Windschitl, P. D., Kruger, J., & Simms, E. N. (2003). The influence of egocentrism and focalism on people's optimism in competitions: When what affects us equally affects me more. Journal of Personality and Social Psychology, 85, 389-408..

Six experiments investigated people's optimism in competitions. The studies involved hypothetical and real competitions (course grades in Experiments 1-2, a trivia game in 3-5, and a poker game in 6) in which the presence of shared adversities and benefits (factors that would generally hinder or help the absolute performance of all competitors) was manipulated. Shared adversities tended to reduce people's subjective likelihoods of winning, whereas shared benefits tended to increase them. The findings suggest that when people judge their likelihood of winning, their assessments of their own strengths and weaknesses have greater impact than their assessments of their competitors' strengths and weaknesses. We identify egocentrism and focalism as two causes of the bias. The experiments revealed moderators of this bias, but also illustrated its robust nature across a variety of conditions.