Morphophonological patterns in the lexicon influence past-tense production in aphasia
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1
New York University, Communicative Sciences and Disorders, United States
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2
The New School for Social Research, United States
Introduction
Research has indicated that the distribution of morphophonological patterns within the lexicon impacts the likelihood of using regular or irregular inflections for novel verbs (Albright & Hayes, 2003), as well as the production of known words in an individual with acquired morphological deficit (Rimikis & Buchwald, 2015). In the current study, we examine the past-tense production of 16 individuals with anomia and post-semantic deficits, and demonstrate that the morphophonological patterns within the lexicon have a broad impact on production. We quantified the likelihood of a verb taking a given past-tense inflection using the Albright-Hayes learner (2003) which calculates a “confidence score” for each inflection based on the number and proportion of similar verbs that take the same inflectional pattern. Higher confidence scores are associated with inflectional changes for which a large number and proportion of phonological neighbors take the same inflectional change (e.g., sleep→slept, weep→wept, sweep→swept, etc.). The learner also generates a score for other inflections that could apply to a stem given the patterns in the lexicon (e.g., sweep→swept; sweep→sweeped; see Table 1). Confidence scores were computed for both regular and irregular verbs, and predicted both accuracy and error types across our sample.
Procedure
Sixteen individuals with aphasia including post-semantic word-finding deficits were administered a past-tense elicitation task. Sentence frames including regular and irregular verbs were presented verbally and visually (e.g., “Every day I run a mile. Just like every day, yesterday I ____ a mile.” The participants produced an average of 185 distinct verbs (2987 total across participants). Logistic-regression mixed-effects models were used to assess the impact of confidence score on participants’ production above that of other lexical variables (e.g., frequency, neighborhood density, etc.), with item and participant included as random factors.
Results
Confidence score was a significant predictor of performance for both regular and irregular verbs. Regular verbs with higher confidence scores for the +ed inflection were more likely to be produced accurately. To ensure that these effects were not driven by differences between the three allomorphic patterns of the regular past tense (i.e., /d/, /t/, and /@d/) we examined the production of verbs that take the syllabic –ed ending (e.g., painted, added, minded; n=399). In this subset, we also found an effect of confidence score on regular past-tense production. For irregular verbs, the confidence score for regularization (e.g., the score for bite→bited) predicted the likelihood of regularization errors.
Discussion
The distribution of morphophonological patterns in the lexicon influenced both accuracy and error patterns in 16 subjects with aphasia. Specifically, these distributions predicted the rate at which the regular past-tense rule is applied, both correctly in regular verbs and as errors in irregular verbs. The accuracy differences were also found within allomorphic groupings (i.e., syllabic –ed affixation). These results extend previous findings and indicate that the distribution of morphophonological patterns within the language impacts the production of known words, a finding which requires explanation within accounts of morphological production.
References
Albright, A., & Hayes, B. (2003). Rules vs. analogy in English past tenses: A computational/experimental study. Cognition, 90(2), 119-161.
Rimikis S and Buchwald A (2015). Do morphophonological rules impact both regular and irregular verb inflection? Evidence from acquired morphological impairment. Front. Psychol. Conference Abstract: Academy of Aphasia 53rd Annual Meeting. doi: 10.3389/conf.fpsyg.2015.65.00028
Keywords:
morphology,
Morphophonology,
Aphasia,
past-tense verbs,
morphological production
Conference:
54th Annual Academy of Aphasia Meeting, Llandudno, United Kingdom, 16 Oct - 18 Oct, 2016.
Presentation Type:
Platform Sessions
Topic:
Student Submissions
Citation:
Rimikis
S,
Buchwald
A and
Miozzo
M
(2016). Morphophonological patterns in the lexicon influence past-tense production in aphasia.
Front. Psychol.
Conference Abstract:
54th Annual Academy of Aphasia Meeting.
doi: 10.3389/conf.fpsyg.2016.68.00121
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Received:
30 Apr 2016;
Published Online:
15 Aug 2016.
*
Correspondence:
Ms. Stacey Rimikis, New York University, Communicative Sciences and Disorders, New York, NY, United States, stacey.rimikis@nyu.edu