Do we always know the reasons for our actions? Or is our behavior sometimes unknowingly and unintentionally influenced by what we have recently perceived? It has been traditionally assumed that the automatic influence of knowledge in memory is limited to people's interpretation of the world, and stops short of shaping their actual behavior. Researchers in experimental social psychology have begun to challenge this assumption by documenting how people's behaviors can be unknowingly influenced by knowledge that is incidentally activated in memory during social perception. We review findings that suggest that the social knowledge that is incidentally activated while reading words or imagining events subsequently affects participants' behaviors across a range of ostensibly unrelated domains.