title: Are semantic and phonological fluency based on the same or distinct sets of cognitive processes? Insights from factor analyses in healthy adults and stroke patients.
abstract: Verbal fluency for semantic categories and phonological letters is frequently applied to studies of language and executive functions. Despite its popularity, it is still debated whether measures of semantic and phonological fluency reflect the same or distinct sets of cognitive processes. Word generation in the two task variants is believed to involve different types of search processes. Findings from the lesion and neuroimaging literature further suggest a stronger reliance of phonological and semantic fluency on frontal and temporal brain areas, respectively. This evidence for differential cognitive and neural contributions is, however, strongly challenged by findings from factor analyses, which have consistently yielded only one explanatory factor. As all previous factor-analytical approaches were based on very small item sets, this apparent discrepancy may be due to methodological limitations. In this study, we therefore applied a German version of the verbal fluency task with 8 semantic (i.e. categories) and 8 phonological items (i.e. letters). An exploratory factor analysis with oblique rotation in N=69 healthy young adults indeed revealed a two-factor solution with markedly different loadings for semantic and phonological items. This pattern was corroborated by a confirmatory factor analysis in a sample of N=174 stroke patients. As results from both samples also revealed a substantial portion of common variance between the semantic and phonological factor, the present data further demonstrate that semantic and phonological verbal fluency are based on clearly distinct but also on shared sets of cognitive processes.
authors.affiliation: Dept. of Neurology, University Medical Center Freiburg, Germany; Freiburg Brain Imaging Center, University of Freiburg, Germany; Biological and Personality Psychology, Dept. of Psychology, University of Freiburg, Germany; BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Germany; Faculty of Medicine, University of Freiburg, Germany. Electronic address: charlotte.schmidt@uniklinik-freiburg.de.
authors.forename: Charlotte S M
authors.initials: CSM
authors.lastname: Schmidt
authors.affiliation: Freiburg Brain Imaging Center, University of Freiburg, Germany; Faculty of Medicine, University of Freiburg, Germany; Dept. of Neuroradiology, University Medical Center Freiburg, Germany; Medical Psychology and Medical Sociology, University of Freiburg, Germany.
authors.forename: Lena V
authors.initials: LV
authors.lastname: Schumacher
authors.affiliation: Freiburg Brain Imaging Center, University of Freiburg, Germany; Faculty of Medicine, University of Freiburg, Germany.
authors.forename: Pia
authors.initials: P
authors.lastname: Römer
authors.affiliation: Social Psychology and Methodology, Dept. of Psychology, University of Freiburg, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Leonhart
authors.affiliation: Dept. of Neurology, University Medical Center Freiburg, Germany; Freiburg Brain Imaging Center, University of Freiburg, Germany; BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Germany; Faculty of Medicine, University of Freiburg, Germany.
authors.forename: Lena
authors.initials: L
authors.lastname: Beume
authors.affiliation: Dept. of Neurology, University Medical Center Freiburg, Germany; Freiburg Brain Imaging Center, University of Freiburg, Germany; BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Germany; Faculty of Medicine, University of Freiburg, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Martin
authors.affiliation: Dept. of Neurology, University Medical Center Freiburg, Germany; Freiburg Brain Imaging Center, University of Freiburg, Germany; BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Germany; Faculty of Medicine, University of Freiburg, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Dressing
authors.affiliation: Dept. of Neurology, University Medical Center Freiburg, Germany; Freiburg Brain Imaging Center, University of Freiburg, Germany; BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Germany; Faculty of Medicine, University of Freiburg, Germany.
authors.forename: Cornelius
authors.initials: C
authors.lastname: Weiller
authors.affiliation: Dept. of Neurology, University Medical Center Freiburg, Germany; Freiburg Brain Imaging Center, University of Freiburg, Germany; BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Germany; Faculty of Medicine, University of Freiburg, Germany. Electronic address: christoph.kaller@uniklinik-freiburg.de.
authors.forename: Christoph P
authors.initials: CP
authors.lastname: Kaller
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003071:Cognition; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D007807:Language Tests; D008297:Male; D008875:Middle Aged; D010700:Phonetics; D012660:Semantics; D020521:Stroke / Q000523:psychology; D055815:Young Adult
keywords: Cognitive processes; Confirmatory factor analysis; Exploratory factor analysis; Verbal fluency