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Graduate Student Supervision
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Dissertations completed in 2010 or later are listed below. Please note that there is a 6-12 month delay to add the latest dissertations.
Reading success in a second language (L2) is crucial for billions of people worldwide, but it is well known that it remains difficult for L2 learners to automatize the L2 processing in general. I investigated how long-term reading experience in a first language (L1) might change the neural L1 orthographic processing, and if these results can be generalized to L2 orthographic processing. I recruited adult monolingual English readers and adult Mandarin readers with late-language learning of English. By contrasting single-letters with pseudoletter visual stimuli (a pseudoletter effect) in L1, the reaction time data showed that reading experience makes letter processing faster than in pseudoletter processing. The electroencephalogram data showed that the L1 pseudoletter effect was manifested in a left-dominant oscillatory activity and network dynamics. The electroencephalogram data also showed that the L1 pseudoletter effect was robust, regardless of the level of attention paid; letters elicited more of left-lateralized neural connectivity desynchronization than did pseudoletters. Additionally, the data from L2 showed that the magnitude of the L2 pseudoletter effect in the N170 in the left hemisphere was correlated with L2 proficiency. Taken together, I concluded that with reading experience, the brain has automatized orthographic processing, which is evidenced by being (1) more specific by shifting the processing demands to different neural regions within visual processing networks—left dominant for well experienced orthographies, (2) being more obligatory, at least, at the single-letter level, and (3) faster by completing the process of differentiating letters from pseudoletters at fairly early stages of visual processing. Further, I concluded that some of the above changes appear to be ready throughout adulthood; orthographic development appears to be free from the fossilization or critical period hypotheses.
Sentence production requires the integration of activated words with a syntactic plan; however, there has been little investigation of how the integration process affects children’s productions. Research with adults shows that lexical activation order can influence syntactic planning, placing earlier-activated words in earlier-occurring grammatical roles. It has also been proposed that the relationship between lexical activation and syntactic planning can affect processing ease. When lexical activation order and sentence structure are in conflict, a speaker may need to resolve the conflict prior to speaking, and/or buffer the early-activated word until it is produced late in the sentence. This investigation examined the effects of lexical activation order on sentence structure and processing outcomes for 4- and 7-year-old children, using a semantic priming manipulation. In Study 1, children described transitive scenes and also completed a primed picture-naming task. The results documented that the children produced active transitives as the default sentence pattern, and that the older children alternated to patient-subject sentences more often than the younger children when pressured to do so by a cloze prompt. The results also documented facilitative effects of semantic priming on lexical activation speed. Study 2 integrated the semantic primes with sentence production. In one half of the trials, a patient-related prime preceded the scene description. The analyses examined whether patient-subject sentences occurred more often following patient-related primes, and whether early activation of the patient produced negative consequences to sentence onset speed, grammatical integrity, and/or fluency in (agent-subject) active transitive sentences. The results revealed that the patient-related primes did not increase the rate of patient-subject sentential descriptions. However, when children produced active transitive sentences, they were slower to begin speaking following patient-related primes than control primes. There was no significant effect of the primes on fluency or auxiliary omission rates, no difference in prime effects as a function of age group, and no correlation between prime effects and working memory ability. The results indicate a strong constraint of syntactic preferences on children’s sentence planning, and support the conclusion that conflicts between lexical activation and syntactic planning can negatively affect the speed of children’s sentence planning.
Master's Student Supervision
Theses completed in 2010 or later are listed below. Please note that there is a 6-12 month delay to add the latest theses.
Background: The recent interest in the use of mobile devices (like iPads and their application programs; apps) in aphasia therapy has been motivated in part by a belief that they could facilitate self-directed home practice with minimal therapist supervision. Such practice in turn could allow people with aphasia to receive more therapy, without taxing current clinical resources even further. However, it is unknown whether mobile technology can feasibly facilitate self-directed practice. Furthermore, it is unclear whether this kind of therapy can improve outcomes, and there are doubts about the quality of the therapy process when therapy is provided without the expertise of a therapist. Aims: This study aimed to explore the feasibility, therapeutic effect, and therapy process of a naming therapy using an iPad-based therapy app for minimally-supervised self-directed home practice in chronic post-stroke aphasia. Method: A single-subject experiment using a multiple baseline design was replicated across three participants with chronic aphasia, who independently used an iPad-based therapy app to practice naming pictures with the support of cues. Outcome measures included extensive usage and accuracy data unobtrusively collected using the app’s internal logging system, pre- and post-therapy language measures, and qualitative semi-structured interviews to explore participants’ experiences of therapy and perceptions of therapy effects.Results: Therapy was found to be accessible and acceptable for participants with aphasia; however, problems were identified with the therapist’s administrative role in developing and managing word sets, and monitoring therapy progress. Participants demonstrated medium to large naming accuracy gains for practiced words, but minimal gains for unpracticed words. Enabling participants to direct their own therapy process led them to spontaneously enact therapy in ways generally similar to how a therapist might. Conclusion: Despite limitations, self-directed practice using mobile technology may have the potential to improve outcomes by making ongoing long-term gains feasible, and to foster greater collaboration and shared expertise between therapists and people with aphasia. Findings were discussed in terms of suggestions for future research and therapy app development that could allow mobile technology to deliver on this potential.
Previous research on the influence of lipreading on speech perception has failed to consistently show that individuals with aphasia benefit from the visual cues provided by lipreading. The present study was designed to replicate these findings, and to investigate the role of lipreading at the discourse level. Six participants with aphasia took part in this study. A syllable discrimination task using the syllables /pem, tem, kem, bem, dem, gem/, and a discourse task consisting of forty short fictional passages, were administered to the participants. The stimuli were presented in two modality conditions, audio-only and audio-visual. The discourse task employed two grammatical complexity levels to examine the influence of lipreading on the comprehension of simple and moderately-complex passages. Response accuracy was used as the dependent measure on the discrimination task. Two measures were used in the discourse task, on-line reaction time from an auditory moving window procedure, and off-line comprehension question accuracy. A test of working memory was also administered. Both inferential statistics and descriptive analyses were conducted to evaluate the data. The results of the discrimination task failed to consistently show that the participants benefited from the visual cues. On the discourse task, faster reaction times were observed in the audio-visual condition, particularly for the complex passages. The comprehension question accuracy data revealed that the two participants with the most severe language comprehension deficits appeared to benefit from lipreading. These findings suggest that the benefits of lipreading primarily relate to processing time, and that these benefits are greater with increased stimulus complexity and context. In addition, a strong positive correlation between working memory and comprehension question accuracy was found, supporting the claim that working memory may be a constraint in language comprehension. No correlation was found between participants’ accuracy scores on the discourse and discrimination tasks, replicating previous research findings. The results from this study provide preliminary support for the clinical use of lipreading and working memory capacity for the treatment of language comprehension difficulties in individuals with aphasia.