The Influence of Feedback on Supra-postural Task Performance and Postural Sway Variability

<p>Postural sway variability is reduced when a person lightly touches a surface with the fingertip, even when the amount of force produced is insufficient to mechanically stabilize the body. Manipulating feedback about a supra-postural task, such as isometric light force, alters task constraints. Postural sway variability will potentially modulate differently in order to facilitate task completion, in accordance with the supra-postural task hypothesis. The sensory modality used to present feedback as well as frequency of feedback could affect force-production performance and have consequences for any postural modulations supporting touching performance. This experiment investigated the effects of light touch feedback modality (auditory vs. visual) and the effects of feedback type (discrete vs. continuous) on postural sway. </p><p>Forty-two undergraduates received either low-or high-gain auditory or visual continuous feedback about light force production in Experiment 1, and received either continuous or discrete visual feedback about light force production in Experiment 2. Fingertip force was measured by the mean and standard deviation (SD) of force production and postural sway was operationalized by the SD, LSD, and path length of the center of pressure (COP) in both the medio-lateral (ML) and anterior-posterior (AP) directions. Fingertip force-COP coupling strength was also examined and sample entropy (SampEn) was used as a measure of complexity of postural sway and fingertip force time series. </p><p>The results indicated that the sensory modality used to present feedback about force-production performance did not have a large effect on postural sway. However, the sensory modality did affect force-production performance. Mean force produced in the auditory feedback condition was significantly lower than both the target force of 1 N and the mean force produced in the visual feedback condition. Fingertip force variability was significantly higher in the auditory feedback condition while fingertip force complexity (SampEn) was significantly lower in the auditory condition. Results also indicated that while the feedback modality had little impact on postural sway, the coupling patterns between the COP and fingertip force did vary across modalities and were also affected by feedback gain manipulations. The presence of more than one coupling pattern also illustrates that different supra-postural tasks (force production, attending to feedback) may compete for task facilitation. In addition, the relationship between multiple supra-postural tasks as well as the transfer of task demands across sensory modalities is not straightforward. Experiment 2 results suggested feedback frequency and the richness of feedback (i.e., continuous vs. discrete) influenced postural sway variability. SDAP, LSDAP, LSDML, and path length were reduced to a greater extent in the continuous feedback condition than the discrete condition. Overall, richer feedback affords more opportunities to regulate task performance, but the effect is moderated by competing factors, such as task difficulty. In order to exploit this affordance provided by the richer feedback and enhance fingertip force production performance, postural sway must be regulated to a greater extent—the richer the feedback, the greater the potential benefit that could result from modulating postural sway. The relationship among multiple supra-postural tasks has not yet been specified from the supra-postural task hypothesis perspective.</p>

Name thesis:degree_name

PhD

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Arts and Sciences: Psychology

Grantor dc:publisher

University of Cincinnati

Year dc:date

2012

Author dc:creator

• Saunders, Nichole

Contributors dc:contributor

• Riley, Michael

• Psychology
• postural sway
• supra-postural

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=ucin1352993214

OAI identifier oai:identifier

oai:etd.ohiolink.edu:ucin1352993214