Stroop Effect Test

Demonstration of Stroop Effect – "Name that color" test

(This is a demonstration only. It is not to be used as diagnosis or any other purpose.)

The easy practice test:
Name the COLOR (not what the word says).
(To time your response, click "Start" when you are ready to begin; click "Finish" when you are done.)

RED	YELLOW	BLUE	GREEN	BLACK
PINK	ORANGE	BROWN	GRAY	PURPLE
GREEN	GRAY	BLACK	BLUE	YELLOW
GRAY	BROWN	PINK	ORANGE	BLUE
YELLOW	RED	GREEN	BLACK	GRAY
BLACK	BROWN	PURPLE	ORANGE	PINK
PURPLE	BLACK	YELLOW	RED	GREEN
ORANGE	PINK	BROWN	GRAY	PURPLE

The real hard test:
Name the COLOR (not what the word says).
(Note that it is the same list of words but written in different color.)
(PAY ATTENTION: The COLOR of the word is different from what the word says.)

RED	YELLOW	BLUE	GREEN	BLACK
PINK	ORANGE	BROWN	GRAY	PURPLE
GREEN	GRAY	BLACK	BLUE	YELLOW
GRAY	BROWN	PINK	ORANGE	BLUE
YELLOW	RED	GREEN	BLACK	GRAY
BLACK	BROWN	PURPLE	ORANGE	PINK
PURPLE	BLACK	YELLOW	RED	GREEN
ORANGE	PINK	BROWN	GRAY	PURPLE

Do you notice it takes much longer time to complete the second test than the first test?

The first test is easy because the color and meaning of the word are congruent. There is no conflict.

The second test is hard because the color and meaning of the word are incongruent. This creates a conflict that the brain has to resolve.

The reason why it takes longer is because the brain has to suppress the wrong answer that interferes with the right answer, before the right answer comes through.

The above demonstration does not even take into account the incorrect responses in naming the colors.

If you let the wrong answer to slip through impulsively, without waiting for the right answer to come through, it's because the brain does not have enough inhibition to suppress the wrong choice.

The reaction time will increase with fatigue and/or inattention to the task, so if you retake the test, it will show slightly different reaction times and error rates.

Repeat the above a few times to get an average of your response time.

Here's the correct answer for the incongruent test:

BLUE	BROWN	RED	PURPLE	GRAY
YELLOW	PINK	BLACK	BLUE	RED
ORANGE	GREEN	YELLOW	ORANGE	PINK
PURPLE	RED	BROWN	BLACK	GREEN
RED	BLUE	PURPLE	RED	BROWN
BLUE	BLACK	GRAY	PINK	RED
ORANGE	YELLOW	PINK	GREEN	ORANGE
BLACK	BROWN	GREEN	PURPLE	GRAY

John Ridley Stroop first reported this effect in his Ph.D. thesis published in 1935, commonly known as "Stroop Effect":

When the meaning of a word and its color are congruent, such as the word "BLUE" written in blue color, it is easy to recognize the actual color of the word.
But when the meaning of the word is incongruent with the color, such as "BLUE" written in red color, it creates a conflict between the color and the word's meaning.
The "conflict" between two brain processes are word-recognition and color-recognition.
This conflict requires extra processing time for the brain to resolve.
It turns out that we are so fluent in our language that word-recognition is slightly faster/stronger than color-recognition.
Most people will recognize the meaning of the word before recognizing the color.
In order to name the color correctly, the two processes compete for the final decision-making process.
The brain has to inhibit the faster/stronger word-recognition process in order to allow the color-recognition to win in the final response.
This inhibition requires "selective attention" (attentional focus) to inhibit the competing conflicting process.
The reaction time is an indicator of the "attentional process" in the brain – it increases with attentional fatigue and/or inattentiveness.
The error in recognizing the correct color when a conflict is present is associated with the "impulsivity" that the brain is unable to suppress.
Thus, Stroop Effect is widely used to indicate mental process of attentional fatigue and/or the decreased ability to inhibit ongoing competing conflicts often associated with ADHD (Attention Deficit Hyperactivity Disorder).
ADHD subjects often take much longer time than normal subjects to resolve the conflicts and make more errors due to the insufficient inhibition in the brain circuitry to suppress the ongoing competing processes.
The impulsivity in ADHD patients is due to the insufficient inhibition exerted by the brain circuitry in the prefrontal cortex of the brain that is responsible for executive function in decision making. This inhibition in the prefrontal cortex is mediated by the neurotransmitter dopamine. Pharmcological treatment of ADHD symptoms is restoring the level of dopamine, which results in reducing the impulsivity by increasing the inhibition control in the prefrontal cortex.

References:

Stroop, J. R. (1935). Studies of interference in serial verbal reactions. Journal of Experimental Psychology,18:643-662.

Stroop, J. R. (1938). Factors affecting speed in serial verbal reactions. Psychological Monographs, 50:38-48.