Stroop Effect

Background

The Stroop effect, first reported by John Ridley Stroop (1935), is one of the most robust and well-replicated findings in experimental psychology. It demonstrates cognitive interference: when the name of a color word is printed in a different ink color, naming the ink color is slower and more error-prone than when the word and ink color match.

Why It Happens

Reading is a highly practiced, automatic process. When you see the word "RED" printed in blue ink, your brain automatically reads the word, creating a conflict with the task of naming the ink color. Resolving this conflict takes additional processing time.

Three Conditions

Congruent: Word matches ink color (e.g., RED in red ink) — fastest
Neutral: Non-color word (e.g., CHAIR in red ink) — intermediate
Incongruent: Word conflicts with ink color (e.g., RED in blue ink) — slowest

Important Note

The classic Stroop task uses vocal color naming. This keyboard version measures a related but somewhat different form of interference. Effect sizes may differ from published norms, which typically report 50–100 ms interference using vocal responses (MacLeod, 1991).

References

Stroop, J.R. (1935). Studies of interference in serial verbal reactions. Journal of Experimental Psychology, 18, 643–662.
MacLeod, C.M. (1991). Half a century of research on the Stroop effect: An integrative review. Psychological Bulletin, 109, 163–203.
Algom, D., Chajut, E., & Lev, S. (2004). A rational look at the emotional Stroop phenomenon. Journal of Experimental Psychology: General, 133, 323–338.

Color words will appear on screen in different ink colors. Your task is to identify the INK COLOR, not read the word.

Press the key corresponding to the ink color:

R = Red B = Blue G = Green Y = Yellow

There are 48 trials total (16 per condition). Respond as quickly and accurately as possible.

Stroop Effect

Your Results