This investigation examined the effects of task difficulty on aphasic individuals' naming performance. Subjects were presented lists of easy-to-name and difficult-to-name items. In the high success condition, difficult lists were interspersed among a larger number of easy lists. In the low success condition, easy lists were interspersed among a larger number of difficult lists. Percentages of correct responses for administration of each list were calculated for each subject. Group means for each list were derived by averaging the individual scores. Group means in the high success and the low success conditions were compared with baseline measures to determine experimental effects. No statistical analyses were performed. Results did not find that task difficulty effects aphasic individuals' naming performance.

Children's narrative language plays a critical role in guiding the transition between oral language and literacy (Roth & Spekman, 1989; Westby, 1989). Narrative comprehension and production by normally achieving and language delayed school-aged children have been studied. Many of these studies have involved story retellings. Few have studied how spontaneously produced narratives are organized especially by young children.

The purpose of this study was to compare and contrast within and between participant performance on three different measures of listening effort: a dual-task paradigm, pupillometry, and skin conductance; participants also subjectively rated the difficulty of their experience. A repeated measures design was used to address the reliability and validity of each measure. 20 participants were recruited and attended two sessions; the second occurred a minimum of one week after the first. Participants listened to sentences presented in stationary noise at four different signal-to-noise ratios: quiet, 0, -3, and -5 dB SNR. The variables of interest were: change in peak-to-peak pupil diameter, change in reaction time from baseline, skin conductance response amplitude, and skin conductance response quantity. The results indicated that as SNR decreased, speech perception performance decreased and subjective listening effort increased. Participants accurately and consistently rated the more difficult conditions as requiring more listening effort. The change in reaction time from baseline, peak-to-peak pupil diameter, and skin conductance response quantity increased as SNR decreased; skin conductance response amplitude did not vary as task difficulty increased, but skin conductance response amplitude was larger for incorrect responses than it was for correct responses. There was a significant practice effect observed for the reaction time data. The dual-task paradigm and pupillometry measures had the greatest reliability and validity. This study demonstrated that listening effort can successfully be quantified both subjectively and objectively by using a variety of tasks. Future studies may be able to use these measures to further assess listening effort in the clinic and in the real-world.

This thesis introduces a new theoretical framework from which to view the factors that contribute to stuttering variability. The speech and monitoring interaction (SAMI) framework proposes that there are two systems that account for stuttering variability: the speech production system and the monitoring system. Each system has unique factors that modulate them. Within SAMI, the interaction of these two categories of factors is formalized in a mathematical equation. What is particularly novel about SAMI is the use of a mathematical equation to formalize the interaction between these systems and the specific proposal of the biological substrates of the monitoring system and its interaction with the speech system. The focus of this thesis is on the anticipation of stuttering, which is one of the factors from SAMI that modulates the monitoring system. The goals of the studies were to 1) characterize the degree to which people who stutter (PWS) anticipate stuttering and how accurately they can predict actual stuttering, 2) investigate the correlation between stuttering expectancy on words and the verbal response time to say those word in word naming tasks, and 3) make a qualitative comparison of the behavioral results and the results from a neural network model. Utilizing the SAMI framework it was hypothesized that stuttering expectancy would be positively correlated with the response time and the results from the simulations would qualitatively match the behavioral results. The key finding was that across the group of PWS, there was positive correlation between stuttering expectancy scores and relative reaction times on those words. The degree to which stuttering expectancy was correlated with reaction time within subjects was positively correlated with stuttering severity. A qualitative comparison showed a good fit in between results of the simulations and the behavioral study. This is the first study to show that the expectation of stuttering has an effect on fluent speech production, providing evidence that the anticipation of stuttering is not only correlated with moments of stuttering but may also be a contributing factor to stuttering. The model provides a means of hypothesizing and testing specific neural substrates associated with anticipation of stuttering and its effects on the speech production process.

Language impairment (LI) and ADHD are two relatively common developmental disorders that frequently co-occur and have thus been said to be comorbid. The overall aim of this research is to investigate the nature of comorbidity between LI and ADHD in a large population-based sample. The project comprises two parts. The first study aims to quantify the extent of comorbidity between LI and ADHD, and asks whether there is any evidence for a shared liability between the two disorders on the basis of family history data. The second study hypothesizes that comorbidity between LI and ADHD arises because the two disorders share a common genetic etiology. Genetic variants previously associated with ADHD are tested for association to LI. Association is found with the dopamine receptor D4 (DRD4) and the serotonin transporter gene (SLC6A4). Implications for this in relation to language are discussed with respect to reinforcement and associative learning.

Purpose: Research has shown that children who stutter (CWS) demonstrate poor adaptive functioning, or poor functional, social, and psychological skills, when compared to children who do not stutter (CWNS). Previous work has also shown that preschool CWS demonstrate significantly lower effortful control than CWNS. High effortful control, or the ability to inhibit a dominant response, is predictive of high adaptive functioning in children who are exposed to a range of adversities. The purposes of this study were fourfold: (a) to investigate if the differences between preschool CWS and CWNS in effortful control extended to school-aged children; (b) to determine if effortful control could uniquely explain adaptive functioning after controlling for a diagnosis of stuttering; (c) to investigate whether effortful control was more influential to CWS than to CWNS; and (d) to investigate whether effortful control uniquely explained adaptive functioning in CWS after controlling for stuttering frequency. Methods: Effortful control and seven core areas of adaptive functioning were investigated in 46 school-age CWS and 46 CWNS. Eight independent two tailed t-tests were used to assess whether CWS demonstrated lower effortful control than CWNS and lower adaptive functioning than CWNS in seven adaptive functioning areas: communication competence, peer competence, internalizing behaviors, externalizing behaviors, general anxiety, social anxiety, and depression. Correlation and hierarchical regression analyses were used to examine the extent to which each component of adaptive functioning was related to effortful control when controlling for age, intelligence, parent-child relationship, and stuttering group membership. Hierarchical regression analyses were used to assess the extent to which each separate component of adaptive functioning was related to effortful control in CWS only. Results: CWS demonstrated significantly lower effortful control when measured by the Early Adolescent Temperament Questionnaire (a parent report measure of hot effortful control) than CWNS. CWS also performed more poorly in all aspects of adaptive functioning; however statistical significance was only reached for internalizing behaviors and general anxiety. The hierarchical linear regressions indicated that effortful control predicted the majority of the variance in five areas of adaptive functioning: peer competence, externalizing behaviors, internalizing behaviors, general anxiety, and depression. In the group of CWS, stuttering frequency predicted internalizing behaviors, general anxiety, and social anxiety. However, stuttering was the most important contributor to only one of the seven components of adaptive functioning, social anxiety. Conclusions: This study with school-aged CWS extends previous work indicating that preschool CWS exhibit lower effortful control than their normally fluent peers. The fact that emotional aspects of effortful control were a stronger predictor of social functioning, internalizing behaviors, and externalizing behaviors than either a stuttering diagnosis or the quantity of stuttering, may explain the adaptive functioning deficits often observed in CWS. Because effortful control is both a powerful contributor to adaptive functioning, and is reduced in CWS, clinical therapy approaches, which boost effortful control skills, have the potential to greatly lessen the impact of stuttering for CWS.

Syntactic anomalies reliably elicit P600 effects in natural language processing. A survey of previous work converged on a conclusion that the mean amplitude of the P600 seems to be associated with the goodness of fit of a target word with expectation generated based on already unfolded materials. Based on this characteristic of the P600 effects, the current study aimed to look for evidence indicating the influence of input statistics in shaping grammatical knowledge/representations, and as a result leading to probabilistically-based competition/expectation generation processes of online sentence processing. An artificial grammar learning (AGL) task with 4 different conditions varying in probabilities were used to test this hypothesis. Results from this task indicated graded mean amplitude of the P600 effects across conditions, and the pattern of gradience is consistent with the variation of the input statistics. The use of the artificial language to simulate natural language learning process was further justified with statistically undistinguishable P600 effects elicited in a natural language sentence processing (NLSP) task. Together, the results indicate that the same neural mechanisms are recruited for both syntactic processing of natural language stimuli and sentence strings in an artificial language.

Bandpass filtered transient-evoked otoacoustic emission (TEOAE) waveforms are composed of short-latency (SL) and long-latency (LL) portions. The LL portion has latency consistent with generation through linear coherent reflection at the tonotopic place on the basilar membrane. The short-latency (SL) portion occurs earlier in time and exhibits less compressive growth. Several mechanisms have been hypothesized to explain generation of the SL portion, including 2f1-f2 intermodulation distortion and coherent reflection basal to the tonotopic place. Two experiments were designed to examine the generation mechanism and generation location of the SL portion. Experiment 1 tests the hypothesis that the SL portion results from low-side, cubic intermodulation distortion. Experiment 2 determines the region along the basilar membrane at which the SL portion of the TEOAE is generated. The null hypothesis that the SL portion of the TEOAE is generated through low-side, cubic intermodulation distortion requires stimuli with broad frequency content. Stimulus energy at different frequencies (f1 and f2) is presumed to interact simultaneously across the cochlear partition, generating a distortion-source OAE. To test this hypothesis, OAEs were evoked using 2 kHz tone-bursts with durations spanning the time-frequency continuum between a click and a pure tone. As tone-burst duration increases, stimulus energy at the primary frequencies (f1 and f2) decreases and the input to any nonlinear distortion source is reduced. Accordingly, if generated through 2f1-f2 distortion, the magnitude of the SL portion of the TEOAE was expected to decrease as tone-burst duration increased. Results were inconsistent with generation of the SL portion through intermodulation distortion. As tone-burst duration increased, the SL portion remained present in the TEOAE. The presence of the SL portion influenced the level-dependency of TEOAE latency and magnitude to the same extent across all tone-burst durations. The region of generation along the cochlear partition of the SL portion has implications for the mechanism through which it is generated. Generation through low-side, cubic intermodulation distortion (2f1-f2) would occur near the f2 tonotopic place. If generation is through coherent reflection, a generation region basal to that of the tonotopic place is hypothesized. To determine the cochlear region where the SL portion is generated, TEOAEs were evoked by 2 kHz tone-bursts in the presence of different suppressor stimuli. The amount of suppression induced by each suppressor on the OAE was measured, and the suppressor frequency causing greatest suppression of a given portion of the TEOAE was interpreted as corresponding to that portion's generation place along the basilar membrane. For analysis purposes, the SL portion was divided into two SL time-windows (SL1 and SL2). The LL portion of the TEOAE was maximally suppressed by a 2.07 kHz tone, consistent with generation at the tonotopic place. Both SL components were generated basal to the tonotopic place. The later-occurring SL portion of the TEOAE (SL1) was generated between 1/4-1/3-octave basal to the tonotopic place while the earlier-occurring SL portion (SL2) was generated 3/5-octave basal to the tonotopic place. The generation region of the SL1 portion of the TEOAE was too apical to be consistent with generation through 2f1-f2 distortion. Although the generation region of the SL2 portion was what would be expected for a 2f1-f2 distortion-source OAE, the latency was too early. Generation of both SL portions may be explained through basal linear coherent reflection. Per this mode of generation, the SL1 and SL2 portions of the TEOAE each likely mirror the underlying mechanics at different regions along the cochlear partition.

Recent speech surveys conducted in Box Elder County showed that approximately 17% of the elementary school children there had speech defects of such seriousness that they needed clinical attention. A remedial speech program was organized and remedial speech training given at four schools in Box Elder County. The purpose of this project was to study this remedial speech program, as it was in operation, in an effort to determine the feasibility and value of such a program.

This thesis suggests that the range of vocabulary in an individual’s lexicon has an influence on in their assessment of nonword wordlikeness. The study included thirteen Spanish-English bilinguals who participated in a language dominance questionnaire, standardized assessments of Spanish and English vocabulary knowledge, and Spanish and English wordlikeness judgment tasks. Resulting data demonstrated moderate correlations between vocabulary knowledge and performance on nonword wordlikeness judgement tasks in Spanish and English. Participants with larger lexicons appeared more tolerant of less probable nonwords, those with low phonotactic probability, while those with smaller lexicons were less accepting of nonwords with low phonotactic probability. The results suggest that an individual’s processing of low probability phonological constituents is influenced by the diversity and complexity of their linguistic knowledge and specifically, their vocabulary acquisition.