Flanker

A row of arrows appears, and you respond only to the central one, usually by indicating whether it points left or right. The catch is the surrounding arrows, the flankers. Sometimes they point the same way as the target, and sometimes the opposite way. Your task is to lock onto the middle and treat everything around it as noise.

That is selective attention combined with interference control. When the flankers point the wrong way, they activate the competing response, and part of your brain starts preparing the wrong answer before you can suppress it. Your score reflects how well you filter out that irrelevant information and stay focused on the one thing that matters.

This is the Eriksen flanker task, introduced by Barbara Eriksen and Charles Eriksen in 1974. Their key insight was that flankers create response competition: when the surrounding items map onto a different response than the center, they interfere, and when they map onto the same response, they help. By comparing those conditions, you can measure how much the distractors cost you.

Trials come in two flavors. A congruent trial has flankers pointing the same way as the target, so everything agrees. An incongruent trial has flankers pointing the opposite way, so the display fights itself. People are faster and more accurate on congruent trials because there is no conflict to resolve.

The headline measure is the congruency effect, also called the flanker effect. You compute it by subtracting your average congruent reaction time from your average incongruent reaction time:

• Congruency effect = incongruent RT − congruent RT.

The result is almost always positive, because incongruent trials are slower. A typical congruency effect lands in the range of a few tens of milliseconds. A small effect suggests you filtered the distractors efficiently; a large effect means the flankers pulled at you more. Accuracy matters too, since incongruent trials also produce more mistakes, especially when you rush.

Read the difference score, not just raw speed. A person with slow reaction times can still show a small congruency effect, which is what the task is really about. The point is the extra cost of conflict, not how fast you are overall.

You can shrink your congruency effect a little with practice, mainly by narrowing your focus onto the central target and settling into the pace. Be honest about the ceiling, though: the interference effect is robust and hard to eliminate, and the gains you do make are largely specific to this task rather than a general boost to attention.

• Fixate the center. Keep your gaze locked on where the target appears so the flankers stay in peripheral vision.
• Do not rush the conflict. Trying to go faster on incongruent trials usually raises errors rather than helping.
• Warm up. Your first block often understates you as you learn the mapping.
• Accept regression to the mean. One unusually small effect may not repeat, so judge yourself by your typical difference score.

Remember that this is a self-testing tool for curiosity, not a clinical or diagnostic measure. A large congruency effect on one session does not label your attention; it just reflects how much the distractors cost you today, on this device, in this mood.

Conditions shift both your raw speed and your congruency effect, so read a single run as approximate. The spacing of the arrows, the pace, and your focus all matter. Flankers placed close to the target interfere more than ones spread far apart.

• Letting your eyes wander: if you scan the whole row instead of fixating the center, the flankers grab more influence.
• Rushing incongruent trials: pushing for speed under conflict inflates errors and can distort the effect.
• Anticipating: guessing before the arrows resolve produces fast but wrong responses.
• Practice effects: your difference score usually settles after the first few blocks.
• Fatigue and distraction: interference control weakens when you are tired, enlarging the congruency effect.