Browsing by Author "Schnur, Tatiana T"

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    Temporal characteristics of semantic perseverations induced by blocked-cyclic picture naming
    (Elsevier, 2009-03) Hsiao, Esther Y; Schwartz, Myrna F.; Schnur, Tatiana T; Dell, Gary S
    When unimpaired participants name pictures quickly, they produce many perseverations that bear a semantic relation to the target, especially when the pictures are blocked by category. Evidence suggests that the temporal properties of these "semantic perseverations" may differ from typical lexical perseverations in aphasia. To explore this, we studied semantic perseverations generated by participants with aphasia on a naming task with semantic blocking [Schnur, T. T., Schwartz, M. F., Brecher, A., & Hodgson, C. (2006). Semantic interference during blocked-cyclic naming: Evidence from aphasia. Journal of Memory and Language, 54, 199-227]. The properties of these perseverations were investigated by analyzing how often they occurred at each lag (distance from prior occurrence) and how time (response-stimulus interval) influenced the lag function. Chance data sets were created by reshuffling stimulus-response pairs in a manner that preserved unique features of the blocking design. We found that the semantic blocking manipulation did not eliminate the expected bias for short-lag perseverations (recency bias). However, immediate (lag 1) perseverations were not invariably the most frequent, which hints at a source of inconsistency within and across studies. Importantly, there was not a reliable difference between the lag functions for perseverations generated with a 5 s, compared to 1 s, responsestimulus interval. The combination of recency bias and insensitivity to elapsed time indicates that the perseveratory impetus in a named response does not passively decay with time but rather is diminished by interference from related trials. We offer an incremental learning account of these findings.
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    The Cognitive and Neural Bases of Bilingual Word Selection
    (2016-06-30) Hughes, Julie Walker; Schnur, Tatiana T
    When bilinguals speak, do words from both languages compete for selection? Under one hypothesis of bilingual word selection, bilinguals select words for speech similarly to monolinguals because word selection is restricted to the response language (language specific selection; e.g., Costa & Caramazza, 1999). Alternatively, bilinguals may select words for speech such that words from both languages are considered during selection (language non-specific selection; e.g., Green, 1998). Critically, if bilinguals choose words from among both the response and non-response languages, then they must manage the activation levels of two competing languages in order to select the correct word. It is assumed that bilinguals accomplish this process by exerting inhibitory control over non-response language words to reduce their activation level (e.g., Meuter & Allport, 1999), which may grant bilinguals an inhibitory control advantage in comparison to monolinguals because bilinguals constantly recruit and exercise inhibitory control processes (e.g., Bialystok, Craik & Luk, 2012). However, it remains an open question whether bilingual word selection proceeds differently from that of monolinguals. Thus, the main goal of this dissertation was to characterize bilingual word selection during speech. Specifically, I manipulated a factor known to influence word selection processes (i.e., whether a picture has more than one name or not (name agreement (NA)), e.g., sofa/couch; e.g., Vitkovitch & Humphreys, 1995) to determine how bilinguals select words for speech. I investigated bilingual word selection by comparing bilingual and monolingual speakers’ behavioral performance and neural activation patterns on a picture naming task that manipulated response and non-response language NA. The results show that bilinguals’ behavioral performance and level of neural activation are not influenced by non-response language NA. However, bilinguals did show neural connectivity patterns that were influenced by non-response language NA. I interpreted this pattern of results to suggest that bilinguals select words from both languages and that they use inhibitory control processes to do so. The results thus not only characterize how bilinguals produce words fluently in one language over another but also shed light on the potential link between bilingual word selection processes and the possible cognitive advantages associated with bilingualism.