Language and motor control

Abstract

We investigated the possible influence of automatic word reading on processes of visuo-motor transformation. Subjects reached and grasped an object on which the following Italian words were printed: 'VICINO' (near) or 'LONTAN' (far) on an object either near or far from the agent (experiments 1, 2); PICCOLO (small) or 'GRANDE' (large) on either a small or a large object (experiment 4); and 'ALTO' (high) or 'BASSO' (low) on either a high or a low object (experiment 5). The kinematics of the initial phase of reaching-grasping was affected by the meaning of the printed words. Namely, subjects automatically associated the meaning of the word with the corresponding property of the object and activated a reach and/or a grasp motor program influenced by the word. No effect on initial reach kinematics was observed for words related to object properties not directly involved in reach control (experiment 3). Moreover, in all the experiments, the presented words poorly influenced perceptual judgement of object properties. In experiments 5-7, the effects of the Italian adjectives 'ALTO' (high) and 'BASSO' (low) on reaching-grasping control were compared with those of the Italian adverbs 'SOPRA' (up) and 'SOTTO' (down). Adjectives influenced visual analysis of target-object properties, whereas adverbs more directly influenced the control of the action. We suggest that these effects resemble the structure of a sentence, where adjectives are commonly referred to nouns, and adverbs to verbs. In other words, class of words and, in a broad sense, grammar influenced motor control. The results of the present study show that cognitive functions such as language can affect visuo-motor transformation. They are discussed according to the notion that a strict relation between language and motor control exists, and that the frontal cortex can be involved in interactions between automatic word reading and visuo-motor transformation.