Stroop test

The Stroop Task is one of the best known psychological experiments named after John Ridley Stroop. The Stroop phenomenon demonstrates that it is difficult to name the ink color of a color word if there is a mismatch between ink color and word. For example, the word GREEN printed in red ink.

Colin MacLeod’s (1991) review article in the influential psychological journal Psychological Bulletin is frequently cited when discussing the effect.

There are many variations on the basic effect using other stimuli than colored words.

Here we present a simple application of the task implemented in mobile-phone.

Technical details:

The participant is asked to pressed a colored button at the bottom of the screen. There are three possible colors: red, green and blue. In each trial, a colored text appears at the center of the screen and the participant has maximum 1,5 s to select the color of the text. After pressing a button, a feedback of the accuracy (Correct/Incorrect/Late) is provided for 500 ms. The inter-trial interval ranges randomly between 300 and 500 ms.

There are three possible conditions: congruent, incongruent and control. In congruent trials the color of the text and the meaning of the text are equal. In the incongruent trials, there is a mismatch between the color and the meaning of the text. In the control trials, the text is a set of colored, meaningless characters (“#####”).

Given the nature of the conditions, there are three possible congruent and control trials, and six possible incongruent trials. The total number of trials is 180, equally distributed in the twelve possible trial-types. The order of the trials is constructed with two conditions: 1) two same trial-types cannot occur occur consecutively, and 2) three same conditions cannot occur consecutively.

The results collected (accuracy, reaction time) are groupped by conditions for each participant.

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