Selective Attention Test

Your visual system does not read one object at a time. When you look at a row of arrows, the flankers feed their direction into the same response-selection process as the target. The result is a competition between two answers. When they agree, the right answer wins cleanly. When they disagree, both answers are active at once and the brain has to resolve the conflict.

That resolution takes time. The gap between the two conditions is the distractor cost, and this test measures it in milliseconds. It is a direct read on how well your attention filters out irrelevant information when it sits in the same space as the target.

The task was published in 1974 by Barbara and Charles Eriksen. They placed noise letters either side of a target letter and showed that the flankers changed responses even when volunteers were told to ignore them.

The test has been run in thousands of studies since. It shows up in ageing research, clinical attention work and neuroscience studies. It is one of the cleanest ways to put a number on selective attention. The target and the distractors sit in different spatial positions and still interfere.

This version uses arrows because direction is easier to read than letter identity under time pressure and it avoids any reading-skill confound. The arrows are chosen at random each trial, and left and right targets appear equally often.

Both scores measure the cost of conflict, so it is worth being precise about where the conflict lives. In the Stroop test a colour word is printed in a different ink. The conflict is inside a single stimulus: the word and the ink are the same object. Reading the word happens whether you want it to or not.

In this test the conflict is spatial. The flankers are separate objects beside the target. The mechanism is response competition rather than automatic reading. That is why people who are slow on Stroop are not necessarily slow here, and vice versa.

The Stroop article what the Stroop effect actually shows explains the subtraction method that both tests share. Both scores use the same logic: compare a hard condition with an easy one and take the difference. That subtraction cancels out your baseline speed, your mouse and your screen.

A distractor cost around 38 ms sits in the middle of the reference distribution. Numbers below 20 ms and above 80 ms are both common. A small cost is not proof of superior attention. A large one is not a fault. Fatigue, stimulus size and how well you know the key mapping all move it.

The reliable comparison is your own across days or conditions. Caffeine, sleep and time of day all shift this number. The extras on the result card show your raw times for each condition separately. That lets you see whether a big cost came from slow incongruent trials or from unusually fast congruent ones.

For how much baseline reaction time changes with age, see average reaction time by age. Distractor costs move less steeply with age than simple reaction time does, which is one reason researchers find them useful.