Nonverbal indicators of deception: How iconic gestures reveal thoughts that cannot be suppressed

This study explores the morphology of iconic gestures during deception. Participants narrated a static cartoon story twice. In one condition they provided an accurate account of the story, in the other they were instructed to introduce false details. Participants produced significantly fewer iconic gestures when describing plot-line events deceptively than when narrating comparable episode units truthfully. Deceptive gestures had significantly fewer post-stroke holds and shorter stroke phase durations than those produced alongside truthful utterances. Following Beattie (Visible thought: The new psychology of body language, Routledge, 2003) three narrators in the deceptive condition produced gestures that in their morphology contradicted the semantic information encoded in their speech stream, and ultimately signaled possible deceit.