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Biomedical subjects

C H Shea

Publications and source records attributed to C H Shea.

At least 19 recordsLinked to original sources
PubMed2001

Planning and executing simple movements: contributions of relative-time and overall-duration specification.

In 3 experiments, the authors used a precuing protocol to examine the nature and cost of programming and the subsequent reprogramming of a movement's relative time and overall duration. Initial programming followed a fixed-order specification; knowledge of the necessary relative time was required before information regarding overall duration could be used in a manner that expedited response planning. In the case of reprogramming, however, when a modification had to be made in either the relative time or overall duration of the anticipated and already-prepared response, performers chose to completely reprogram the entire response. Complete reprogramming occurred even when the performer had correctly prepared the higher order relative-time component and only had to modify the overall duration of the movement. The data indicate that organizing movement timing before movement initiation is accomplished in a fundamentally different manner depending on whether the movement is being initially compiled or modified.

Adult↗
PubMed2001

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.

Auditory Perception↗
PubMed2001

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.

Computers↗
PubMed2001

Manipulating generalized motor program difficulty during blocked and random practice does not affect parameter learning.

Blocked practice engenders more trial-to-trial response stability, which is thought to be crucial for developing the generalized motor program (GMP) but not parameter learning (Lai, Shea, Wulf, & Wright, 2000). It was hypothesized that reducing the difficulty of the GMP might permit additional cognitive resources to be allocated to learning the parameter requirements. However, GMP theory maintains the independence of the memories governing the GMP and parameters. This notion suggests that manipulating the difficulty of the GMP should have no effect on the blocked practice participant's ability to successfully specify the appropriate parameters. Participants learned a simple or complex relative timing pattern under either blocked or random practice conditions. Smaller GMP errors were exhibited for the simple relative timing patterns, but this was not associated with improvements in parameter specification following blocked practice. A clear advantage for parameter specification was evident in transfer following random practice. Taken together, these data support the theoretical separation of the GMP and parameter processes.

Analysis of Variance↗
PubMed2001

Reducing the saliency of intentional stimuli results in greater contextual-dependent performance.

Wright and Shea (1991) described intentional stimuli as explicitly identified information necessary to successfully perform a task, whereas incidental stimuli are not explicitly identified as crucial to task performance but have the potential to become associated with particular responses because of their selective presence in the training environment. Shea and Wright (1995), using a speeded-choice RT task, indicated that manipulating the strength of association between incidental information and the responses, by changing the discriminability of incidental stimuli while fixing the strength of the association between the intentional stimuli and each response, had a significant impact on task performance. The present experiment further examined the role played by incidental stimuli when the strength of association between the intentional stimuli and the associated responses was reduced, by minimising stimulus-response compatibility. It was assumed that this latter manipulation would have a similar impact as increasing the strength of incidental stimuli-response relationships. That is, the relative contribution of the incidental stimuli would increase, resulting in an increase in context-dependent behaviour during tests in which the intentional and incidental stimuli activated different responses. The results were in agreement with this prediction and consistent with a model for contextual-dependent performance proposed by Shea and Wright (1995) as well as with the outshining hypothesis forwarded by Smith (1988, 1994).

Analysis of Variance↗
PubMed2001

Surfing the implicit wave.

Implicit learning was investigated in two experiments involving a complex motor task. Participants were required to balance on a stabilometer and to move the platform on which they were standing to match a constantly changing target position. Experiment 1 examined whether a segment (middle third) that was repeated on each trial would be learned without participants becoming aware of the repetitions (i.e., implicitly). The purpose of Experiment 2 was to determine the relative effectiveness of explicit versus implicit learning. Here, two identical segments were presented on each trial (first and last thirds), with participants only being informed that one segment (either first or last) was repeated. The acquisition results from both experiments indicated large improvements in performance across 4 days of practice, with performance on the repeated segments being generally superior to that on the non-repeated segment. On the retention tests on Day 5, errors on the repeated segment(s) were smaller than those on the random segment(s). Furthermore, in Experiment 2, the errors on the repeated-known segment, although smaller than those on the random segment, were larger than those on the repeated-unknown segment. Interview results indicated that participants were not consciously aware that a segment was repeated unless they were informed. These results suggest that implicit learning can occur for relatively complex motor tasks and that withholding information concerning the regularities is more beneficial than providing this information.

Humans↗
PubMed2001

The automaticity of complex motor skill learning as a function of attentional focus.

The present experiment was designed to test the predictions of the constrained-action hypothesis. This hypothesis proposes that when performers utilize an internal focus of attention (focus on their movements) they may actually constrain or interfere with automatic control processes that would normally regulate the movement, whereas an external focus of attention (focus on the movement effect) allows the motor system to more naturally self-organize. To test this hypothesis, a dynamic balance task (stabilometer) was used with participants instructed to adopt either an internal or external focus of attention. Consistent with earlier experiments, the external focus group produced generally smaller balance errors than did the internal focus group and responded at a higher frequency indicating higher confluence between voluntary and reflexive mechanisms. In addition, probe reaction times (RTs) were taken as a measure of the attention demands required under the two attentional focus conditions. Consistent with the hypothesis, the external focus participants demonstrated lower probe RTs than did the internal focus participants, indicating a higher degree of automaticity and less conscious interference in the control processes associated with the balance task.

Attention↗
PubMed2000

Physical and observational practice afford unique learning opportunities.

In 2 experiments, the authors studied the effectiveness of physical and observational practice on learning and the effect on learning of combining physical practice and observation, as compared with providing physical practice alone. In Experiment 1, retention and transfer performance of 30 university students after physical, observational, or no practice were contrasted. Consistent with findings from other studies, the retention results indicated that observational practice is inferior to physical practice. The transfer data indicated no differences between observation and physical practice groups. In Experiment 2, retention and transfer performance of 30 participants in physical and combined (alternating physical and observational) practice groups were contrasted. The retention results showed no differences between the combined and physical practice groups, but the combined group performed significantly better than the physical practice group on the transfer test. Those findings suggest that a combination of observation and physical practice permits unique opportunities for learning beyond those available via either practice regimen alone.

Analysis of Variance↗
PubMed2000

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.

Adult↗
PubMed2000

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.

Feedback↗
PubMed2000

Optimizing generalized motor program and parameter learning.

Two experiments examined generalized motor program (GMP) and parameter learning. Experiment 1 examined the effects of bandwidth knowledge of results (KR) about relative timing in constant and variable practice. The purpose was to determine if movement stability created by the bandwidth manipulation is associated with increased GMP learning and if bandwidth KR interacts with constant and variable practice. Participants were asked to depress four keys sequentially, using the same relative timing structure. Constant practice had one absolute timing requirement, whereas variable practice had three different absolute timing requirements. The results indicated that GMP learning was enhanced by constant practice (independent of the bandwidth KR condition) and by bandwidth KR, when variable practice was used. The findings suggest practice conditions (bandwidth KR, constant practice) that increase movement stability during practice enhance GMP learning. Parameter learning (during transfer), however, was enhanced by variable practice. Experiment 2 attempted to determine how constant and variable practice conditions could be combined to enhance both GMP and parameter learning. The results indicated that developing a stable GMP early in practice--by providing learners with constant practice early in practice--and refining parameter learning later in practice--by providing them with variable practice late in practice--were effective for both GMP and parameter learning. This suggests a hierarchy in the development of programmed actions with a stable GMP being a requisite for developing an effective and stable parameter rule.

Adult↗
PubMed2000

Effects of modeled auditory information on a sequential timing task.

The purposes of the present experiment were to determine (a) whether an auditory model enhanced relative or absolute timing, (b) the extent to which the reduced frequency presentation of the auditory model resulted in enhanced retention, and (c) the degree to which executing the timing sequence was independent of the role of the effectors in carrying out the movement sequence. Participants (N = 45) were asked to alternately press two keys on a computer keyboard in an attempt to match the goal intervals presented on the computer monitor. Groups differed in terms of the frequency with which an auditory model (100, 50, or 0%) was presented. The results indicated that the auditory model (100% or 50% groups) enhanced relative timing performance and learning but not the learning of absolute timing. In addition, the 50% group did not appear to become dependent on the auditory model. However, significant decrements in performance were seen for the 100% group when the model was withdrawn. Last, participants were able to execute the timing sequences equally well when they reversed the hand used to execute the timing sequence. This was interpreted as strong evidence for the effector independence (Schmidt, 1975, 1988) and modularity of the timing sequence (Keele, Davidson, & Hayes, 1998).

Female↗
PubMed1999

The role of reduced frequency of knowledge of results during constant practice.

Two experiments were conducted to further examine the effects of reduced knowledge of results (KR) frequency on the learning of motor skills during constant practice. In Experiment 1, participants in five KR conditions (100% KR, 50% KR-fade, 50% KR-reverse fade, 50% KR-alternative, and 50% KR-random) practiced a movement timing task. In Experiment 2, participants in two KR conditions (100% KR and 50% KR-fade) practiced a waveform reproduction task. The results of both experiments failed to indicate that reduced KR frequency was more effective in promoting learning than the 100% KR conditions. The present study adds to the increasing number of experiments that do not find a benefit of reduced KR frequency on learning in constant practice.

Adult↗
PubMed1996

Contextual dependencies during perceptual-motor skill acquisition: gone but not forgotten!

The development and resiliency of contextual dependencies developed during perceptual-motor skill acquisition was assessed. Incidental aspects of the stimulus used to instigate the production of previously practised typing sequences were manipulated during either an immediate or delayed retention test. The findings from the immediate test offered further support for the existence of contextual-dependent performance for perceptual-motor responding. However, the dependency was attenuated by using a delayed retention test. Experiment 2 pursued two alternative explanations for the diminished dependency effect revealed in Experiment 1. In Experiment 2 some subjects were explicitly encouraged to reinstate aspects of the incidental contextual information that was present during training prior to administration of a delayed test. The dependency present only in the immediate test in Experiment 1 reemerged after contextual reinstatement. The present data are discussed with respect to the inclusion of incidental contextual stimuli as part of the long-term sensorimotor memory representation.

Analysis of Variance↗
PubMed1995

Contextual dependencies: influence on response latency.

The present experiments were designed to examine the influence of contextual stimuli on perceptual-motor performance. Experiment 1 revealed that contextual dependencies can develop for simple perceptual-motor tasks. Furthermore, the extent of the dependency is mediated in part by whether the contextual information is removed or replaced with alternative contextual information at the time of test. Data from Experiment 2 and 3 showed that manipulating the potency of incidental contextual stimuli results in a systematic decrement or increment in subsequent performance, depending on whether the contextual stimuli during the test were changed or reinstated. To date, such an orderly influence of contextual stimuli is more commonly demonstrated in the animal learning literature than with human experimentation.

Adolescent↗
PubMed1991

Composition of practice: influence on the retention of motor skills.

The purpose of these experiments was to investigate further the variable practice effect found by Shea and Kohl (1990). Experiment 1 was an initial attempt to determine the locus of the retention benefits demonstrated by subjects provided variable practice experiences. All groups received 20 acquisition blocks consisting of five test trials per block at a target of 150 N. The interval between test trials was either unfilled or filled, with additional trials consisting of the same target force, variable target forces, or practice on an unrelated motor task. The results indicated retention was not incremented (relative to an unfilled interval) by requiring subjects to perform an unrelated motor task in the intertest-trial interval. However, when the interest-trial interval was filled with practice on related motor tasks, retention was significantly improved. Experiment 2 assessed the impact of increasing the number of related motor tasks interpolated between test trials. The results indicated filling the intertest-trial interval with one motor task resulted in large retention benefits relative to an unfilled interval. Further increases in the number of related motor tasks (3) interpolated between test trials resulted in only modest increments to retention. The results were consistent with the elaboration perspective proposed by Shea and Zimny (1983). The elaboration perspective proposes that the simultaneous presence of related items in working memory facilitates interitem elaborative and distinctive processing that ultimately results in retention benefits.

Adult↗