Stroop Task Demo Demo Experiment Run Experiment

Stroop Task Demo

Jaap Murre

Demo of the classic Stroop Task adjusted for the online use.

In the real Stroop task, the subject reads words or colors from a printed list. Here, we adopt to the online situation with the added advantage that we can automatically record reaction times. Note that this is only the 'say color' condition. It may be contrasted with 'say word' condition, which is expected to have much faster reaction times. This conditions only requires minimal changes to the script: different instructions and different scoring logic. We leave this as an exercise for the user.

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var i, event, total_correct = 0, total_RT = 0;

var trials = [
    {word: 'RED', color: 'green', key: 'g'},
    {word: 'BLUE', color: 'green', key: 'g'},
    {word: 'GREEN', color: 'red', key: 'r'},
    {word: 'RED', color: 'blue', key: 'b'},
    {word: 'GREEN', color: 'red', key: 'r'},
    {word: 'BLUE', color: 'green', key: 'g'},

    {word: 'BLUE', color: 'red', key: 'r'},
    {word: 'RED', color: 'blue', key: 'b'},
    {word: 'GREEN', color: 'blue', key: 'b'},
    {word: 'GREEN', color: 'red', key: 'r'},
    {word: 'BLUE', color: 'green', key: 'g'},
    {word: 'RED', color: 'blue', key: 'b'}
];

shuffle(trials); // Randomize trial order

// Here you might a condition with just XXXX instead of the word. This gives faster trials.

instruction("Press the first letter of the color in which the word is printed, ignoring the word itself: r, g, or b.");

text("The experiment will start shortly. Get ready!");
await(2000);

for (i = 0; i < trials.length; i++) {
    text("+").style("color","black");
    await(500);
    clear();
    await(Math.random());
    text(trials[i].word).style("color",trials[i].color);
    event = await("keypress");
    total_RT = total_RT + event.RT;
    if (event.key === trials[i].key) {
        total_correct = total_correct + 1;
    }
    clear();
    await(1000);
}

text("Finished!").style("color","black");
await(1000);
instruction("You had " + total_correct + " correct, out of " + trials.length
            + ", with an average RT of " 
            + (total_RT/trials.length).toFixed(1) + " ms.","OK","Result");
            
text("Thank you for participating!");
await(2000);
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