Abstract

Objective: To examine to what extent processing speed influences the relationship between executive planning and nonverbal Performance IQ (PIQ). Method: Forty-one community-dwelling older adults (mean age = 71.44 years, SD = 5.01; 54% male) with an average of 15.85 years of education (SD = 2.26) from the Cognitive and Physical Exercise Study (CAPES) completed a battery of neuropsychological assessments including Neuropsychological Assessment Battery Mazes (measuring executive planning), Weschler Abbreviated Scale of Intelligence Matrix Reasoning and Block Design subtests (measuring PIQ), and Trails A (measuring psychomotor processing speed). Mediation analyses were conducted with Hayes' (2013) process macro, which uses an ordinary least squares or logistic regression-based path analytical framework for estimating direct and indirect effects, utilizing bootstrapping methods for bias-corrected 95% confidence intervals for indirect effects. Results: The relationship between PIQ and executive planning was mediated by processing speed. PIQ had a significant direct effect (t = 3.87, p = .0004) and total effect (direct effect + indirect effect, t = 3.11, p = .0036) on executive functioning. The standardized indirect effect of PIQ on executive functioning was .05, Κ2 = .07 (95% CI .003 −.290). Conclusion(s): WASI PIQ significantly predicted executive planning to the extent that psychomotor processing speed is intact. These results show processing speed is a relevant component when considering how fluid nonverbal reasoning (e.g., PIQ) influences the ability to successfully plan. Given two individuals with the same PIQ, information about their processing speed adds to the ability to predict success on a planning task. Implications and future directions will be discussed.