Can Temperament Change? What the Research Says

How many times have you promised yourself that next time you would react differently, and next time it turned out exactly the same? That experience sits behind most questions about changing temperament, and the answer is neither "you can" nor "you can't". It is more accurate to split temperament into two parts, because one of them holds for a lifetime and the other shifts even without you noticing.

The professional view of this difference was summed up best by the psychologist Mary Rothbart. In her account temperament is made up of reactivity, meaning what fires in you on its own, and self-regulation, meaning the ability to slow that reaction or steer it elsewhere. Reactivity is largely a given. Self-regulation develops from an early age onward and in adulthood can be trained on purpose.

What twin studies show

Behavioral genetics tackles a simply worded question: how much of the difference between people is down to genes and how much to environment. The strongest tool is twins, above all identical twins raised apart. If two people with the same genetic makeup stay similar after years in different families, it is hard to credit that to upbringing.

Thomas Bouchard and Matt McGue summarized this literature repeatedly, among other places in a 2003 review. The result holds remarkably steady across studies: roughly half the differences between people in personality traits are explained by genes, the rest goes to environment. And here comes the first surprise. The environments that make the difference are mostly what is called non-shared. In other words, siblings growing up in the same household are not much more alike than randomly chosen people once you subtract the genes.

It is only fair to add what that number does not mean, because this is where most arguments about heritability break down. It is not a claim that half your character comes from genes and the other half from upbringing. Heritability is a statistic about a group, not about an individual: it describes what portion of the differences between people in a given population is linked to genes. About you personally it says nothing at all and it predetermines nothing. In a stable environment where everyone has similar conditions the value even rises, because the only thing left to explain the differences between people is their genetic makeup.

For temperament in the narrower sense, meaning pace, irritability and emotional reactivity, the heritable component tends to be higher than for learned attitudes and values. This very difference is why psychology describes temperament and character separately and why each is worked with differently. The details are covered in the piece on the difference between temperament, character and personality.

The second pillar is the work of Jerome Kagan. Even in four-month-old infants he distinguished highly reactive from low-reactive children by how strongly they responded to new stimuli, and then followed them for years. High reactivity predicted reserve and caution at a later age, but not as straightforwardly as you would expect. Only some of these children, roughly a third, carried marked reserve into later years. The rest landed somewhere in between. Almost none of them, though, flipped to the opposite extreme and became a carefree type nothing can rattle.

Personality matures even when you do not notice

Alongside heritability stands a second question: what happens to traits over time. The answer was offered by a large meta-analysis published by Brent Roberts, Kate Walton and Wolfgang Viechtbauer in 2006. They went through dozens of long-term studies and tracked how average trait levels shift with age.

What came out is a pattern known as the maturity principle. Over the course of adulthood people on average gain in emotional stability, conscientiousness and social dominance. Openness to new things peaks in younger adulthood and declines slightly later on. The changes are not dramatic, but they run in the same direction for a large part of the population, and the biggest chunk of movement falls between the ages of twenty and forty.

This means that a person with an explosive character will be calmer at fifty than they were at twenty-five. They will still be more explosive than a peer who was calm at twenty-five. The ordering between people holds far more firmly than the absolute values, and the older you get, the more stable it becomes.

What drives that shift is not age itself but the roles a person steps into. Anyone with a job they carry responsibility for, or somebody at home who depends on them, gets daily training in reliability and in keeping emotions on a leash. Life starts demanding behavior from you that you did not need before, and after a few years of repetition it becomes a trait.

And now the counterintuitive part. In 2013 Jonathan Quoidbach, Daniel Gilbert and Timothy Wilson published research in Science on thousands of people and found a systematic error in the way they saw themselves. Participants at every age reported that they had changed a good deal over the past ten years, but that they would change only a little over the next ten. The authors call it the end of history illusion. We reliably recognize change in retrospect and just as reliably underestimate it going forward.

What cannot be changed and what can

The division is fairly sharp once you specify what level the question is aimed at. Basic reactivity stays. The threshold at which something fires in you, the speed of onset and the time it takes you to return to a resting level all belong to the wiring you came into the world with.

A melancholic will not stop picking up what is left unsaid and will not stop replaying a sentence that came out wrong. No amount of training will lengthen a choleric's fuse to a phlegmatic's. A sanguine will not start taking pleasure in three hours of silence over a spreadsheet. What does change, and changes a great deal, is the repertoire of what you do with the reaction.

At ten, Tom refused to go and buy bread on his own, because it would have meant talking to the person behind the counter. Today he is thirty-five and runs full-day training sessions for twenty people without anybody spotting a trace of nerves. It looks like a transformation of temperament. It is not. On the way home from every session he drives for an hour in complete silence with no radio, and in the evening he does not pick up the phone. The reactivity stayed the same; what changed were the skills and, above all, the way Tom builds his day around them.

That is precisely the distinction worth remembering. You are not changing what fires in you. You are changing what follows, how long it lasts and the environment the whole thing happens in.

Wishing is not enough: change happens through behavior

Nathan Hudson and Chris Fraley (2015) gave an interesting answer to the question of whether you can simply order the change. They followed students who wanted to change one of their traits over several months. The group that stayed with the wish did not move anywhere. The group that set a specific behavior in a specific situation every week moved measurably.

The difference between "I want to be more patient" and "when a colleague is explaining a problem to me, I will let them finish even though I already know the answer" is that the first sentence cannot be carried out. The second one can, including at a moment when you do not feel like it.

It is worth remembering that a measurable shift in such research is not a transformation. It is a modest movement along a scale, not a change of type. Anyone expecting to become somebody else after six months of practice will be disappointed. Anyone expecting to stop needlessly hurting somebody close once a month has a realistic goal.

Approaches that work with your temperament, not against it

The best results tend to come from methods that put your natural tendency to use instead of fighting it. A sanguine will not last studying alone but will manage it with a friend. A melancholic will not force themselves to improvise, but preparing three options in advance is well within reach.

• Name the bodily signal that arrives before the reaction. Most people have one and most people ignore it.
• Put a mechanical obstacle between the stimulus and the response: write it and do not send it, get up from the desk, postpone the decision until morning.
• Instead of fighting yourself, adjust the environment. Somebody who is easily overloaded needs a predictable routine more than another resolution.
• Practice with small stakes. Disagreement gets rehearsed over the choice of restaurant, not over a salary negotiation.
• Bring in one person who will give you feedback on how you come across. Self-assessment has a blind spot for your own behavior.
• Count on regression. When you are tired and short on sleep, everybody falls back to their original setting, and it does not mean the work was for nothing.

You can find out where your strong and weak spots sit faster than a year of self-observation would tell you. The temperament test has 24 questions and takes about four minutes; besides the main type it shows the streak and the least pronounced component, which is usually the one worth training. How the four types mix together is covered in the piece on temperament combinations.

When wanting change makes sense and when it does not

Not every dissatisfaction with your own character calls for training. Sometimes it calls for a change of environment. An introverted melancholic in an open-plan office with ten phone calls an hour does not have a problem with temperament, they have a problem with the place where they spend eight hours a day.

A useful question runs: is that quality stopping you from getting where you want to go, or does it merely bother you that you are not like somebody else? The first case is worth working on. The second tends to be a comparison that leads nowhere, because every type has its value and its bill. With children the question is even more delicate, and parents run into it before anything else, as described in the piece on temperament in children.

And one more boundary. When ordinary reactivity turns into something that takes your sleep, your appetite for things or your ability to function over a long period, this is no longer temperament and no self-help strategy will resolve it. That belongs with professional help, not with another round of resolutions. Where exactly that boundary lies for each of the types is covered in the piece on how the temperaments cope with stress.

For the coming month, try picking a single situation that recurs at least once a week and writing one sentence about what you will do differently in it. Not a trait, not a resolution, one sentence about behavior. In a month you will see a difference in yourself that a wish alone would not have brought you in a year.