Where does this theory come from?
According to Jasper Bergink, a 1996 study by Lykken and Tellegen compared well-being levels of samples of pairs of identical and non-identical twins in Minnesota, either raised together or apart. This differentiation allows to test both the impact of same or different genetics (identical vs non-identical) vs same or different environment (raised together or apart), e.g. both nature and nurture effects. Namely, identical twins share the same genes, and non-identical ones do not.
Lykken and Telleken found that the correlation of levels of well-being of identical twins in both cases are around 50%, significantly higher than for non-identical ones (2-8%). As such, they conclude that around half the variation is determined by genetics. This would leave another half determined by other factors. But it is important to note that this particular study has a limited sample. The smallest groups consists of only 36 pairs or 72 people. From a sample of twins in Minnesota, it is hard to draw so strong conclusions for human population as such.
The variance in happiness is not the full answer. In a comment of the preference of positive psychologists to favour well-rounded figures, Todd Kashdan in an article notes a couple of other issues with genetics.
The first points is that personal traits – influenced by genetics – are not stable over life. Traits are shaped by a process called ‘emergenesis’. When a characteristic is ‘emergenic’, it is affected by the interaction of a couple of genes together. This might result in a behavioural predisposition to be extravert, self-controlled, or any other trait. Kashdan goes on to contest that toxins or nutriments in a person’s environment can switch genes ‘on’ and ‘off’. In turn, the functioning of an individual gene can affect such an emergenic factor. If you add or take away a block from a tower, it will look different.
Genes interact with the environment
According to Kashdan, another important issue is the interaction of genes and environment.
Much of what influences our personality has to do with the presence of (positive and negative) life events and our response to choice points. Do I approach or avoid my co-worker who regularly demeans me? Do I wake up early and workout or sleep in? Do I ask out the girl I’ve had a crush on for months or do I keep my feelings to myself? No single decision matters but the patterns do. The decisions we make, the people we surround ourselves with, and the behaviors we engage in, are the building blocks for the quality of our lives. Small changes accumulate over time leading to large changes in who we become.
Our personality is the result of a complex process, in which genes and environment interact. Can we really put a hard number on that?
Happiness is not a formula
Jasper Bergink, concludes: What we can say, is that our genes play an important role in determining happiness. But so do other factors, including our circumstances, environment, and our actions.
Happiness is not a hard science.
It is a way too complex phenomenon to quantify.
But maybe that’s one of the reasons why it is so fascinating.