Abstract
Freud's thinking was influenced by evolutionary ideas. He built his theory about the instincts of sexuality and aggression. A third phylogenetically given propensity for behaviour, that of attachment, has been added to traditional theory following the work of Bowlby. We propose that the origins of certain psychiatric disturbances, most notably cluster B personality disorders, are to be found not in those drives which are ancient in evolutionary terms but through a disruption of that which has been most recently evolved, and which involves symbolization. It is manifest developmentally as symbolic play. A case report illustrates the hypothesis.