In the field of Cognitive Science, when studying about the Stroop effect, the claim is often made that it had been used during the Cold War by the American counter-intelligence units in order to identify Russian spies.

For example, this blog article How To Catch A Russian Spy quotes from the book Willpower:

the Stroop task became a tool for American intelligence officials during the cold war. A covert agent could claim not to speak Russian, but he’d take longer to answer correctly when looking at Russian words for colors.

The idea is that you can't control the effect that your native language has on your performance on this task, so it can be used to uncover your native language. Is there any historical evidence of this usage?

  • 1
    Explaining the claim here, via a quote, would be helpful. Jun 30, 2018 at 14:23
  • 4
    Of course that would not work to find Americans who spied for the Russians. And if someone admits he comes from Russia but claims not to be a spy, that test cannot tell if he is a spy, although it might possibly indicate he came from Russia at a different time than he says. Jun 30, 2018 at 19:02
  • 1
    The claim isn't that the Strood test is universally useful in catching all spies, but that it can reveal whether someone is a native / fluent Russian speaker, which may be a useful test in the case of a suspected spy who claims not to speak Russian. So the question is whether there are any confirmed cases where the test did provide critical information in uncovering a spy.
    – PhillS
    Jun 30, 2018 at 20:40
  • 8
    Re Stroop, the claim is that it can reveal whether someone is a native/fluent speaker of any language in which the test is given, it's not specific to Russian. The question is whether it was even attempted, let alone really yielded results. Jul 1, 2018 at 3:05
  • I found the claim repeated on a PT blog but with no more specifics, alas. Jul 1, 2018 at 5:05

1 Answer 1


As a partial answer, according to the 1987 book Systems and Theories of Psychology, volume 2, page 410:

We conclude our discussion of the Stroop effect with a story for whose veracity we cannot vouch. It seems a man was accused of being a Russian agent, a charge which he vehemently denied. He claimed to know nothing even of the Russian language. His questioners gave him the Stroop test in the Russian language, which he duly failed; that is, he said "blue" much more slowly when the word was the Russian for "yellow!" If the story is true, the Stroop test has been used to reveal something considerably more applied than the nature of unconscious cognitive processes.

So this story existed by at least 1987.

  • Not definitive but interesting. Could you please quote a larger excerpt to get the entire context?
    – gaspar
    Jul 2, 2020 at 15:17
  • 1
    @gaspar I expanded the quote on both ends. Not sure of chapter name, subchapter name is "The Stroop Effect" which starts on page 409.
    – DavePhD
    Jul 2, 2020 at 17:15
  • 1
    I just did the stroop Test myself in English and failed miserably although I’m not even a native speaker. This doesn’t prove the test was actually used to identify Russian spies but makes it very plausible. Anyone who falsely claims not to know any Russian will have a hard time passing the test. Jul 2, 2020 at 18:16
  • 1
    "It seems" does not suggest a confident source. Jul 3, 2020 at 7:59
  • 2
    @JackAidley Neither does "for whose veracity we cannot vouch." Jul 8, 2020 at 18:14

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .