Why the “optimism bias” rules our hopes for the future

What actually is optimism? One approach is to consider it as a psychological trait — an individual personality characteristic that affects an individual’s behaviour, doesn’t change much over time, and is fairly consistent in most situations. All these are true of dispositional optimism, the generalised tendency to look on the bright side. Different people may have different levels of a trait: Some people are more extroverted than others, for example. And some people are more optimistic than others. If optimism is a good thing, we might hope that we can increase our levels of it.

The received wisdom used to be that traits were largely settled by the time we reach adulthood, and that’s largely but not entirely true. Much therapy aims to move the needle on traits, and the line between traits and more transitory “states” — feeling nervous before a job interview, say, and elated afterwards — can be blurry. So maybe it’s possible to change our levels of optimism, at least for a while. But to do so, it would be helpful to understand how those levels are set in the first place.

When it comes to the scientific study of any trait, the inevitable question is whether we are born or made that way. And the inevitable answer is “both.” We’re shaped by our genes and by our environments, and by the phenomenally complex interactions of the two. Unpacking these factors can be a formidable challenge. Height, for example, might seem a straightforward vital statistic, but it wasn’t until 2022 that we had a full list of the twelve thousand genetic variants that influence it — and we’re only just starting to understand how they’re activated or deactivated by, say, our diet or childhood infections.

Scientists often investigate these questions by studying twins. Identical twins have (almost) exactly the same genes, while non-identical twins have the same degree of genetic difference as any other siblings. Comparing identical and non-identical twins therefore allows us to tease out the contribution that genetics makes to a trait. Comparing twins who are raised together with those raised apart (because they were independently adopted, for example), further allows us to investigate the effects of upbringing.

One of the earliest twin studies to look at optimism was published in 1991 by a team led by the American psychologist Robert Plomin. It looked at more than 500 pairs of twins, half raised together and half apart, and found that around a quarter of the variability in levels of optimism could be explained through their genes. A larger twin study, reported in 2015 by Timothy Bates of the University of Edinburgh, concluded that optimism is indeed heritable but that there are “significant (and substantial) effects of family-level environment and of personal or unique environmental influences.” So what happens to us after we’re born also determines how optimistic we are. That is mostly about learning not to expect the best, because we are all born optimists. In fact, more than that: We’re born hyperoptimists.

As anyone who has ever met a young child will know, they look to the future with the very rosiest of expectations and give scarcely any mind to potential obstacles. That intuition is backed up by research using child-friendly tests of optimism, including a junior edition of the Life Orientation Test. Little kids expect that they will become strong, knowledgeable, and competent. They assume their weaknesses will over time transform into great strengths — from clumsiness to athleticism, messiness to neatness, foolishness to wisdom. They may even believe it’s possible to overcome such deficits as poor eyesight or a missing finger. They also believe the same is true for their friends. In Garrison Keillor’s fictional Lake Wobegon, “All the children are above average.” Children seem to believe that’s literally true.

This isn’t hard to explain. Since children’s skills and abilities aren’t fully developed, they’re generally correct to assume that these will improve greatly in future. As to how much they will improve by, they’re usually surrounded by older kids and adults who seem supremely capable — so much so that it may not be obvious that their skills and abilities vary, too, or that they have any limit at all. As the cliché has it, “You can do anything if you put your mind to it.” That’s something else children are led to believe is literally true.

At a deeper level, optimism may serve to further youngsters’ learning. [The] function of optimism may be to propel us out of inactivity in pursuit of reward, like the mouse deciding whether to leave its cosy nest. You would expect that motivation to be especially necessary for children, for whom perseverance is critically important. If we were easily deterred, we would probably never learn to write our names, tie our shoelaces or ride a bike. So children might be expected to pay much more attention to positive experiences while learning than negative ones — and they do.

A University College London team asked just over a hundred London schoolchildren, in three age groups ranging from eight- to seventeen-years-old, to play a game about a rocket flying from planet to planet. If they mashed the control button rapidly enough in a five-second period, they would get to the next planet, where they would be rewarded with a stash of virtual coins; if not, they would see the reward, but not receive it. Both the number of button presses needed and the number of coins on offer varied randomly, but the kids weren’t told that: they were simply asked before each round to predict how many times they would need to press the button and how many coins they would get if they succeeded.

As it turned out, all the children systematically overestimated the number of coins they could expect. But the youngest group — the eight- and nine-year-olds — predicted significantly more coins than the early adolescents (aged twelve and thirteen), who were in turn notably more optimistic than the late adolescents (seventeen and eighteen). While all groups paid attention to how close their guess had been to the actual answer and updated their next guess accordingly, the younger children paid less attention to negative results than the older kids. They gained false confidence from near misses, but didn’t make corresponding adjustments when they were way off the mark. The net result was that the youngest children ended up expecting considerably more coins than adolescents.

When we’re small, we do indeed learn from our successes and ignore our failures. And we carry on doing so. The defining feature of optimism, in the psychological sense, is that it gives rise to unsupported positive beliefs about the world. Error management theory predicts that, overall, these “mistaken” beliefs work for us: We benefit from outcomes we couldn’t reasonably have anticipated. But nonetheless we’ll also encounter some outcomes that go against our expectations. Things will go wrong; our plans will fall apart; we will be disappointed. In fact, this will happen time after time, and sometimes the experience will be deeply painful. One of my own unrealistic expectations was that no one in my immediate family would ever fall seriously ill; I was entirely wrong about that. How did my optimism survive this blunt encounter with reality? How does anyone’s optimism survive a lifetime of such definitive truths?

The neuroscientist Tali Sharot decided to find out. She and her colleagues asked people to estimate their personal chances of suffering undesirable events, such as a dementia diagnosis. Then the researchers told them what the average likelihoods of those events actually were, and asked them to estimate their personal risk again. What they found was that people made a bigger adjustment to their individual estimates if the new information was positive (if, for example, the average likelihood compared favourably to their original estimate) than if it was negative.

In other words, we pay more attention to information when it holds positive implications for our futures and less when it has negative implications. Keep that up over a lifetime, and it turns into a persistent and wide-ranging optimism bias.