Poster B75, Sunday, March 26, 8:00 – 10:00 am, Pacific Concourse
The effects of aphasia on nonverbal counting tasks
Alexander Kranjec1,2, John Verbos1, Sarah Wallace1; 1Duquesne University, 2Carnegie Mellon University
Both English-speakers whose access to number language is artificially compromised by verbal interference and the Pirahã (an Amazonian tribe without exact number words) appear to rely on analog magnitude estimation for representing non-symbolic exact quantities greater than 3. Here, participants with left-hemisphere damage from stroke and resulting aphasia performed the same 5 nonverbal matching tasks from previous studies. Nonverbal matching performance was poorest when targets were not visible during response (71% correct) and best when targets were presented as subitizable groups of 2 and 3 (98% correct). Coefficients of variation for particular tasks, and significant correlations between target magnitude with both error rate and size across tasks, suggest use of analog magnitude estimation for verbally impaired participants. Western Aphasia Battery-Revised subtest scores were reliably correlated with performance across counting tasks suggesting ways that diverse forms of language impairment may contribute to errors on nonverbal counting tasks. A subset of participants completed additional numeric tests (numeral elicitation, confrontation naming with Arabic numerals, and free counting tests) and tests of nonverbal semantic processing and short-term memory (pyramid and palm trees, and semantic category probe tests) in order to better understand errors on nonverbal matching tasks. Results indicate that deficits reflected by major impairments on verbal counting tests and more general semantic impairments can both contribute to errors in the representation of exact-quantity. This study suggests ways that investigations of neurological populations may help us to better understand the bases for language-related effects on nonverbal processing across diverse neurotypical populations.
Topic Area: LANGUAGE: Semantic