Assessment of Age Differences in Mental Workload while Driving using Verbal versus Visual-Spatial Subsidiary Tasks

Abstract

Age differences in mental workload demands imposed by driving were investigated using a dual-task paradigm. Two subsidiary tasks, thought to tax separate attentional resource pools (verbal versus visual-spatial), were compared. Dual-task cost ratios [RTdual-task/RTsingle-task] using each subsidiary task were collected from young (mean age = 20.6) and older (mean age = 72.4) drivers at midblock locations (low driving task load) and while approaching intersections (high driving task load). Consistent with expectations, age differences were exacerbated on the visual-spatial subsidiary task. However, the expected workload increase at intersections (relative to midblock locations) was not observed. Instead, a more complex 3-way interaction of roadway location with subsidiary task and task order was obtained. This pattern of results has important implications with regard to the following two issues: 1) the use of discrete versus continuous subsidiary task probes during real world driving, and 2) the sensitivity and specificity of subsidiary task approaches in the assessment of age-related cognitive deficits and their potential impact upon driving performance.