Pii: S0010-0277(02)00171-3

To reason competently about novel entities, people must discover whether the entity is alive and/or sentient. Exactly how people make this discovery is unknown, although past researchers have proposed that young children – unlike adults – rely chiefly on whether the object can move itself. This study examined the effect of goal-directed versus aimless autonomous movement on children’s and adults’ attributions of biological and psychological capacities in an effort to test whether goaldirectedness affects inferences across documented periods of change in biological reasoning. Half of the participants (adults, and 4-, 5-, 7-, and 10-year-olds; Ns 1⁄4 32) were shown videos of unfamiliar blobs moving independently and aimlessly, and the other half were shown videos of identical blobs moving identically but toward a goal. No age group was likely to attribute biological or psychological capacities to the aimless self-moving blobs. However, for 5-year-olds through adults, goal-directed movement reliably elicited life judgments, and it elicited more biological and psychological attributions overall. Adults differed from children in that goal-directed movement affected their attributions of biological properties more than their attributions of psychological properties. The results suggest that both young children and adults consider the capacity for goal-directed movement to be a decisive factor in determining whether something unfamiliar is alive, though other factors may be important in deciding whether the thing is sentient. q 2002 Elsevier Science B.V. All rights reserved.