Stroop Test: Name the Color, Not the Word

What is the Stroop test?

The Stroop test shows you color words printed in the “wrong” color — the word BLUE in red ink, say — and asks you to name the ink, not the word. It sounds trivial. It isn’t: almost everyone is slower and makes more mistakes when the word and the ink disagree, because reading is so automatic that you cannot switch it off.

That slowdown is the Stroop effect. It is one of the most replicated findings in psychology, and versions of the test are used in research and in neuropsychological assessment to measure attention and the ability to override a habit.

Where the Stroop test comes from

The idea is older than the name. In 1886, James McKeen Cattell, a doctoral student of Wilhelm Wundt, found that naming a patch of color takes longer than reading the color word, because reading has become automatic. A 1929 study by E. R. Jaensch may have been the first to print a color word in a clashing ink, as Colin MacLeod’s review points out.

The test we use today comes from J. Ridley Stroop, a graduate student at George Peabody College, who published “Studies of interference in serial verbal reactions” in the Journal of Experimental Psychology in 1935. In one experiment, 70 undergraduates read 100 color words printed in clashing inks; that took only 2.3 seconds longer than reading them in black, a difference Stroop judged unreliable. In another, 100 students named the ink colors instead. Plain colored squares took them 63.3 seconds on average; color words in clashing inks took 110.3 seconds, 74% longer. That lopsided result is why Part 2 above feels so much easier than Part 1.

By 1991, when MacLeod reviewed Half a Century of Research on the Stroop Effect, there were more than 700 Stroop-related articles. Clinicians use it too: a 2017 review found Golden’s 1978 Stroop Color and Word Test to be the most widely used scoring method.

Memo’s version adds a rule switch halfway through, which borrows from a second research tradition: task switching. As psychologist Stephen Monsell summarized in 2003, people are slower and make more mistakes right after a change of task, and a moment to prepare shrinks that “switch cost” but doesn’t erase it.

How the test above works

1. Part 1 — pick the ink. Ten words. Tap the swatch that matches the color the word is printed in.
2. The switch. The rule flips.
3. Part 2 — pick the meaning. Ten more words. Now tap the color the word says, and ignore the ink.

A wrong tap flashes and you try again, so mistakes cost time rather than points. Your score is the total time for both parts. This is exactly how the game works in Memo, where it is called Brain Speed.

What the Stroop test measures

• Inhibitory control — holding back the automatic response (reading the word) to give the one you were asked for (the ink).
• Selective attention — focusing on one feature of what you see while ignoring another that is louder.
• Processing speed — how quickly you resolve the conflict and act.
• Task switching — Part 2 adds a twist that the classic test does not: after ten rounds of one rule, you have to drop it for the opposite rule. The first few answers after a switch are usually the slowest.

Most people find Part 2 easier than Part 1. Naming what a word says is close to reading, which you do effortlessly; naming the ink means fighting your reading reflex on every single word.

How to get faster at the Stroop test

• Soften your focus on the letters. Look at the middle of the word as a blob of color rather than reading it left to right. Some people find squinting slightly helps at first.
• Learn the swatch positions. If you know where red is without searching, you remove a visual search from every answer.
• Say the color, silently. Naming the ink in your head (“red”) gives your brain a competing word to the printed one.
• Don’t rush the switch. Take half a second after the rule flips to say the new rule to yourself. One clean answer beats two fast wrong ones.
• Practice briefly and often. Your time will drop over the first sessions as the task becomes familiar. That is real improvement at the task; whether it makes you better at ignoring distractions in daily life is a much harder claim, and the evidence for it is weak.

Does it improve your brain? What the research says

Practice reliably makes you faster at the Stroop test itself. Whether that spills over into the rest of your life is a different question, and the answer so far is “not much.”

• You get better at the task. In Stroop’s own third experiment, 32 students practiced naming ink colors on clashing cards for eight days, 200 answers a day. Their times dropped by about a third, and the interference shrank but never disappeared. There was a twist: afterward, reading the words got slower, because the newly practiced habit now got in the way. That is the effect Memo’s rule switch puts on the clock.
• Training self-control tasks may not train self-control. In a randomized, double-blind study of 122 healthy adults, three weeks of harder and harder “stop” tasks improved performance, but no more than an easy version did, at the end of training or four months later. The researchers also checked an untrained Stroop task and found no convincing evidence of a real gain.
• Task-switching practice is a more hopeful case. A 2009 study of children, young adults and adults aged 62 to 76 found that switching practice carried over to similar tasks, and reported gains on other executive tasks too. It was one study, and later reviews remain cautious.
• Big studies find little transfer. In a BBC-run study, 11,430 adults trained at least 10 minutes a day, three times a week, for six weeks. They improved on every trained task but not on untrained tests, even closely related ones.
• The overall picture. A 2016 review of the studies that brain-training companies cite found extensive evidence for gains on the trained tasks, less for closely related tasks, and little for distant tasks or everyday thinking.

Variations of the Stroop test

• Classic (color-word): name the ink color of conflicting color words — Part 1 above.
• Reverse Stroop: read the word and ignore the ink — Part 2 above. The interference is much smaller.
• Emotional Stroop: name the ink of emotionally loaded words. A 1996 review found that people with anxiety and other conditions are often slower to name the color of words tied to their concerns.
• Numerical Stroop: pick the bigger number when font size disagrees (a small 9 beside a big 3).

If you like this kind of fast, rule-based game, try mental math next, or test a different kind of attention with the Chimp Test.