Cognitive, home, and family factors that theoretically could influence whether or not preschoolers' interests were focused on domains characterized by the acquisition of knowledge concerning object concepts (e.g., dinosaurs, horses) were assessed in a short-term longitudinal investigation of 211 4-year-olds. Boys were six times as likely as girls to manifest such interests. Logistic regression analysis indicated that children's cognitive skills in conjunction with the degree to which families emphasized consistency, communication, educational activities, and provided time for free play were important in determining whether preschoolers would sustain their interests and begin to develop knowledge about conceptual domains. Implications of gender differences in interests aligned with conceptual domains for both the development of childhood expertise and the development of science literacy are considered.