Arm and mouth coordination during the eating action in humans: a kinematic analysis.

The kinematic characteristics of the eating action in humans were assessed. Ten subjects were asked to bring to the mouth pieces of cheese of different sizes (0.7 cm and 2 cm). The pattern of mouth aperture with respect to the size of the food was similar to that found for grasping differently sized objects with the hand. Mouth aperture was appropriately scaled and the time of maximum aperture was reached earlier for the smaller than for the larger piece of cheese. The deceleration phase of the arm was prolonged when the small piece of cheese had to be brought to the mouth with respect to when the large piece of cheese had to be brought to the mouth. Temporal coupling between the time of maximum peak deceleration and the maximum mouth aperture was found in seven of the ten subjects. Taken together these preliminary results suggest that coordinated actions are subserved by the use of a common coordinating schema independently from the effectors involved.