The goal of this study was to examine word learning in preschool children with low socioeconomic status (SES) to inform an understanding of the limited word knowledge of this population. There is evidence to suggest that impoverished linguistic input explains substantial variability in word knowledge of children with low SES. Research has not yet considered the ways that children with low SES make use of linguistic input. Participants, preschool children with low SES, completed a part-term fast-mapping task. Specific cues of a familiar whole object, possessive syntax, and whole-part juxtaposition were provided to children in linguistic input using standard verbal scripts. As a group, participants provided more part-term responses when provided with cues than when no cues were presented. Participants provided the most part-term responses when multiple cues were presented in combination. Thus, children with low SES appear to use word learning strategies to make use of information in the linguistic input, similar to peers with higher SES. Participants with limited word knowledge, as defined by performance on a norm-referenced measure, were less accurate on the part-term task than peers with age-appropriate word knowledge. This finding suggests that children with low SES and limited word knowledge are inefficient word learners.

ASSESSMENT OF A MEASURE OF RESPONSE CONFIDENCE FOR A SPEECH RECOGNITION TASK IN NOISE <p> JOHN ANDREW DUNDAS <p> Dissertation under the direction of Gary P Jacobson, Ph.D. <p> The development of a measure of response confidence for a speech understanding task is presented in this dissertation. Normal hearing participants completed speech understanding tasks in background noise and rated confidence in their responses. In experiment 1, the relationships between measured performance, perceived performance and confidence in the correctness of responses were investigated. In experiment 2, the effect of sentence context on response confidence was investigated. The main findings of this study are; 1. Confidence ratings of speech intelligibility performance can be consistently measured using simple tools, 2. Confidence ratings are strongly correlated with measured performance, 3. Confidence ratings are highly repeatable, 4. Sentence based test materials with a high degree of context result in the most accurate calibration to measured performance, and, 5. Low context sentences result in a faster growth of confidence (i.e., overconfidence). These findings suggest that confidence ratings could be a useful outcome measure in the evaluation of treatment efficacy in the hearing impaired population.

The purpose of this project is to define for young, middle age, and elderly subjects the best frequency(cies) to record both the cVEMP and the oVEMP. An additional objective of this study is to describe the age related changes in the frequency tuning of both the cVEMP and oVEMP. Our hypothesis is that damage to the saccule or utricle, as a result of aging, would alter the resonant frequency of the end organ thus altering the frequency tuning characteristics of the vestibular system. Our results show that there are no significant differences in VEMP amplitude evoked by a 500 Hz, 750 Hz, and 1000 Hz air conduction tone bursts for our subjects. Our findings also show that aging results in an overall flattening or loss of frequency tuning in older adults for the cVEMP, but not the oVEMP. Additionally, the frequency tuning of both the cVEMP and oVEMP shifts to a higher frequency in the older adult group compared to the middle age and young adult groups. Accordingly, for dizzy patients over the age of 60 years, a 500 Hz air conduction tone burst may not be the ideal frequency to elicit a VEMP response. We recommend using a stimulus frequency of 750 Hz or 1000 Hz in this population.

This thesis is concerned with auditory motion perception and the combinations of cues that contribute to human sensitivity of signals that change in spatial position. Measurement of how sensitive individuals are to the rates of change for auditory cues are difficult because of confounds between duration, extent, and velocity of the changing signal. Dooley and Moore (1988) proposed a psychometric tool for measuring sensitivity to rate of auditory cue change using a duration discrimination task. They reported that duration discrimination was improved when an additional cue based on rate of change (of intensity or frequency) was present. This provided a back door approach to measuring sensitivity to rate of change. The current experiments were designed to measure sensitivity to the rate of change in intensity and spatial position. Experiment 1 investigated whether performance was enhanced in a duration discrimination task when additional cues consisting of rate of intensity change (partial replication of Dooley and Moore, 1988), rate of spatial position change, or both cues were provided. Duration discrimination was not enhanced by these cues, in fact, it was worse. Experiment 2 assessed whether duration discrimination could be used to measure sensitivity to rates of changes in intensity and motion if the rate differences were larger. As in Experiment 1, duration discrimination was not improved, and tended to worsen, when the velocity cues were present. Experiment 3 shifted the focus to a direct velocity discrimination task to determine whether sensitivity to rates of spatial change varied with the mix of directional and distance information that specified velocity. Performance was better when both directional and distance cues were provided, compared to conditions where only one of these cues was available. Moreover, the benefit from having both types of information was significantly better when direction and distance cues were weighted to be perceptually equal for each participant.

Binaural hearing results in a number of listening advantages relative to monaural hearing, including enhanced hearing sensitivity and better speech understanding in adverse listening conditions. These advantages are facilitated by the ability to detect and utilize interaural cues within the central auditory system. It is well understood that infants and children with Down syndrome have unique auditory structures resulting from congenital and acquired influences (e.g., Balkany, Mischke, Downs, & Jafek, 1979; Becker, Armstrong, & Chan, 1986; Bilgin, Kasemsuwan, Schachern, Paparella, & Le, 1996; Blaser, et al., 2006). Structural anomalies within the central auditory system and alterations in synaptic communication could adversely affect binaural hearing. However, binaural hearing capabilities have not been examined in these children. This study was designed to determine if the binaural abilities of children with Down syndrome are compromised relative to those of typically-developing children on a masking level difference task and a binaural intelligibility level difference task. Participants included typically-developing children aged 3 to 13 years (N=46) and children with Down syndrome aged 6 to 16 years (N=11). In addition, typically-developing adults (N=6) and adults with Down syndrome (N=3) were included to obtain an estimate of adult performance for the experimental tasks. Despite normal hearing sensitivity children with Down syndrome in this study had higher masked thresholds for our experimental stimuli and exhibited less release from masking than typically-developing children. These observations suggest that children with Down syndrome have similar speech recognition in noise as typically-developing children aged 3 to 5 years. The binaural advantages afforded to typically-developing children, such as enhanced hearing sensitivity and better speech understanding in adverse listening conditions, were not present for children with Down syndrome in this study. The reduced binaural benefit experienced by children with Down syndrome suggests that they will require more favorable signal-to-noise ratios than typically-developing children to achieve optimal performance in adverse listening conditions. This has important implications for the planning of educational and therapeutic interventions for individuals with Down syndrome.

This project is concerned with the relationship between type-1 diabetes and auditory pathology. In this dissertation I compared hearing sensitivity, cochlear function, and peripheral auditory neural function (afferent and efferent) in young adults with type-1 diabetes in comparison to matched controls. As a secondary objective I explored the influence of covariates, such as diabetes control, sex, and noise exposure. My findings suggest that the persons with type-1 diabetes demonstrated early signs of cochlear pathology and that this damage was related to sex and history of noise exposure. In addition, I demonstrated the utility of low-level stimulus evoked otoacoustic emissions in showing reduced cochlear function in participants with higher noise exposure and type-1 diabetes despite otherwise normal auditory function outcomes. Identification and recognition of early indices of cochlear pathology may allow intervention and prevention of noise related hearing loss in persons with and without type-1 diabetes.

Historically, spelling has been considered an academic skill that relies primarily on visual memory. Recent research indicates that spelling skill is also dependent on linguistic knowledge. However, the contribution of linguistic knowledge to spelling skill is not well understood. The purpose of Study 1 in this investigation was to explore systematically the relation of phonological processing, morphological knowledge, and orthographic knowledge to spelling performance independent of visual memory in elementary school children. After controlling for age, nonverbal intelligence, articulation, and visual memory, orthographic knowledge and morphological knowledge contributed unique variance to spelling performance for children with typical language. To understand the nature of spelling difficulties in children with SLI, it is important to elucidate the areas of linguistic knowledge that influence childrens spelling. The purpose of Study 2 in this investigation was to (a) to evaluate the contribution of linguistic knowledge to spelling in children with SLI and (b) to compare the linguistic knowledge predictors of spelling by children with SLI to those of children with typical language. After controlling for age, nonverbal intelligence, articulation, and visual memory, only morphological knowledge contributed unique variance to spelling performance of children with SLI; the contributions of phonological processing and orthographic knowledge, despite explaining approximately 10% of the total variance each, were not statistically significant. Interaction effects of linguistic variables and language group status were not statistically significant, although examination of the individual models for children with SLI and children with typical language revealed differences in the types of knowledge that predicted spelling in each group. The results indicate that spelling instruction should take into account childrens linguistic knowledge and explicitly relate their linguistic knowledge to spelling and that it likely is necessary to teach spelling to children with language impairment using approaches that may differ in some ways from those used to teach children with typical language.

The brain is continuously processing many sources of sensory information. One of the key strategies it uses to determine what stimuli are associated with one another is the temporal delay between multisensory inputs. When stimulus onset asynchronies (SOAs) are sufficiently short, multisensory signals are highly likely to be bound. Extensive research in adults has characterized the temporal structure of audiovisual integration and the alterations in behavior and perception induced by such interactions. However, no prior work has investigated developmental changes in multisensory temporal processing in the period between infancy and adulthood. Here, we present a series of studies detailing maturational changes in the temporal window of audiovisual integration for basic stimuli and speech. Results of our early work revealed age-related differences in 10 and 11 year olds and adults on a nonspeech audiovisual simultaneity judgment task, which suggested that processing alterations persist beyond the first decade of life for basic stimuli. These findings provided the foundation for follow-up studies which sought to characterize the trajectory of multisensory temporal processing maturation from early childhood to early adulthood. To that end, the simultaneity judgment measure previously employed was administered to a group of participants ranging in age from 6 to 23 years. Comparison of responses across subjects indicated that multisensory temporal binding windows were larger in children and adolescents than adults, suggesting that the younger groups were more likely to bind asynchronous audiovisual pairings. To examine whether this developmental effect was generalizable to speech, subjects completed an audiovisual identification task wherein incongruent auditory and visual speech tokens were presented at a range of SOAs. Surprisingly, findings indicated that the temporal binding window for audiovisual speech matures earlier; window sizes were comparable in children, adolescents and adults. Overall, results suggest that the trajectory to realization of adult-like multisensory temporal processing differs for nonspeech and speech stimuli. The role of experience in mediating faster window contraction for speech is speculated upon and the implications of delayed maturation of multisensory processing on overall development are reviewed.

Purpose: The purpose of this study was to assess attention problems and intratest scatter (variability) of responses to standardized tests of expressive language by preschool-age children who do (CWS) and do not stutter (CWNS). Method: Participants were 40 preschool-age CWS (30 males) and 46 CWNS (32 males). Between-group comparisons of attention were made using attention subscales of the Child Behavior Checklist for Ages 1 ½ - 5 (CBCL; Achenbach & Rescorla, 2000). Likewise, between-group comparisons of intratest scatter were based on participant responses to the Expressive subtest of the Test of Early Language Development 3 (TELD-Exp; Hresko, Reid, & Hamill, 1999) and the Expressive Vocabulary Test 2 (EVT-2; Williams, 2007). Furthermore, within-group assessment of the relation between CWS scatter and their stuttering frequency was conducted. Results: Results indicated no significant between-group differences in intratest scatter on the TELD-Exp and EVT-2, nor significant correlations between scatter and Attention Problems on the CBCL. Findings did indicate that for CWS, categorical scatter on the EVT-2 was positively correlated with their stuttering frequency. Conclusions: Consistent with earlier findings, variability in speech-language performance appears to be related to CWS stuttering, suggesting that perhaps some other underlying cognitive-linguistic variable (e.g., cognitive load) may be common to both variables and salient to a better understanding of developmental stuttering.

The purpose of this paper was to evaluate the possible benefit of hearing aids for reducing listening effort in quiet and in noise. An additional purpose was to investigate the possible relationship between the magnitude of listening effort benefit and individual listeners working memory capacity or lipreading skill. Thirty-six participants with bilateral sensorineural hearing loss were fitted with linear behind-the-ear hearing aids and tested using a dual-task paradigm. The primary task was monosyllable word recognition and the secondary task was a visual reaction time task. In addition, participants rated their perceived effort after each condition. The test conditions varied by hearing aids (unaided, aided), visual cues (auditory-only, auditory-visual), and background noise (present, absent). For all participants, the signal-to-noise ratio was set individually so that speech recognition performance in noise was approximately 50% in both the auditory-only and auditory-visual conditions. In addition to measures of listening effort, lipreading ability and working memory capacity were measured. In general, the effects measured using the objective measure of listening effort were small. The results of this study suggest that, on the average, hearing aids improve objective listening effort; however, this only occurs after a period of acclimatization. Also, people who are not good lipreaders may derive hearing aid benefit when using auditory-visual stimuli, generally because people who are good lipreaders expend less listening effort. Therefore, it is speculated that the addition of the hearing aid provides little, if any, additional benefit. Good lipreaders were also more likely to derive benefit from the presence of visual cues than people who are not good at lipreading. Background noise increased objective listening effort, but neither working memory capacity nor lipreading ability predicted susceptibility to noise. Finally, it should be noted that the magnitude of listening effort was generally small in this study, potentially obscuring the effects of the predictive variables. Further investigation is needed to determine if other methods, which might include more complex secondary tasks, result in greater measured listening effort effects.