Figure 1.

Experimental procedure. (A) Experiment 1. Participants began Hand-to-Food reaches with their right index finger and thumb in a closed pinch position, resting on their chin (i). Participants then reached out toward a cube of cheese (ii) and grasped it with a precision grip (iii). Once the food item was within the participant’s grasp, an inwardly directed reach toward the mouth (Hand-to-Mouth) was performed (iv), ending the reach with a precision bite using the upper and lower incisor teeth (v). (B) Experiment 2. Participants performed the same movement as (A) except that instead of using the index finger and thumb to capture and transport the food item, a fork was used to pierce the cheese and bring it to the mouth to bite (i–v). Zoomed views at the top of the figure show the placement of markers (infrared-emitting diodes, IREDs) on the index finger and thumb (red circles; to measure hand aperture), on the temple and lower jaw (red squares; to measure mouth aperture), and on the hand or fork (blue square and blue triangle respectively; to measure transport kinematics).