A convincing deceiver must act in discordance with their knowledge of the truth. To do so requires the deceiver to resolve competition between what is known to be true and what is intended to be false. We investigated the temporal signature of this competition by examining the action dynamics of arm movement while participants responded falsely or truthfully to autobiographical information. The participants answered no or yes by navigating a Nintendo Wii Remote to no and yes regions on a large projector screen. Trajectory analyses of the fine-grained arm movements show increased complexity in false responding relative to truthful responding, with the greatest difference in false yes answers. The dynamic motor movements also reveal greater strength of competition during the act of false responding, thereby extending traditional response time measures that capture latent competition alone. These results suggest that deceptive processes may be detectable when action is allowed to covary with thought. Supplemental figures and a list of the sentence stimuli may be downloaded from http://pbr.psychonomic-journals.org/content/supplemental.