Defense Date

8-29-2018

Graduation Date

Fall 12-21-2018

Availability

Immediate Access

Submission Type

dissertation

Degree Name

PhD

Department

Psychology

School

McAnulty College and Graduate School of Liberal Arts

Committee Chair

Alexander Kranjec

Committee Member

Sarah E Wallace

Committee Member

Elizabeth Fein

Keywords

linguistic relativity, number, aphasia

Abstract

The linguistic relativity hypothesis argues that language influences non-linguistic cognition. One version of the hypothesis suggests that language is a set of tools or technologies that variously enhance or dampen an individual’s capacity to perceive and operate upon the world in certain ways. A domain in which this may be tested is number, where it is hypothesized that counting language allows us to bridge our innate capacities for recognizing small exact quantities (subitizing) and approximating quantities larger than three or four (analog magnitude estimation). To test this, previous studies have asked adult participants who have limited or no access to counting language to represent non-symbolic exact quantities—that is, for participants to create an array of objects equal in number to a target array of objects presented to the participant. In these studies, both English-speakers whose access to number language was artificially compromised by verbal interference and the Pirahã—an Amazonian tribe whose language does not contain exact number words—appeared to rely on analog magnitude estimation for representing non-symbolic exact quantities greater than three. This suggests that the ability to consistently and accurately recognize and represent non-symbolic exact quantities is impaired by having limited or no access to counting language. Here, sixteen participants with left-hemisphere damage from stroke and resulting aphasia performed the same five non-verbal, non-symbolic matching tasks from these previous studies. It was expected that coefficients of variation for particular tasks, and correlations between target magnitude with both respect to both error rate and error size across tasks, would suggest use of analog magnitude estimation by these verbally impaired participants. Participants also completed three additional number tasks (number elicitation, confrontation naming with Arabic numerals, and a count list recitation task) and a subset of participants completed nonverbal semantic processing and short-term memory tasks (Pyramids and Palm Trees and a verbal semantic category probe) to better understand errors on nonverbal matching tasks. Results indicated that for people with aphasia, non-symbolic exact quantity representation was more difficult than for people without aphasia, except when target quantities were presented in subitizable groups. Overall, participants made more frequent and larger errors when representing larger quantities and struggled when the target was not visible. Participants who had difficulty with tasks where the target was visible during response also had difficulty with tasks where the target was not visible during response. However, another group of participants only had difficulty with tasks where the target was not visible during response. Additionally, participants who had difficulty with non-verbal aphasia assessment subtests were more likely to err on non-symbolic exact quantity representation tasks where the target was visible during response, while participants who had difficulty with aphasia assessment subtests that required verbal responses were more likely to err on non-symbolic exact quantity representation tasks where the target was not visible during response. These results, alongside correlations with aphasia assessment battery performance, suggest that (1) accuracy on non-symbolic exact quantity matching tasks where the target is visible on response rely more heavily on visuospatial abilities than on language or memory; (2) tasks involving subitizing small exact quantities do not appear to require the same visuospatial capacities; and (3) non-symbolic exact quantity matching tasks where the target is not visible on response rely upon language and memory abilities—especially the capacity for verbal counting. Taken together, these findings reinforce the notion that verbal counting facilitates the consistent and accurate recognition and representation of exact quantities larger than three or four by bridging innate human capacities for subitizing and analog magnitude estimation. Overall, the present results further inform our understanding of tasks previously used to understand the relationship between language and number in a culture lacking words for number concepts.

Language

English

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