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Task constraints in verbal fluency predict age-related changes

Jean K. Gordon1* and Carly Garcia1
  • 1 University of Iowa, United States

Aging involves declines in many cognitive functions, particularly those involving fluid intelligence, with relative maintenance of crystallized intelligence (Park, 2000). This paradox is clearly evident in the language domain: lexical access becomes slower and less accurate, despite well-preserved vocabulary knowledge (e.g. Goral, Spiro, Albert, Obler, & Connor, 2007). Verbal fluency tasks are often used to assess the integrity of the lexicon and the processing abilities required to retrieve items from it. Two versions are common—semantic fluency, in which items from the same semantic category are named, and letter fluency, in which items beginning with the same letter are named. It is hypothesized that semantic fluency reflects semantic knowledge, while letter fluency more strongly reflects executive functioning (e.g. Baldo, Schwartz, Wilkins, & Dronkers, 2010; Luo, Luk, & Bialystok, 2010). Based on the pattern of age-related cognitive decline described above, this task difference predicts a greater impact of aging on letter than on semantic fluency. However, the opposite is typically observed (e.g. Goral et al., 2007; Kave & Knafo-Noam, 2015). To investigate this asymmetry, we collected verbal fluency data from 86 adults aged 30 to 89 years old. Multiple regression analyses investigated the impact of demographic characteristics (age, education, gender); cognitive scores (digit span, matrix reasoning, and vocabulary scaled scores (Wechsler, 2008)); and picture naming accuracy and speed on semantic (animal) and letter (FAS) fluency responses, as well as the discrepancy between the two tasks (cf. Vaughan, Coen, Kenny, & Lawlor, 2016). We also examined how the most commonly produced responses were affected by lexical characteristics across age groups. As in previous studies, the number of words produced declined with age more drastically in semantic fluency than in letter fluency. Semantic fluency was significantly affected by age (p<.0001), digit span (p=.018), matrix reasoning (p=.029), and naming latency (p=.028). Letter fluency was affected by age (p=.0002), digit span (p<.010), and vocabulary (p=.0001). Discrepancy scores were influenced by vocabulary (p=.023) and naming accuracy (p=.026), such that higher vocabulary scores were related to smaller discrepancies between semantic and letter fluency, whereas more accurate naming was related to larger discrepancies. Qualitative analyses showed similar effects of word length and lexical frequency across age groups and tasks. In semantic fluency, the age groups also produced very similar breakdowns of sub-categories. In letter fluency, however, older adults produced a wider variety of syntactic categories (see Figure). These findings suggest that, contrary to previous explanations, semantic fluency relies more heavily on online retrieval skills, whereas letter fluency relies more on vocabulary knowledge. We propose that the differential constraints of the two tasks result in this pattern. Both tasks involve executive function demands; however, older adults’ letter fluency performance is facilitated by two factors. First, the letter constraint acts as a cue facilitating access to words forms, the stage of retrieval with which older adults have the most difficulty (Burke, MacKay, Worthey, & Wade, 1991). Second, the lack of semantic and syntactic constraints provides greater opportunities for older individuals to take advantage of their relatively preserved vocabularies. Figure 1: Breakdown for each age group of semantic sub-categories in semantic fluency (top) and syntactic categories in letter fluency (bottom).

Figure 1
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References

Baldo, J. V., Schwartz, S., Wilkins, D. P., & Dronkers, N. (2010). Double dissociation of letter and category fluency following left frontal and temporal lobe lesions. Aphasiology, 24(12), 1593-1604.
Burke, D. M., MacKay, D. G., Worthey, J. S., & Wade, E. (1991). On the tip of the tongue: What causes word-finding failures in younger and older adults. Journal of Memory and Language, 30, 542-579.
Goral, M., Spiro, A., Albert, M. L., Obler, L. K., & Connor, L. T. (2007). Change in lexical retrieval skills in adulthood. The Mental Lexicon, 2(2), 215-240.
Kave, G., & Knafo-Noam, A. (2015). Lifespan development of phonemic and semantic fluency: Universal increase, differential decrease. Journal of clinical and Experimental Neuropsychology, 37(7), 751-763.
Luo, L., Luk, G., & Bialystok, E. (2010). Effect of language proficiency and executive control on verbal fluency performance in bilinguals. Cognition, 114, 29-41.
Park, D. C. (2000). The basic mechanisms accounting for age-related decline in cognitive function. In D. C. Park & N. Schwarz (Eds.), Cognitive Aging: A Primer (pp. 3-21). Philadelphia, PA: Psychology Press.
Vaughan, R. M., Coen, R. F., Kenny, R. A., & Lawlor, B. A. (2016). Preservation of the semantic verbal fluency advantage in a larger population-based sample: Normative data from the TILDA sample. Journal of the International Neuropsychological Society, 22, 570-576.
Wechsler, D. (2008). Wechsler Adult Intelligence Scale, 4th edition (WAIS-IV). New York, NY: Pearson.

Keywords: Aging, word retrieval, lexical access, verbal fluency, cognitive decline

Conference: Academy of Aphasia 55th Annual Meeting , Baltimore, United States, 5 Nov - 7 Nov, 2017.

Presentation Type: poster or oral

Topic: General Submission

Citation: Gordon JK and Garcia C (2019). Task constraints in verbal fluency predict age-related changes. Conference Abstract: Academy of Aphasia 55th Annual Meeting . doi: 10.3389/conf.fnhum.2017.223.00003

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Received: 30 Apr 2017; Published Online: 25 Jan 2019.

* Correspondence: Dr. Jean K Gordon, University of Iowa, Iowa City, United States, jean-k-gordon@uiowa.edu