The mapping between transformed reaction time costs and models of processing in aging and cognition.

Petroc Sumner,Craig Hedge,Georgina Powell

doi:10.1037/pag0000298

Abstract

Older adults tend to have slower response times (RTs) than younger adults on cognitive tasks. This makes the examination of domain-specific deficits in aging difficult, as differences between conditions in raw RTs (RT costs) typically increase with slower average RTs. Here, we examine the mapping between 2 established approaches to dealing with this confound in the literature. The first is to use transformed RT costs, with the z-score and proportional transforms both being commonly used. The second is to use mathematical models of choice RT behavior, such as the drift-diffusion model (Ratcliff, 1978). We simulated data for younger and older adults from the drift-diffusion model under 4 scenarios: (a) a domain specific deficit, (b) general slowing, (c) strategic slowing, and (d) a slowing of nondecision processes. In each scenario we varied the size of the difference between younger and older adults in the model parameters, and examined corresponding effect sizes and Type I error rates in the raw and transformed RT costs. The z-score transformation provided better control of Type I error rates than the raw or proportional costs, though did not fully control for differences in the general slowing and strategic slowing scenarios. We recommend that RT analyses are ideally supplemented by analyses of error rates where possible, as these may help to identify the presence of confounds. To facilitate this, it would be beneficial to include conditions that elicit below ceiling accuracy in tasks.

Highlights

It has been well established that elderly people are typically slower on choice response times (RTs) tasks compared with younger adults (Anstey, Dear, Christensen, & Jorm, 2005; Bugg, Zook, DeLosh, Davalos, & Davis, 2006; Salthouse, 1985, 1996)
Such an interpretation is confounded when comparing groups that differ in their overall response speed, as RT costs generally increase with slower RTs (Faust, Balota, Spieler, & Ferraro, 1999).The potential contamination of task specific effects has led to different methods being used to control for general slowing in aging, the appropriateness of which have been the subject of much discussion in the literature (e.g., Cerella, 1991; Faust et al, 1999; Myerson, Adams, Hale, & Jenkins, 2003; Ratcliff, Spieler, & McKoon, 2000; Salthouse & Hedden, 2002)
Transformed RT costs have been used prominently in the aging literature to examine whether older adults show deficits in specific cognitive mechanisms in the presence of general slowing (e.g., Colcombe et al, 2005; Gold et al, 2013; Gratton et al, 2009; Henry et al, 2015; Lawo & Koch, 2014; Truong & Yang, 2014; Yang & Hasher, 2007; Zhu et al, 2010)

Summary

Introduction

It has been well established that elderly people are typically slower on choice RT tasks compared with younger adults (Anstey, Dear, Christensen, & Jorm, 2005; Bugg, Zook, DeLosh, Davalos, & Davis, 2006; Salthouse, 1985, 1996). We used the drift diffusion model (DDM; Ratcliff, 1978; Ratcliff & Rouder, 1998) to simulate four hypothetical scenarios that could affect RT costs and/or average RTs, based on parameter values that have been reported in a study of younger and older adults These scenarios correspond to a domain specific deficit, general slowing, strategic slowing, and a slowing of perceptual-motor (i.e., nondecision) processes. We conduct a simulation using an alternative model, the Linear Ballistic Accumulator (Brown & Heathcote, 2008), in supplementary material B

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Conclusion