Gestures must be natural to be convincing. Again, it is experience that teaches the speaker how to use them. Use of precise or expansive gestures tells the audience that the speaker has confidence as a communicator.
Certainly it is often the body that betrays the speaker. Their stance is not firm when they don’t feel firm. Thus, confidence in speaking underlies successful use of gestures and movement; being relaxed is the key to using expansive gestures convincingly.
Science Makes Sense Creationism 