Dustin York conducted an experiment with four identical university classes (80 students, total). Each class had a guest presenter. Two presenters used effective nonverbal communication; the others used poor nonverbal communication.
Each presentation was the same, word for word. The PowerPoint was the same and the presentation length was the same. The only difference? A few nonverbal tactics.
After the presentation, students took the same test on the information given. Students in the effective nonverbal communication courses scored almost 30% higher than people in the poor nonverbal communication courses.