Boas gave her graduate credit for the courses that she had completed at the New School for Social Research. Benedict wrote her dissertation "The Concept of the Guardian Spirit in North America", and received the PhD in anthropology in 1923. Benedict also started a friendship with Edward Sapir who encouraged her to continue the study of the relations between individual creativity and cultural patterns. Sapir and Benedict shared an interest in poetry, and read and critiqued each other's work, both submitting to the same publishers and both being rejected. They also were both interested in psychology and the relation between individual personalities and cultural patterns, and in their correspondences, they frequently psychoanalyzed each other. However, Sapir showed little understanding for Benedict's private thoughts and feelings. In particular, his conservative gender ideology jarred with Benedict's struggle for emancipation. While they were very close friends for a while, it was ultimately the differences in worldview and personality that led their friendship to strand.