We examined the effect of perceptions of advantage and disadvantage on the variability and stability of efficacy beliefs in a competition. Perceptions of advantageous or disadvantageous opening position were experimentally manipulated (keeping the actual positions equal) and pre- and post-competition efficacy beliefs were observed. Perceiving an advantage resulted in more variability and less stability in efficacy beliefs. These results are explained by the higher sensitivity of the advantaged to the experiences of the competition.