Whether and how an understanding of biological explantation changes with development was explored in interviews with 24-first graders, 24 third graders, and 24 adults. Participants were asked about the changeability of biological and psychological characteristics and the causal mechanisms underlying biological, psychological, and mechanical phenomena (using both open-ended and forced-choice questions). In saying how characteristics might be changed, children and adults similarly distinguished between biology and psychology; they also responded similarly to questions about specific processes underlying biological change. Children's attributions of intention or agency to biological organs or body parts (i.e., vitalistic attribution) did not differ from adults', contrary to previous findings. The authors concluded that children's thinking about biology is not necessarily more vitalistic than adults'.