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Accuracy demands in natural prehension
Human Movement North-Holland
Science
339
12 (1993) 339-345
Research note
Accuracy demands in natural prehension Frank T.J.M. Zaal a and Reinoud a Free University, Amsterdam, The Netherlands
J. Bootsma
*
b
h Centre National de la Recherche Scientifique, Marseille, France
Abstract Zaal, F.T.J.M. and R.J. note). Human Movement
Bootsma, 1993. Accuracy Science 12, 339-345.
demands
in natural
prehension
(Research
In a recent kinematic analysis of prehensile movements directed toward cylindrical objects of different diameter, Marteniuk, Leavitt, MacKenzie and Athenes (1990) reported a negative linear relationship between object diameter and movement time. The present study was set up to investigate whether this effect was due to the manipulation of (i) object size, or (ii) surface area available for contact. The findings of Marteniuk et al. were not be replicated, as no effect on movement time was found for the range of object diameters studied (3-7 cm). However, a significant difference in movement time was found to exist between differently shaped objects, suggesting that the area available for contact is an important determinant of movement duration.
In a recent study on manual prehension, Marteniuk et al. (1990) reported a negative linear relationship between movement time and disk size. The association of shorter movement times with larger disk sizes, Marteniuk et al. argued, is not in line with the suggestion that object size only influences the grasp component, and not the transport component of the prehensile action (Jeannerod 1981, 1984). However, Jeannerod’s (1981) meaning of object size would seem to relate principally to the minimal hand aperture needed in order to enclose the object, while increasing the diameter of a round object (as was done by Marteniuk et al. 1990) not only affects this parameter, but Correspondence to: F.T.J.M. Zaal, Department of Psychology, Faculty of Human Movement Sciences, Free University, Van der Boechorststraat 9, 1081 BT Amsterdam, The Netherlands. * The authors wish to acknowledge the financial support of the Netherlands Organization for Scientific Research, grant no. 560-259-045, and the Royal Netherlands Academy of Arts and Sciences. We thank Ron Marteniuk for helpful comments.
0167-9457/93/$06.00
0 1993 - Elsevier
Science
Publishers
B.V. All rights reserved
340
F. T.J.M. Zaal, R.J. Bootsma /Accuracy
in prehension
also leads to a larger amount of surface area available for contact. The latter, we suggest, constitutes a change in the spatial accuracy demands for the transport component. Hence, the finding of Marteniuk et al. (1990) that the diameter of a round disk influences movement time may have been the result of an (inadvertent) manipulation of surface area available for contact, rather than speaking to a dependency of the transport component on the aperture to which the hand must be minimally opened. The present study was set up to evaluate the effects of these two object properties (object size and surface area available for contact) independently. To this end, we compared kinematic characteristics of the transport and grasp components of subjects’ movements when they reached to grasp objects of different sizes that were either round or oblate in shape.
Method Seven male and three female volunteers, between 21 and 31 years of age, participated in the experiment. Subjects were seated at a table, with the right arm and hand in line with the shoulder, assuming a standardized initial hand configuration. The object to be grasped was situated 30 cm away from the starting position of the hand along the sagittal plane. Subjects were asked to reach to pick up the object, using an index finger-thumb opposition, and place it on a target position, halfway between the starting position and the object position. No time restrictions were imposed. Fig. 1 visualizes the geometry of the two types of the object employed. In total, six wooden disks t
;u
ROUND
3cm
OBLATE
(
‘ 1:
(--)
Fig. 1. Geometry
5 cm
7cm
. 1;
i------j
of the objects used.
+ 15
F. T.J.M. Zaal, R.J. Bootsma / Accuracy in prehension
341
were used, all 2 cm in height. Three of them had a cylindrical, round form, with diameters of 3, 5, and 7 cm. The other three were modifications of similar cylindrical disks (denoted ‘oblate’). Two parts of the cylinder had been removed, resulting in the same contact surface of 2 x 2 cm for this entire set. The order of presentation of the Size and Type of objects was randomized over subjects. For each object size and type condition, five practice trials were followed by ten experimental trials. Data was collected using a MILCU opto-electrical system (Den Brinker et al. 198.51, with the camera situated 2.4 m above the table surface, facing straight down. Four LEDs were sampled with a frequency of 200 Hz. They were placed on .(i> the target, (ii) the upper medial corner of the thumb nail, (iii) the upper lateral corner of the index finger nail, and (iv) above the styloid process on the radial side of the wrist. Following data acquisition, high frequency noise was removed from the signals using a second order recursive Butter-worth filter (cutoff frequency 10 Hz).
Results Dependent variables were analyzed with 2 (Type of object: round vs. oblate) x 3 (Size of object: 3, 5, and 7 cm> repeated measures ANOVAs. Table 1 presents, as a function of object size and type, the means (and average intra-individual standard deviations) of the dependent variables analyzed. The transport movement time, defined as the time elapsed between the first forward movement of the wrist and the reversal,of direction of wrist movement, was found to be significantly affected by Type (F(1,9) = 24.64, p < O.OOl>, but not by Size. These results do not seem to be in agreement with the findings of Marteniuk et al. (19901, who reported a significant negative relationship between MT and object size. Subsequent linear regression analyses on the data of individual subjects also failed to reveal a systematic relation between MT and object size: for both the round and the oblate objects, only 4 of the 10 subjects revealed statistically significant correlations (but even these were not consistently negative, see table 2). Nevertheless, given the smaller surface area available for contact for the oblate objects, the significant effect of Type of object (round vs. oblate) is consistent with
F. T.J.M. Zaal, R.J. Bootsma / Accuracy in prehension
342
Table 1 Means and intra-individual standard deviations (in parentheses) of kinematic characteristics of transport and grasp components for objects of different size and type, averaged over 10 subjects. Round
Transport Movement Time (ms) Duration of acceleration phase (ms) Duration of deceleration phase (ms) Peak velocity (mm/s) Grasp Peak aperture
Oblate
3cm
5 cm
7 cm
3 cm
5 cm
7cm
(52.7) 325 (38.7) 518 (44.0) 876 (56.6)
861 (75.9) 346 (59.8) 515 (52.1) 868 (55.2)
871 (73.8) 326 (54.1) 546 (52.5) 875 (65.4)
907 (75.3) 351 (61.6) 556 (48.2) 856 (62.5)
944 (103.4) 363 (67.4) 581 (60.9) 862 (60.8)
913 (78.8) 331 (55.6) 582 (57.2) 878 (59.9)
94.3 (3.2) 207 (56.7) 153 (32.3)
110.6 (3.5) 223 (66.1) 127 (26.7)
82.1
100.1
120.1
(4.2) 241 (75.2) 195 (36.7)
(3.0) 239 (61.0) 171 (36.9)
(3.7) 236 (68.2) 171 (34.4)
78.5
(mm) Closing time
(3.5) 237 (81.9) 177 (37.6)
(ms) Peak closing velocity (mm/s)
the hypothesis that more severe constraints on the surface area available for contact lead to longer movement times. On average, MT was 8.58 ms for the round and 921 ms for the oblate objects. When movement time was partitioned into an acceleration and a deceleration phase, the effect of Type of object on total movement time was found to have been caused by a differential lengthening of the deceleration phase (F( 1,9> = 13.67, p < 0.01). Other characteris-
Table 2 Pearson product-moment correlation coefficients between movement time and target object size for individual subjects (using all 30 trials - 3 sizes X 10 trials) for the round and oblate objects. Subject
Round Oblate
1
2
3
4
0.095 0.049
0.014 0.000
0.052 0.052
0.582 ’ 0.199 - 0.606 a 0.604 ’ 0.371 a -0.186 0.149 - 0.563 a -0.439 a 0.293 - 0.212 0.649 ” 0.411 ” - 0.039
a p < 0.05.
5
6
7
8
9
10
F. T.J.M. Zaal, R.J. Bootsma
/ Accuracy
in prehension
343
tics of the transport component, such as the peak velocity attained, were not influenced by either Type or Size. The magnitude of the peak hand aperture (calculated as the maximal distance between the IREDS on the two fingers) was found to depend on both the Size (F(2,18) = 810.74, p < 0.001) and the Type of object (F(1,9) = 29.96, p < 0.001). The interaction of Size X Type also reached significance (F(2,18) = 5.05, p < 0.05). In agreement with the findings of Marteniuk et al. (1990), peak aperture was found to increase with object size, for both the round and the oblate objects (Aperture [mm] = 54.34 + 0.80 *Object Size [mm], r(3) = 1.00, for the round objects; Aperture [mm] = 53.27 + 0.95 *Object Size [mm], r(3) = 1.00, for the oblate objects, respectively). Note that the differential effect on peak aperture of the two types of object is the result of a difference in slope, while the intercepts are virtually similar. The time taken to execute the grasp (i.e., the time between the moment of occurrence of peak aperture and the first movement of the target object) was found to be affected by Type (F(1,9) = 6.21, p < 0.051, but not by Size. The peak closing velocity of the hand was influenced by both Size (F(2,18) = 16.32, p < 0.001) and Type (F(1,9) = 13.05, p < 0.01). Peak hand closing velocity was found to be a function of the distance to be covered by the fingers: Peak Closing Velocity (mm/s) = - 85.83 + 5.28 * [Peak Aperture - Object Size] (mm), r(6) = 0.96, F(1,4) = 46.36, p < 0.001. An analysis on individual subjects also supported this relationship: correlations calculated per subject using the data from all 60 trials (3 sizes with 2 types X 10 trials) ranged from 0.53 to 0.83, p’s < 0.001.
Discussion The influence, reported by Marteniuk et al. (19901, of the diameter of cylindrical target objects on the time taken to complete a prehensile movement could not be replicated for the range of diameters used in the present experiment (3-7 cm). Reexamination of the Marteniuk et al. (1990) data revealed that the effect was primarily caused by the longer MT’s found for 1 and 2 cm disks. For the range of disk diameters used in the present experiment, the best linear fit to their data is described by MT (ms> = 635 + 2.3 *Disk Diameter (cm), F(1,4) = 0.52, ns, which is consistent with the present results. The fact that
344
F. T.J.M. Zaal, R.J. Bootsma / Accuracy in prehension
smaller disk diameters (1 and 2 cm) led to larger MT’s is consistent with the hypothesis that surface area available for contact is the prime determiner of MT. In the present study, a significant main effect of object type was found, also supporting the hypothesis that movement time is affected by the amount of surface area available for contacting the object, rather than by the minimal hand aperture required. The former constitutes a spatial constraint on the transport component. The longer movement time found for the oblate as compared to the round objects could be attributed to a differential lengthening of the deceleration phase. This observation is in line with the ‘precision effect’ reported by MacKenzie et al. (1987) for aiming movements and Marteniuk et al. (1987) for prehensile movements. We suggest that the spatial accuracy demands of the task at hand determine the duration of the deceleration phase, while the amplitude of the movement determines the duration of the acceleration phase (and the magnitude of the peak velocity attained). Taken together, these findings point to a type of control that is driven primarily by global distance-to-becovered information during the initial phase of the movement, but shifts to more refined spatio-temporal information near the end (cf. Bootsma and Van Wieringen 19921. The greater spatial constraints on the transport component in reaching for the oblate objects was accompanied by an increase of the maximal aperture reached during the movement (for similar sized objects), in line with the findings of Wing et al. (1986). The velocity with which the hand was closed appeared to be a function of the distance to be covered by the fingers, with systematically higher movement speeds being attained for larger distances. This increase in peak hand closing velocity, however, was smaller than required for isochronous grasping times, giving rise to longer grasping movement times for the oblate objects.
References Bootsma, R.J. and P.C.W. van Wieringen, 1992. Spatio-temporal organisation of natural prehension. Human Movement Science 11, 205-215. Den Brinker, B.P.L.M., J.D. Krol and R. Zevering, 1985. ‘Een bewegingsanalyse-systeem voor “real-time” coordinatie-feedback’ [A movement analysis system for real-time coordination feedback]. In: F.J. Maarse, W.E.J. van de Bosch, E.A. Zuiderveen and P. Wittenberg (eds.1, Computers in de psychologie. Lisse: Swets & Zeitlinger.
F. T.J.M. Zaal, R.J. Bootsma / Accuracy in prehension
345
Jeannerod, M., 1981. ‘Intersegmental coordination during reaching at natural visual objects’. In: J. Long and A. Baddeley (eds.), Attention and performance IX. Hillsdale, NJ: Erlbaum. Jeannerod, M., 1984. The timing of natural prehension movements. Journal of Motor Behavior 16, 235-254. MacKenzie, C.L., R.G. Marteniuk, C. Dugas, D. Liske and B. Eickmeier, 1987. Three-dimensional movement trajectories in Fitt’s task: Implications for control. Quarterly Journal of Experimental Psychology 39A, 629-647. Marteniuk, R.G., J.L. Leavitt, CL. MacKenzie and S. Athenes, 1990. Functional relationships between grasp and transport components in a prehension task. Human Movement Science 9, 149-176. Marteniuk, R.G., C.L. MacKenzie, M. Jeannerod, S. Athenes and C. Dugas, 1987. Constraints on human arm movement trajectories. Canadian Journal of Psychology, 41, 365-378. Wing, A.M., A. Turton and C. Fraser, 1986. Grasp size and accuracy of approach in reaching. Journal of Motor Behavior 18, 245-260.
Science
339
12 (1993) 339-345
Research note
Accuracy demands in natural prehension Frank T.J.M. Zaal a and Reinoud a Free University, Amsterdam, The Netherlands
J. Bootsma
*
b
h Centre National de la Recherche Scientifique, Marseille, France
Abstract Zaal, F.T.J.M. and R.J. note). Human Movement
Bootsma, 1993. Accuracy Science 12, 339-345.
demands
in natural
prehension
(Research
In a recent kinematic analysis of prehensile movements directed toward cylindrical objects of different diameter, Marteniuk, Leavitt, MacKenzie and Athenes (1990) reported a negative linear relationship between object diameter and movement time. The present study was set up to investigate whether this effect was due to the manipulation of (i) object size, or (ii) surface area available for contact. The findings of Marteniuk et al. were not be replicated, as no effect on movement time was found for the range of object diameters studied (3-7 cm). However, a significant difference in movement time was found to exist between differently shaped objects, suggesting that the area available for contact is an important determinant of movement duration.
In a recent study on manual prehension, Marteniuk et al. (1990) reported a negative linear relationship between movement time and disk size. The association of shorter movement times with larger disk sizes, Marteniuk et al. argued, is not in line with the suggestion that object size only influences the grasp component, and not the transport component of the prehensile action (Jeannerod 1981, 1984). However, Jeannerod’s (1981) meaning of object size would seem to relate principally to the minimal hand aperture needed in order to enclose the object, while increasing the diameter of a round object (as was done by Marteniuk et al. 1990) not only affects this parameter, but Correspondence to: F.T.J.M. Zaal, Department of Psychology, Faculty of Human Movement Sciences, Free University, Van der Boechorststraat 9, 1081 BT Amsterdam, The Netherlands. * The authors wish to acknowledge the financial support of the Netherlands Organization for Scientific Research, grant no. 560-259-045, and the Royal Netherlands Academy of Arts and Sciences. We thank Ron Marteniuk for helpful comments.
0167-9457/93/$06.00
0 1993 - Elsevier
Science
Publishers
B.V. All rights reserved
340
F. T.J.M. Zaal, R.J. Bootsma /Accuracy
in prehension
also leads to a larger amount of surface area available for contact. The latter, we suggest, constitutes a change in the spatial accuracy demands for the transport component. Hence, the finding of Marteniuk et al. (1990) that the diameter of a round disk influences movement time may have been the result of an (inadvertent) manipulation of surface area available for contact, rather than speaking to a dependency of the transport component on the aperture to which the hand must be minimally opened. The present study was set up to evaluate the effects of these two object properties (object size and surface area available for contact) independently. To this end, we compared kinematic characteristics of the transport and grasp components of subjects’ movements when they reached to grasp objects of different sizes that were either round or oblate in shape.
Method Seven male and three female volunteers, between 21 and 31 years of age, participated in the experiment. Subjects were seated at a table, with the right arm and hand in line with the shoulder, assuming a standardized initial hand configuration. The object to be grasped was situated 30 cm away from the starting position of the hand along the sagittal plane. Subjects were asked to reach to pick up the object, using an index finger-thumb opposition, and place it on a target position, halfway between the starting position and the object position. No time restrictions were imposed. Fig. 1 visualizes the geometry of the two types of the object employed. In total, six wooden disks t
;u
ROUND
3cm
OBLATE
(
‘ 1:
(--)
Fig. 1. Geometry
5 cm
7cm
. 1;
i------j
of the objects used.
+ 15
F. T.J.M. Zaal, R.J. Bootsma / Accuracy in prehension
341
were used, all 2 cm in height. Three of them had a cylindrical, round form, with diameters of 3, 5, and 7 cm. The other three were modifications of similar cylindrical disks (denoted ‘oblate’). Two parts of the cylinder had been removed, resulting in the same contact surface of 2 x 2 cm for this entire set. The order of presentation of the Size and Type of objects was randomized over subjects. For each object size and type condition, five practice trials were followed by ten experimental trials. Data was collected using a MILCU opto-electrical system (Den Brinker et al. 198.51, with the camera situated 2.4 m above the table surface, facing straight down. Four LEDs were sampled with a frequency of 200 Hz. They were placed on .(i> the target, (ii) the upper medial corner of the thumb nail, (iii) the upper lateral corner of the index finger nail, and (iv) above the styloid process on the radial side of the wrist. Following data acquisition, high frequency noise was removed from the signals using a second order recursive Butter-worth filter (cutoff frequency 10 Hz).
Results Dependent variables were analyzed with 2 (Type of object: round vs. oblate) x 3 (Size of object: 3, 5, and 7 cm> repeated measures ANOVAs. Table 1 presents, as a function of object size and type, the means (and average intra-individual standard deviations) of the dependent variables analyzed. The transport movement time, defined as the time elapsed between the first forward movement of the wrist and the reversal,of direction of wrist movement, was found to be significantly affected by Type (F(1,9) = 24.64, p < O.OOl>, but not by Size. These results do not seem to be in agreement with the findings of Marteniuk et al. (19901, who reported a significant negative relationship between MT and object size. Subsequent linear regression analyses on the data of individual subjects also failed to reveal a systematic relation between MT and object size: for both the round and the oblate objects, only 4 of the 10 subjects revealed statistically significant correlations (but even these were not consistently negative, see table 2). Nevertheless, given the smaller surface area available for contact for the oblate objects, the significant effect of Type of object (round vs. oblate) is consistent with
F. T.J.M. Zaal, R.J. Bootsma / Accuracy in prehension
342
Table 1 Means and intra-individual standard deviations (in parentheses) of kinematic characteristics of transport and grasp components for objects of different size and type, averaged over 10 subjects. Round
Transport Movement Time (ms) Duration of acceleration phase (ms) Duration of deceleration phase (ms) Peak velocity (mm/s) Grasp Peak aperture
Oblate
3cm
5 cm
7 cm
3 cm
5 cm
7cm
(52.7) 325 (38.7) 518 (44.0) 876 (56.6)
861 (75.9) 346 (59.8) 515 (52.1) 868 (55.2)
871 (73.8) 326 (54.1) 546 (52.5) 875 (65.4)
907 (75.3) 351 (61.6) 556 (48.2) 856 (62.5)
944 (103.4) 363 (67.4) 581 (60.9) 862 (60.8)
913 (78.8) 331 (55.6) 582 (57.2) 878 (59.9)
94.3 (3.2) 207 (56.7) 153 (32.3)
110.6 (3.5) 223 (66.1) 127 (26.7)
82.1
100.1
120.1
(4.2) 241 (75.2) 195 (36.7)
(3.0) 239 (61.0) 171 (36.9)
(3.7) 236 (68.2) 171 (34.4)
78.5
(mm) Closing time
(3.5) 237 (81.9) 177 (37.6)
(ms) Peak closing velocity (mm/s)
the hypothesis that more severe constraints on the surface area available for contact lead to longer movement times. On average, MT was 8.58 ms for the round and 921 ms for the oblate objects. When movement time was partitioned into an acceleration and a deceleration phase, the effect of Type of object on total movement time was found to have been caused by a differential lengthening of the deceleration phase (F( 1,9> = 13.67, p < 0.01). Other characteris-
Table 2 Pearson product-moment correlation coefficients between movement time and target object size for individual subjects (using all 30 trials - 3 sizes X 10 trials) for the round and oblate objects. Subject
Round Oblate
1
2
3
4
0.095 0.049
0.014 0.000
0.052 0.052
0.582 ’ 0.199 - 0.606 a 0.604 ’ 0.371 a -0.186 0.149 - 0.563 a -0.439 a 0.293 - 0.212 0.649 ” 0.411 ” - 0.039
a p < 0.05.
5
6
7
8
9
10
F. T.J.M. Zaal, R.J. Bootsma
/ Accuracy
in prehension
343
tics of the transport component, such as the peak velocity attained, were not influenced by either Type or Size. The magnitude of the peak hand aperture (calculated as the maximal distance between the IREDS on the two fingers) was found to depend on both the Size (F(2,18) = 810.74, p < 0.001) and the Type of object (F(1,9) = 29.96, p < 0.001). The interaction of Size X Type also reached significance (F(2,18) = 5.05, p < 0.05). In agreement with the findings of Marteniuk et al. (1990), peak aperture was found to increase with object size, for both the round and the oblate objects (Aperture [mm] = 54.34 + 0.80 *Object Size [mm], r(3) = 1.00, for the round objects; Aperture [mm] = 53.27 + 0.95 *Object Size [mm], r(3) = 1.00, for the oblate objects, respectively). Note that the differential effect on peak aperture of the two types of object is the result of a difference in slope, while the intercepts are virtually similar. The time taken to execute the grasp (i.e., the time between the moment of occurrence of peak aperture and the first movement of the target object) was found to be affected by Type (F(1,9) = 6.21, p < 0.051, but not by Size. The peak closing velocity of the hand was influenced by both Size (F(2,18) = 16.32, p < 0.001) and Type (F(1,9) = 13.05, p < 0.01). Peak hand closing velocity was found to be a function of the distance to be covered by the fingers: Peak Closing Velocity (mm/s) = - 85.83 + 5.28 * [Peak Aperture - Object Size] (mm), r(6) = 0.96, F(1,4) = 46.36, p < 0.001. An analysis on individual subjects also supported this relationship: correlations calculated per subject using the data from all 60 trials (3 sizes with 2 types X 10 trials) ranged from 0.53 to 0.83, p’s < 0.001.
Discussion The influence, reported by Marteniuk et al. (19901, of the diameter of cylindrical target objects on the time taken to complete a prehensile movement could not be replicated for the range of diameters used in the present experiment (3-7 cm). Reexamination of the Marteniuk et al. (1990) data revealed that the effect was primarily caused by the longer MT’s found for 1 and 2 cm disks. For the range of disk diameters used in the present experiment, the best linear fit to their data is described by MT (ms> = 635 + 2.3 *Disk Diameter (cm), F(1,4) = 0.52, ns, which is consistent with the present results. The fact that
344
F. T.J.M. Zaal, R.J. Bootsma / Accuracy in prehension
smaller disk diameters (1 and 2 cm) led to larger MT’s is consistent with the hypothesis that surface area available for contact is the prime determiner of MT. In the present study, a significant main effect of object type was found, also supporting the hypothesis that movement time is affected by the amount of surface area available for contacting the object, rather than by the minimal hand aperture required. The former constitutes a spatial constraint on the transport component. The longer movement time found for the oblate as compared to the round objects could be attributed to a differential lengthening of the deceleration phase. This observation is in line with the ‘precision effect’ reported by MacKenzie et al. (1987) for aiming movements and Marteniuk et al. (1987) for prehensile movements. We suggest that the spatial accuracy demands of the task at hand determine the duration of the deceleration phase, while the amplitude of the movement determines the duration of the acceleration phase (and the magnitude of the peak velocity attained). Taken together, these findings point to a type of control that is driven primarily by global distance-to-becovered information during the initial phase of the movement, but shifts to more refined spatio-temporal information near the end (cf. Bootsma and Van Wieringen 19921. The greater spatial constraints on the transport component in reaching for the oblate objects was accompanied by an increase of the maximal aperture reached during the movement (for similar sized objects), in line with the findings of Wing et al. (1986). The velocity with which the hand was closed appeared to be a function of the distance to be covered by the fingers, with systematically higher movement speeds being attained for larger distances. This increase in peak hand closing velocity, however, was smaller than required for isochronous grasping times, giving rise to longer grasping movement times for the oblate objects.
References Bootsma, R.J. and P.C.W. van Wieringen, 1992. Spatio-temporal organisation of natural prehension. Human Movement Science 11, 205-215. Den Brinker, B.P.L.M., J.D. Krol and R. Zevering, 1985. ‘Een bewegingsanalyse-systeem voor “real-time” coordinatie-feedback’ [A movement analysis system for real-time coordination feedback]. In: F.J. Maarse, W.E.J. van de Bosch, E.A. Zuiderveen and P. Wittenberg (eds.1, Computers in de psychologie. Lisse: Swets & Zeitlinger.
F. T.J.M. Zaal, R.J. Bootsma / Accuracy in prehension
345
Jeannerod, M., 1981. ‘Intersegmental coordination during reaching at natural visual objects’. In: J. Long and A. Baddeley (eds.), Attention and performance IX. Hillsdale, NJ: Erlbaum. Jeannerod, M., 1984. The timing of natural prehension movements. Journal of Motor Behavior 16, 235-254. MacKenzie, C.L., R.G. Marteniuk, C. Dugas, D. Liske and B. Eickmeier, 1987. Three-dimensional movement trajectories in Fitt’s task: Implications for control. Quarterly Journal of Experimental Psychology 39A, 629-647. Marteniuk, R.G., J.L. Leavitt, CL. MacKenzie and S. Athenes, 1990. Functional relationships between grasp and transport components in a prehension task. Human Movement Science 9, 149-176. Marteniuk, R.G., C.L. MacKenzie, M. Jeannerod, S. Athenes and C. Dugas, 1987. Constraints on human arm movement trajectories. Canadian Journal of Psychology, 41, 365-378. Wing, A.M., A. Turton and C. Fraser, 1986. Grasp size and accuracy of approach in reaching. Journal of Motor Behavior 18, 245-260.