Hearing & Speech Sciences Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2776
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Item EFFECTS OF COGNITIVE DEMAND ON WORD ENCODING IN ADULTS WHO STUTTER(2011) Tsai, Pei-Tzu; Bernstein Ratner, Nan; Hearing and Speech Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The etiology of persistent stuttering is unknown, but stuttering has been attributed to multiple potential factors, including difficulty in processing language-related information, but findings remain inconclusive regarding any specific linguistic deficit potentially causing stuttering. One particular challenge in drawing conclusions is the highly variable task demands across studies. Different tasks could potentially reflect either different processes, or different levels of demand. This study examined the role of cognitive demand in semantic and phonological processes to evaluate the role of linguistic processing in the etiology of stuttering. The study examined concurrent processing of picture naming and tone-identification in typically fluent young adults, adults who stutter (AWS) and matched adults who do not stutter (NS), with varying temporal overlap between the dual tasks as manipulation of cognitive demand. The study found 1) that in both AWS and NS, semantic and phonological encoding both interacted with non-linguistic processing during concurrent processing, suggesting that both linguistic processes are demanding in cognitive resources, 2) that there was no observable relationship between dual-task interference to word encoding and stuttering, 3) that AWS and NS showed different trends of phonological encoding under high but not low cognitive demand, suggesting a subtle phonological deficit in AWS, and 4) that the phonological encoding effect correlated with stuttering rate, suggesting that phonological deficit could potentially play a role in the etiology or persistence of stuttering. Additional findings include potential differences in semantic encoding between typically fluent young adults and middle-age adults, as well as potential strategic differences in processing semantic information between AWS and NS. Findings were taken to support stuttering theories suggesting specific deficits in phonological encoding and argue against a primary role of semantic encoding deficiency or lexical access deficit in stuttering.Item The effects of phonological neighborhoods on spoken word recognition in Mandarin Chinese(2007-08-27) Tsai, Pei-Tzu; Bernstein Ratner, Nan; Hearing and Speech Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Spoken word recognition is influenced by words similar to the target word with one phoneme difference (neighbors). In English, words with many neighbors (high neighborhood density) are processed more slowly or less accurately than words with few neighbors. However, little is known about the effects in Mandarin Chinese. The present study examined the effects of neighborhood density and the definition of neighbors in Mandarin Chinese, using an auditory naming task with word sets differing in density levels (high vs. low) and neighbor types (words with neighbors with a nasal final consonant vs. words without such nasal-final neighbors). Results showed an inhibitory effect of high neighborhood density on reaction times and a difference between nasal-final neighbors and vowel-final neighbors. The findings suggest that neighbors compete and inhibit word access in Mandarin Chinese. Yet, other factors at the sublexical level may also play a role in the process.