggressive and criminal behavior later.

A fetus's surroundings also affect its later propensity for aggression. Tests establishing fitness for medical service showed that men who had been severely malnourished in the womb during the Dutch famine in the winter of 1944–1945 were two and a half times more likely to have an antisocial personality disorder (see
chapter 2
). Malnourishment in the womb still occurs, even in our affluent society, when a placenta malfunctions. A combination of genetic factors and a mother's smoking during pregnancy can increase a child's risk of ADHD by a factor of nine, and ADHD is associated with greater aggression and a greater likelihood of delinquency (see
chapter 2
).

It's not just our level of aggression that's largely determined before birth. This isn't a new idea, simply one that was regarded as taboo when faith in social engineering was at its highest. Charles
Darwin (1809–1882) came to the same conclusion in his autobiography, writing that he was “inclined to agree with Francis Dalton [his cousin] that education and environment produce only a small effect on the mind of anyone, and that most of our qualities are innate.” That puts the potential influence of parents and a host of well-meaning social organizations in the right perspective (see later in this chapter).

We're born with different propensities for aggressive behavior depending on our gender, our genetic background, the amount of nourishment we received from the placenta, and our mother's consumption of nicotine, alcohol, and medication during pregnancy. The likelihood of our displaying uninhibited, antisocial, aggressive, or delinquent behavior increases in puberty as testosterone levels rise. And there are considerable gender-based differences in such behavior. Men are five times more likely than women to commit a murder. Moreover, men murder a relative or acquaintance only in 20 percent of cases, as opposed to 60 percent of cases for women. The age at which men commit murders follows a stereotypical curve. As testosterone levels rise during puberty, so too does the incidence of murder. This peaks around twenty to twenty-four years, then declines to low values around fifty to fifty-four years. An identical age pattern for murders has been found in very different parts of the globe, from the United States to England, Wales, and Canada. The decline in criminal behavior among people in their late twenties doesn't mirror declining testosterone levels but is attributed to the late development of the prefrontal cortex (
fig. 15
), which restrains impulsiveness and promotes moral behavior. A logical consequence
would be to apply adult criminal law only when this brain structure is mature, around the age of twenty-three to twenty-five. However, politicians take no account of this development pattern, preferring to drum up votes from a fearful electorate by urging just the opposite—that is, lowering the age of criminal responsibility. The functioning of the prefrontal cortex is inhibited by alcohol, which can lead to sudden, mindless violence after a night out. Damage to the prefrontal cortex in the first years of life can also disrupt social and moral behavior later in life.

Testosterone stimulates aggression. Some men have higher testosterone levels than others and are therefore more likely to become aggressive. Men imprisoned for rape and other violent offenses have been found to have higher levels of testosterone than other types of offenders, and these levels are higher in prisoners in general and in military recruits with antisocial behavioral tendencies than in the rest of the population. The same link between higher testosterone levels and greater aggression applies to female prisoners too, by the way. The aggression shown by hockey players during games can easily be measured by the incidence of blows with sticks. Here, too, a link has been found between aggression and blood testosterone levels. So it's worrying that such huge amounts of anabolic steroids are currently taken in the world of sports to increase muscle mass, because this hormone also increases aggression.

Environmental factors play a role, too. Violent films and computer games have recently been shown to heighten aggression. Interestingly, the same effect is produced by reading biblical passages in which God sanctions killing (but only in people who are religious). What's more, physical factors like temperature and light greatly affect our actions. Everyone knows that long, hot summers can spark violent incidents. The influential factor in decisions to go to war turns out not to be military strategy but the amount of daylight and the temperature. This emerged from Gabriel Schreiber's study of 2,131 conflicts in the last 3,500 years, which found a pattern of annual rhythms. For centuries, the decision to declare war has largely
been made in the summer in both the northern and southern hemispheres, while season didn't play a role in equatorial regions.

Factors such as a deprived background and lack of education have of course long been known to contribute to aggression and delinquent behavior. Indeed, these are the only factors to have been researched in previous generations. When the Italian criminologist Cesare Lombroso (1835–1909) was accused of paying too little attention to the social causes of crime, he answered that this had already been done by countless academics, adding that it was “pointless to prove that the sun shines.” Until recently, the Dutch Ministry of Justice also focused only on the social causes of crime, but it's now showing interest in other factors that increase levels of aggression and the likelihood of criminality.

Rules on criminal liability have been in place ever since Daniel M'Naghten killed the British prime minister's secretary in 1843 and—to the general shock of Victorian England—wasn't jailed but put in a lunatic asylum. Under the “M'Naghten rules,” as they came to be known, criminals with mental disorders could be judged “guilty but insane” and placed in a secure hospital facility rather than sent to prison. Yet although we agree that such individuals can't be held criminally liable, prisons today are full of people with psychiatric or neurological diseases. According to the Dutch forensic psychiatrist Theo Doreleijers, 90 percent of young people in prison have a psychiatric disorder, and 30 percent of individuals detained under hospital orders have ADHD.