This is a long post. I write this as a response to reactions on my shorter post on ‘Psychopathy’ as a trait dimension. In that post I had hinted, very cautiously, that some human behaviour may have a heritable, genetic component.
While many experts in the field concurred, there has been genuine criticism, for example, from my friend Jithin, a psychiatrist, and Prasobh.
These criticisms have centred on the following themes:
Human behaviour is shaped by the environment.
It is misleading to put emphasis on the heredity of mental traits.
Psychopathy is not there in DSM5.
Strangely, I agree with all these!
But, I do stick with my earlier stand too. This article is an attempt to provide a panoramic view.
In the first comment, I have given a link to a review article on Psychopathic Trait. I request everyone who is interested, to please read that.
What is Mind?
Let us just say that it is generally agreed that the term ‘mind’ is applied to the sum total of the workings of the human brain.
How do we study it?
The details of the neurochemistry, fluorescent tagging, squid neurons, sodium gated channels, and the entire messy field of experimental physiology, I simply omit. I can’t do it. I apologise. Feel free to delve into the net and drink to your fill and saturate your poor neurons.
One can make experimental lesions in animals like monkeys and find out the effects on various parts of the brain. We can use animals to study motivation, aggression, learning etc by designing mazes, rewards, deterrents and the like. We can study behaviour and how they solve problems and co-operate with each other with careful experiments.
Due to stroke, trauma, tumours, or with surgery, human patients may lose the function of parts of their brains. The disabilities produced can be observed. Brain imaging is very important in this.
Modern brain imaging like MRI, PET and indirect image of the EEG enables us to observe human brains in real time. Variations in blood flow tell us when an area of the brain gets activated. Scientists can tell the areas that light up and in what sequence it does so when a person feels happy doing something, for instance.
Purely psychological approaches- observing behaviour of subjects, studying self-reported states of the mind, and psychological experiments involving individuals or groups of people. These types of experiments involving observing behaviour under different conditions are very important in psychology.
It is to this last mentioned field of Psychology, that most complex traits of Humans, like Intelligence and personality, belong. This is the only way we can study such complex topics, though with some help from things like imaging, in recent times.
What are we?- Are we a product of our genes? By ‘we’ I mean our minds. Our emotions, behaviour, personality- what we are. Or does the environment shape us from childhood? Are we, as children, pristine clay, the world shaping us through the years and our experiences chiselling our fine lines? The so called nature versus nurture debate.
What are the concerns about emphasizing heredity in behaviour?
-It may lead us to brand people. If we brand someone a Psychopath, demands may come from the public that he or she is locked up for life. Similar screw-ups are common in history.
-This may aid socially conservative reactionaries to justify things like inequality and unfair distribution of resources in society- ‘They are like that from birth. They don’t deserve this’. Or- ‘Females are genetically, meant to do this or that’, etc.
-The pseudo science of ‘social Darwinism’ was used by despots, notably, Hitler, to argue, that some humans are inherently better than others.
-A thing called ‘Eugenics’ was popular in the USA and Europe, in the 1920s and thirties. Misguided policy makers, including some scientists, sought to categorise people on the basis of measurable things like intelligence. The ‘inferior’ people should be locked up, or even sterilized, to prevent them from having children, and thus, improving the human race! A few sterilizations actually happened!
-The Idea appears harsh and judgemental, to many people. That includes me.
So, the concerns of some liberal, good people are real.
But these kinds of nonsense and misuse are not based on real science. It is a wrong interpretation of the facts by interested parties.
Concerns exist, but they cannot be the basis for not conducting an honest enquiry.
Why should we look at the truth?
The argument that all human behaviour depends on upbringing is damaging at many levels.
-It is wrong to deny that there are variability in the inherent capacities, interests and inclinations in the pattern of thoughts and behaviours of ordinary people. It puts all the responsibility of every personal misery, on an individual’s lack of resolve to correct him or herself.
– It causes enormous misery to parents everywhere, especially mothers. They are held squarely responsible for the way their children turn out. Many generations of fathers and mothers underwent horrible guilt trips for their children becoming habitual criminals, and even Schizophrenics and Autistic ones! This folly continues today.
– The truth should be the basis of policy decisions.
Twin Studies and Adoption studies:
One of the first study in this type is called the ’Minnesota Study of Twins Reared Apart’ (MISTRA).. They have an active twin research centre, though now they cannot study twins reared apart, because adoption agencies take care to keep them together.
The original MISTRA had 81 monozygotic and 56 dizygotic twins. Monozygotic twins (Identical twins) have 100 percent similar DNA. They have identical genes. Dizygotic (Fraternal twins) twins have only 50 percent of similarity in their DNA. That is, they are just like normal siblings, but have the same age. Twin studies have a lot to tell us about the heritability of behaviour. Thomas Bouchard was the chief researcher who pioneered these kinds of studies.
Twins of both types, reared together and apart, adopted but unrelated children brought up by the same parents under identical conditions and all such similar factors have now been studied in strictly controlled conditions. Many of the results have come from massive studies in Scandinavian countries, where the authorities keep detailed databases on their citizens. These studies have used the most thorough and best validated measuring instruments known to Psychology. The main conclusions from the study are:
Identical twins are far more similar than fraternal twins, whether raised apart or together.
Identical twins raised apart are highly similar, sometimes more than when they are raised together.
Biological siblings, whether raised apart or together are far more similar than adoptive siblings raised in the same family.
Examples of how genes might have an effect on behaviour:
Mathew D Liebermann and Baldwin Way of the Psychology Department at UCLA, were reviewing research on the genes that control the brain’s serotonin system. Serotonin is a neurotransmitter. Neurotransmitters are chemicals that enable electrical signals to pass across synaptic junctions between neurons. Variation in the level of serotonin has been linked to Depression in humans.
Way discovered that individuals of Eastern and Western descent show differentially distributed variations within the regulatory region of the serotonin transporter gene- 5-HTTLPR. There are three variants of the gene- short-short, long-short, and long-long. Two-thirds of East Asians have the short-short variant, but only one-fifth of Americans and Western Europeans have it. This is a very significant difference, shown in multiple studies.
This short-short variant of the gene is related to depression and social sensitivity. Risk of depression is greater in people with this variant, who lack adequate social support.
Or if they had a stressed childhood.
Their well-being depends upon the cohesion and support with their communities. These people are likely to be more sensitive to the social environment in general.
Dopamine is a neurotransmitter that is released in response to excitement. In optimum levels in the brain, release of this chemical cause small ‘hap’ hits. It is basically part of a reward system. It makes the person want the surge again. Cocaine and amphetamines release Dopamine. It is associated with attention, alert states and learning. Excess of an effect of dopamine, is but unpleasant. Dean Hamer of the National Cancer Institute in Maryland, USA Studied a gene called D4DR. A variation of the gene, the long variant, he found was almost universally found in certain ‘novelty junkies’. They constantly seek new experiences and find happiness in taking risks. They are prone to addictions, and are impulsive. Routine just bores them to death. Their brains are less sensitive to the effects of Dopamine. So they seek out experiences that maximise its output. A group of people with the short variant are highly sensitive to this neurotransmitter. They quickly become overwhelmed with newness. They can take in very little excitement.
But please note that, here too, it is the gene-environment interaction that is important. So, the environment is crucial.
What are personality traits?
People see you as a person. Even if your appearance alters by age, disease or injury, they recognise your personality.
The personality is your feelings, thoughts and attitudes- yes. But other people can assess it only by your behaviour. A measure of personality should be able to predict someone’s behaviour, at least in broad terms.
Are there stable components to our personality? A lot of research suggests there is.
For example, in one of the accepted models, there are five major components to personality. Each component varying across the spectrum of a trait. This is only one model, and there are well studied other traits, like Psychopathy, for example.
- Openness to experience: Someone sticking to a predictable routine and at the other end seeking constant new experiences.
- Extroversion-Introversion spectrum
- Agreeableness- antagonism spectrum (A trait also deemed likability)
- Neuroticism- stability: Anxious and fearful to stable and unflappable.
People vary in their traits in a Normal Distribution. That is, most people fall in the centre, with 69 percent within one standard deviation from the mean. But there will always be people at the extreme ends.
Personality tests ask people to agree or oppose statements. “Many of my friends talk badly behind my back”, “I think it is ok not to help a person cross the street when you are too busy” etc are examples. Some may think it’s validity doubtful. But they are repeatable. Same person gives almost same responses when tested with different sets of statements. It agrees with what other people has to say about a person. They also make accurate predictions, like achievement, stability of marriage, criminality etc.
A Thing called Heritability:
Heritability of a character can be calculated in twin and adoption studies by looking at the variance, and a thing called the correlation coefficient. I will not go into the math. Better come to the crux.
The results of a multitude of well done research, was summarised by the Psychologist Eric Turkheimer as ‘the three laws of behavioural genetics’.
First law: All human behavioural traits are heritable. Heritability refers to the inheritance of variation of a trait within the human species. It turns out that intelligence is 60 to 70 percent heritable, and all the above mentioned personality factors are 50 to 60 percent heritable.
The second law: The effect of being raised in the same family is smaller than the effect of the genes.
The third law: A good portion of the variation in complex human traits is not accounted for by the effects of genes or families.
A good portion of the variation in complex human traits is not accounted for by the effects of genes or families.
We saw that slightly more than 50 percent of our traits are innate or genetic. But let us not forget that it leaves a substantial 40 to 50 percent as environmental effects.
Just to give perspective, remember that height is 90 percent heritable, in advanced societies.
What puzzled researchers in twin and adoption studies are that the ‘shared environment’ had only a measly 10 percent effect on the various facets of personality. Shared environment means the parents and immediate family. Going by the example given above, the peers and the general cultural environment has a big influence. More than parents. Many unfortunate immigrant couples have found this out the hard way.
What was even more frustrating was the fact that among twins and siblings, most of the peer group and environment is similar. That still leaves a good 30 percent of variation between them unaccounted for. What is this mysterious factor?
No one knows for sure. Psychologists call it ‘the unique environment’ or non-shared environment. It is actually random chance. It could be the spontaneous differences in brain wiring, later accentuated by the person’s unique responses to events and experiences. Call it free will. Whatever you name it, we are not fully determined manufactured cars that will run just as predicted.
Environment is very important!
By the eighties and nineties, neuroscientists reached the conclusion that the brain is a fixed machine that is fully formed by five or six years of age. Neurons cannot replicate. They cannot be renewed. Separate brain regions cater to different functions. They cannot be altered. These conclusions have been proved wrong, by modern imaging and methods of study.
New neurons are formed in the Hippocampus of the brain.
The brain is a computational organ that keeps changing throughout our life. New connections are formed and old synaptic connections are pruned away. The prefrontal cortex that is concerned with long term planning and social functioning goes on growing and maturing till the twenties and early thirties.
The sea gypsies are a tribe in Southeast Asia that practically live in the seas. They learn to swim before they can walk, and dive for collecting sea cucumbers and shellfish. They can hold their breaths underwater for record times, and see clearly under water. Our pupils dilate under water as a reflex. The sea gypsies constrict their pupils to more than 20 percent normally possible, to achieve this feat. Constricting pupils is supposed to be a hardwired unconscious reaction.
We know that arm wrestlers have awesome biceps in their competing arm. This is due to the work that it is put to. But do you know that London taxi drivers have measurably bigger posterior hippocampus in their brains to store complex routes and spatial information? This study was done by Eleanor Maguire and Katherine Woollet. It has been proved that new neurons are constantly produced in the Hippocampus, cerebellum and possibly other areas in the adult human brain.
Optometrists can put prismatic lenses in reading glasses that inverts images. If you put these glasses on, whatever you see looks upside down. You can read books the wrong side up and amaze your friends. But if you keep wearing them, the brain rearranges the images so that your view of the world rights itself. Walk around like that for some days. Then remove the glasses. Lo! Everything looks upside down! We can read the newspaper upside down without glasses now. The friends will be even more amazed. Fortunately for you, this is temporary.
In addition to brain plasticity, the Heritability is sensitive to social factors. It seems that there is a threshold on the notion of ‘Ideal environment and upbringing. Above that threshold, the heritability factor of a desirable trait like intelligence increases. In middle class children and above, the Heritability for intelligence is 60 percent, but it is seen that in Socio Economically deprived children, it is only 40 percent! The same kind of change is noticed in the trait of height! This is very important. It shows that it is the society that has to ensure that minimum standards are made available to each and every child!
Psychopathy and DSM
Psychopathy is a well established trait dimension in Psychology.
DSM is just a consensus method of classifying mental disorders, so that we can intervene when needed. It is not a comprehensive exposition on Psychology.
It is a categorical, and not a Dimensional classification system. While many variables, like Depression, and Psychopathy, for that matter, are definitely continuous variables. DSM aims to provide a cut-off, above which, intervention may be desirable.
The Psychopathy is omitted from DSM for reasons of political correctness and to avoid judgemental labelling. The term Sociopathic Personality Disorder aims to capture the behavioural and rule- violating nature of this trait, without going into the affective, or consciencelessness and thought aspects.
(The points on Psychopathy are well expostulated in the Reference:
THE CRIMINAL PSYCHOPATH: HISTORY, NEUROSCIENCE, TREATMENT, AND ECONOMICS