The Effects of Task-Irrelevant Olfactory Information on the Planning and the Execution of Reach-to-Grasp Movements

Previous evidence indicates that, when reaching to grasp a target object, the presence of nontarget irrelevant information (i.e., distractor) presented either in the visual or olfactory modality determines significant interference effects on temporal parameters, such as reaction time and movement time, and on movement kinematics. While research on “visual” distractor has also revealed that such interference effects disappear when prior knowledge about the target is given to participants, this aspect for olfactory distractors has yet to be investigated. Therefore, here we asked participants to reach towards and grasp a small or a large visual target following the delivery of an odor evoking either a small or a large object. When the type of grasp evoked by the odor did not coincide with that for the visual target, interference effects were evident on reach duration and reaction time, but kinematics of hand shaping remained unaltered. This study demonstrates that, when participants knew in advance which object was the target, olfactory nontargets produced no interference effects on movement kinematics, but they did on key temporal measures, i.e., reaction time and reach duration. These findings are discussed in light of current theories put forward to explain the sensory processes underlying the control of action.