Psychologists have long thought that people tend to underestimate the odds of something bad happening to them and overestimate the chances of good things happening to them. Now a new study suggests this view may not be accurate.

The studies that have suggested that people tend to be inherently optimistic may have had flawed methods of measuring this so-called "optimism bias," the researchers said.

Optimism bias, for example, is thought to occur in people who are told their statistical chance of experiencing a bad life event such as cancer. Previous research has shown that, because of their excessive optimism, people don't fully acknowledge their chances of getting cancer. [9 DIY Ways to Improve Your Mental Health]

But the new research is calling this optimism into question. "Previous studies, which have used flawed methodologies to claim that people are optimistic across all situations and that this bias is 'normal,' are now in serious doubt," Adam Harris, a psychologist at University College London and co-author of the study, said in a statement. "We need to look for new ways of studying optimism bias to establish whether it is a universal feature of human cognition or not."

The new results show that these previous studies have merely generated patterns of data that create an illusion that people are inherently optimistic, said the study, published Tuesday (Aug. 16) in the journal Cognitive Psychology.

At this point, there is no strong evidence that such bias exists, the researchers said. "There is no evidence that people use desirable information differently from undesirable information," Harris told Live Science.

However, experts who were not involved in the new study said the findings are unlikely to cause the idea of optimism bias to fall out of favor among psychologists in the field.

Tali Sharot, a neuroscientist at University College London who studies optimism bias and who was not involved in the new study, said she disagreed with the conclusion that there is no evidence for optimism bias. "It is absolutely false," she told Live Science, adding that numerous previous studies have suggested the existence of such bias.

John Petrocelli, a psychologist at Wake Forest University in Winston-Salem, North Carolina, who was not involved in the study, said he was also skeptical about the researchers' claims. "I don't agree with their broader conclusion that the unrealistic optimism bias doesn't exist," he told Live Science.

"Social psychology is full of examples of" people being overly optimistic, he said. One such example is the so-called gambler's fallacy, in which a gambler is positive that he or she will win the next round of blackjack, just after losing multiple rounds in a row, Petrocelli said.

In the new study, the researchers did experiments with 13 participants, asking them to rate the likelihood of 80 possible life events. Some of the events were good things (having a healthy child, finding money in the street), and some were negative (being robbed, getting cancer).

But the researchers also created computerized simulations that were designed to act in a rational, unbiased manner in response to receiving information about the statistical chance of a negative or positive life event. Because these simulations are artificial and are not actual humans, they are not capable of being intrinsically optimistic, and thus they could not possibly have a bias toward optimism, the researchers said.

However, the researchers found that the computer simulations produced patterns of data that looked as if these simulations did actually have a bias toward optimism. This finding suggests that scientists' impression of such bias may arise purely from statistical processes that are not grounded in people's real reactions, the researchers found. [5 Wacky Ways to Quantify Happiness]

The authors of the new study said that it is true that certain people might be optimistic in certain situations: For example, football fans might be particularly optimistic about the chances of their favorite team winning a game. However, this fact does not prove that humans as a species are inherently optimistic across all situations or that such potential optimism bias is a feature of human cognition, they said.

The new findings suggest that the wide application of the concept of optimism bias to real-life projects should be reconsidered, the researchers said. "This assumption that people are optimistically biased is being used to guide large infrastructure projects, with the aim of managing expectations around how much projects will cost and how long they will take to complete," Harris said.

"Our research supports a re-examination of optimism bias before allowing it to guide clinical research and policy."

Originally published on Live Science.

Copyright 2016 LiveScience, a Purch company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.