Projective identification is a core concept in psychoanalysis
that many students have difficulty understanding.
Basically, this term refers to the process by which a patient's behaviors pull a therapist into behaving in a manner characteristic of members of the patient's past. For example, a patient who expects others to be hostile (i.e., projection) may behave so as to elicit hostility from others (i.e., the other person has identified with the projected hostility).
By the nature of the patient's behaviors, he or she draws the therapist into behaving in a manner that is quite unlike how the therapist usually behaves. Once the therapist recognizes that he or she is behaving in an uncharacteristic manner (i.e, recognizes the counter-transference pull), the therapist can behave otherwise and work to have the patient understand the patient's expectations (i.e., internal representations) and the influence they have on others.
The therapist's actions that are not congruent with the patient's projections become assimilated by the patient (i.e., reintrojected) and in so doing provide one mechanism of change in psychoanalysis.