Assessing with the head: a motor compatibility effect

Research within the embodiment perspective has found that cognitive processing proceeds easier when bodily actions (mostly arms motion) are compatible with the conceptual meaning of verbal expressions (concrete or abstract, or with positive and negative values). Facilitation effects involving head motion, however, have not yet been investigated. The present work aims to test the motor compatibility hypothesis between directional head movements, usually performed to communicate agreement and disagreement, and truth evaluation. Five experiments were designed: participants were asked to assess a series of sentences as true or false, according to their meaning (objectively) or on the basis of personal preferences (subjectively), in compatible and incompatible motion conditions and with different response modalities. Response times were shorter only when true sentences, or about a liked content, were moved vertically, and when false sentences, or about a disliked content, were moved horizontally, with the head. Results confirm the hypothesis that higher cognitive processing is grounded in bodily motion, and shed light on the possibility to manipulate vertical and horizontal head movements in order to reveal attitudes.