He sat by his phone, skeptical that it would ring. “I didn’t think that anyone would want to respond,” said Samuel D. Smithyman, now 72 and a clinical psychologist in South Carolina.

But the phone did ring. Nearly 200 times.

At the other end of the line were a computer programmer who had raped his “sort of girlfriend,” a painter who had raped his acquaintance’s wife, and a school custodian who described 10 to 15 rapes as a means of getting even with “rich bastards” in Beverly Hills.

By the end of the summer, Dr. Smithyman had completed 50 interviews, which became the foundation for his dissertation: “The Undetected Rapist.” What was particularly surprising to him was how normal these men sounded and how diverse their backgrounds were. He concluded that few generalizations could be made.

Over the past few weeks, women across the world have recounted tales of harassment and sexual assault by posting anecdotes to social media with the hashtag #MeToo. Even just focusing on the second category, the biographies of the accused are so varied that they seem to support Dr. Smithyman’s observation.