Similarity has been regarded as a primary means by which lexical representations are organized, and hence an important determinant of processing interactions between lexical items. A central question on lexical-semantics similarity is how it influences lexical processing. There have been much fewer investigations, however, on how lexical-semantic similarity might influence novel word learning. This dissertation work aimed to fill this gap by addressing one kind of lexical-semantic similarity, similarity among the novel words that are being learned concurrently (concurrent similarity), on the learning of phonological word forms. Importantly, it aimed to use tests that eliminated the real time processing confound at test so as to provide convincing evidence on whether learning was indeed affected by similarity. The first part of the dissertation addressed the effect of concurrent referent similarity on the learning of the phonological word forms. Experiment 1 used a naming test to provide evidence on the direction of the effect. Experiment 2 and Experiment 3 used the stem completion test and the recognition from mis-pronunciation test that controlled for real time processing between conditions. Then a 4-layer Hebbian Normalized Recurrent Network was also developed to provide even more convincing evidence on whether learning was affected (the connection weights). Consistently across the three tasks and the simulation, a detrimental effect of referent similarity on the phonological word form learning was revealed. The second part of the dissertation addressed the effect of cohort similarity on the learning of the phonological word forms. The recognition from mis-pronunciation on partial words was developed to control for real time processing between conditions so as to capture the effect of learning. We examined the effect of cohort similarity at different syllable positions and found a detrimental effect at the second syllable and non-effect at the third syllable. This is consistent with the previous finding that competition among cohorts diminishes as the stimulus is received, suggesting that the effect of cohort similarity depends on the status of competition dynamics among cohorts. The theoretical and methodological implications of this study are discussed.

Purpose: This study investigates one possible reason for individual differences in vocabulary learning from written context. A Latent Semantic Analysis (LSA) model is used to motivate the prediction of a causal relationship between semantic knowledge for words in a text and the quality of their hypotheses about the semantics of novel words, an effect mediated by reading comprehension. The purpose of this study was to test this prediction behaviorally, using a within subject repeated measures design to control for other variables affecting semantic word learning. Methods: Participants in 6th grades (n=23) were given training to increase semantic knowledge of words from one of two texts, counterbalanced across participants. After training, participants read untreated and treated texts, which contained six nonword forms. Measures were taken of reading comprehension (RC) and the quality of the readers' hypotheses about the semantics of the novel words (HSNW). Text difficulty and semantic informativeness of the texts about nonwords were controlled. Results: All participants had increases in semantic knowledge of taught words after intervention. For the group as a whole, RC scores were significantly higher in the treated than untreated condition, but HSNW scores were not significantly higher in the treated than untreated condition. Reading comprehension ability was a significant moderator of the effect of treatment on HSNW. A subgroup of participants with lower scores on a standardized reading comprehension measure (n=6) had significantly higher HSNW and RC scores in the treated than untreated condition. Participants with higher standardized reading comprehension scores (n=17) showed no effect of treatment on either RC or HSNW. Difference scores for RC and difference scores for HSNW were strongly related, indicating that within subjects, there is a relationship between RC and HSNW. Conclusions: The results indicate that for a subgroup of readers with weaker reading comprehension, intervention to enhance lexical semantic richness had a substantial and significant effect on both their reading comprehension and on the quality of hypotheses that they generated about the meanings of novel words. Neither effect was found for a subgroup of readers with stronger reading comprehension. Clinical and educational implications are discussed.

Purpose: This study examines the classification accuracy and interrater reliability of a dynamic assessment (DA) of inferential word learning designed to accurately identify kindergarten through sixth-grade students with and without language disorder. Method: The participants included 127 school-age children from a mountain west school district who were administered a DA of inferential word learning that entailed a pretest, a teaching phase, an examiner rating of the child's ability to infer word meaning (modifiability), and posttests. Results: Hierarchical logistic regression and receiver operator characteristic (ROC) analyses revealed that combining all posttests, the modifiability total, and the final examiner judgement scores from this DA yielded the strongest sensitivity (.83) and specificity (.80). The static measures and the dichotomized final examiner judgement had excellent reliability; yet the individual modifiability measures (with the exception of disruption and frustration) had poor reliability. Conclusion: In concordance with a previous study, results indicate that a dynamic assessment of inferential word learning may be an efficacious method of identifying language disorders in school-age populations.

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Purpose: This study examines the classification accuracy and interrater reliability of a dynamic assessment (DA) of inferential word learning designed to accurately identify kindergarten through sixth-grade students with and without language disorder. Method: The participants included 127 school-age children from a mountain west school district who were administered a DA of inferential word learning that entailed a pretest, a teaching phase, an examiner rating of the child's ability to infer word meaning (modifiability), and posttests. Results: Hierarchical logistic regression and receiver operator characteristic (ROC) analyses revealed that combining all posttests, the modifiability total, and the final examiner judgement scores from this DA yielded the strongest sensitivity (.83) and specificity (.80). The static measures and the dichotomized final examiner judgement had excellent reliability; yet the individual modifiability measures (with the exception of disruption and frustration) had poor reliability. Conclusion: In concordance with a previous study, results indicate that a dynamic assessment of inferential word learning may be an efficacious method of identifying language disorders in school-age populations.

abstract: Purpose: The goal of this study was to examine how vocabulary size and inhibitory control affect word learning in bilingual (English-Spanish) children with hearing loss. Experiment 1 examined whether children with larger vocabularies learn and retain more words than children with smaller vocabularies. Experiment 2 examined whether children with better inhibitory control learn and remember more words than children with poorer inhibitory control. In addition, monolingual and bilingual children with and without hearing loss were compared on word learning and inhibitory control tasks. Method: Seventy-three children between 8 and 12 years of age participated in the study. Forty children had normal hearing (20 monolingual and 20 bilingual) and 33 had hearing loss (20 monolingual and 13 bilingual). For Experiment 1, children completed a receptive vocabulary test in English and Spanish and three word learning tasks consisting of a training and a retention component in English, Spanish, and Arabic. For Experiment 2, children completed the flanker task for inhibitory control. Results: In Experiment 1, larger total (English + Spanish) receptive vocabularies were predictive of better word training outcomes in all languages and better Spanish word retention, after controlling for age, degree of hearing loss, and maternal education. Children with hearing loss performed more poorly in Spanish and Arabic word training and retention than children with normal hearing. No differences were observed between children with normal hearing and hearing loss in English word learning. In Experiment 2, inhibitory control only predicted English retention outcomes. Children with hearing loss showed poorer inhibitory control than hearing peers. No differences were observed between monolingual and bilingual children, with and without hearing loss, in word learning or inhibitory control. Conclusions: Language experience (measured by total vocabulary size) helps children learn new words and therefore children with hearing loss should receive well-fitted hearing aids and school accommodations to provide them with access to spoken language. Bilingual exposure does not impair nor facilitate word learning. Bilingual children showed similar difficulties with word learning and inhibitory control as monolingual peers with hearing loss. Hearing loss, probably via language deprivation, has broad effects on children’s executive function skills. / Dissertation/Thesis / Doctoral Dissertation Speech and Hearing Science 2019

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