becomes the superego, which intercedes against the desires of the id (which works on the basis of the pleasure principle). Freud speculated that "it is perhaps the emergence of the super-ego which provides the line of demarcation between primal repression and after-pressure". Therapy Neurosis may occur when the personality develops under the influence of the superego and the pressure of the repressed impulses, leading to behavior that is irrational, self-destructive, or antisocial. A psychoanalyst may try to ameliorate this behavior by seeking to discover the repressed aspects of the patient's mental processes and reintroducing them to their conscious awareness - "assuming the role of mediator and peacemaker ... to lift the repression". Reactions The philosopher Jean-Paul Sartre maintained that there is no "mechanism" that represses unwanted thoughts. Since "all consciousness is conscious of itself" we will be aware of the process of repression, even if skilfully dodging an issue. The philosopher Thomas Baldwin stated in The Oxford Companion to Philosophy (1995) that Sartre's argument that Freud's theory of repression is internally flawed is based on a misunderstanding of Freud. The philosopher Roger Scruton argued in Sexual Desire (1986) that Freud's theory of repression disproves the claim, made by Karl Popper and Ernest Nagel, that Freudian theory implies no testable observation and therefore does not have genuine predictive power, since the theory has "strong empirical content" and implies testable consequences. Later developments The psychoanalyst Otto Fenichel stressed that 'if the disappearance of the original aim from consciousness is called repression, every sublimation is a repression (a "successful" one: through the new type of discharge, the old one has become superfluous)'. The psychoanalyst Jacques Lacan stressed the role of the signifier in repression — 'the primal repressed is a signifier' — examining how the symptom is 'constituted on the basis of primal repression, of the fall, of the Unterdrückung, of the binary signifier ... the necessary fall of this first signifier'. Family therapy has explored how familial taboos lead to 'this screening-off that Freud called "repression"', emphasising the way that 'keeping part of ourselves out of our awareness is a very active process ... a deliberate hiding of some feeling from our family'. Experimental attempts to study repression According to the psychologist Donald W. MacKinnon and his co-author William F. Dukes, American psychologists began to attempt to study repression in the experimental laboratory around 1930. These psychologists were influenced by an exposition