Cognitive ability and party affiliation: The role of the formative years of political socialization

•Time affects the relationship between intelligence and Democratic Affiliation in US.•This effect is due to the formative years of the development of political identity.•The later the formative years, the more positive is this relationship.•The results shed light on recent conflicting findings about this relationship.

We study the effect of time on the relationship between intelligence and party affiliation in the United States. Our results indicate that time affects this relationship, and that this effect is due to the formative years in which political preferences were developed rather than the time in which the survey was conducted. For people who were born in the 20th century, the later their formative years, the more positive the relationship between intelligence and Democratic, as opposed to Republican, affiliation. The current results shed light on recent conflicting findings about the relationship between intelligence and party affiliation in the US, and suggest that the effect of intelligence on party affiliation changes with time.