Demonstration of Stroop Effect – "Name that color" test

 

Explanation of the Stroop Effect:

• Stroop effect is caused by interference between recognizing the word and the color of the word.
• When the color of the word is different from the word itself, the brain has to choose between reading the word and naming the color.
• This creates a conflict, which is defined as: Given two chooses, you have to choose one, but not both. Choosing one would nullify the other choice.
• Because the color and the word are different, you can only choose either naming the color or recognizing the word, which is a conflict.
• Stroop Test is a test for resolving this conflict.
• In order to recognize the color, you have to suppress recognizing the word.
• This suppression process requires inhibition in the prefrontal cortex (PFC) of the brain.
• This inhibition is produced by releasing dopamine (an inhibitory neurotransmitter) in the PFC.
• It is the dopamine D4-receptor in the PFC.
• ADHD (attention deficit hyperactivity disorder) is linked to the insensitization of the D4-receptor in PFC.
• This causes insufficient inhibition to suppress the alternative choice in conflict resolution.
• This leads to impulsivity in ADHD patients, due to the inability to suppress impulses.
• Stroop Test is used to measure the ability to suppress the impulsive alternative choice due to interference of the color and the name of the word in this cognitive task.
• The time and accuracy to complete this task is dependent on the concentration by focusing on recognizing the color, but not letting the word to interfere with the recognition task.
• Fatigue and impulsivity will often lead to an increase in timing and errors made to recognize the color.
• It can be used for screening for impulsivity and attention deficiency.

(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).

This is the congruent color test.

That is, the color and the word are the same.

(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

Elapsed time: sec

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The real hard test:
Name the COLOR (not what the word says).

This is the incongruent color test.

That is, the color and the word are not the same.

You have to name the color, not the word.
(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

Elapsed time: sec

 

 

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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

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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.

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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.