At one time or another every parent is struck by the differences between their children. Not only will they vary in physical appearance, but in character, temperament and intellect. One may be tall and slim, another short and tubby. Perhaps their first son is a dreamy introvert who loves stories, while his younger brother is a boisterous extrovert who cannot sit still for five minutes. But what explains such differences? Are they inborn or the result of different experiences? This is known as the nature-nurture debate.
Ask a group of psychology professors which side they take and you may be shocked by the anger the debate arouses. In essence, the question is this: is an individual's psychological make-up, personality and temperament determined by their genes or by the things that happen to them? Of course, few believe that everything can be explained solely by genes or environment. Even those who believe personality is mostly inherited will admit that a beaten and unloved child is more likely to suffer poor self-esteem than one who is loved and cared for; and those who believe that environment is key will admit that it is no coincidence when a Mathematician's son excels in his father's subject.
Behaviorists, for example, largely disregard genetics and focus on environmental influences instead. For them, most of our behavior can be explained by conditioning. Abraham Maslow also favoured nurture over nature, emphasizing the way society influences a person's sense of self. At the other end of the spectrum are those who focus on genetics and try to relate specific genes to specific characteristics – if there is a gene that determines your height, weight and vulnerability to breast cancer, then maybe someone's temper or lack of confidence can also be traced back to a gene. The Psychoanalysts, however, emphasize both nature and nurture: Freud's sexual and aggressive drives are hard-wired, but what happens during the crucial psychosexual stages is obviously down to the parents.
Those who emphasize nature over nurture are sometimes referred to as nativists. In arguing their case, they would probably begin with what is known to be genetic. So, for example, John's curly hair, dark skin, and brown eyes are inherited. They have nothing to do with his upbringing. If that is so, then maybe his shy, introverted nature is also inherited. Critics would point out that genetics has so far produced little evidence to support such a claim. The nativist would reply to this criticism with two words – 'not yet!'
Many people instinctively recoil from the nativist position. If it is true, they say, then what is the point of psychotherapy and counselling? If we are trapped by the genes we inherit, then no one can hope to change. The nativist argument has proved especially controversial when applied to IQ. Professor Arthur Jenson, for example, argued that African-Americans scored lowest on IQ tests because they were genetically different to Asians and whites. Others replied that the tests were biased and that African-Americans had less opportunity to develop their intellects because of poverty and bad schooling. Jenson in turn replied that intelligence is 80% inherited and so this could not be the case.
Critics also argue that should the nativists be proved right it would bolster the argument in favor of eugenics. For example, if it could be proved that criminals inherited their urge to rape and steal, should they be discouraged from having children? If empathy is inherited and cannot be nurtured, no matter how much love and kindness is shown to a child, should those who lack the empathy gene also be discouraged? It is worth remembering that eugenics wasn't always a dirty word. Before the Nazis discredited it in the mid-20th century, many moderate, progressive thinkers supported eugenics – even men like Aldous Huxley and Bertrand Russell.
In general, those who take the nurture side argue that not only is our behavior and psychological make-up shaped by what happens to us (even in the womb), but that we should be glad this is so. If someone's depression and anxiety can be traced back to the messages they absorbed as children, then perhaps they can be 're-programmed'. One of the most famous experiments in favor of nurture was conducted by the American psychologist Bandura in the 1960s. Using inflated 'Bobo dolls', he demonstrated how children learn to be aggressive by imitating the behavior of adults. Of course, this only proves that aggression can be learnt; it does not prove that aggression cannot also be inherited. Others would argue that certain children inherit a predisposition to be aggressive and that those are the ones most likely to imitate the aggressive adult.
This debate remains as controversial as ever. In 2016, for example, the British Psychologist Oliver James published a book with the provocative title Not in Your Genes. James argued strongly in favor of those on the nurture side. In the radio discussions and newspaper columns that followed, tempers quickly frayed. James argued that, while hair and eye color may be inherited, geneticists had completely failed to prove that things like schizophrenia, promiscuity or alcoholism had anything to do with genes. He even insinuated that this fact has been suppressed by the scientists and drug companies in their own interest. Critics soon hit back. The geneticist Stuart Ritchie, for example, accused James of scientific illiteracy and pointed out that it was still very early days. After all, argued Ritchie, the human genome project wasn't completed until 2003.
Most scientists would more or less agree that you are you because of a complex interplay between genes and environment. So closely intertwined are the two that it is absurd to try and separate them. For example, when a serial killer strikes, people demand answers. They want to know how such a thing could happen. What on earth creates such monsters? Are they born that way? Or is it down to a childhood of abuse and neglect? It now seems clear that such people do inherit this urge. In other words, a psychopath can be born that way. But such predispositions then have to be 'switched on' – which demands a certain kind of environment. And that seems to be true of human psychology in general.