The Stroop effect on the internet Clas Linnman a , Per Carlbring a, * ,A ˚ sa A ˚ hman a , Ha ˚kan Andersson a , Gerhard Andersson a,b a Department of Psychology, Uppsala University, P.O. Box 1225, 751 42 Uppsala, Sweden b Department of Behavioural Sciences, Linko ¨ ping University Available online 11 November 2004 Abstract The classical Stroop color-naming task was converted to a Web administered version and tested against a conventional computerized version. In the first experiment, 20 male and 20 female participants were tested individually on both Stroop versions in random order. Both versions resulted in strong Stroop effects, but response times were slower overall for the Web-Stroop. A second experiment with 28 participants showed that the test results on the Web-Stroop could be replicated in a less controlled experimental setting, for example in the participantÕs own home. In conclusion, findings suggest that administration of the Stroop col- or-naming test, and response time measurement in milliseconds on a personal computer, is possible via the Internet. Ó 2004 Elsevier Ltd. All rights reserved. 1. Introduction The Stroop task was developed to study interference effects on attention (Stroop, 1935). In this task, the participant is instructed to name the color of a word while ignoring the meaning of the word written. When, for example, the word ‘‘Green’’ is written in blue color, the result is an interference effect, resulting in increased re- sponse time. This finding has been replicated in numerous studies (MacLeod, 1991). 0747-5632/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.chb.2004.09.010 * Corresponding author. Tel.: + 46 18 4712152; fax: +46 18 4712123. E-mail address: per.carlbring@psyk.uu.se (P. Carlbring). Computers in Human Behavior 22 (2006) 448–455 www.elsevier.com/locate/comphumbeh Computers in Human Behavior