This study explores the ways in which infants reason about h u m a n action. Although recent research supports the view that young infants' reasoning about object physics is guided by a set of core principles. there is little evidence for early principles of this sort in infants' reasoning about human action. T o explore this issue, a habituation study was done comparing 7- month-olds' reasoning about simple causal sequences involving people to their reasoning about those involving inanimate objects. Our findingssuggest that although 7-month-olds expect that the motion of inanimate objects will be constrained by the principle of contact (an object affects the motion of another object if and only if the two objects come into contact), they do not expect human motion to be constrained in this way. These findings provide preliminary evidence diat infants have principled expectations to guide their reasoning and learning about human action.