The Optimism Bias

The probability of death for motorcyclists in the United States is 37 times higher than for automobile passengers. Yet every motorcyclist, even if they know this statistic, estimates the likelihood of danger happening to themselves to be lower. In reality, they are optimistic about their own future.

Even if we know the statistics and rates of cancer among smokers, divorce, bankruptcy, job loss, failing an exam, life expectancy, workplace accidents, cataracts or skin cancer caused by sunlight exposure, addiction to alcohol and drugs, the likelihood of developing diabetes from excessive consumption of sweets, or atherosclerosis resulting from eating fatty foods, our estimate of these events occurring to ourselves is still lower than the actual statistical probability.

In other words, when it comes to ourselves, we become optimistic and underestimate risks. This is a characteristic found in approximately 80% of people.

In 2011, Tali Sharot asked volunteers participating in her research to answer questions about their own characteristics. For example, she asked whether they considered themselves to be among the bottom 25% or the top 50% in terms of their ability to establish relationships with others. Everyone answered that they belonged to the top 50%. Obviously, this cannot be true for everyone, and it demonstrates an optimistic bias regarding oneself.

Tali Sharot placed her volunteers in an fMRI scanner to examine how their brain activity changed when they received estimates that were better or worse than their own predictions.

First, participants made estimates about themselves. For example, they might say that, considering their lifestyle, they believed there was a 10% chance they would develop cancer due to smoking or a 30% chance they would develop Alzheimer’s disease. They were then provided with information about the actual statistical risks.

When the information they received contained statistics that were better than their own estimates, their frontal lobes showed considerable activity—for example, when someone who had estimated a 30% chance of developing Alzheimer’s disease was told that the actual probability was only 10%.

However, when the information presented statistics that were worse than their own estimates, their frontal lobes did not show much increase in activity. For example, if someone who had estimated a 10% chance of developing smoking-related cancer was told that, given their lifestyle, the probability was actually 30%, their frontal lobe showed no significant increase in activity.

It was as if they ignored this information and did not consider it worthy of processing.

The volunteers were then asked again to provide estimates in each area they had previously assessed, this time taking into account the new information they had received.

When the new information was favorable to them, participants adjusted their estimates considerably and moved much closer to the scientific estimates. However, when they disliked the information they had received and the scientific data should have convinced them to change their patterns and habits of living, they changed their previous estimates only slightly.

For example, if they had previously estimated a 10% chance of developing cancer due to smoking, after learning that the actual probability was 30%, they still did not significantly change their estimate about themselves and might say that they now believed the chance was only 13%. [1]

Tali Sharot published the results of her research in a book titled “The Optimism Bias.” [2]

It can be said that our brain resists negative information about ourselves. Of course, this resistance does not apply when negative information concerns other people; we only avoid processing negative information about ourselves.

We may be highly pessimistic about economic conditions or air pollution, yet underestimate the effects of these same issues on our own lives. Optimism can motivate us to move forward in many of our activities, encourage us to take risks, and help us create changes in our lives and in the world around us. On the other hand, it can expose us to the danger of continuing with ineffective methods and harmful lifestyle habits.

If a religious believer is told that, given the fact that their religion is only one among thousands of religions and belief systems in the world, the probability that their beliefs are mistaken is quite high (just as they themselves consider the beliefs of followers of those thousands of other religions to be mistaken), this perspective may fail to receive their attention.

Their frontal lobe may not show increased activity in response to such a statement, and as a result, they may continue to estimate the probability that their religious beliefs are correct as much higher than it objectively is. In this way, they avoid having to alter their everyday way of life and undertake the effort of studying and evaluating their beliefs.