Chapter 2. Prehension

476 THE GRASPING HAND
Pen, as grasped object, 21,27,28
Pencil, as grasped object, 275
Perceptron, definition, 391n
Perceptual constraints, on grasping, 325
Perceptual constraints on gras ing, 308t
Performatory movements, 2 4 336-37
distribution of temporal frequencies,
267f
and motor control, 268
and task requirements, 281
Periosteum, 210
Peripheral vision
and grasping, 178, 179-84, lSOf, 181f
and maximum aperture, 181f
and transport component, 200
Perturbations
effect on grasping, 58
and grasp forcefload force ratio, 258,
and Fitts' Law, 317, 318
and object velocity, 14%
and spatial location, 119,120
velocity rofiles, 123, 125,129
Position, o?contact point, zs
Postures, hand. see Classificatio,
prehensile; Grasp types; Hand,
postures, classification of
Power grasp, 19t, 2Ot, 23,24f, 25,26f, 29,
30,36,262,263t, 263-64,369,37Ot,
371t. 372f. 374,380
Power requirements, of prehension, 23-25
Precision effect, 125, 154, 199,292
Precision grasp, 19t, 2Ot, 23,24f, 25,26f,
28f. 29.35, 171, 174.263-64.369,
37Ot, 37 It
Precision requirements. See als~ Asymmetric
velocity profiles; Fitts' Law
and deceleration of movement, 167
and dynamic grasps, 25-28
and object size, 167
Prehensile classifications.
Classification, prehensile
Prehension
259
and hand transport, 158f
kinematics of, 164f
of load force, during grasping, 258-60
of object direction, 160f. 161,165
of object distance, 161-62.165
of object location, 79.80
as black box.
of object orientation, 79,80,162
. 6,7f. . 43f. . . 198f. . 28Of. .
33Of
and object perception, 77-79
constraints on
of object shape, 162-63, 165
high level, 316-19
of object size, 163, 165-67
physical, 307-12
and pad Opposition, 157,158,167
sensorimotor, 312-16
and palm opposition, 167
summary, 305-7,308t
and selection of grasp type, 166-67
definition, 3,6,15,23,204,279,330
and selection of opposition type, 167
phases, 284f, 285. 339-41.34Of
and stable grasp, 244
research approaches, 7-15
studies, 156-66
Preload phase, of lifting, Zlf, 252.2%
and task requirements, during loading or
Premotor cortex, 175
unloading, 260
Preshape Schema. See als~ Shape, of object
thumb, 157-58
Phases of prehension
and ballpark model, 188
and conceptual models, 59-60
and Coordinated Control Program, 189-90
criteria for defiie. 60-61
in palm-focused model of grasping,
Physiological const&ts on grasping, 15,
194-95,195f, 196,291f
16,308t. 325
Presha@ng
Pinch gras ,2Ot, 22,27,78f, 270,272t.
as Merent from enclosing, 191,192
369, f7Ot, 371t, 372f, 374
and gras component, 145
Plan. definition. 63
phases, $2
Planes of the &dy, 349-50
and proprioceptive information, 185-86,
Planning of prehension. See als~ Task plans;
186f
and sensory information, 178,191-92
Trajectory planning
time spent in, 152
aspects, 63-64
Pressure, and hardness perception, 231,232f.
and ballpark model, 200-201
233t, 234
hand location and orientation, 94-105
Primary dermal papillae, 208f. 209
perceiving object properties, 76-83
Primary ridges, 209
selecting grasp strategy, 83-94
Prismatic grasp, 25,26f
task plans, 65-76
Pronation (movement), 357% 358
theories, 64-65
Proprioception
Point contact, 236f
definition, 8
Poinling
map. 118,119
deceleration phase of, 146, 147f
Roprioceptive information
as different from grasping, 148, 155
and grasp formation, 177
(Letters after page numbers: f=figure; n=fmtnote; t-table.)