Gredebäck, G., & Melinder, A. (2011) Teleological reasoning in 4-month-old infants:Pupil dilations and contextual constraints. PlosOne.

Four-month-old infants were presented with feeding actions performed in a rational or irrational manner. Infants reacted to the irrational feeding actions by dilating their pupils, but only in the presence of rich contextual constraints. The study demonstrates that teleological processes are online at 4 months of age and illustrates the usefulness of pupil dilations as a measure of social cognitive processes early in infancy.