“…Considering prior literature indicating that the effects of age and cognitive ability on PAF are likely nonlinear (Dickinson et al, 2022; Rempe et al, 2023) and that these relations differ based on the diagnostic group (Dickinson et al, 2018; Dickinson et al, 2022; Edgar et al, 2015; Edgar et al, 2019), a generalized additive model (GAM; Hastie & Tibshirani, 1990) was fit using the mcgv package in R (Wood, 2011) to assess the joint effect of age, cognitive ability, and diagnostic status on PAF. In contrast to linear regression which estimates constant regression coefficients (β coefficients) for effects of interest, GAMs allow for more flexible modeling and detection of nonlinear effects by estimating smooth basis functions for predictors interest.…”