Want to win over investors when delivering a pitch? Look passionate.

That is the conclusion of 12 studies by researcher Chia-Jung Tsay, an associate professor at the University of Wisconsin-Madison. She gave investors different types of records of pitch competitions—such as video only or audio only—and asked them to guess which entrepreneur had won each round. The investors who made the best guesses saw only visual images of people making pitches, with no sound or information about the pitch itself.