Abstract: Verbal fluency is typically measured by generative naming tasks. The two types of verbal fluency that are generally tested are (1) phonemic fluency, in which the subjects generate words beginning with a particular letter, and (2) semantic fluency, in which the subjects produce items from a specified category. Most of the previous studies primarily focused on the contribution of the central executive function to phonemic and semantic fluency; however, little attention was paid to the contribution of the phonological loop and the visuospatial sketchpad.
Based on the work of Rende, the present study explored the effects of the articulary loop and visuospatial sketchpad on verbal fluency. The following two types of secondary tasks were used: (1) articulatory suppression and sound judgment and (2) grapheme judgment and rotation judgment.
Methods
Forty four undergraduates, including 22 women, participated in Exp.1. The writing speed of all participants was estimated. Subsequently, the participants were given a familiar topic, such as “my college life,” and were required to write as many words as possible in one minute. All of them produced more than 30 words per minute, which satisfied the experimental requirement. Thereafter, they were required to assess their Chinese language level based on a 5-point scale. The scores of all the participants were equal to or higher than 3. Exp. 2 involved 40 subjects, including 20 women. The participants were given the same topic as Exp.1 and were required to talk on the subject for one minute in order to test their oral speed. They spoke rather fluently and none of them stuttered or spoke slowly. Similar to Exp. 1, the Chinese level of all participants was equal to or higher than 3. Both experiments employed a two-factor within-subject design, 2 (phonemic and semantic fluency) × 2 (single- and dual-task conditions).
Results
(1) The results of Exp.1 indicated that the articulatory loop had a substantial impact on verbal fluency. When the secondary task was articulatory suppression, the participants produced more words during the semantic fluency task than during the phonemic fluency task; however, they produced fewer words in the dual-task condition than in the single-task condition. Further, the cluster size was smaller in the dual-task condition than in the single-task condition. The participants generated more switches during the semantic fluency task than during the phonemic fluency task; however, they generated fewer switches in the dual-task condition than in the single-task condition. When the secondary task was sound judgment, the pattern of results was similar to that when the secondary task was articulatory suppression, with the exception that there were no significant differences in the cluster sizes across the different tasks and different conditions. Therefore, the negative impact of articulatory suppression and sound judgment was significantly stronger for the phonemic fluency task than for the semantic fluency task.
(2) The results of Exp.2 indicated that visuospatial sketchpad had a substantial impact on verbal fluency. When the secondary task was grapheme judgment, the participants produced more words during the phonemic fluency task than during the semantic fluency task; however, they produced fewer words in the dual-task condition than in the single-task condition. Further, the cluster size was larger in the semantic fluency task than in the phonemic fluency task. The participants generated more switches during the phonemic fluency task than during the semantic fluency task; however, they generated fewer switches in the dual-task condition than in the single-task condition. When the secondary task was rotation judgment, the pattern of results was similar to that when the secondary task was grapheme judgment. Therefore, the negative impact of grapheme judgment and rotation judgment was significantly stronger for the semantic fluency task than for the phonemic fluency task.
(3) A detailed analysis showed that Chinese subjects adopt different strategies in different fluency tasks, using the oral verbatim and reading silently strategies for phonemic fluency tasks and the mental image strategy for semantic fluency tasks.
Conclusions
(1) Articulatory suppression and sound judgment tasks influenced phonemic verbal fluency more than semantic fluency.
(2) Grapheme judgment and rotation judgment tasks influenced semantic fluency more than phonemic fluency.
(3) The strategies adopted in phonemic fluency tasks reflected language&nb

Key words: verbal fluency, phonemic fluency, semantic fluency, working memory