Visuo-olfactory integration during action observation and execution of reach to grasp movements

Observing the actions of others prompts the motor system to perform a similar action. However, visual cues are not the only source of sensory information for the motor system, which is affected by stimuli presented in all modalities even when they are irrelevant for action completion. The current experiment explored whether (and how) olfactory stimuli can influence the performance of a reach-to-grasp movement to visual objects differing in size (small and large) in the context of an automatic imitation task. Odours could match-or not- the size of a to-be-grasped visual target, or be nonexistent. Movement duration, an integral index of motor control, was significantly shorter when participants previously observed the same action. Addition of the odour component suggested that when the odour matched the size of a small target, a facilitation effect was found. Results are discussed in terms of olfactory-visual integration mechanisms and how they relate to embodied cognition.