Flanker Test — Free 60-Trial Interference Control Task

The flanker task, introduced by Barbara and Charles Eriksen in 1974, places distractors on either side of a target and measures how much they disturb your judgment. What it captures is interference control — the strand of selective attention that suppresses irrelevant information in view and responds only to the target.

Five arrows appear in a row, and you answer within two seconds with the direction of the center arrow only. Congruent trials, where the four flankers point the same way as the center, and incongruent trials, where they point the opposite way, come 30 times each — 60 trials in random order. On incongruent trials the flankers strongly pull toward the wrong answer, so responses tend to slow down or go wrong.

The gap between congruent and incongruent conditions directly reflects the extra time the brain spent suppressing the distractors, which is why it is widely used as an index of attentional control distinct from raw reaction speed.

The headline score is overall accuracy across the 60 trials, in percent. Below it, the interference effect is the mean reaction time on incongruent trials minus that on congruent trials, using correct responses only, in milliseconds. A larger value means the flanking arrows pulled you more. Accuracy for congruent and incongruent trials is also shown separately.

Even in healthy adults the interference effect is not zero — a few tens of milliseconds is normal. So rather than the mere presence of an effect, what matters is whether accuracy drops sharply on incongruent trials and whether the effect grows across repeated measurements.

Responses are timed within a two-second limit. Touch latency adds roughly equally to both conditions, so it barely affects the interference effect itself, but it can shift absolute reaction times by tens of milliseconds. Accuracy often improves over the first attempt or two through practice.

Interference control is sensitive to fatigue and lost sleep: after a poor night the interference effect grows and incongruent-trial errors increase. Caffeine speeds responses but can also add hasty errors, and with age the interference effect tends to grow slightly along with overall reaction time. On small screens the arrows sit closer together, which can increase interference.

Soundary saves your results and compares them with your previous test. Repeating every one to two weeks on the same device at a similar time, and following the trend in interference effect and incongruent accuracy, helps you tell daily fluctuation from steady change. This is a self-check, not a diagnostic tool.

If incongruent-trial errors stay high even after you are rested and familiar with the task, and in daily life you are easily pulled off course by surrounding stimuli and struggle to finish things, consider discussing an attention assessment with a psychiatrist or other professional.