Developing a biological understanding of goal -directed action.

Abstract

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. Three studies examined the effect of self-versus goal-directed movement on children's and adults' attributions of biological and psychological capacities to novel entities. In Study 1, 16 adults were shown videos of unfamiliar blobs moving independently, and another 16 were shown videos of identical blobs moving identically but toward a goal. Adults were unlikely to attribute any biological or psychological properties to the blobs moving independently, but they were likely to attribute biological but not psychological properties to the blobs that moved toward goals. In Study 2, these same videos were presented to 4-, 5-, 7-, 10-year-olds, and adults (<italic>N</italic>s = 32) to test whether goal-directedness affects biological and psychological inferences across documented periods of change in biological reasoning. Again, no age group was likely to attribute biological or psychological capacities to the 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. Because adults often identified these goal-directed blobs as (insentient) microorganisms, Study 3 presented adults (N = 48) with videos of triangles that moved with the same rotation, speed, and trajectory as the blobs in Studies 1 and 2. Again, adults were unwilling to attribute biological and psychological capacities to triangles that moved independently; however, they were likely to say that the goal-directed triangles were alive and could want, and goal-directedness affected their biological and psychological attributions equally. The results of these three studies suggest that both young children and adults consider the capacity for goal-directed movement to be a decisive factor in whether something unfamiliar is alive, though other factors may be important in deciding whether the thing is sentient.