Humans tend to “suffer” from an optimistic bias:
Tali Sharot, a neuroscientist at University College London, has studied how our brains perpetuate this bias. One factor appears to be that we selectively incorporate positive feedback into our future expectations, but ignore negative feedback.
Dr. Sharot and her team have conducted a series of studies in which participants are told to estimate the likelihood that they will face a negative event, such as dying before age 60. Then, participants are told the real probability of the event happening in the broader population.
When the likelihood is smaller than what participants’ thought, people incorporate the feedback into their estimates. When asked a second time to guess the likelihood of that negative event befalling them, they become more optimistic that it won’t.
But if the chance of something bad happening is higher than they thought, they basically just ignore the new information. They justify it by saying that feedback doesn’t apply to them—they aren’t as likely to die before 60 as other people, for instance, because they have grandparents who lived into their 90s, or because they are avid gym goers with low blood pressure.
The mechanism behind this bias appears to be located in a specific part of the brain, the left inferior frontal gyrus, which is involved in language, among other functions. In a study published in October in the journal Proceedings of the National Academy of Sciences, the researchers found that the participants no longer selectively considered just the positive information when the functioning of that part of the brain was disrupted with electric current.