https://en.wikipedia.org/wiki/Psychological_projection
Projection (German: Projektion) was conceptualised by Sigmund Freud in his letters to Wilhelm Fliess,[12] and further refined by Karl Abraham and Anna Freud. Freud considered that, in projection, thoughts, motivations, desires, and feelings that cannot be accepted as one's own are dealt with by being placed in the outside world and attributed to someone else.[13] What the ego refuses to accept is split off and placed in another.[14]
Freud would later come to believe that projection did not take place arbitrarily, but rather seized on and exaggerated an element that already existed on a small scale in the other person.[15] (The related defence of projective identification differs from projection in that the other person is expected to become identified with the impulse or desire projected outside,[16] so that the self maintains a connection with what is projected, in contrast to the total repudiation of projection proper.)[17]
Some studies were critical of Freud's theory. Research on social projection supports the existence of a false-consensus effect whereby humans have a broad tendency to believe that others are similar to themselves, and thus "project" their personal traits onto others.[37] This applies to both good and bad traits; it is not a defense mechanism for denying the existence of the trait within the self.[38] A study of the empirical evidence for a range of defense mechanisms by Baumeister, Dale, and Sommer (1998) concluded, "The view that people defensively project specific bad traits of their own onto others as a means of denying that they have them is not well supported." [38] However, Newman, Duff, and Baumeister (1997) proposed a new model of defensive projection in which the repressor's efforts to suppress thoughts of their undesirable traits make those trait categories highly accessible—so that they are then used all the more often when forming impressions of others. The projection is then only a byproduct of the real defensive mechanism.[39]