Stroop Task Demo
Jaap MurreDemo 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;
// The following is an array with objects
// E.g., see https://www.w3schools.com/js/js_arrays.asp for how to use these
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 also have 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 <b>printed</b>, 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());
// Access your trial objects like this:
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);
// Give some feedback
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);
You can download the files as follows: Click on the file (link) and then right-click and choose Save as... from the menu. Some media files (e.g., sound) will have a download button for this purpose.