The past century of theory about human development has placed much responsibility for normal socio-emotional development on the social interactions experienced in infancy. The reliance on nurture over nature in each of these theories may need to be tempered in light of some recent proposals about a variety of richly structured innate mechanisms to interpret social stimulation detectors for perceiving another person's intention and eye direction; teleological stance for interpreting another's action]. Even if incorporating one or more of these specific interpretive mechanisms, however, these diverse theories will surely continue to rely heavily on an assumption they share, at least implicitly, to the effect that human infants are sensitive to the existence of contingencies between their behavior and environmental events.