Effects of aging in a task-switch paradigm with the diffusion decision model

Abstract

We investigated aging effects in a task-switch paradigm with degraded stimuli administered to college students, 61-74 year olds, and 75-89 year olds. We studied switch costs (the performance difference between task-repeat and task-switch trials) in terms of accuracy and mean reaction times (RTs). Previous aging research focused on switch costs in terms of mean RTs (with accuracy at ceiling). Our results emphasize the importance of distinguishing between switch costs indexed by accuracy and by RTs because these measures lead to different interpretations. We used the Diffusion Decision Model (DDM; Ratcliff, 1978) to study the cognitive components contributing to switch costs. The DDM decomposed the cognitive process of task switching into multiple components. Two parameters of the model, the quality of evidence on which decisions were based (drift rate) and the duration of processes outside the decision process (nondecision time component), indexed different sources of switch costs. We found that older participants had larger switch costs indexed by nondecision time component than younger participants. This result suggests age-related deficits in preparatory cognitive processes. We also found group differences in switch costs indexed by drift rate for switch trials with high stimulus interference (stimuli with features relevant for both tasks). This result suggests that older participants have less effective cognitive processes involved in resolving interference. Our findings show that age-related effects in separate components of switch costs can be studied with the DDM. Our results demonstrate the utility of using discrimination tasks with degraded stimuli in conjunction with model-based analyses. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Figure 1

Example of the stimulus for letter discrimination (correct response: T).

Figure 2

Example of the stimulus for brightness discrimination (correct response: bright).

Figure 3

Plots of accuracy and mean correct response time (RT) for the letter discrimination (left panel) and the brightness discrimination task (right panel) and for each trial type, averaged over participants of each group, respectively. The left side presents the data for letter discrimination. The right side presents the data for brightness discrimination. Accuracy and mean correct RTs were averaged over the short and long response-stimulus intervals (RSIs). The bars in the top left (for mean correct RTs), and the bottom left (for accuracy) represent the standard deviations averaged over trial types for each participant group. For a given participant group, the standard deviation of each participant was averaged to obtain the average standard deviation.

Figure 4

Graphical illustration of age-related switch costs.