Figure 7. Figure highlights deleterious effects of ceiling effects on commonly used effect size d_p using both Henry et al. [14] data set and much larger data set included in the present study.

Panel A shows d_p calculated by Henry et al. [14] as a function of older adults performance (test difficulty) for laboratory conditions that were free of age-confounds only (color of the circles indicate prospective memory subdomain: red = event-cued prospective memory proper, blue = event-cued vigilance, green = time-cued vigilance). Panel A highlights that the size of age declines measured by effect size index d_p decreases as performance of older adults increases, as the test becomes easier and data are more afflicted by ceiling effects. Panel B demonstrates this deleterious effect of ceiling effects on d_p using much larger data set identified for the current study. Panel C highlights that even age declines measured by d_probit are dependent on the test difficulty but, consistent with previous simulations [43], less so. Finally, Panel D highlights that d_p underestimates the size of age decline relative to d_probit; age declines measured by d_p are smaller then age declines measured by d_probit.