This article uses longitudinal data from the National Child Development Study (NCDS) to investigate the determinants of voter turnout in the 1997 British general election. It introduces measures of cognitive ability and personality into the participation literature and finds that they are significant determinants of turnout. It also shows that standard turnout models may be biased by the inclusion of the much used ‘interest in politics’ measure. A bivariate probit model of turnout and political interest finds that individuals with high comprehension ability and an aggressive personality are more likely to both turn out to vote and have an interest in politics.