Master of Science, The Ohio State University, 2023, Industrial and Systems Engineering

Introduction: Musculoskeletal disorders in the workforce are highly prevalent, especially in material handling operations. In addition to completing physically demanding work that is required in this domain, workers must also manage concurrent mental demands present in their tasks. Few studies have examined the effect of concurrent mental demands in occupationally-relevant tasks. This study attempted to fill this void by quantifying the effects of varying degrees of cognitive loads and task precision demands on a material handling task by examining these effects on the kinematics and muscle activity of the trunk and shoulders. Methods: Twelve subjects lifted and placed a 5 kg box on a rack at one of three destination heights (low, middle, high) while under a simultaneous cognitive load (no load, simple load, complex load) and/or precision constraint (low precision, high precision). Cognitive load consisted of time-based arithmetic questions where participants were tasked with determining the amount of time remaining from a given time to a target time (e.g., Get to 4:00 PM from 3:15 for simple load or get to 4:10 PM from 3:27 PM for complex load). The primary dependent measures were the angular velocities of the trunk and shoulders as well as muscle activity in the erector spinae, rectus abdominus, external oblique, latissimus dorsi, and anterior deltoid muscles. Results: Significant decreases in angular velocities for both higher cognitive load complexities and higher precision conditions were observed. Additionally, lower 90th percentile normalized muscle activity values were observed as complexity and precision increased. Cumulative muscle activity, however, increased with these increases in complexity and precision. Conclusions: This study examined the impact of varying levels of cognitive and precision conditions on muscle activity and kinematics of the trunk and shoulders. Results indicated that increased complexity and precision led to longer lift t (open full item for complete abstract)

Committee: Carolyn Sommerich (Committee Member); Steven Lavender (Advisor) Subjects: Behavioral Sciences; Biomechanics; Engineering; Health Sciences; Industrial Engineering; Kinesiology; Occupational Safety

Master of Science in Exercise Science, University of Toledo, 2022, Exercise Science

Context: Many factors have been previously examined in relation to anterior cruciate ligament (ACL) injury, including neurocognition and corticomotor function. Those with lower neurocognition and corticomotor function display landing biomechanics and muscle function that may increase risk of injury. However, it is not known if poor landing mechanics resulting from the addition of a dual task may be exacerbated by diminished corticospinal excitably or neurocognitive function. Objective: Investigate the relationships between neurocognitive performance and corticomotor function and biomechanical dual-task cost during a landing assessment. Design: Descriptive laboratory study. Setting: Laboratory. Patients or Other Participants: 18 physically active (Tegner Activity Level ≥ 5), healthy females between the ages18 and 30 years old. Participants with a history of lower extremity surgery, history of lower extremity injury in the past 6 months, documented exclusion criteria for transcranial magnetic stimulation(TMS) were excluded. Intervention(s): Participants will complete single leg squats, a computer-based neurocognitive assessment, jump landing task, memory exercises, and mental arithmetic. Main Outcome Measures: Corticospinal excitability was assessed through active motor threshold measured by TMS during a single leg squat. Kinematic and kinetic data of the knee, hip, ankle, and trunk were assessed with 12 camera 3D analysis. Neurocognitive function was assessed through composite scores of the ImPACT. Results: For the number dual task cost, there was a moderate negative correlation between visual motor composite score and knee flexion angle. For the visual dual task cost, there was a moderate negative correlation between active motor threshold and hip adduction angle. Conclusions: Worse neurocognition and corticospinal excitability are associated with changes in landing patterns consistent with greater knee flexion angles and more neutral hip positions d (open full item for complete abstract)

Committee: Grant Norte (Committee Chair); Amanda Murray (Committee Member); David Bazett-Jones (Committee Member) Subjects: Biomechanics; Kinesiology; Sports Medicine

Doctor of Philosophy, The Ohio State University, 2013, Allied Medical Professions

Both motor and cognitive factors contribute to increases in gait variability and fall risk in individuals with neurologic disorders. Tasks requiring simultaneous mobility and cognition (i.e. dual-tasks) have been linked with accidental falls. Although these deficits have been well documented in elderly adults, relapsing remitting multiple sclerosis (RRMS), Parkinson's disease, traumatic brain injury and stroke, the individual contributions of mobility and cognition have not been explored and there are few studies exploring rehabilitation for these impairments using dual-task training. In order to move toward interventional techniques that effectively improve dual-tasking in individuals with neurologic conditions, a better understanding of tasks that amplify gait variability, the contribution of cognition to mobility and who may benefit from such programs is needed. Together, a systematic review of the literature and a case study provided evidence to support the importance of the interaction between mobility and cognition, the presence of dual-task deficits, and the feasibility of dual-task training in neurologic disorders. Gaps in the literature identified in the systematic review were used to direct the research questions of this document. The results of cross-sectional and baseline data from a randomized controlled trial suggest that tasks that amplify gait variability may be related to falls and underlying cognition. Backward walking amplified gait variability in both elderly adults and individuals with RRMS, and a backward walking velocity of <0.6 m/s accurately predicted elderly fallers. Dual-task walking amplified gait variability in individuals with RRMS, and higher gait variability correlated with lower performance on neuropsychological tests (p<0.01). Diffusion imaging is a useful tool to examine neural connectivity in individuals with RRMS. The supplemental motor area (SMA) has been implicated in cognitive dual-tasks, but its relationship with motor (open full item for complete abstract)

Committee: Deborah Larsen PT, PhD (Advisor) Subjects: Neurology; Neurosciences; Physical Therapy; Rehabilitation

Master of Science (MS), Bowling Green State University, 2024, Communication Disorders

The purpose of this study was to examine the interaction between cognitive demands during speech production and concurrent performance of a visuomotor tracking task. Participants performed a working memory task involving embedding a numerical response in a carrier phrase. To modulate cognitive load, participants performed two speech task variants with different degrees of mental tracking effort. For the low-demand variant, participants completed the carrier phrase by counting forward from one, a task that is relatively simple and considered automatic. For the high-demand variant, participants completed the carrier phrase by performing serial subtraction by three, requiring a modest amount of mental tracking effort. Both tasks were performed in isolation and while performing a concurrent visuomotor tracking task. Concurrent serial subtraction led to a reduction in visuomotor tracking accuracy, whereas counting forward did not affect tracking accuracy. Compared to counting forward, serial subtraction was associated with a decrease in speech intensity, lip opening and closing range, and lower lip opening and closing velocities. Compared to speaking insolation, participants exhibited a reduction in lower lip opening and closing velocities and utterance-to-utterance variability when performing the visuomotor tracking task. This pattern suggests that increasing cognitive demands, compounded by divided attention requirements, can affect processing and speech production.K

Committee: Jason Whitfield Ph.D (Committee Chair); Alexander Goberman Ph.D (Committee Member); Adam Fullenkamp Ph.D (Committee Member) Subjects: Acoustics; Biomechanics; Biomedical Research; Biostatistics; Communication; Health; Health Care; Health Sciences; Language; Occupational Therapy; Physiology; Psychology; Scientific Imaging; Speech Therapy; Statistics

Master of Science, University of Toledo, 2023, Exercise Science

Context: Lower extremity injury is highly prevalent in physically active females. Biomechanical assessments are used to identify those with higher biomechanical risk factors of injury. Biomechanical assessments (e.g. jump-landings) are typically single-motor tasks performed in controlled environments. In neurocognitive research, the concept of dual-task cost has suggested that single-task assessments may fail to identify injury risk patterns. Dual-task concepts have been studied in length in laboratories, but evidence is lacking in clinical settings. The purpose of this study was to evaluate a clinically accessible dual-task paradigm using the landing error scoring system (LESS). We hypothesized that dual-task conditions would have higher LESS scores and thus indicate poorer biomechanical patterns. Methods: Twenty physically active female participants were enrolled in this cross-sectional study. Participants performed one single-task and two dual-task conditions (number, visual) during a single session. Trials were filmed with two-dimensional cameras in the sagittal and frontal planes, and scored by a single rater. We used a one-way ANOVA with post hoc Tukey correction to compare LESS scores across task conditions. We used a chi-square test to assess differences in the frequency of item-specific errors across conditions. Results: The visual dual-task condition resulted in higher sagittal plane (2.62±1.29 vs. 1.55±1.04, p=.013) and total (6.57±1.55 vs. 4.90±1.68, p=.008) LESS scores compared to the single-task condition. The number dual-task condition resulted in higher frontal plane LESS scores compared to the single-task condition (4.40±1.31 vs. 3.35±1.22, p=.019). There were no significant differences in the proportion of errors based on the item-specific analysis (all p>.05). Conclusions: The LESS is able to capture a dual-task cost in motor performance among physically active females. Both visual and number-based cognitive tasks are able to illicit a dual-ta (open full item for complete abstract)

Committee: Grant Norte (Committee Chair); Amanda Murray (Committee Member); David Bazett-Jones (Committee Member) Subjects: Biomechanics; Kinesiology; Sports Medicine

Doctor of Philosophy (PhD), Wright State University, 2019, Human Factors and Industrial/Organizational Psychology PhD

The progression of technology and adaptive automation has shown tremendous promise in reducing both physical and mental task demands, while allowing the maintenance or improvement of overall performance. Consequently, a user is able to maintain task performance with relatively more ease and reallocate spare time and energy to additional tasks. Quantifying the resources that one has left is an ongoing, relatively open, research objective for human factors psychologists. Here, we created a standardized, individual-level metric to serve as an estimate of multi-tasking efficiency. We go beyond just rank-order, or categorical labels of suffering from, benefiting from, or adequately maintaining performance in multiple tasks. We quantify the extent that participants could sufficiently take on additional tasks by comparing their observed performance to what their performance would be assuming they were an efficient multi-tasker. A multi-task context necessarily has more task demands and assuming that each single-task is relatively challenging in isolation, is predicted to cause performance decrements. The degree that performance decrements occur may vary depending on the characteristics of the single-tasks. Specifically, multiple resource theory (MRT; Wickens, 1984) provides a theoretical modeling framework to make predictions about what tasks will produce more (or less) performance decrements when paired together. In Chapter 2 we used a computational characterization of MRT to compute multi-task conflict in a three dual-task subsets of a larger relatively complex multi-tasking environment. We used the MRT measure of conflict to make rank-order hypotheses about which specific dual-task pairs should cause more (or less) performance decrements relative to the others. In Chapter 3 we develop a measure of multi-tasking throughput (MT) and test MRT hypotheses by computing and comparing participant's MT coefficients across several multi-tasking combinations. In Chapter 4 (open full item for complete abstract)

Committee: Joseph Houpt Ph.D. (Advisor); Pamela Tsang Ph.D. (Committee Member); Assaf Harel Ph.D. (Committee Member); Gregory Funke Ph.D. (Committee Member); Tamera Schneider Ph.D. (Committee Member) Subjects: Psychology

Master of Science (MS), Bowling Green State University, 2018, Communication Disorders

Dysfunction of the basal ganglia circuit in Parkinson disease (PD) affects both speech and non-speech movements. Additionally, performing more than one task at a time (i.e., dual-tasking) often exacerbates movement deficits associated with PD. The goal of the current investigation was to determine the extent to which concurrent performance of an extemporaneous speaking task and a simple oscillatory manual task differentially affected participants with PD and neurologically healthy controls. Participants with and without PD produced extemporaneous speech and counterclockwise circle drawing movements in isolation (i.e., under single-task conditions) and concurrently (i.e., under dual-task conditions). Several measures of handwriting kinematics and speech acoustics were collected to examine changes in performance between the single- and dual-task conditions. Compared to control speakers, individuals with PD demonstrated significantly smaller circling movements in both the vertical and horizontal ranges of motion, as well as greater variation in the movement spectrum. For the speech task, individuals with PD exhibited a smaller working vowel space, larger standard deviation of articulation rate, less variation in fundamental frequency, and longer pauses than controls. During concurrent task performance, individuals with PD exhibited a significant increase in the range and speed of manual movement variability that was accompanied by a significant decrease in mean pause duration for the speaking task. Conversely, controls exhibited only slight a slowing of the peak manual movement frequency from the single- to dual-task condition, while no changes in any of the speech production variables were observed. These data suggest that individuals with PD, and not controls, experienced bidirectional dual-task interference, exhibiting changes in the performance of both tasks from the single- to dual-task condition.

Committee: Jason Whitfield Ph.D. (Advisor); Ronald Scherer Ph.D. (Committee Member); Brent Archer Ph.D. (Committee Member) Subjects: Speech Therapy

Master of Science (MS), Ohio University, 2017, Athletic Training (Health Sciences and Professions)

Background: Several studies have investigated biomechanical deficits in jump landing; however, these studies are often performed in a laboratory with little distraction to the participant. Injury has been shown to occur during sport-specific distraction where the individual is cognitively loaded during motor performance. Purpose: The purpose of this study was to determine the effect of a cognitive task on jump-landing mechanics. Methods: A dual-task design was used to determine the effects a cognitive dual task on the tuck-jump assessment and peak vertical ground reaction force in 20 participants. There were three cognitive conditions (no cognitive task, easy cognitive task, and difficult cognitive task). Results: There were significant differences in overall tuck-jump score from baseline to easy cognitive task and baseline to difficult cognitive task. The cognitive dual task elicited statistically significant changes in overall tuck-jump score across the conditions with tuck-jump score increasing from 3.52 ± 1.64 baseline to 4.37 ± 1.25 with the easy cognitive task to 4.67 ± 1.24 with the difficult cognitive task. No significant differences were found in vGRF across the three conditions. Conclusion: The dual-task conditions affected jump-landing mechanics as measured by the tuck-jump score. Although there was a decrease in vGRF, no statistical significance was found over the three conditions.

Committee: Dustin Grooms PhD, AT, CSCS (Committee Member); Jae Yom PhD (Committee Member); Janet Simon PhD, AT (Committee Member) Subjects: Biomechanics; Health Sciences; Sports Medicine

Doctor of Philosophy (Ph.D.), University of Dayton, 2016, Mechanical Engineering

One in three older adults fall each year; many falls resulting in moderate to severe injuries. Falls are a multi-faceted problem, with risk factors that include balance and gait impairments. Balance and movement assessments are often used to identify individuals at risk of falls by identifying a change in the center of pressure excursions or movements. This study examined two fall risk assessments, posturography analyzed through traditional time-domain measures and newer non-linear measures and the instrumented Timed Up and Go (iTUG), under standard and dual-task conditions, to determine better ways to distinguish individuals with subtle deficits contributing to fall risk. One hundred fifty older adult fallers and non-fallers performed quiet-standing posturography and iTUG methodologies. Test conditions included standard testing conditions, cognitive dual-task, manual dual-task, and cognitive+manual dual task. Five traditional postural sway parameters, four non-linear postural sway parameters were calculated, and eight iTUG parameters were calculated. One-way multivariate analysis of variance (p<0.05) was used to compare fallers versus non-fallers and to compare each type of dual task. Effect sizes were calculated using the Cohen's d method. Stepwise logistic regression was performed to identify the postural sway and iTUG parameters that best differentiated fallers from non-fallers for the traditional Timed Up and Go Test, iTUG test, posturography test and a combined model including the iTUG and posturography tests. Results demonstrated that not just one dual-task prevailed over the overs, rather when analyzing posturography data through traditional measures the manual dual-task provided greater differentiation between fall risk groups, when analyzing posturography data through non-linear measures the cognitive dual-task provided greater differentiation between fall risk groups, and when utilizing the iTUG test the cognitive+manual dual-task affected the iTU (open full item for complete abstract)

Committee: Kimberly Bigelow (Advisor); Wiebke Diestelkamp (Committee Member); Kurt Jackson (Committee Member); Allison Kinney (Committee Member) Subjects: Biomechanics; Mechanical Engineering

Doctor of Philosophy (Ph.D.), Bowling Green State University, 2014, Communication Disorders

Motor learning relies on the integrity of sensorimotor circuits in the brain, which are largely affected in individuals with Parkinson disease (PD). Additionally, data suggest normal aging can affect various stages of motor learning. Though data are available on the nature of non-speech motor learning, fewer studies have examined how adults with and without motor speech disorders learn speech articulatory sequences. The aim of the current investigation is to examine speech motor sequence learning in normal aging and PD. A speech motor sequence learning task was developed and implemented to examine acquisition, consolidation, and automatization over two days. On Day 1, participants learned a sequence of six monosyllabic nonwords to examine acquisition. This speech motor sequence was re-tested on Day 2 in single- and dual-task conditions to evaluate consolidation and automatization, respectively. Learning was inferred from gains in speed and accuracy of the speech motor sequence. There were no observed effects of aging or PD on speech motor sequence acquisition, as all groups exhibited comparable gains in speed and accuracy on Day 1. However, aging and PD were observed to affect speech motor consolidation following night-time sleep. Specifically, at the Day 2 re-test, young adults exhibited offline gains in speed and accuracy, older adults maintained speed and accuracy (without offline gains), and individuals with PD exhibited offline losses in speed. Only younger adults demonstrated automatization, exhibiting negligible dual-task effects when concurrently performing the speech motor sequence with a visuo-motor task. Conversely, both older adults and individuals with PD exhibited significantly poorer performance of the speech motor sequence in the dual-task condition, with individuals with PD experiencing the largest degree of bidirectional dual-task interference. Overall, the current findings suggest that speech motor learning is affected by both Parki (open full item for complete abstract)

Committee: Alexander Goberman Ph.D. (Advisor); Ronald Scherer Ph.D. (Committee Member); Miriam Krause Ph.D. (Committee Member); Howard Cromwell Ph.D. (Committee Member); Patricia Sharp Ph.D. (Committee Member) Subjects: Acoustics; Behavioral Sciences; Cognitive Psychology; Neurosciences; Speech Therapy

Doctor of Philosophy, University of Toledo, 2013, College of Health Sciences

Background: Changes in gait due to simultaneous performance of an attention-demanding dual task, such as walking while talking on the phone, may be caused by competing demands for attentional resources. As dual-tasking during gait is common, assessment of this paradigm is becoming highly important for mobility research. The objective of this study is to examine changes in gait and verbal response while performing a timed up and go test (TUG) with a concurrent cognitive task of counting backwards and a motor task of carrying a meal tray in order to understand the role of cognitive factors in gait-related balance control. Significance: Exploring the influence of attention processes on gait may represent an efficient way to- 1) improve the assessment of the falling risk among older adults, 2) help in promoting healthy senile life by focusing on cognitive development, and 3) improve post fall rehabilitation interventions by inclusion of cognitive tasks in addition to improving musculoskeletal impairments. Methods: Community dwelling healthy older adult volunteers participated in a timed get up and go (TUG) test while their movements were recorded by a 3D motion analysis system and force plates. Statistical Analysis: Multiple one-way repeated measures ANOVAs were performed for each of the kinematic and kinetic variables to examine differences across task conditions. Post hoc tests with Bonferroni corrections were conducted for significant main outcome variables. T tests were performed to assess cognitive skills. Results: The study successfully examined 15 healthy older adults between ages 65 and 88, scores of > 25 on MMSE test on their performance of dual task conditions in an attempt to get an insight into their gait and dynamic balance control system. We found that the most complex task situation of carrying the food tray and counting backward had the most adverse effect on gait performance in healthy older adults that resulted in 24% more time required t (open full item for complete abstract)

Committee: Charles Armstrong (Advisor); Phillip Gribble (Committee Member); Martin Rice (Committee Member); Peggy Arnos (Committee Member) Subjects: Biomechanics; Health Care; Health Sciences; Kinesiology; Physical Therapy

Doctor of Philosophy (PhD), Wright State University, 2009, Human Factors and Industrial/Organizational Psychology PhD

The present study tested the hypothesis that three visual pathways (i.e. parvocellular, magnocellular, and koniocellular pathways) may influence the degree of dual-task interference using dual-task methodology. The magnocellular pathway consists of feature-coding mechanisms that are sensitive to transients and motion, and is thought to process information about the locations and movements of objects. The parvocellular pathway consists of feature-coding mechanisms that are sensitive to red-green and brightness information, while the koniocellular pathway consists of feature-coding mechanisms that are sensitive to blue-yellow chromatic information. Both the parvocellular and the koniocellular pathway are thought to process information useful for identifying objects. The hypothesis predicted that engaging in two search tasks that were mediated by feature-coding mechanisms in two different pathways would result in less dual-task interference in performance than two tasks that were mediated by feature-coding mechanisms in the same pathway. Magnocellular stimuli were defined by brief luminance transients and motion, and parvocellular and koniocellular stimuli were defined by color. The most interference was observed for task pairs that were different in nature and mediated in one pathway. Two tasks mediated by the two different pathways resulted in a small interference, while two identical task pairs mediated by one pathway resulted in no dual-task interference. No significant negative contingency was observed in any task pair. Dual-task interference consistent with a sampling model (e.g. Bonnel et al., 1992) and an independence model (e.g. Morrone et al., 2002 and 2004) were observed. No task pairs produced dual-task interference consistent with the prediction of a switching model (e.g. Duncan, 1996).

Committee: Allen Nagy PhD (Committee Chair); Scott Watamaniuk PhD (Committee Member); Pamela Tsang PhD (Committee Member); Michael Hennessy PhD (Committee Member) Subjects: Psychology

Doctor of Philosophy (PhD), Wright State University, 2009, Industrial and Human Factors Engineering

Real-world scenarios are complex dynamic systems that are often overloaded with information. Effective performance of these dynamic systems depends on the objects in such systems and the relationship among them. The control of many of these systems is semi-automated. Human operators constantly monitor and control these systems, assess the situation and often make decisions under time pressure. However, this supervisory control paradigm in a dual-task environment can be a very challenging task. Existing interface design methodologies and techniques have not delved deeply enough into defining information displays for complex, dynamic, time-critical, dual-task environments with capabilities for rapid task change awareness and task resumption while continuously maintaining situation awareness. This research focuses on designing user displays with advanced cueing techniques to support performance in complex dynamic dual-task environments. A primary question addressed in this study is whether visualization methods such as status-at-a-glance displays, interruption recovery tools, and course of action planning tools would assist in maintaining situation awareness, resuming tasks quickly, and effectively perform decision making tasks. The research examines interface design methods to support supervisory awareness in primary and secondary task situations, rapid assimilation when switching to a secondary task, rapid re-assessment upon return to the primary task or secondary task, a course of action solution explorer for successful mission planning/re-planning, and notification systems such as alerts to inform operators about interrupting tasks. This research provides a means to realize an “at-a-glance” decision making environment. The methodology adopted in this research effort used a three-stage process. In stage one, the effect of interruptions on trust and coordination among team members was studied. For stages two and three, the operator tasks and the interface protocol (open full item for complete abstract)

Committee: Raymond Hill PhD (Advisor); Raymond Hill PhD (Committee Chair); Frank Ciarallo PhD (Committee Member); Yan Liu PhD (Committee Member); Sundaram Narayanan PhD, P.E. (Committee Member); Edward Pohl PhD (Committee Member); Dan Voss PhD (Committee Member) Subjects: Design; Engineering; Industrial Engineering; Information Systems; Systems Design

MA, University of Cincinnati, 2005, Arts and Sciences : Psychology

This study tested predictions derived from resource-depletion and effort-regulation models of performance effects associated with transition from a high to a low level of task demand. Demand transition was accomplished by shifting participants from a dual-task condition in which they performed concurrent tracking and vigilance tasks (induction phase) to a single task condition in which only tracking was required (transition phase). When the tracking task was difficult, dual-task participants performed more poorly than single-task controls during both phases of the study, a result consistent with expectations derived from the resource-depletion model. Just the opposite effects occurred when the tracking task was easy, a result consistent with expectations derived from the effort-regulation model. Clearly, task difficulty is a critical factor to consider in testing models of the performance effects associated with workload transition. Participants in all experimental conditions reported the experiment to be stressful.

Committee: Dr. Joel Warm (Advisor) Subjects:

MA, University of Cincinnati, 2005, Arts and Sciences : Psychology

Recent evidence suggests that the postural control system and the cognitive system interact when engaged concurrently. However, the literature is inconsistent with regard to whether cognitive activity degrades or facilitates postural control, and with regard to whether distinct types of cognitive activity differentially affect postural control. The aim of this project was to assess the effects of working memory tasks on postural control. Participants were instructed to perform simultaneously a posture task and a working memory task, which varied across trials along three dimensions: a) type of information (verbal and visual), b) working memory component (phonological loop, visual sketchpad and central executive), and c) cognitive process (encoding and rehearsal). Results showed a general tendency for postural sway to decrease during rehearsal and to increase during encoding of cognitive information, but these effects were not specific to the working memory component that was presumably engaged by the verbal and visual tasks.

Committee: Michael Riley (Advisor) Subjects: Psychology, Experimental

Doctor of Philosophy, The Ohio State University, 2010, Psychology

The present study tests sequential sampling models of processing in the flanker task. In a standard flanker task, participants must identify a central target that is flanked by items that indicate the same response (congruent) or the opposite response (incongruent). The standard finding is that incongruent flankers produce interference that primarily affects the early component of the decision process. The goal was to contrast different mechanisms of visual attention and to identify a simple processing model that can be used to augment analyses of this task. Several models were contrasted in their ability to account for flanker data from experiments that manipulated response bias, speed/accuracy tradeoffs, attentional focus, and stimulus configuration. Models that assume dynamic focusing of attention provided the best overall account of the behavioral data. Among the dynamic models, a spotlight model that assumes gradual narrowing of attention provided the best balance of fit and parsimony, though dual process models that assume discrete selection of the target also captured the main trends in the data when only standard congruent and incongruent conditions were used. Importantly, the experimental manipulations were reflected by the appropriate model parameters, supporting future use of these models to decompose behavioral data from the flanker task into meaningful psychological constructs. The results of this study also indicate that standard flanker experiments do not provide strong evidence for contrasting gradual versus discrete target selection, and consequently they do not provide strong evidence to support or refute theories of the underlying mechanisms of dynamic attention models.

Committee: Roger Ratcliff PhD (Advisor); Simon Dennis PhD (Committee Member); Alex Petrov PhD (Committee Member); Gail McKoon PhD (Committee Member) Subjects: Psychology

Doctor of Philosophy (PhD), Ohio University, 2009, Speech-Language Science (Health Sciences and Professions)

In addition to language impairments, individuals with aphasia frequently have difficulties allocating attention that contribute to language processing, as it has been assessed repeatedly using dual-task experiments. The goal of this study was to develop a method to assess attention allocation during auditory linguistic processing using eye tracking in a dual-task paradigm. A dual-task experiment included an auditory linguistic processing task, in which sentences were presented auditorily, and a visual search task, in which participants were trained to find a visual target in a display that included one target and three nontarget foils. Attention demands were manipulated by varying the complexity of each of the two tasks. Changes in attention demands were indexed through performance on the visual search task using eye-tracking measures. Thirty-three adults with aphasia participated and 34 adults free of neurogenic impairments served as control participants. Significant increases in attention demands were observed from single- to dual-task conditions and from simple to complex verbal and visual stimulus processing, indicated through decreases in the following eye-tracking measures: proportion of fixation duration on the target (PFDT), proportion of number of fixations on the target (PNFT), average fixation on the target (AFDT), first-pass gaze duration on the target (FPGDT); and latency until first fixation on the target (LFFT). Significant differences between participant groups indicated that individuals with aphasia have greater difficulty allocating attention properly according to task demands on linguistic and nonlinguistic tasks. These results are consistent with findings described in other studies indicating that individuals with aphasia have significantly greater difficulty than controls in allocating attention. PFDT and PNFT most consistently indexed changes in attention allocation. Correlations between aphasia severity as indexed by the aphasia quotient from (open full item for complete abstract)

Committee: Brooke Hallowell (Committee Chair); James Montgomery (Committee Member); John McCarthy (Committee Member); Alexander Sergeev (Committee Member); Danny Moates (Committee Member) Subjects: Speech Therapy

Master of Science in Exercise and Health Studies, Miami University, 2009, Physical Education, Health, and Sport Studies

The current study investigates whether typing on a computer while walking (using the active workstation) results in decrements in performance on either task and also seeks to assess the effectiveness of two different dual task practice protocols. A significant difference in participants' typing performance (WPM, p < .00; ACC, p < .03; ERR, p < .02; AWPM, p < .00) was found between baseline measurements and pre-test, as well as, significant changes in gait (knee height, p < . 03; stride length, p < .00). Secondly, between baseline measurements and post-test, there was no significant improvement in typing performance in the massed practice group (p < .06), and a significant improvement in the distributed practice group (p < .00), while both groups exhibited significant increases in stride length. The initial result of walking while typing elicited a negative effect on typing performance and changed the gait pattern of the user, yet with distributed practice these variables reverted back towards baseline measurements.

Committee: Mark Walsh PhD (Committee Chair); Ronald Cox PhD (Committee Member); Thelma Horn PhD (Committee Member) Subjects: Health