Perceptt~aland Motor Shills, 1979, 48, 783-788.

@ Perceptual and Motor skills 1979

SPATIAL-TEMPORAL STRUCTURE OF COINCIDENT-TIMING RESPONSES1 CHARLES H. SHEA AND CARL P. GABBARD Texas AGM University

Summary.-The spatial temporal structure of coincident timing responses was invesrigated using an 86-cm movement from a microswitch to a barrier. The speed of the movement was monitored by a series of photocells placed at equal intervals along the movement line. Subjects ( N = 2 4 ) watched a timer and attempted to displace the barrier at the precise moment that the timer sweephand reached a "target position" (250, 500, 1000 msec.) All subjects were given 100 trials of practice at a particular target position. The results indicate that rapid responses have similar spatial temporal structures but that this pattern is altered in slower movements.

The schema theory of discrete motor skill learning (Schmidt, 1975) posits an open-loop mode of control based on a "generalized" motor program. Presumably, all that is necessary for a novel response to be "run off" is experience with a particular class of movements, information concerning the demands of the environment, and the objective of the movement. Given this information, a unique program that is in tune with the variations in the initial conditions and in the way the movement is to be performed can be extrapolated from the "generalized motor program pool." Schmidt ( 1977) likens this program to a phonograph record with the recorded information in control of the response for 200 to 300 msec. and possible as long as 1 to 2 sec. By varying the speed, i.e., rpms, the response could be run off rapidly or slowly, maintaining the spatio-temporal structure of the response. That is, if an "x" cm movement was made at various speeds, the faster movements should appear as speeded-up copies of the slower movement. The notion that a motor program can be run off at various speeds without changing the basic structure of the sequence and temporal relationship among the motor commands is supported by indirect evidence. For example, Brooks (1974) rewarded cebus monkeys for slamming a handle back and forth as rapidly as possible between two mechanical stops separated by 90'. When the positions of the stops were unexpectedly changed so as to restrict the range - of movement, a number of the monkeys continued to exert force for the duration that had been appropriate for the originally learned task. Insread of oscillating as rapidly as possible, they now pressed the handle against the stops, keeping the rhythm of the movement the same as that originally learned. It appeared as though a centrally strucrured motor command specified 'Requests for reprints should be sent to Charles H. Shea, Motor Behavior Laboratory, Department of Health and Physical Education, Texas A&M University, College Station, Texas 77843.

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an over-all speed of execution. This finding, however, does not differentiate whether the timing of a skill is an intrinsic part of the fixed program presentation or whether it is a parameter that is free to vary depending on the demands of the task. Studies by Armstrong ( 1970), Glencross ( 1973), Summers ( 1975 ) , and Shapiro (1976) suggest that movement rate is a parameter input into the program at the time of execution. Glencross (1973) utilizing a handwheelcranking task observed that the pattern of cranking remained constant even though the speed varied from subject to subject. That is, the duration of the various components, when expressed as a proportion of the total movement time, remained relatively constant across subjects. Likewise, Armstrong, using a serial movement task, found the movement time of a particular segment was determined by changes in the speed of the total movement. Investigating within-subject changes in movemenc patterns, Summers ( 1975 ) and Shapiro ( 1976) had subjects practice a movemenc pattern with particular timlng characteristics. Then, on a transfer task, the subjects were instructed to abandon the timing element of the movemenc and to produce the movement as fast as possible. When the subjects increased their speed of movement, they could not or chose not to eliminate the timing of the previously learned movement. The movements appeared to be only speeded up copies of the original movement. This suggests that a spatio-temporal relationship is inherent in motor programs for a number of discrece tasks and that subjects are able to run off the program at various speeds. The present investigation is an attempt to determine if the "phonograph record" phenomenon holds for discrece coincident-timing tasks. Evidence by Schmidt and Russell ( 1972), Schmidt and McCabe (1976), and Wrisberg and Shea ( 1977) suggests otherwise. That is, subjects engaged in coincident-timing tasks increase their utilization of feedback to guide their movement as movement time increases. These works suggest that only very rapid, i.e., 250 msec., movements are managed by specifications of pre-programmed movement.

Subjects were right-handed, Inale and female undergraduate volunteers ( N = 24) from the basic instructional program at Virginia Polytechnic Institute and State University. None had experience'on the experimental task. Apparatus

The apparatus required the subjects to make 86-cm. movements from a microswitch to a hinged barrier. The speed of the movement to the barrier was monitored by a series of photocells placed ar equal intervals along the niovement line. In addition, a .Ol-sec. timer was in full view of the subject

COINCIDENT-TIMING RESPONSES

785

with the sweep-hand movement indicating when the responses should be initiated and terminated.

Design and Procedare After recruitment, subjects were randomly assigned to one of three groups with the restriction that each group contain four males and four females. The independent variable which differentiated the groups was target time. Following the initial 1-sec. sweep of the clock hand, a 250-msec. group attempted to displace the barrier at precisely one-quarter revolution of the .Ol-sec. timer, while the 500-msec. and 1000-msec. groups attempted to displace the barrier at one half and one full revolution, respectively. All subjects were given 100 trials of practice. In all other respects, including trial to trial interval, each group was treated identically. Measures

On each response there were six measures recorded; as illustrated in Fig. 1 (Note: the temporal sequence illustrated moves from left to right). Following a constant 1-sec. delay the sweep hand on the clock began to move in a clockwise direction ("clock begins"). This event was followed by the initiation ("subject begins") and completion ("subject arrives") of the subject's movement. As the subject moved to the barrier, he passed three photocells ("passes PC") located at equal intervals along the microswitch target line. In the schematic shown the subject reached the barrier ("subject arrives") before the clock hand reached "X" rnsec. ("clock arrives"). Thus, algebraic error (AE) was the difference with respect to sign between when the subject displaced the barrier and the arrival of the clock hand at "X" msec. Early responses received a negative algebraic sign and late responses a positive sign. Total movement time (MT) was the time from initiation to termination of the subject's response, while each segment's movement time (SEG.) was that portion of the total movement utilized in traversing a particular segment. Thus, the sum of the four segments' movement time equalled the total movement time. The movement time of the segments was used to calculate two values termed segmental movement time and segmental variability. Segmental movement time was the mean movement time for a particular segment over "N" trials while segmental variability was the standard deviation of that segment's SBJEO

m55=

P-s

.PASEES

-cCI

CLOCK

CLOCK

BEGINS

6RRIKS

FIG. 1. Diagram illustrating movement time (MT) and algebraic error ( A E ) in a trial during which the subject terminated the movement too early. T h e subject's movement time was further subdivided into segments (SEG.) by passlng through three photocells (PC).

C. H. SHEA

786

6r

C. P. GABBARD

movement time over those trials. The use of these measures was based on the premise that segmental movement time and variability characterized the spatialtemporal pattern of a movement. That is, it was assumed that the movement time of a particular segment was dependent, in part, on the extent to which an error was detected and subsequently corrected. It seems reasonable to assume that, if responses are of sufficient duration for feedback loops to operate, subjects may compare the time which remains with the distance which remains to be traversed and on this basis modify the rate of movement in an attempt to arrive at the target on time. If the progress of the movement is modified consistently in this manner, segmenpl movement time and variability would reflect this modification.

RESULTS The primary finding was that the spatial-temporal movement pattern of the 1000-msec. responses differed from that of the 500- and 250-msec. responses which did not differ from each other. The spatial-temporal pattern of responses, characterized by segmental movement time and variability is given in Table 1. Analysis of variance performed on segmental movement time indicated main effects of both groups ( F 2 , a o = 212.63, 9 < 0.05) and segments ( P 3 , t ~ ~ = 8.39, fi < 0.05). Duncan's new multiple-range test indicated that segmental movement time increased as instructed movement time (groups) inTABLE 1

MEANSEGMENTAL MOVEMENT TIMEAND VARIABILITY* FOR THREE INsTRuCTTD MOVEMENT TIMESBY SEGMENTS Instructed Movement Time (Groups)

Segment

Grand M

3

4

184.48 28.57 7.78

178.83 26.82 6.87

251.69 163.70 42.60

233.00 70.55 19.66

151.32 53.23 32.71

96.03 19.70 7.83

83.55 16.19 6.26

122.37 24.34 8.19

113.32 28.37 13.74

70.54 23.38 13.28

57.60 12.80 11.73

45.12 6.47 2.70

71.43 9.28 2.09

61.17 12.98 7.45

179.64 46.57 22.46

112.70 20.36 9.11

102.50 16.49 5.27

148.49 65.77 17.62

135.83 37.30 13.62

1

2

*

317.01 63.09 21.40

M u

1,000 msec.

Movement Time Variability

M u

500 msec.

Movement Time Variability 250 msec.

Movement Time Variability

M u

Grand Mean Movement Time Variability

M u

"Standard

deviation of

variability.

COINCIDENT-TIMING RESPONSES

787

creased and that subjects traversed segments 1 and 4 more slowly than segments 2 and 3. The analysis of segmental variability revealed main effects of groups (F2,-o = 5.97, p < 0.05) and segments (F3,G0= 3.21, p < 0.05) and an interaction of groups X segments (FG,Go = 2.68, p < 0.05). Simple main effects indicated that the segmental variability of the 250- and 500-msec. groups remained stable across segments while the segmental variability of the 1000-msec. group flusmated across segments. Specifically, segment 4 for the 1000-msec. group was more variable than segment 4 which in turn was more variable than segments 2 and 3.

DISCUSSION The analyses suggest that rapid coincident-timing responses, i.e., 250, 500 msec., have similar spatial-temporal structures. This finding is compatible with the notion proposed by Schmidt (1975, 1977), which suggests that a motor program can vary along the dimension of rate. Indeed, evidence by Schmidt and Russell (1972) and Wrisberg and Shea (1977) suggest thac responses of this duration are preprogrammed. However, the finding that the spatial-temporal pattern of the 1000-msec. response deviates from the movement pattern of more rapid responses suggests there are severe limitations in the extent to which a motor program can vary in terms of movement rate. That is, in slower movements, feedback becomes the mosc effective means of movement control. Presumably subjects making the 1000-msec. response compared the time which remained with the distance which remained to be traversed and on this basis modified the rate of movement in an attempt co arrive at the barrier on time. This position is supported by extremely large segmental variability for segment 4 of the 1000-msec. movement. Moreover, a study by Schmidt and McCabe (1976) suggests that coincident-timing responses of this duration are primarily feedback controlled. While the results are suggestive, a replication of the experiment using a repeated-measures design and a 750-msec. group is needed. The experiment does, however, provide evidence that rapid responses share a similar spatialtemporal pattern but thac this pattern is disrupted in slower movements. REFERENCES

ARMSTRONG, R. R. Training for the production of memorized movement patterns.

Technical Report 26, Human Performance Cenrer, Ann Arbor, Michigan, 1970.

BROOKS, V. B. Some examples of programmed limb movements. Brain Rerearch, 1974, 7 1. 299-308.

GLENCROSS, D. J. The effects of changes in the direction, load, and amplitude of move-

ment on gradation of effort. Journal of Motor Behavior, 1973, 5, 207-216. SCHMIDT,R. A. A schema theory of discrete motor skill learning. P~ychological Review, 1975, 82, 225-260. SCHMLDT.R. A. Schema theory: implication for movement education. Motor Skills: Theory inlo Practice, 1977, 2, 36-38.

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SCHMIDT,R. A., & MCCABE, J. F. Motor program utilization over extended practice. Joarnal o f Human Movement S~udies, 1976, 2, 239-247. SCHMIDT, R. A., & RUSSELL,D. G. Movement velocity and movement time as determiners of degree of preprogramming in simple movements. Joz~rnalof Experimental Psychology, 1972, 96, 315-320. SHAPIRO,D.C. A preliminary experiment to determine the length of a motor program. Proceedings of the NASPSPA National Conference, Austin, Texas, 1976. S ~ M B R SJ. , J. The role of timing in motor program representation. Journal o f Motor Behaeior, 1975, 7 , 229-242. WRISBERG, C. A., & SHEA. C. H. Practice effects on the programming of a coincident t ~ m i n gresponse. In D. M. Landers & R. W. Christina (Eds.), Psychology o f motor behavior and sports-1977. Champaign, Ill.: Human Kinetics Publishers, 1978. Pp. 272-281. Accepted March 10, 1979.

Spatial-temporal structure of coincident-timing responses.

Perceptt~aland Motor Shills, 1979, 48, 783-788. @ Perceptual and Motor skills 1979 SPATIAL-TEMPORAL STRUCTURE OF COINCIDENT-TIMING RESPONSES1 CHARLE...
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