You will see color words written in different colors. Select the COLOR of the text, not the word itself. For example, if you see RED, the answer is Blue.
Example
BLUE
The word says "BLUE" but it is written in GREEN. The correct answer is GREEN.
Very Easy
70% matching colors -- no time limit. Great for learning the task.
Easy
50% matching colors -- no time limit
Medium
25% matching colors -- no time limit
Hard
10% matching colors -- 30 second time limit
Expert
5% matching colors -- 20 second time limit. Maximum interference.
Scientific Background
Based on: Stroop Color-Word Test (Stroop & undefined, 1935)