Optimism bias involves a belief that things will turn out better than they do. Pessimism bias a belief that things will turn out worse. Both misjudge the actual risk and likelihood of outcome.


Optimism bias overlaps with ego bias, while pessimism bias overalps with reverse ego bias.


In both biases the person acknowledges that there are risks present. The difference in outcome is affected by individual performance and fortune (skill and luck).



Positive Outcome

Negative Outcome


overestimates chances

underestimates risk


underestimates chances

overestimates risk


Optimism bias may be seen in young adults who tend to see themselves as invincible while their peers are more vulnerable.


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