Picture the scene: you’re sat down relaxing one day, when your phone rings. You answer – it’s a good friend of yours. She explains that she needs to predict how happy someone will be in ten years time. She heard that you read some articles about happiness on the internet, and wants your help. She’s rushed – it’s very important and you only have time to offer one suggestion. What one piece of information is the best way to predict someone’s happiness, ten years down the line?

Really think about this. What would you suggest? Their income level? Whether they’re married? How good their health is? What line of work they’re in? Which country they live in?

The surprising truth is that the most accurate single predictor of how happy someone will be in ten years time, is how happy they are right now. What’s the one thing that stays with you for all this time, and doesn’t change at all? No, not your taxes. It’s your genes: the DNA code inside every one of your cells. Your genes are the recipe for how to make a you. Research has shown that about 50% of the variation we see in happiness is down to variation in genes.

There’s a common misunderstanding that if something is said to be ‘genetic’, then it is also fixed and unchangeable – this isn’t true. When people talk about genes vs environment, an analogy could be building a house. Genes are the blueprint for a house, and environment is how and where it is built.

Take that blueprint, and give it to different contractors, build it in different locations, different weather conditions, and it will come out differently each time. The houses won’t be completely different – they do have the same blueprint after all – but changes will have to be made. Likewise, a gene doesn’t dictate how something will definitely end up in the real world. Genes are more like instructions for the living things that host them, telling them how to respond to different stimuli they might come across.

For example, at some point in evolution, muscles developed the ability to grow bigger and stronger when they are being worked harder than normal. This helped us adapt to our environments, which allowed us to survive. The recipe for this system is contained in the genes. Put simply, it probably goes something like this: “If muscle is under x amount of stress, increase it’s size by y.”

There’s a genetic element to muscle growth. The genes will ‘tell’ the organism how much they should grow by; how much of certain hormones to release, how much protein to synthesise, what stress threshold the muscles need to be under for this process to begin, and things like that. This is all genetic. But there’s also an environmental element – if you don’t exercise, the genes won’t get activated. There isn’t a gene ‘for’ big muscles as such, but rather genes for a system that makes muscles easier to build – if conditions are right.

The way to find out how much of something is caused by the blueprint and how much by the environment is to study twins. Identical twins have 100% of the same genes. Non-identical twins share about 50% of their genes. When twins are brought up together, you’ll often find that they grow up in a very similar environment – they usually get the same room, wear similar clothes, are in the same school, and so on.

When identical twins are separated at birth and brought up separately, their environments are very different. Not completely different of course: you don’t send one twin to live with a middle-class family in Berkshire and the other off to hunt seal with the Inuit. They’ll both probably live in a house, have a family, work for money etc. But it’s a different house, different family, different job – maybe even different values.

How do genes influence happiness?

You can discover the influence of genes on just about any trait by comparing twins. But we’re talking about happiness at the moment.

If you correlate the happiness levels of identical twins who have been reared together, you find there is a strong relationship. If one twin is generally happy, the other usually is. If one twin is generally unhappy, the other usually is. Fairly predictable finding, since they share the same genes and the same environment.

But interestingly, this correlation is almost as strong when identical twins are separated at birth and reared apart.

If you do the same test with non-identical twins, the results are very different. Remember, non-identical twins share 50% of their genes. This time, the correlation is much smaller. In fact, the correlation for non-identical twins brought up together, is only half that of identical twins reared apart.

This means that the genes we are born with are having a strong effect on how happy we are. As I mentioned earlier, the studies suggest that about 50% of the variation in happiness is caused by genetics – although you’ll never get the exact figure.

Just as with the muscle example above, this doesn’t mean is that there is a ‘happiness gene’. It just means that some inherited traits are guiding us to a particular range of happiness.

The question is, how do they do that? Maybe they trigger more activity in the left hemisphere of the brain, which is associated with positive emotions. Or maybe our inherited personality leads us to do certain things. As an example, social relationships are a source of happiness. Extraversion is a personality trait that leads people to be more sociable (among other things, like taking more risks and being impulsive). And extraversion happens to be strongly heritable.

So there’s a genetic side to happiness, but there’s no reason not to worry. ‘Genetic’ doesn’t mean ‘fixed’. Plus, 50% leaves does leave a lot of leeway, and remember that, these twin studies are never done on people who deliberately and consciously try to make an improvement in a particular domain. So who knows what the effect of a conscious, persistent and long-term attempt to increase happiness would be?

Recommended Reading:

• The How of Happiness: A New Approach to Getting the Life You Want

References

Lykken, D., & Tellegen, A. (1996). Happiness is a stochastic phenomenon. Psychological Science, 7, 186-189.

Tellegen, A., Lykken, D. T., Bouchard, T. J., Wilcox, K. J., Segal, N. L., & Rich, S. (1988). Personality similarity in twins reared apart and together. Journal of Personality and Social Psychology, 54, 1031-1039.

This entry was posted on Monday, March 16th, 2009 at 11:26 pm and is filed under Happiness and Well-Being.