Shared processing of planning articulatory gestures and grasping

It has been proposed that articulatory gestures are shaped by tight integration in planning mouth and hand acts. This hypothesis is supported by recent behavioral evidence showing that response selection between the precision and power grip is systematically influenced by simultaneous articulation of a syllable. For example, precision grip responses are performed relatively fast when the syllable articulation employs the tongue tip (e.g., [te]), whereas power grip responses are performed relatively fast when the syllable articulation employs the tongue body (e.g., [ke]). However, this correspondence effect, and other similar effects that demonstrate the interplay between grasping and articulatory gestures, has been found when the grasping is performed during overt articulation. The present study demonstrates that merely reading the syllables silently (Experiment 1) or hearing them (Experiment 2) results in a similar correspondence effect. The results suggest that the correspondence effect is based on integration in planning articulatory gestures and grasping rather than requiring an overt articulation of the syllables. We propose that this effect reflects partially overlapped planning of goal shapes of the two distal effectors: a vocal tract shape for articulation and a hand shape for grasping. In addition, the paper shows a pitch-grip correspondence effect in which the precision grip is associated with a high-pitched vocalization of the auditory stimuli and the power grip is associated with a low-pitched vocalization. The underlying mechanisms of this phenomenon are discussed in relation to the articulation-grip correspondence.