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Biomedical subjects

J P Maxwell

Publications and source records attributed to J P Maxwell.

8 recordsLinked to original sources
PubMed2003

The role of working memory in motor learning and performance.

Three experiments explore the role of working memory in motor skill acquisition and performance. Traditional theories postulate that skill acquisition proceeds through stages of knowing, which are initially declarative but later procedural. The reported experiments challenge that view and support an independent, parallel processing model, which predicts that procedural and declarative knowledge can be acquired separately and that the former does not depend on the availability of working memory, whereas, the latter does. The behaviour of these two processes was manipulated by providing or withholding visual (and auditory) appraisal of outcome feedback. Withholding feedback was predicted to inhibit the use of working memory to appraise success and, thus, prevent the formation of declarative knowledge without affecting the accumulation of procedural knowledge. While the first experiment failed to support these predictions, the second and third experiments demonstrated that procedural and declarative knowledge can be acquired independently. It is suggested that the availability of working memory is crucial to motor performance only when the learner has come to rely on its use.

Adult↗
PubMed2002

Drifting towards a diffuse control model of exploratory motor learning: A comparison of global and within-trial performance measures.

Accurate measurement is crucial for understanding the processes that underlie exploratory patterns in motor learning. Accordingly, measures of learning should be sensitive to the changes that take place during skill acquisition. Most studies, however, use trial-based global measures that assess performance but do not actually measure gradual changes taking place within trials. The present study attempted to remedy this shortcoming by analysing a visual adaptation task, and comparing traditional global measures of learning with new, within-trial measures. Movement time was the only global measure sensitive to changes in the movement trajectory during learning. Three new measures were expected to reveal changes to the movement trajectory that are associated with learning: (i) the length of runs, (ii) change of trajectory angle in relation to the target, and (iii) drift (change in distance from the target). All three measures were sensitive to learning and indicated a gradual straightening of the movement trajectories over trials. Furthermore, three different methods to partition trajectories into segments were examined. The new within-trial measures, irrespective of partitioning method, prove promising for the development of a diffuse control model of exploratory learning.

Exploratory Behavior↗
PubMed2001

The implicit benefit of learning without errors.

Two studies examined whether the number of errors made in learning a motor skill, golf putting, differentially influences the adoption of a selective (explicit) or unselective (implicit) learning mode. Errorful learners were expected to adopt an explicit, hypothesis-testing strategy to correct errors during learning, thereby accruing a pool of verbalizable rules and exhibiting performance breakdown under dual-task conditions, characteristic of a selective mode of learning. Reducing errors during learning was predicted to minimize the involvement of explicit hypothesis testing leading to the adoption of an unselective mode of learning, distinguished by few verbalizable rules and robust performance under secondary task loading. Both studies supported these predictions. The golf putting performance of errorless learners in both studies was unaffected by the imposition of a secondary task load, whereas the performance of errorful learners deteriorated. Reducing errors during learning limited the number of error-correcting hypotheses tested by the learner, thereby reducing the contribution of explicit processing to skill acquisition. It was concluded that the reduction of errors during learning encourages the use of implicit, unselective learning processes, which confer insusceptibility to performance breakdown under distraction.

Adult↗
PubMed2000

Antimalarial sulfide, sulfone, and sulfonamide trioxanes.

A series of trioxanes featuring sulfide, sulfone, and sulfonamide substituents in diverse positions has been prepared. Structure-activity relationship (SAR) generalizations highlight two major factors controlling the antimalarial potency of these new chemical entities: (1) the proximity of the sulfur-containing substituent to the crucial peroxide bond and (2) the oxidation state of the sulfur-containing substituent. Generally, sulfones are more antimalarially potent than the corresponding sulfides.

Antimalarials↗
PubMed2000

From novice to no know-how: a longitudinal study of implicit motor learning.

The aim of this study was to ascertain whether the performances of implicit and explicit learners would converge over an extended period of learning. Participants practised a complex motor skill--golf putting--for 3000 trials, either with a concurrent secondary, tone-counting task (implicit learning) or without such a task (explicit learning). The cognitive demands of the secondary task were predicted to prevent the accumulation of verbalizable rules about the motor task. The implicit group reported significantly fewer rules than the explicit group on subsequent verbal protocols. The performance of the implicit group remained below that of the explicit group throughout the learning phase. However, no significant differences were found between groups during a delayed retention test. Additionally, for the participants in the explicit group only, a Reinvestment Scale score correlated positively with the number of rules accrued and negatively with overall putting performance during the learning phase. We use the results to argue against the excessive use of verbal instruction during skill acquisition, which might be unnecessary and ultimately might hamper performance under stressful conditions.

Adult↗
PubMed1996

Evaluation of the effectiveness of a community-based enriched model prenatal intervention project in the District of Columbia.

OBJECTIVE: To evaluate an enriched prenatal intervention program designed to reduce the risk of low birth weight. STUDY SETTING: Freestanding community-based prenatal intervention project located in a poor inner-city community, serving mostly African American women. STUDY DESIGN: All women less than 29 weeks pregnant were eligible to participate. They were compared to women who lived in neighborhoods with similar rates of poverty. DATA COLLECTION: The birth certificate was the source of data on maternal age, education, marital status, timing and frequency of prenatal care attendance, parity, gravidity, prior pregnancy terminations, fetal and child deaths, and birth weight. PRINCIPAL FINDINGS: Thirty-eight percent of the women who delivered live-born infants in the study area participated in the program. There were no differences in low- and very low birthweight rates in the study and comparison groups. In a secondary analysis comparing participants and nonparticipants in the study census tracts, participants were at higher risk for low and very low birth weight, and they adhered more closely to the schedule of prenatal visits than nonparticipants. Low- and very low birthweight rates were lower among participants than among nonparticipants and comparison women. CONCLUSION: The Better Babies Project did not have an effect on the overall low- and very low birthweight rates in the study census tracts. This was probably due to the low participation rates and the high population mobility.

Adult↗