title: Random local temporal structure of category fluency responses.
abstract: The Category Fluency Test (CFT) provides a sensitive measurement of cognitive capabilities in humans related to retrieval from semantic memory. In particular, it is widely used to assess progress of cognitive impairment in patients with dementia. Previous research shows that, in the first approximation, the intensity of tested individuals' responses within a standard 60-s test period decays exponentially with time, with faster decay rates for more cognitively impaired patients. Such decay rate can then be viewed as a global (macro) diagnostic parameter of each test. In the present paper we focus on the statistical properties of the properly de-trended time intervals between consecutive responses (inter-call times) in the Category Fluency Test. In a sense, those properties reflect the local (micro) structure of the response generation process. We find that a good approximation for the distribution of the de-trended inter-call times is provided by the Weibull Distribution, a probability distribution that appears naturally in this context as a distribution of a minimum of independent random quantities and is the standard tool in industrial reliability theory. This insight leads us to a new interpretation of the concept of "navigating a semantic space" via patient responses.
authors: Case Western Reserve University, 11900 Euclid Avenue, Cleveland, OH 44106, USA.
authors: David J
authors: DJ
authors: Meyer
authors: Jason
authors: J
authors: Messer
authors: Tanya
authors: T
authors: Singh
authors: Peter J
authors: PJ
authors: Thomas
authors: Wojbor A
authors: WA
authors: Woyczynski
authors: Jeffrey
authors: J
authors: Kaye
authors: Alan J
authors: AJ
authors: Lerner
mesh_terms: D000293:Adolescent; D000367:Age Factors; D000368:Aged; D003072:Cognition Disorders / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D011939:Mental Recall / Q000502:physiology*; D008875:Middle Aged; D009275:Names; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D011930:Reaction Time / Q000502:physiology; D015203:Reproducibility of Results; D016008:Statistical Distributions; D018709:Statistics, Nonparametric; D014705:Verbal Behavior / Q000502:physiology*; D014825:Vocabulary; D055815:Young Adult