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 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 the psychodynamics of women, were either not supported or contradicted by research. Reviewing the issues again in 1996, they concluded that much experimental data relevant to Freud's work exists, and supports some of his major ideas and theories.