While for Freud there was a hierarchy of dangerous situations, for Janov the key event in the child's life is an awareness that the parents do not love it. Janov writes in The Primal Scream (1970) that primal therapy has in some ways returned to Freud's early ideas and techniques. Ellen Bass and Laura Davis, co-authors of The Courage to Heal (1988), are described as "champions of survivorship" by Frederick Crews, who considers Freud the key influence upon them, although in his view they are indebted not to classic psychoanalysis but to "the pre-psychoanalytic Freud... who supposedly took pity on his hysterical patients, found that they were all harboring memories of early abuse... and cured them by unknotting their repression." Crews sees Freud as having anticipated the recovered memory movement by emphasizing "mechanical cause-and-effect relations between symptomatology and the premature stimulation of one body zone or another", and with pioneering its "technique of thematically matching a patient's symptom with a sexually symmetrical 'memory.'" Crews believes that Freud's confidence in accurate recall of early memories anticipates the theories of recovered memory therapists such as Lenore Terr, which in his view have led to people being wrongfully imprisoned or involved in litigation. Science Research projects designed to test Freud's theories empirically have led to a vast literature on the topic. American psychologists began to attempt to study repression in the experimental laboratory around 1930. In 1934, when the psychologist Saul Rosenzweig sent Freud reprints of his attempts to study repression, Freud responded with a dismissive letter stating that "the wealth of reliable observations" on which psychoanalytic assertions were based made them "independent of experimental verification." Seymour Fisher and Roger P. Greenberg concluded in 1977 that some of Freud's concepts were supported by empirical evidence. Their analysis of research literature supported Freud's concepts of oral and anal personality constellations, his account of the role of Oedipal factors in certain aspects of male personality functioning, his formulations about the relatively greater concern about the loss of love in women's as compared to men's personality economy, and his views about the instigating effects of homosexual anxieties on the formation of paranoid delusions. They also found limited and equivocal support for Freud's theories about the development of homosexuality. They found that several of Freud's other theories, including his portrayal of dreams as primarily containers of secret, unconscious wishes, as well as some of his views about