Stroop Test Guide & the Interference Effect
The Stroop task asks you to name the colour a word is printed in while ignoring the word itself. When the two disagree -- the word RED printed in blue -- responses slow down and errors rise. Stroop reported the effect in 1935, and it has proved one of the most robust results in experimental psychology (Stroop, 1935).
Half a century of follow-up work established that the interference is essentially universal in healthy adults, that it shrinks with practice but never disappears, and that it is asymmetric: colour never interferes with reading the way reading interferes with colour naming (MacLeod, 1991). Reading is the more automatic process, so it wins unless inhibition holds it back -- and stopping a response you have already begun is its own process, racing the one that started it (Logan & Cowan, 1984).
Timing methodology: every event is timestamped with the browser's performance.now() high-resolution clock, entirely on your device. Browser timers are deliberately coarsened as a Spectre mitigation (typically to about 1 ms), and your display quantizes each change to its refresh interval -- about 16.7 ms per frame at 60 Hz, 6.9 ms at 144 Hz and 4.1 ms at 240 Hz (Woods et al., 2015). Treat differences smaller than about 5 ms as measurement noise, and compare your own runs on the same hardware rather than against someone else's setup.
Data transparency: SkillDrills collects no aggregate data. Your scores and settings live only in your browser's localStorage and are never uploaded, so this site publishes no user averages, percentiles or player counts. Every figure quoted here comes from the published work listed in the References panel below.
This drill is a free browser game for practice and interest. It is not a medical device, a diagnostic instrument, or a screening or treatment tool for any condition, and no score here says anything about your health. If you have concerns about your attention, memory or thinking, speak to a qualified clinician.