Reaction time and ERP analysis of single-item Stroop color-word test: Impact of task design and possible use as a diagnostic tool

Grega Repovš(1), Marko Pišljar(2), Zvezdan Pirtošek(3)
(1) Department of Psychology, Faculty of Arts and Sciences, Washington University in Saint Louis
(1) Department of Psychology, Faculty of Arts, University of Ljubljana
(2) Idrija Psychiatric Hospital, Idria, Slovenia
(3) Neurology Clinic, University Medical Centre Ljubljana, Ljubljana, Slovenia

The Stroop color-word task is a premier tool of research on attention and cognitive control and has been long established as a key diagnostic test of attention. Both in clinical setting and especially in research, the Stroop color-word task is used in a variety of forms. While classical card version of the test is still standard in clinical use, single-item computerized versions of the task have become the norm in research on cognition. While single-item version of the task can provide more detailed information useful for clinical setting as well, differences in design of the task, such as verbal vs. manual response mode, and the choice of neutral stimuli, have not been extensively tested, making comparison between studies and development of clinical norms difficult.

To directly assess possible differences between verbal and manual response mode versions of the task, and to compare two types of neutral stimuli (strings of Xs and color unrelated words), reaction times and ERP measurements of 22 students of psychology performing both verbal and manual response versions of the task were recorded and analyzed.

Results revealed overall longer reaction times for the manual version of the task, while reaction times to color unrelated neutral words were relatively longer in the verbal response mode. Qualitative difference between the two versions of the task as well as neutral stimuli employed were reflected also in the ERPs, warning against a direct comparison of results obtained with different response modes and supporting inclusion of different types of neutral stimuli.

To assess the feasibility of its use in clinical setting, the verbal single-item version of the task was further used to test for ERP and reaction time differences in Stroop color-word task performance between depressed and non-depressed older adults. Showing qualitative differences between the groups, the results encourage further testing of the single-item version of the task as a diagnostic tool.