Proportional and nonproportional transfer of movement sequences

Two experiments were designed to determine participants' ability to transfer a learned movement sequence to new spatial locations. A 16-element dynamic arm movement sequence was used in both experiments. The task required participants to move a horizontal lever to sequentially projected targets. Experiment 1 included 2 groups. One group practised a pattern in which targets were located at 20, 40, 60, and 80° from the start position (long sequence). The other group practised a pattern with targets at 20, 26.67, 60, and 80° (mixed sequence). Both groups were tested 24 hours later on the long, mixed, and short sequence. The short sequence was considered a proportional transfer for the long acquisition group because all the amplitudes between targets were reduced by the same proportion. Nonproportional transfer occurred when the amplitudes between targets did not have the same proportions as those for their practice sequence (e.g., long sequence to mixed sequence or vice versa). The results indicated that participants could effectively transfer to new target configurations regardless of whether the transfer required proportional or nonproportional spatial changes to the movement pattern. Experiment 2 assessed the effects of extended practice on proportional and nonproportional spatial transfer. The data indicated that while participants can effectively transfer to both proportional and nonproportional spatial transfer conditions after 1 day of practice, they are only effective at transferring to proportional transfer conditions after 4 days of practice. The results are discussed in terms of the mechanism by which response sequences become increasingly specific over extended practice in an attempt to optimize movement production.     

The transfer of movement sequences: effects of decreased and increased load

A number of recent experiments have demonstrated that a movement structure develops during the course of learning a movement sequence that provides the basis for transfer. After learning a movement sequence participants have been shown to be able to effectively produce the sequence when movement demands require that the sequence be rescaled in amplitude or produced with an unpractised set of effectors. The purpose of the present experiment was to determine whether participants, after learning a complex 16-element movement sequence with a 0.567-kg load, could also effectively produce the sequence when the load was decreased (0.0 kg) or increased (1.134 kg). The results indicated that participants were able to effectively compensate for decreased and increased load with virtually no changes in performance characteristics (displacement, velocity, acceleration, and pattern of element durations) while electromyographic (EMG) signals demonstrated that smaller (reduced load) or larger forces (increased load) were spontaneously generated to compensate for the change in load. The muscle activation patterns of the biceps and triceps as well as the level of coactivation appeared to be generally upscaled to generate and dissipate the changes in force requirement needed to compensate for the increased load.     

The transfer of movement sequences: Effects of decreased and increased load

A number of recent experiments have demonstrated that a movement structure develops during the course of learning a movement sequence that provides the basis for transfer. After learning a movement sequence participants have been shown to be able to effectively produce the sequence when movement demands require that the sequence be rescaled in amplitude or produced with an unpractised set of effectors. The purpose of the present experiment was to determine whether participants, after learning a complex 16-element movement sequence with a 0.567-kg load, could also effectively produce the sequence when the load was decreased (0.0 kg) or increased (1.134 kg). The results indicated that participants were able to effectively compensate for decreased and increased load with virtually no changes in performance characteristics (displacement, velocity, acceleration, and pattern of element durations) while electromyographic (EMG) signals demonstrated that smaller (reduced load) or larger forces (increased load) were spontaneously generated to compensate for the change in load. The muscle activation patterns of the biceps and triceps as well as the level of coactivation appeared to be generally upscaled to generate and dissipate the changes in force requirement needed to compensate for the increased load.     

The effects of sequence difficulty and practice on proportional and nonproportional transfer

Two experiments were designed to determine participants' ability to transfer a learned movement sequence to new spatial locations. A 16-element dynamic arm movement sequence was used in both experiments. The task required participants to move a horizontal lever to sequentially projected targets. Experiment 1 included two groups. One group practised a relatively easy 16-element movement sequence (easy long). The other group practised a more difficult 16-element movement sequence (difficult long). Approximately 24 hours after practice with their respective sequence both groups were administered a retention and two transfer tests. The only difference between the retention and transfer tests was the location of the targets. The short transfer target configuration was considered a proportional transfer because all the amplitudes between targets were reduced by the same proportion. The mixed transfer configuration was considered a nonproportional transfer because the targets did not have the same proportional distances between targets as the sequence they practised. The results indicated that participants could effectively transfer the difficult long sequence to the new target configurations regardless of whether the transfer required proportional and nonproportional spatial changes to the movement pattern. However, the easy long sequence was only effectively transferred in the proportional transfer condition. Experiment 2 assessed the effects of extended practice of the easy long sequence on proportional and nonproportional spatial transfer. The data indicated that participants could again effectively transfer the easy long sequence to proportional but not the nonproportional spatial transfer conditions regardless of the amount of practice (1 or 4 days). The results are discussed in terms of the mechanism by which response sequences become increasingly specific over extended practice in an attempt to optimize movement production and how this process interacts with the difficulty of the sequence.     

The effects of sequence difficulty and practice on proportional and nonproportional transfer

Two experiments were designed to determine participants' ability to transfer a learned movement sequence to new spatial locations. A 16-element dynamic arm movement sequence was used in both experiments. The task required participants to move a horizontal lever to sequentially projected targets. Experiment 1 included two groups. One group practised a relatively easy 16-element movement sequence (easy long). The other group practised a more difficult 16-element movement sequence (difficult long). Approximately 24 hours after practice with their respective sequence both groups were administered a retention and two transfer tests. The only difference between the retention and transfer tests was the location of the targets. The short transfer target configuration was considered a proportional transfer because all the amplitudes between targets were reduced by the same proportion. The mixed transfer configuration was considered a nonproportional transfer because the targets did not have the same proportional distances between targets as the sequence they practised. The results indicated that participants could effectively transfer the difficult long sequence to the new target configurations regardless of whether the transfer required proportional and nonproportional spatial changes to the movement pattern. However, the easy long sequence was only effectively transferred in the proportional transfer condition. Experiment 2 assessed the effects of extended practice of the easy long sequence on proportional and nonproportional spatial transfer. The data indicated that participants could again effectively transfer the easy long sequence to proportional but not the nonproportional spatial transfer conditions regardless of the amount of practice (1 or 4 days). The results are discussed in terms of the mechanism by which response sequences become increasingly specific over extended practice in an attempt to optimize movement production and how this process interacts with the difficulty of the sequence.     

Distributed planning of movement sequences

Three experiments are reported that examine whether fast finger-tapping sequences are entirely planned before execution starts (advance planning), or if they can be started while planning is still under way (distributed planning). Subjects performed finger tapping sequences of three to eight taps at a high rate, under both simple and 2-choice reaction time (RT) conditions. The sequences differed in the location of an accentuated element within them. The RT to choose between sequences with different accent locations progressively decreased as an inverse function of the time-distance between the initial tap and the first point at which the alternative sequences differed. The shortening in choice reaction time (CRT) was never accompanied by noticeable changes in the inter-response times or force patterns of the tapping sequences. The RT to initiate sequences with accent location known beforehand (SRT condition) showed, in two of three experiments, a weak decreasing trend as the accentuated tap shifted away from the beginning of the sequence. The SRT results suggest a possible predominance of advance planning when the same sequence is repeated over a series of trials. The CRT results are taken as evidence that planning of the sequence beyond the unpredictable tap could be distributed before and after sequence initiation. Several factors are discussed that may influence the balance between planning in advance of, and planning in parallel with, sequence execution.     

Part-whole practice of movement sequences

A 16-element movement sequence was taught under part-whole and whole-practice conditions. Participants (N = 18) produced a right-arm lever movement to sequentially presented target locations. The authors constructed part-whole practice by providing practice on only the 1st 8 elements on the 1st day of practice (100 repetitions of the 8-element sequence) and on all 16 elements on the 2nd day of practice (100 repetitions of the 16-element sequence). The whole-practice group practiced all 16 elements on both days (100 repetitions of the 16-element sequence per day). No differences in sequence structure or in movement duration of the 16-element sequence were noted on the retention test (Day 3). On transfer tests in which the 1st and last 8 elements were tested separately, however, the participants in the part-whole practice group performed more quickly than the participants in the whole-practice group, especially on the last 8 elements. Participants in the whole-practice group appeared to code the sequence so that it was relatively difficult to fully partition it into separate movements. Thus, on the transfer tests, there continued to be residual effects of the 8 elements that did not have to be produced but slowed down the rate of responding for the whole-practice group. That finding was not observed for the part-whole practice group.     

Rhythm and the timing of movement sequences

Summary Many motor skills involve a sequence of movements phased over a period of time. The present study investigated the importance of rhythmic timing structures in the acquisition and control of a serial key-pressing task. Four groups of subjects received extensive practice on 9-element finger sequences varying in the form of the inherent temporal structure. Following a training period, the stability of the various timing patterns was examined by requiring subjects to perform the key-pressing task concurrently with a verbal memory task. The memory task involved reporting back a sequence of visually-presented words with a lag of one word. A comparison was made of performance on the two tasks under dual task and control (single task) conditions. The results suggested that natural rhythmic timing structures require less attention for production than unnatural temporal patterns. A breakdown of the temporal patterns into within-group and between-group intervals showed that patterns containing within-group intervals that related as 1:1 or 1:2 evidenced good stability under dual-task conditions. These results were taken as support for the suggestion by Fraisse (1946) that the perception and production of rhythms can be understood by an internal representation that allows only two distinct durations that relate as 1:2. Furthermore, it was suggested that relative timing may become an invariant property of motor program representation only in those instances in which the timing sequence completely fits the internal timing structure.     

Coding of on-line and pre-planned movement sequences

Recent experiments have demonstrated that complex multi-element movement sequences were coded in visual-spatial coordinates even after extensive practice, while relatively simple spatial-temporal movement sequences are coded in motor coordinates after a single practice session. The purpose of the present experiment was to determine if the control process rather than the difficulty of the sequence played a role in determining the pattern of effector transfer. To accomplish this, different concurrent feedback conditions were provided to two groups of participants during practice of the same movement sequence. The results indicated that when concurrent visual feedback was provided during the production of the movement, which was thought to encourage on-line control, the participants performed transfer tests with the contra-lateral limb better when the visual-spatial coordinates were reinstated than when the motor coordinates were reinstated. When concurrent visual feedback was not provided, which was thought to encourage pre-planned control, the opposite was observed. The data are consistent with the hypothesis that the mode of control dictates the coordinate system used to code the movement sequence rather than sequence difficulty or stage of practice as has been proposed.     

Hierarchical control of rapid movement sequences

Are movement sequences executed in a hierarchically controlled fashion? We first state explicitly what such control would entail, and we observe that if a movement sequence is planned hierarchically, that does not imply that its execution is hierarchical. To find evidence for hierarchically controlled execution, we require subjects to perform memorized sequences of finger responses like those used in playing the piano. The error data we obtain are consistent with a hierarchical planning as well as execution model, but the interresponse-time data provide strong support for a hierarchical execution model. We consider three alternatives to the hierarchical execution model and reject them. We also consider the implications of our results for the role of timing in motor programs, the characteristics of motor buffers, and the relations between memory for symbolic and motor information.     

Central and peripheral coordination in movement sequences

Summary Motor coordination has been too poorly defined to be a useful construct in studying the control of movement. In general, motor coordination involves controlling both the timing and the kinematics of movement. Yet the motor behaviors typically used for the study of coordination have required controlling only the timing or the spatial aspects of a movement. To understand better the basis of motor behavior, this study examined movement sequences, a class of movement in which both the timing and the kinematics must be controlled. In one experiment we studied a reaching and grasping movement sequence to characterize the central coordination of movement sequences. In another experiment we studied a throwing movement sequence to characterize the peripheral (kinesthetic) coordination of movement sequences. An heuristic model is presented to explain how central and peripheral mechanisms of coordination might interact to produce accurate movement.     

The programming of structural properties of movement sequences

Summary The present paper investigates the role of abstract structural properties in the programming and execution of movement sequences. Three experiments, using converging methods, demonstrate that the motor system represents the abstract structural properties of movement sequences. The first two experiments show that hierarchical structures over a sequence of tapping movements can be used to prepare the motor program, even if the specific elements of the sequence are still unknown. Experiment 2 also shows that the preliminary programming of structural properties of a movement sequence takes more time than the programming of specific elements ( start elements). Experiment 3 suggests that abstract structural properties can be generalized from a special sequence and that they are transferable to other sequences. Abstract structural properties are assumed to be an important component of generalized motor programs.     

Transfer of movement sequences: bigger is better

Experiment 1 was conducted to determine if proportional transfer from "small to large" scale movements is as effective as transferring from "large to small." We hypothesize that the learning of larger scale movement will require the participant to learn to manage the generation, storage, and dissipation of forces better than when practicing smaller scale movements. Thus, we predict an advantage for transfer of larger scale movements to smaller scale movements relative to transfer from smaller to larger scale movements. Experiment 2 was conducted to determine if adding a load to a smaller scale movement would enhance later transfer to a larger scale movement sequence. It was hypothesized that the added load would require the participants to consider the dynamics of the movement to a greater extent than without the load. The results replicated earlier findings of effective transfer from large to small movements, but consistent with our hypothesis, transfer was less effective from small to large (Experiment 1). However, when a load was added during acquisition transfer from small to large was enhanced even though the load was removed during the transfer test. These results are consistent with the notion that the transfer asymmetry noted in Experiment 1 was due to factors related to movement dynamics that were enhanced during practice of the larger scale movement sequence, but not during the practice of the smaller scale movement sequence. The findings that the movement structure is unaffected by transfer direction but the movement dynamics are influenced by transfer direction is consistent with hierarchal models of sequence production.     

Effects of interlimb practice on coding and learning of movement sequences

An interlimb practice paradigm was designed to determine the role that visual–spatial (Cartesian) and motor (joint angles, activation patterns) coordinates play in the coding and learning of complex movement sequences. Participants practised a 16-element movement sequence by moving a lever to sequentially presented targets with one limb on Day 1 and the contralateral limb on Day 2. Practice involved the same sequence with either the same visual–spatial or motor coordinates on the two days. A unilateral practice condition (control) was also tested where both coordinate systems were changed but the same limb was used. Retention tests were conducted on Day 3. Regardless of the order in which the limbs were used during practice, results indicated that keeping the visual–spatial coordinates the same during acquisition resulted in superior retention. This provides strong evidence that the visual–spatial code plays a dominant role in complex movement sequences, and this code is represented in an effector-independent manner.     

Representation of movement sequences is related to task characteristics

Recent experiments have produced mixed results in terms of performance when, after learning a sequential task, the same visual-spatial coordinates or the same motor coordinates were reinstated on a subsequent effector transfer test. Given the diversity of tasks and especially sequence characteristics used in previous experiments, the cross-experimental comparison makes inferences and unambiguous interpretations difficult. The purpose of the present experiment was to determine in a principled manner how the spatio-temporal structure of a sequence influences the way the sequence is represented. The results indicated that after limited amount of practice relatively more simple sequences (S1) are coded more efficiently in a mirror (motor) representation which requires the same pattern of homologous muscle activation. Conversely, relatively more complex sequences (S2) are more efficiently coded in a visual-spatial coordinate system which requires movements to the same spatial locations as during acquisition. The data are also consistent with the notion that sequences with different spatio-temporal structures rely to a different degree on distinct control mechanisms (pre-planned vs. on-line, respectively).     

Preprogramming vs. on-line control in simple movement sequences

In the present experiment the acceleration traces produced during a repetitive arm extension/flexion movement were measured in addition to the RT required to initiate such a movement. The speed at which this task was completed as well as the number of extension/flexion segments were varied to allow for either preprogramming or on-line control. Evidence from the acceleration traces and the RT data suggested that the movements completed as quickly as possible were preprogrammed; whereas, those completed more slowly were controlled on-line. Furthermore, the topologies of the power spectral density functions from the acceleration traces of each type of movement displayed characteristics typical of these forms of control.     

Concatenating familiar movement sequences: the versatile cognitive processor

Earlier studies demonstrated that practicing a series of key presses in a fixed order yields memory representations (i.e., motor chunks) that can be selected and used for sequence execution as if familiar key pressing sequences are single responses. In order to examine whether these motor chunks are robust in different situations and whether preparation for one sequence may overlap with execution of another one, two experiments were carried out in which participants executed two highly practiced keying sequences in rapid succession in response to two simultaneously presented stimuli. The results confirmed robustness of motor chunks, even when the sequences included only two elements, and showed that preparation (and in particular, selection) of a forthcoming sequence may occur during execution of the earlier sequence. Sequences including only two keys appeared to be slowed more by concurrent preparation than longer sequences. Together these results suggest that the execution of familiar keying sequences is predominantly carried out by a dedicated motor processor, and that the cognitive processor can be allocated to preparing a forthcoming sequence (e.g., during execution of an earlier sequence) or, some times, to selecting individual sequence elements in parallel to the motor processor.