Truth is in the head. A nod and shake compatibility effect

Stefania Moretti, Alberto Greco
  • Acta Psychologica, April 2018, Elsevier
  • DOI: 10.1016/j.actpsy.2018.02.010

When we assess truth, we simulate nodding and shaking head gestures

What is it about?

According to the "embodiment" view, when we understand language some parts of our body which are involved in the meaning are activated silently (this is called a simulation). Our experiments have shown that when evaluating if a sentence is true we simulate the head gesture of nodding, and to evaluate if a sentence is false we simulate the gesture of shaking. This is an effect of compatibility. We used an innovative technique, which consists in making sentences move on a screen with the movement of the head, detected by a webcam.

Why is it important?

This result extends other findings in the embodiment research, regarding the direction expressed in sentences and compatible arm movements (this effect is called ACE, Action-sentence Compatibility Effect): e.g. when understanding "give" expressions the compatible arm extension away from the body is activated, and with "receive" the arm movement towards the body is involved.


Alberto Greco
University of Genoa

Our finding would not only concern assessing objective true and false sentences, but it may be extended to the evaluation of subjective truth (i.e. preferences, and even attitudes). We have already shown this in other studies.

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The following have contributed to this page: Alberto Greco