Flanker Task
Jaap MurreThis 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.<br /></br />'
+ 'If it is a < character, tap on the <b>"< Button"</b>. '
+ 'You may also click the button with the mouse or press the Left Arrow Key on the keyboard. <br /><br />'
+ 'If it is a > character, tap or click the <b>"> Button"</b>, or press the Right Arrow Key.<br /><br />');
instruction('The middle character is surrounded by similar characters, which you must ignore.<br /><br />'
+ 'When you see >><>> or <<<<< tap the "< Button" (or <- Arrow Key). <br /><br /> '
+ 'With <<><< or >>>>> click the "> Button" (or -> Arrow Key).<br /><br />'
+ 'Please, try to respond as fast as possible (within 2 seconds)<br /><br />'
+ ' 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<br /><br />'
+ 'On a one-tailed T-Test, this gives alpha = ' + alpha + ', which is statistically '
+ (alpha < 0.05 ? 'significant.' : 'not significant.') + "<br /><br />"
+ 'Press the Exit to leave the experiment');
exit = addblock(44,90,12,7,"lightgrey","Exit");
exit.await('click');
exit.destroy();
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