Data from CCAB verbal fluency tests

Published in PLoS ONE.ABSTRACT. In verbal
fluency (VF) tests, subjects articulate words in a specified category during a short
test period (typically 60 s). Verbal fluency tests are widely used to study
language development and to evaluate memory retrieval in neuropsychiatric
disorders. Performance is usually measured as the total number of correct words
retrieved. Here, we describe the properties of a computerized VF (C-VF) test that
tallies correct words and repetitions while providing additional lexical measures
of word frequency, syllable count, and typicality. In addition, the C-VF permits
(1) the analysis of the rate of responding over time, and (2) the analysis of the
semantic relationships between words using a new method, Explicit Semantic
Analysis (ESA), as well as the established semantic clustering and switching measures
developed by Troyer et al. (1997). In Experiment 1, we gathered normative data
from 180 subjects ranging in age from 18 to 82 years in semantic (“animals”)
and phonemic (letter “F”) conditions. The number of words retrieved in 90 s
correlated with education and daily hours of computer-use. The rate of word
production declined sharply over time during both tests. In semantic conditions,
correct-word scores correlated strongly with the number of ESA and Troyer-defined
semantic switches as well as with an ESA-defined semantic organization index
(SOI). In phonemic conditions, ESA revealed significant semantic influences in
the sequence of words retrieved. In Experiment 2, we examined the test-retest
reliability of different measures across three weekly tests in 40 young subjects.
Different categories were used for each semantic (“animals”, “parts of the body”,
and “foods”) and phonemic (letters “F”, “A”, and “S”) condition. After regressing
out the influences of education and computer-use, we found that correct-word z-scores
in the first session did not differ from those of the subjects in Experiment 1.
Word production was uniformly greater in semantic than phonemic conditions. Intraclass
correlation coefficients (ICCs) of correct-word z-scores were higher for phonemic
(0.91) than semantic (0.77) tests. In semantic conditions, good reliability was
also seen for the SOI (ICC = 0.68) and ESA-defined switches in semantic
categories (ICC = 0.62). In Experiment 3, we examined the performance of
subjects from Experiment 2 when instructed to malinger: 38% showed abnormal
(p< 0.05) performance in semantic conditions. Simulated malingerers with
abnormal scores could be distinguished with 80% sensitivity and 89% specificity
from subjects with abnormal scores in Experiment 1 using lexical, temporal, and
semantic measures. In Experiment 4, we tested patients with mild and severe traumatic
brain injury (mTBI and sTBI). Patients with mTBI performed within the normal
range, while patients with sTBI showed significant impairments in correct-word
z-scores and category shifts. The lexical, temporal, and semantic measures of
the C-VF provide an automated and comprehensive description of verbal fluency
performance.
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