When studying human sexual response, researchers use tools that yield quantitative data, in addition to personal interviews and surveys. The plethysmograph is a tool used both in scientific research and in diagnosis of sexual difficulties.

This particular video clip is part of a longer video about sexual difficulties in men. The doctor explains and demonstrates to a client how a penile plethysmothgraph works and gathers its data. Note how the tool -- here called a Rigiscan -- fits into a compact case, and is designed to be comfortable while the client sleeps.

Please watch the following video clip and answer the corresponding follow-up questions.

The Plethysmograph

1			What does the Rigiscan actually measure?
2			How are these data useful for a doctor making a diagnosis? How might a researcher use a plethysmograph?