Performance and learning of generalized motor programs: relative (GMP) and absolute (parameter) errors

The effects of practice (Experiment 1) and parameter variability (Experiment 2) on the learning of generalized motor programs (GMPs) and movement parameterization were investigated. In each experiment, 2 tasks with different relative force-time structures were tested. Participants (N = 32, Experiment 1; N = 40, Experiment 2) attempted to exert a pattern of force that resembled in force and time a waveform that was displayed on a computer monitor. In both experiments, the analysis suggested that the GMP, although refined over practice, was relatively stable (i.e., resistant to decay and interference), even early in practice (after 20 trials). In addition, the results indicated that constant and variable parameter practice did not differentially affect GMP learning but did degrade the learning of the parameter that was not varied. The data provided additional evidence for the dissociation of the GMP and the parameterization processes proposed in GMP theory. Contrary to schema theory, the present data suggest an interdependence between the force and the time parameters: The manipulation of 1 of the parameters has a negative effect on the learning of the other parameter.     

Strength Recovery Patterns Following Isometric and Isotonic Exercise

In 3 experiments, the author tested the hypothesis that coordination dynamics is the content of a generalized motor program (GMP) for rhythmic interlimb coordination. In Experiment 1, learners (N = 14) practiced a ?90° movement with either identically timed or differently timed limbs. Both acquisition and transfer to novel (effector and pattern) timings were unaffected by the learning condition and were suggestive of the intrinsic dynamics for in-phase and antiphase. In Experiment 2, learners' (N = 13) acquisition of 2 different phase relations (?90° and ?45°) was qualitatively identical. Attractor reconstruction revealed an increase in the predictability of individual movement trajectories and a decrease in attractor dimensionality over learning. Transfer for both ?90° and ?45° was again suggestive of the intrinsic dynamics. In Experiment 3, learning altered participants' (N = 8) performance of in-phase and antiphase relations. Together, the results suggested a single continuum of phase relations, called an attractor landscape, that produces similar patterns of CE and VE for both previously stable and learned coordinations.     

Consistent and Variable Practice Conditions: Effects on Relative and Absolute Timing

The authors conducted the present experiments to resolve the discrepancy between studies in which relative-timing learning has been found to be enhanced by consistent practice conditions and contextual interference experiments in which relative-timing learning has been found to be enhanced more by random practice than by blocked practice. There were 40 participants in Experiment 1 and 48 in Experiment 2. The results of Experiment 1 extended previous findings: The learning of the relative-timing pattern was systematically enhanced by the degree to which the practice conditions promoted movement consistency (constant > blocked > serial > random). Experiment 2 provided evidence that the discrepancy between the relative-timing effects in the 2 groups of studies was a product of the way in which relative-timing goals and feedback were presented. When the feedback was presented as segment times, random practice resulted in generally more stable relative-timing patterns during acquisition than blocked practice did. Thus, in both experiments, the learning of the relative-timing pattern was enhanced by more stable relative-timing conditions during acquisition. Absolute-timing learning, as indexed by the transfer tests, was enhanced by serial or random practice as compared with constant or blocked practice, and was relatively unaffected by feedback conditions directed at the relative-timing pattern. In terms of motor programming theory, those findings are taken as additional evidence for the disassociation of memories supporting generalized motor program (GMP) performance, as indexed by relative timing, and parameter performance, as indexed by absolute timing.     

Consistent and variable practice conditions: effects on relative and absolute timing

The authors conducted the present experiments to resolve the discrepancy between studies in which relative-timing learning has been found to be enhanced by consistent practice conditions and contextual interference experiments in which relative-timing learning has been found to be enhanced more by random practice than by blocked practice. There were 40 participants in Experiment 1 and 48 in Experiment 2. The results of Experiment 1 extended previous findings: The learning of the relative-timing pattern was systematically enhanced by the degree to which the practice conditions promoted movement consistency (constant > blocked > serial > random). Experiment 2 provided evidence that the discrepancy between the relative-timing effects in the 2 groups of studies was a product of the way in which relative-timing goals and feedback were presented. When the feedback was presented as segment times, random practice resulted in generally more stable relative-timing patterns during acquisition than blocked practice did. Thus, in both experiments, the learning of the relative-timing pattern was enhanced by more stable relative-timing conditions during acquisition. Absolute-timing learning, as indexed by the transfer tests, was enhanced by serial or random practice as compared with constant or blocked practice, and was relatively unaffected by feedback conditions directed at the relative-timing pattern. In terms of motor programming theory, those findings are taken as additional evidence for the disassociation of memories supporting generalized motor program (GMP) performance, as indexed by relative timing, and parameter performance, as indexed by absolute timing.     

Differential Transfer Benefits of Increased Practice for Constant,Blocked, and Serial Practice Schedules

The effects of practice schedule and amount of practice on the development of the generalized motor program (GMP) and on parameter estimation were investigated. Participants (N = 108) practiced the same relative timing but different absolute durations of a multisegment timing task. Practice schedules (constant, blocked, or serial) were crossed with amounts of practice (low and high). Inclusion of a constant practice condition allowed the authors to investigate the variability of practice prediction. Participants practiced the same proportional durations in a serial or a blocked schedule, which enabled the authors to examine contextual interference. A constant practice schedule enhanced GMP performance when task parameters remained the same, but varied practice schedules were beneficial when task parameters changed. A serial as opposed to a blocked practice schedule was superior when the performance of a task governed by a different GMP was required. Increased practice led to a consolidated task representation that was unavailable for updating.     

Reducing Knowledge of Results about Relative versus Absolute Timing: Differential Effects on Learning

The purpose of the present experiment was to examine further earlier suggestions that a reduced relative frequency of knowledge of results (KR) can enhance the learning of generalized motor programs (GMPs) but at the same time degrade parameter learning, compared with giving KR after every trial (Wulf & Schmidt, 1989; Wulf, Schmidt, & Deubel, 1993). In contrast to these earlier studies, here KR was given separately for relative timing and absolute timing. Subjects practiced three movement patterns that required the same relative timing but different absolute movement times. KR was provided on 100% or 50% of the practice trials for relative timing or absolute timing, respectively. In retention and transfer tests, the groups that had had 50% KR about relative timing demonstrated more effective learning of the relative-timing structure, that is, GMP learning, than the groups that had had 100% KR about relative timing. The KR frequency had no effect on parameterization during retention; yet, when transfer to a task with a novel overall duration was required, the groups given 100% KR about absolute timing were more accurate in parameterization than the groups provided with 50% KR about absolute timing. Thus, the reduced relative KR frequency enhanced GMP learning but had no beneficial effect, or even a degrading effect, on parameter learning. The differential effects of a reduced KR frequency on the learning of relative timing and absolute timing also provide additional support for the dissociation of GMP and parameterization processes.     

Contextual Interference in Movements of the Same Class: Differential Effects on Program and Parameter Learning

Contextual interference effects in motor learning usually were not found when the tasks to be learned presumably required the same generalized motor program (GMP) and differed only with regard to the movement parameters (see Lee, Wulf, & Schmidt, 1992; Magill & Hall, 1990). Thus, tasks requiring different motor programs (e.g., different relative timings) seemed to be a prerequisite for random practice to be more effective than blocked practice. However, the previous studies (that did not find random/blocked differences) used global error measures that confounded errors in relative timing and errors in absolute timing. In the present study, subjects practiced three movement patterns that had the same relative timing (requiring the same GMP) but different overall durations (requiring different parameters). Errors in relative timing and in absolute timing were assessed separately. The results indicate that random practice is more effective for the learning of relative timing (GMP learning) and less effective for the learning of absolute timing (parameter learning) than blocked practice. Preliminary ideas as to the reasons for this effect are discussed.     

Reducing Knowledge of Results About Relative Versus Absolute Timing: Differential Effects on Learning

The purpose of the present experiment was to examine further earlier suggestions that a reduced relative frequency of knowledge of results (KR) can enhance the learning of generalized motor programs (GMPs) but at the same time degrade parameter learning, compared with giving KR after every trial (Wulf & Schmidt, 1989; Wulf, Schmidt, & Deubel, 1993). In contrast to these earlier studies, here KR was given separately for relative timing and absolute timing. Subjects practiced three movement patterns that required the same relative timing but different absolute movement times. KR was provided on 100% or 50% of the practice trials for relative timing or absolute timing, respectively. In retention and transfer tests, the groups that had had 50% KR about relative timing demonstrated more effective learning of the relative-timing structure, that is, GMP learning, than the groups that had had 100% KR about relative timing. The KR frequency had no effect on parameterization during retention; yet, when transfer to a task with a novel overall duration was required, the groups given 100% KR about absolute timing were more accurate in parameterization than the groups provided with 50% KR about absolute timing. Thus, the reduced relative KR frequency enhanced GMP learning but had no beneficial effect, or even a degrading effect, on parameter learning. The differential effects of a reduced KR frequency on the learning of relative timing and absolute timing also provide additional support for the dissociation of GMP and parameterization processes.     

Contextual interference in movements of the same class: differential effects on program and parameter learning

Contextual interference effects in motor learning usually were not found when the tasks to be learned presumably required the same generalized motor program (GMP) and differed only with regard to the movement parameters (see Lee, Wulf, & Schmidt, 1992; Magill & Hall, 1990). Thus, tasks requiring different motor programs (e.g., different relative timings) seemed to be a prerequisite for random practice to be more effective than blocked practice. However, the previous studies (that did not find random/blocked differences) used global error measures that confounded errors in relative timing and errors in absolute timing. In the present study, subjects practiced three movement patterns that had the same relative timing (requiring the same GMP) but different overall durations (requiring different parameters). Errors in relative timing and in absolute timing were assessed separately. The results indicate that random practice is more effective for the learning of relative timing (GMP learning) and less effective for the learning of absolute timing (parameter learning) than blocked practice. Preliminary ideas as to the reasons for this effect are discussed.     

The Role of Scheduling in Learning Through Observation

In the 2 experiments reported in the present article, participants (N = 40, Experiment 1; N = 60, Experiment 2) learned to solve complex puzzles under different schedules of physical practice, observation, or a combination of the two. The results of both studies indicated that observation, in the absence of any physical practice, allows the development of an accurate but relatively nonfunctional cognitive representation. The data suggest that, even when the motor demands are minimal, the functional significance of the cognitive representation is not maximally realized until physical interaction with the task is possible. Thus, providing the participant with an interspersed practice schedule during acquisition enables that interaction to occur, thereby allowing the absolute number of physical practice trials to be reduced and replaced by observation trials, but leading to equivalent learning.     

Enhancing the Learning of Sport Skills Through External-Focus Feedback

The authors examined how the effectiveness of feedback for the learning of complex motor skills is affected by the focus of attention it induces. The feedback referred specifically either to body movements (internal focus) or to movement effects (external focus). In Experiment 1, groups of novices and advanced volleyball players (N = 48) practiced “tennis” serves under internal-focus or external-focus feedback conditions in a 2 (expertise) × 2 (feedback type) design. Type of feedback did not differentially affect movement quality, but external-focus feedback resulted in greater accuracy of the serves than internal-focus feedback during both practice and retention, independent of the level of expertise. In Experiment 2, the effects of relative feedback frequency as a function of attentional focus were examined. A 2 (feedback frequency: 100% vs. 33%) × 2 (feedback type) design was used. Experienced soccer players (N = 52) were required to shoot lofted passes at a target. External-focus feedback resulted in greater accuracy than internal-focus feedback did. In addition, reduced feedback frequency was beneficial under internal-focus feedback conditions, whereas 100% and 33% feedback were equally effective under external-focus conditions. The results demonstrate the effectiveness of effect-related, as opposed to movement-related, feedback and also suggest that there is a need to revise current views regarding the role of feedback for motor learning.     

The accidental transgressor: morally-relevant theory of mind

To test young children’s false belief theory of mind in a morally relevant context, two experiments were conducted. In Experiment 1, children (N = 162) at 3.5, 5.5, and 7.5 years of age were administered three tasks: prototypic moral transgression task, false belief theory of mind task (ToM), and an “accidental transgressor” task, which measured a morally-relevant false belief theory of mind (MoToM). Children who did not pass false belief ToM were more likely to attribute negative intentions to an accidental transgressor than children who passed false belief ToM, and to use moral reasons when blaming the accidental transgressor. In Experiment 2, children (N = 46) who did not pass false belief ToM viewed it as more acceptable to punish the accidental transgressor than did participants who passed false belief ToM. Findings are discussed in light of research on the emergence of moral judgment and theory of mind.     

Reduced-Frequency Concurrent and Terminal Feedback: A Test of the Guidance Hypothesis

In 2 experiments, the authors manipulated the frequency of concurrent feedback to discern the effects on learning. In each experiment, participants (N = 48, Experiment 1; N = 36, Experiment 2) attempted to reproduce a criterion force-production waveform (5 s in duration) presented on the computer monitor. Consistent with the guidance hypothesis, the results of Experiment 1 indicated very strong guiding effects of concurrent feedback and strong dependence on the feedback, as indicated by participants' extremely poor performance upon feedback withdrawal in retention. As predicted by the guidance hypothesis, dependence on the feedback was reduced as a result of reducing the frequency of the concurrent feedback. The results of Experiment 2 indicated that one can enhance learning by providing concurrent and terminal feedback on 1 trial, with no feedback on the subsequent trial. In that way, the strong guiding effects of concurrent feedback could be realized and the beneficial effects of terminal feedback could also be achieved.     

Preschoolers trust particular informants when learning new names and new morphological forms

Across three studies, we investigated whether 4‐year‐olds would trust a previously reliable informant when learning novel morphological forms. In Experiment 1, children (N= 16) were presented with two informants: one who correctly named familiar objects and another who named them incorrectly. Children were invited to turn to these informants when learning novel labels and morphological forms. The majority of children chose the previously correct labeller when learning novel label and morphology. In Experiment 2, children (N= 16) were presented with an informant who used familiar plurals correctly and one who used them incorrectly. Children chose the previously correct morphologist when learning novel labels and past tense forms. Thus, children track both semantic and morphological accuracy. In Experiment 3, some children (N= 16) were presented with two informants who differed in naming accuracy, whereas others (N= 16) were presented with two informants who differed in morphological accuracy. To forestall any risk of experimenter cuing, one experimenter blind to the training children had received, tested children with novel labels and morphology. The results replicated those of Experiments 1 and 2. Implications for how children's trust in an informant might play a role in their acquisition of morphological forms are discussed.     

Expanding retrieval practice: An effective aid to preschool children's learning

The benefits of expanding retrieval practice for preschool children were explored in two experiments. In Experiment 1, three groups learned names for six plush toy pigs using expanding retrieval practice, a reward incentive, or a control condition. Reward did not significantly improve learning but retrieval practice doubled recall. In Experiment 2, three groups learned names to soft toys, comparing recall following massed elaborative study with either expanding retrieval practice or expanding re-presentation. Recall was tested after 1 minute, 1 day, and 2 days. A very large effect size (d = 1.9) indicated the very considerable benefit from expanding retrieval practice over the elaboration condition. Comparison with the re-presentation condition suggested that half of the benefit of expanding retrieval practice came from spaced scheduling and half from retrieval practice. Expanding retrieval practice provides an effective method to improve learning by young children.     

When do stereotypes become really consensual? Investigating the group-based dynamics of the consensualization process

Although it has long been recognized that stereotypes achieve much of their force from being shared by members of social groups, relatively little empirical work has examined the process by which such consensus is reached. This paper tests predictions derived from self-categorization theory that stereotype consensus will be enhanced (a) by factors which make the shared social identity of perceivers salient and (b) by group interaction that is premised upon that shared identity. In Experiment 1 (N=40) the consensus of ingroup stereotypes is enhanced where an ingroup is judged after (rather than before) an outgroup. In Experiment 2 (N=80) when only one group is judged, group interaction is shown to enhance the consensus of outgroup stereotypes more than those of the ingroup—an apparent ‘outgroup consensus effect’. In Experiment 3 (N=135) this asymmetry is extinguished and group interaction found to produce equally high consensus in both ingroup and outgroup stereotypes when the ingroup is explicitly contrasted from an outgroup. Implications for alternative models of consensus development are discussed. © 1998 John Wiley & Sons, Ltd.     

Effects of an Auditory Model on the Learning of Relative and Absolute Timing

The effects of an auditory model on the learning of relative and absolute timing were examined. In 2 experiments, participants attempted to learn to produce a 1,000- or 1,600-ms sequence of 5 key presses with a specific relative-timing pattern. In each experiment, participants were, or were not, provided an auditory model that consisted of a series of tones that were temporally spaced according to the criterion relative-timing pattern. In Experiment 1, participants (n = 14) given the auditory template exhibited better relative- and absolute-timing performance than participants (n = 14) not given the auditory template. In Experiment 2, auditory and no-auditory template groups again were tested, but in that experiment each physical practice participant (n = 16) was paired during acquisition with an observer (n = 16). The observer was privy to all instructions as well as auditory and visual information that was provided the physical practice participant. The results replicated the results of Experiment 1: Relative-timing information was enhanced by the auditory template for both the physical and observation practice participants. Absolute timing was improved only when the auditory model was coupled with physical practice. Consistent with the proposal of D. M. Scully and K. M. Newell (1985), modeled timing information in physical and observational practice benefited the learning of the relative-timing features of the task, but physical practice was required to enhance absolute timing.     

Task goals and change in dynamical degrees of freedom with motor learning

In this article, the authors examined the hypothesis that the direction of the change (increase or decrease) in the dynamical degrees of freedom (dimension) regulated as a function of motor learning is task-dependent. Adult participants learned 1 of 2 isometric force-production tasks (Experiment 1: constant force output; Experiment 2: sinusoidal force output) over 5 days of practice and a 6th day with augmented information withdrawal. The results showed that over practice, the task goal induced either an increase (Experiment 1) or a decrease (Experiment 2) in the dimension of force output as performance error was reduced. These findings support the proposition that the observed increase or decrease in dimension with learning is dependent on both the intrinsic dynamics of the system and the short-term change required to realize the task goal.     

Changes in Limb Stiffness Under Conditions of Mental Stress

In 2 experiments, the effects of mental stress on limb stiffness were investigated. The relative contribution to arm stiffness of individual muscle activity, co-contraction, muscle reflexes, and postural adjustments were examined. In each experiment, participants (N = 24, Experiment 1; N = 16, Experiment 2) held their supinated hand under a tray that they were required to return to horizontal after it had been suddenly released. Electromyographic activity in the biceps and triceps muscles was recorded, as were elbow and wrist angles and tray displacement. In Experiment 1, mental arithmetic stress was shown to lead to decreased tray displacement (i.e., increased resistance) compared with displacements under the control, unstressed condition, as well as to increased elbow flexion before tray release. In Experiment 2, the increased resistance to perturbation caused by mental stress was found to be independent of initial elbow angle, but to vary as a function of the amount of upward force exerted before tray release. The authors conclude that stress-induced increases in limb stiffness result from changes in the initial position of the elbow, specified by its angle, together with the initial force exerted by participants to counteract the mechanical perturbations.     

Priming is independent of skill learning.

This study examined the relation between repetition priming and skill learning. Priming refers to facilitation in processing a specific item as a result of previous exposure to that item. Skill learning refers to general improvement in task performance as a function of practice. In Experiment 1 (N = 60), skill acquisition occurred in partial-word identification and inverted reading tasks but not in a word-fragment completion task. However, the amount of priming was the same in all three tasks. In Experiment 2 (N = 52), priming effects in partial-word identification did not vary as a function of practice with degraded words. In Experiment 3 (N = 40), skill learning was greater with high- than with low-frequency words, whereas priming was unaffected by word frequency. Experiment 4 (N = 20) ruled out the possibility that explicit retrieval was involved in the implicit memory tasks. These results suggest that priming can be independent of skill learning.