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Title:Measuring changes in cognitive load in language processing through measuring postural sway
Author(s):Jang, John
Director of Research:Shih, Chilin
Doctoral Committee Chair(s):Shih, Chilin
Doctoral Committee Member(s):Sosnoff, Jacob; Yan, Xun; Hernandez, Manuel
Department / Program:Linguistics
Degree Granting Institution:University of Illinois at Urbana-Champaign
Abstract:This thesis investigates the potential for using standing balance as a way to measure changes in cognitive load during language processing. Changes in standing balance are measured as subjects process vocabulary words, sentences, and paragraphs with varying degrees of relative difficulty. It is predicted that the more difficult the content, the more subjects will sway. Although standing itself is a common enough task, the biological requirements of postural control during standing are fairly complex, requiring the involvement of an uninterrupted flow of afferent signals reaching the central nervous system from the muscle, tendon and joint proprioceptors, skin exteroceptors, and vestibular and visual inputs ([Fitzpatrick and McCloskey, 1994]). As such, there are numerous clinical applications in assessing standing balance, as decreasingly stable measured parameters from a standing posture can reflect the increased risk of falls in the elderly ([Maki et al., 1994]), individuals with Parkinson’s Disease ([Błaszczyk et al., 2007]), or patients with multiple sclerosis ([Prosperini and Pozzilli, 2013]). Standing balance is sensitive to psychological perturbations ([Kerr et al., 1985]), and may even be perturbed by language tasks ([Shumway-Cook et al., 1997]), indicating a link between standing and language processing. Based on prior literature, this thesis tests the assumption that there is a link between language processing and postural control. If standing control processes are interrupted by the processing of language, then using balance to measure changes in cognitive load could be used to objectively assess linguistic difficulty. Force plates are used to measure balance, which are laboratory-grade devices used in Biomechanics and Kinesiology to quantify various physical properties of human movement ([Winter, 2009]), ranging from running or jumping ([Chappell et al., 2005], [McLean et al., 2004]), to the more obscure and less conscious overall motions such as the subtle displacements involved in maintaining a standing upright posture ([Murray et al., 1975]). A set of experiments was performed on the auditory processing of three general elements of language: Paragraphs, sentences, and vocabulary words. There are two methods of analysis used, one which tests the overall changes in postural sway, and one which observes changes in postural sway over time. The two parameters used, respectively, are the fiftieth percentile of the radial range of the center of pressure, and the radial distance of the center of pressure over time. The results from the overall changes in postural sway suggest that balance is sensitive to changes in cognitive load due to language processing. For the paragraphs, results suggest that very difficult passages elicit greater changes in postural sway compared to the easier passages. Likewise, in the first of two experiments on sentences, sentences which the literature reports requiring relatively more cognitive load to process exhibit relatively greater changes in postural sway. For the second sentence study, results suggest a correlation between postural sway and the acceptability rankings of four different sentence types, so long as syllable count is accounted for. For the experiment on vocabulary words, increases in postural sway are observed when the difficulty level is increased. The results from the observations of postural sway over time also suggest that balance is sensitive to changes in cognitive load due to language processing. For the paragraphs, the trends of postural sway are different for each of the three difficulty levels tested. For the first of two experiments on sentences, it is shown that the sway is increased in the parts of the sentences where more cognitive load is required. Likewise for the second sentence study, a similar trend in postural sway is found for the regions of time where the sentences should be less acceptable. For vocabulary words, an observable trend is also present, and only a trend exists, implying that a threshold for utilizing postural sway to intuitively measure changes in cognitive load due to language processing is reached in vocabulary words. Overall, the results suggest that postural sway is sensitive to changes in cognitive load for paragraphs, sentences, and possibly vocabulary words. An intuitive interpretation of the results can be found for the studies on paragraphs and sentences, where greater amounts of sway is indicative of greater difficulty encountered during language processing. This trend in the data is present, but less apparent, for the study on the vocabulary words, providing some insight into how small the tested elements of language can be in getting an intuitive interpretation of changes in postural sway as it relates to changes in cognitive load during language processing. These results suggest that postural sway can be used as a practical tool for measuring changes in cognitive load during language processing.
Issue Date:2017-11-29
Rights Information:Copyright 2017 John Jang
Date Available in IDEALS:2018-03-13
Date Deposited:2017-12

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