I took the Stroop test as part of my ASD evaluation and I’ve seen it recently on a list of online autism evaluation tests. While not strictly an autism test, it is often part of the test battery that is given at neuropsychological evaluations for autism.
The format of the Stroop test that I took during my evaluation was:
- verbally reading a list of color words (blue, red, green) printed in black ink
- verbally stating the color of a series of Xs printed in blue, red or green ink
- verbally reading a list of color words that were printed in colored ink (i.e. RED printed in blue ink or RED printed in red ink)
The Stroop test is a test of executive function. Our brain’s natural tendency is to read words that we’re presented with; noticing the color of the ink the word is printed in is a secondary priority. The Stroop test asks us to inhibit our first instinct (reading the word) in favor of stating the color of the ink. Doing so draws heavily upon the executive functions of inhibition and attention.
Because autistic people typically have impaired executive function, we often score below average on the Stroop test. The time taken to complete the test is also seen as a measure of cognitive processing speed, another area where autistic individuals will typically have a below average result.
There are quite a few other conditions that also cause cognitive “interference” on this test, resulting in below average scores, including ADHD, dementia, brain damage, depression, schizophrenia and addiction. While the results of the Stroop test can give you some insight into your executive function abilities, it’s not strictly related to being or not being autistic.
Taking the Test
You can take a mini version of the Stroop test here. The test site is ugly and has lots of ads that you’ll have to ignore. Read the instructions in the center of the page and click the green button when you’re ready to begin. The test has 20 items and will take a couple of minutes to complete. You’ll receive your scores on the final screen of the test.
Scoring the Test
The reason I called this a mini version of the Stroop test is because it has only 20 trials. The version of the test I took at my evaluation had 300 trials across the 3 different types of tasks, with each set of 100 having a 45-second time limit.
The online version presents 15 incongruent (ink color and word do not match) and 5 congruent (ink color and word match) trials. It then gives you a score showing your congruent and incongruent results, with number correct and the average processing time for each. Generally, most people respond more quickly the congruent pairs than the incongruent pairs.
Here are my scores for the online version:
- Congruent: 5 Correct, avg response time: 11.78 seconds
- Incongruent: 15 Correct, avg response time: 10.20 seconds
(Admittedly I have an advantage because I was familiar with the test format and I think my scores reflect that.)
And here are my scores for the paper version (raw score, followed by percentile – in both cases higher is better):
- Word (color words/black ink): 82, 12th percentile
- Color (Xs/3 ink colors): 91, 27th percentile
- Color-Word (color words/3 ink colors): 110, 75th percentile
- Interference (calculated from other scores): 121, 92nd percentile
If you look at both sets of scores, you’ll see that I’m better at the incongruent tasks. I got higher scores on the Color-Word and Interference scores for the paper test and had a faster average response time for the incongruent pairs on the online test.
When I saw my scores from the paper test, I was shocked by how poorly I did on the first two tasks, which felt effortless when I was taking them. I have no explanation for the disparity in my performance, except that maybe when a task is more difficult, I pay closer attention and therefore do well on it. I had a similar outcome on another “easy version-hard version” test during my evaluation which supports this supposition but there may be another explanation that has gotten by me.
The Bottom Line
How useful is the online Stroop test? I think it’s more valuable as a curiosity satisfier than an actual measure of cognitive processing. First, it doesn’t have the “priming” tasks of reading the words in black ink and naming the colors of the Xs, which create performance patterns in the brain, supposedly making the color-word task more difficult.
Second, there is no overall time limit so the test taker doesn’t feel pressured to rush through as many items as possible to complete the test in the allotted time. The response time score compensates for this a bit, but there’s no mention at the beginning of the test that one is being timed.
Finally, the number of items is too few to cause the cognitive fatigue that makes the paper test challenging.