The purpose of this study was to identify sources of individual differences in knowledge acquired under natural conditions. Through its direct influence on background knowledge, crystallized intelligence (Gc) had a major impact on political knowledge, acquired over a period of more than 2 months, but there were independent influences of personality and interest factors, via exposure to political information through activities like reading the newspaper. We also found sex differences in political knowledge, favoring males, and these differences could not be explained in terms of any of the predictor variables we modeled. We discuss theoretical and practical implications of the results. (Contains 1 figure and 3 tables.)