Under normal circumstances, incorporation is the earliest mode of relating in which the infant feels himself to be at one with the other and is unaware of separation between the two personalities (Fenichel, 1945; Searles, 1951; Sterba, 1957). This experience decreases if development proceeds relatively unimpeded. If development is impeded the experience can persist leading to an equation between relatedness and engulfment, in which one personality is felt to be devouring the other (Searles, 1951, p. 39). The impulse to unite incorporatively with the other as a defense against separation anxiety has been discussed by Freud (1900, 1933), Klein (1935), Heimann (1942), Fenichel (1945), Searles (1951), Federn (1952), Greenacre (1958), Segal (1981), Rey (1994) and others. Laplanche and Pontalis (1972) note how physical experiences are a feature of incorporation, in contrast to the fantasy dimension of introjection into the ego, which assumed importance in Klein's (1935) thinking and which she discusses in the context of incorporative activity and the genesis of psychosis.