Flanker Task Demo Experiment Run Experiment

Flanker Task

Jaap Murre

This is a fairly complete demo of the Eriksen Flanker Task, which takes about 2.5 min. It is suitable for use in lectures, where the audience can take the test on a laptop (keyboard) or mobile phone (touch screen). Feedback is given, including a T-Test significance level of how much faster congruent were compared with incongruent trials.

The Eriksen Flanker Task is a classic response inhibition task.

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var i, t, e, fixation = '+', stimuli = ["<<<<<",">>>>>",">><>>","<<><<"],
    // The following is a simple way to do counter-balancing:
    trials = shuffle([0,0,0,0,0,1,1,1,1,1,2,2,2,2,2,3,3,3,3,3]),
    correct_congruent = 0, correct_incongruent = 0,
    rt_correct_congruent = 0, rt_correct_incongruent = 0,
    alpha, rtcc = [], rtci = [], // arrays to save RTs
    left = addblock(30,90,10,7,"lightgrey","<","left"),
    right = addblock(60,90,10,7,"lightgrey",">","right"), exit;

main.setfontsize(60); // Makes the base font size a bit smaller: 60%
instruction('Watch the middle character of the five characters presented.

' + 'If it is a < character, tap on the "< Button". ' + 'You may also click the button with the mouse or press the Left Arrow Key on the keyboard.

' + 'If it is a > character, tap or click the "> Button", or press the Right Arrow Key.

'); instruction('The middle character is surrounded by similar characters, which you must ignore.

' + 'When you see >><>> or <<<<< tap the "< Button" (or <- Arrow Key).

' + 'With <<><< or >>>>> click the "> Button" (or -> Arrow Key).

' + 'Please, try to respond as fast as possible (within 2 seconds)

' + ' The experiment starts when you press OK'); text("Get ready!"); await(1000); for (i = 0; i < trials.length; i++) { clear(); await(1500); t = trials[i]; text(stimuli[t],300); waitfor { // TODO: replace by await_or e = await('click',2000); // Wait for either a mouse click on the button... } or { e = awaitkey('LEFT_ARROW,RIGHT_ARROW'); // ... or a keyboard key: <- or -> } if (e.type === 'timeout') { alert("Please, try to click or tap faster"); continue; } if (!e.event.target.id || e.event.target.id === 'undefined') { alert("Please, click or tap on the < or > buttons"); continue; } if ((e.key && e.key === keys.LEFT_ARROW) || (e.event.target.id && e.event.target.id === 'left')) { if (t === 0) { ++correct_congruent; rt_correct_congruent += e.RT; rtcc.push(e.RT); } else if (t === 2) { ++correct_incongruent; rt_correct_incongruent += e.RT; rtci.push(e.RT); } } else if ((e.key && e.key === keys.RIGHT_ARROW) || (e.event.target.id && e.event.target.id === 'right')) { if (t === 1) { ++correct_congruent; rt_correct_congruent += e.RT; rtcc.push(e.RT); } else if (t === 3) { ++correct_incongruent; rt_correct_incongruent += e.RT; rtci.push(e.RT); } } } alpha = stat.ttest(rtcc,rtci); text('Your average reaction time for congruent stimuli was ' + (rt_correct_congruent/correct_congruent).toFixed(0) // toFixed(0) rounds to 0 decimals + ' ms and for incongruent stimuli ' + (rt_correct_incongruent/correct_incongruent).toFixed(0) + ' ms

' + 'On a one-tailed T-Test, this gives alpha = ' + alpha + ', which is statistically ' + (alpha < 0.05 ? 'significant.' : 'not significant.') + "

" + 'Press the Exit to leave the experiment'); exit = addblock(44,90,12,7,"lightgrey","Exit"); exit.await('click'); exit.destroy();
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