Distribution of nouns, verbs, and adjectives in phonemic fluency tasks

Verbal fluency tests have seen exponential growth in research and clinical practice in recent years, yet little is known about the distribution of grammatical categories spontaneously produced in phonemic fluency tasks. This study examined the distribution of nouns, verbs, and adjectives in phonemic fluency performance in a large Greek sample from the general population and explored their associations with age and education. Greek is particularly suited to this investigation because it has distinct word forms for nouns, verbs, and adjectives.

The phonemic fluency productions of 427 persons aged 16 to 87 years without known pathology, representing a wide range of educational backgrounds, were classified as nouns, verbs, adjectives, or other. Verb-noun and adjective-noun ratios were computed and compared to ratios derived from corpus data. Nonparametric analyses examined differences in the two ratios across age and education groups. Two-step cluster analyses were conducted to identify potential subgroups.

Across the entire sample, the verb-noun ratio (mean = 0.13) and adjective-noun ratio (mean = 0.12) were substantially lower than the ratios derived from corpus data (0.46 and 0.35 respectively, ps ≤ .001). Age, education, and total number of words produced were significantly associated with both ratios but with small to medium effect sizes and large variability. Cluster analyses identified three subgroups for the verb-noun ratio but yielded two highly unequal subgroups for the adjective-noun ratio.

The two ratios derived from fluency tasks are not directly comparable to those derived from corpora. The small-to-medium effect sizes of the variables studied and the subgroup patterns observed for the verb-noun ratio suggest that additional, as yet unexplored, factors contribute to grammatical category production in phonemic fluency. This study provides novel quantitative data regarding content word distributions in phonemic fluency and their demographic correlates. Future research should examine the potential clinical relevance of these ratios.