Paula Caplan, pioneering psychologist, who exposed the pathology of her profession's views on a variety of female traits and social responsibilities including shopping and motherhood, died July 21 at her Rockville, Md. home. She was 74.Emily Stephenson, her daughter, stated that the cause was metastatic melanoma.In the late 1970s Dr. Caplan combined a clinical analysis with a feminist perspective to show that many of the problems psychologists claimed were inherent to mothers and women had actually been caused by discrimination and social structures that made them vulnerable. Then, doctors medicated their inevitable negative reactions.In 1984, she wrote The Myth of Womens Masochism. She also published a book with the same title.Dr. Caplan disproved Freud's claim by first pointing out that women don't get joy from such pain and then showing how frustration and guilt are often the result of unjust expectations by patriarchal societies.