In this study, several theoretically based curve fitting nonlinear models for analyzing the Five Point Test (FPT), a nonverbal fluency test, were examined. One thousand two hundred and one participants from the general population of Germany and the USA completed the FPT. The test scores were analyzed using three process indexes; the number of unique designs, strategy, and repetitions. Participants were stratified by age and level of education, and the resulting data were examined using best-fit nonlinear distribution equations. The study shows that the Weibull Growth three-factor curve fitting model provides equivalent fit as four-factor quadratic or linear curve fitting models for estimates continue normative data the Reliability and Time to Failure Theory of Cognitive Functions. Namely, that neurocognitive abilities remain stable during young adulthood and after reaching a threshold, starts to linearly or exponentially decline. The study also shows that education differentially impacts the asymptote, threshold, and decline rate of the FPT indexes confirming the importance of isolating specific cognitive domains within neuropsychological tests as these indexes might be related to the activation of particular cell assemblies, which in turn are differentially impacted by aging.
Keywords: Aging; nonverbal fluency; reliability theory.