Examined why graduate students take longer to complete humanities and social sciences degrees than natural sciences degrees. Found that field differences in knowledge structures and the organization of research have significant implications for research training. "Hard" fields have a directed supervision model and close relationship…

Examined the submission rates of PhD theses by 3579 doctoral students at the University of Birmingham (England) from 1984 through 1993. The only reliable predictor of successful submission within either a 4-year or 10-year period was whether a student was researching a science-based or an arts and humanities-based subject with science students…