Date of Degree

9-2015

Document Type

Dissertation

Degree Name

Ph.D.

Program

Speech-Language-Hearing Sciences

Advisor(s)

Richard G. Schwartz

Keywords

Brazilian Portuguese; children; cochlear implant; prosodic boundary; prosody; syntax

Abstract

Theoretical Framework: Manipulations of prosodic structure influence how listeners interpret syntactically ambiguous sentences. However, the interface between prosody and syntax has received very little attention in languages other than English. Furthermore, many children with cochlear implants (CI) have deficits in sentence comprehension. Until now, these deficits have been attributed only to syntax, leaving prosody a neglected area, despite its clear deficit on this population and the role it plays in sentence comprehension. Purposes: Experiment 1 investigates prosodic boundary effects on the comprehension of attachment ambiguities in Brazilian Portuguese while experiment 2 investigates these effects in Brazilian Portuguese speaking children with CIs. Both experiments tested two hypotheses relying on the notion of boundary strength: the absolute boundary hypothesis (ABH) and the relative boundary hypothesis (RBH). The ABH states that only the high boundary before the ambiguous constituent influences attachment whereas the RBH advocates that the high boundary before the ambiguous constituent can only be interpreted according to the relative size of an earlier low boundary. Specific predictions of the two hypotheses were tested. Relationships between attachment results and performance on psychoacoustic tests of gap detection threshold and frequency limen were also investigated. Materials: The experiments were designed on E-Prime 2.0 software (Psychology Software Tools, Pittsburgh, PA). The sentences were recorded on Praat software (Boersma & Weenink, 2013), controlling for F0, duration of components and pauses between components. The prosodic boundaries were measured with the ToBI coding system distinguishing acoustic measures of intermediate phrase (ip) and intonational phrase (IPh) boundaries. Methods: Twenty-three normal hearing (NH) adults, 15 NH children and 13 children with CIs who are monolingual speakers of Brazilian Portuguese participated in a computerized sentence comprehension task. The target stimuli consisted of eight base sentences containing a prepositional phrase attachment ambiguity. Prosodic boundaries were manipulated by varying IPh, ip and null boundaries. Participants also engaged on psychoacoustic tests that investigated gap detection threshold and frequency discrimination ability on nonlinguistic stimuli. An adaptive 3-interval forced-choice procedure was used in gap detection. For the frequency discrimination task, participants completed a same-different two-alternative forced choice task. Results and Discussion: Unlike NH adults and children, children with CIs did not exhibit an overall effect of prosody on syntactic disambiguation. Nonetheless, adults and children with NH and children CIs had the same two predictions of the RBH confirmed, suggesting that they perceived and used the relative size of the boundaries similarly. Two predictions of the ABH were confirmed for adults with NH whereas only one was confirmed for children with NH. The ABH does not govern the syntactic disambiguation of children with CIs. Children with NH were significantly slower than adults with NH to indicate a high attachment response in all prosodic types. However, hearing status did not influence processing speed. Gap detection thresholds and frequency limens on nonlinguistic stimuli did not influence the attachment of syntactically ambiguous sentences with different prosodic boundaries in adults and children with NH. Although children with CIs exhibited a decreased ability to perceive the acoustic changes on a nonlinguistic level, no correlation was found between frequency limens and proportion of high attachment. In children with CIs, gap detection thresholds were only correlated with the proportion of high attachment on sentences with strong prosody contrasts, suggesting that gap detection thresholds possibly influenced the attachment of syntactically ambiguous sentences with strong prosodic dissimilarity between boundaries.

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