Phi effect patients insist relatives and close friends are unfamiliar, and that their relatives are impostors who just resemble their relatives.

The description given refers to Capgras syndrome, not the Phi effect. The Phi effect is a phenomenon of visual perception in which lights or images presented in succession at a certain speed appear to move, whereas Capgras syndrome is a psychological condition where the patient believes that a friend, spouse, parent, or other close family member has been replaced by an identical impostor.