*During the Cold War, U.S, intelligence agencies used the Stroop task to identify potential Russian spies by presenting them with a color-word test in Russian, where a native Russian speaker would slow down when encountering incongruent color-word combinations, revealing their ability to read Russian and potentially their true identity as a spy; whereas a non-Russian speaker would not experience the same delay because the words would be meaningless to them.
Why not just make them recite the following and see if they flinch?
"I am not a Russian spy
Cross my heart and hope to die"
