Chapter 2. Prehension

Chapter 3 - Serial Order in Prehension 55
REACHING AND GRASPING
HEAD EYE IPOSITIONING
- FOVEAL GRASPING
IDENTIFICATION LOCATION
Shape cues Positional cues
0 TRIGGERED
Shaped open loop
hand-grip
GUIDED
-
Closed loop
CONTACT-
Mechanical Sensory
action exploration
Oriented I arm movement
Final approach I to the target
Figure 3.4 Paillard’s model of reaching and grasping. Functional
segmentation of reaching behavior is divided into two parallel
visual channels subserving identification and location. Visually
triggered programs presetting the hand grip and orienting the arm
movement might be assisted by visual guidance of grip
positioning and of trajectory in its initial and final stages. Tactile
cues then become prominent to assist manual grasping after
contact with the object is established (from Paillard, 198213;
adapted by permission).
identification channel uses shape cues from central vision for the for-
mation of the hand grip (assisting the ‘pilot’). Contact with the object
ends the parallel processes of visual location and identification, leading
to tactile guidance of grasp, after which follows sensory exploration
and/or mechanical actions with the object.
An alternative model to the distributed ones of Jeannerod, Arbib,
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