Cascading activation in spoken production: Evidence from phonetic analysis of aphasic speech
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1
Rice University, United States
Most contemporary theories of spoken production assume cascading activation, that activation from competitors at one level of representation spreads to the subsequent level. One consequence of this assumption is that traces of phonological plans that are activated, but not selected, should be observed in articulation. Evidence for this claim is relatively limited, with the strongest evidence coming from phonetic analyses of errors produced in tongue twisters, in which competition between phonological plans is created by the task rather than the internal dynamics of the production system (Goldrick & Blumstein, 2006). The current study focuses on analyzing acoustics traces of competition that is generated internal to the spoken production system. Depending on the context, naming a single picture or reading a single word aloud may also result in the generation of multiple phonological plans (e.g. Rastle & Coltheart, 1999). This can be particularly clear in aphasic speakers where errors in spoken production can reveal the level of the system that is impaired. Specifically, we discuss two studies, one in reading aloud and one in speech production, in which we analyze the spoken output of individuals with aphasia to understand of how upstream competition cascades to impact articulation.
Experiment 1 looks at competition generated at a phonological level when reading aloud irregular words. Dual route theories of reading assume that, when we read irregular words, such as BREAD, the lexical and sublexical processes yield competing phonological plans (/bred/ vs. /brid/). If this competition cascades through the system to articulation, we would expect to observe acoustic traces of the phonological plan generated by the sublexical route, even when words are read correctly. We investigated this prediction in a single case study of an individual with a lexical reading deficit (M.K.), as such a patient should show greater competition from the sublexical route when reading aloud. Experiment 2 looks at whether competition at a lexico-semantic level of representation can cascade into articulation. We carried out a single case study of an individual (O.C.) who makes many semantic errors in picture naming to determine if his semantic errors (e.g. calling a dog a “CAT”) showed phonetic traces of the target word (“dog”) compared to cases in which he produced CAT correctly. Taken together the results of these two experiments provide evidence to suggest that competition at early levels of representation may have effects measurable at articulation.
Using methods from laboratory phonology to analyze spoken production has provided novel insights into the processes involved in language production. By using these methods to analyze the speech of individuals with aphasia, we can further test predictions of computational models of speech production and of reading aloud, providing novel insights into the dynamics of activation involved in speaking.
References
Goldrick, M., & Blumstein, S. E. (2006). Cascading activation from phonological planning to articulatory processes: Evidence from tongue twisters. Language and Cognitive Processes, 21(6), 649-683.
Rastle, K., & Coltheart, M. (1999). Serial and strategic effects in reading aloud. Journal of Experimental Psychology: Human perception and performance, 25(2), 482-503.
Keywords:
Laboratory phonology,
cascading activation,
reading aloud,
speech produciton,
Neuropsychology
Conference:
Academy of Aphasia 57th Annual Meeting, Macau, Macao, SAR China, 27 Oct - 29 Oct, 2019.
Presentation Type:
Platform presentation
Topic:
Eligible for student award
Citation:
Irons
ST,
Bradbury
K,
Ciampa
C and
Fischer-Baum
S
(2019). Cascading activation in spoken production: Evidence from phonetic analysis of aphasic speech.
Front. Hum. Neurosci.
Conference Abstract:
Academy of Aphasia 57th Annual Meeting.
doi: 10.3389/conf.fnhum.2019.01.00084
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Received:
01 May 2019;
Published Online:
09 Oct 2019.
*
Correspondence:
Mx. Sarah T Irons, Rice University, Houston, United States, ironsst@gmail.com