Transitivism is a psychoanalytic concept suggested by Charlotte Buhler to designate a special kind of identification often observed with small children. With transitivism we identify with the other in a manner that mirrors (that is reversing) our own image. Lacan associated this reversal with the function of what he called "the mirror stage". He argued that trasivitism demonstrates the confusion between the I and the other which is a part of imaginary identification.
see: Lacanian Terminology