How the Stroop Test Screens for Signs of Early Alzheimer's

This screening test can often identify mild cognitive impairment

The Stroop test, also referred to as the Stroop Color Word Test or the Stroop Effect, is a test dating back to the 1930s that measures cognitive functioning. It may be used as part of the assessment process when conducting an evaluation to determine if someone has mild cognitive impairment, Alzheimer’s, or another type of dementia.

Doctor consulting with an older woman
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The Stroop test is considered by some to be an effective measure of executive functioning—the ability to plan, apply knowledge and make decisions. Executive functioning, along with short term memory impairment, is often one of the symptoms of early-stage Alzheimer’s disease. Impaired executive functioning may also be an early symptom of other kinds of dementia, such as frontotemporal dementia, even when memory is intact.

The Stroop effect was first written about by John Ridley Stroop in 1935 for his Ph.D. dissertation.

What Does the Stroop Test Contain?

The Stroop Test consists of colors that are written in words but in the wrong color ink. The test-taker has to be able to state the color that the word is written in and be able to ignore whatever the actual word is. For example, if you see the word “red” but it’s written in blue ink, the correct answer would be “blue”.

Stroop Test Results

Older adults who do not have any cognitive impairment have, on average, a slower response time than younger and middle-aged adults, but they typically answer the questions correctly.

People with mild cognitive impairment, Alzheimer’s or another dementia, on the other hand, will be slower in answering but also will have a significantly higher rate of incorrect answers because of their decline in processing information and the inability to ignore one stimulus (the word) while focusing on the other one (the color).

The test has been administered across several languages and consistently been shown to be effective in identifying executive functioning impairments. However, results have been shown to be influenced by age, education levels, and sex.

What Does the Stroop Test Identify?

The Stroop Test has been associated with impairment specifically in the prefrontal cortices of the brain, especially in earlier stages of Alzheimer’s. As Alzheimer’s progresses into the middle and late stages, the Stroop effect is not a valid indicator of the location or extent of impairment in the brain.

Variations of the Stroop Test

Variations of the Stroop Test have been developed and tested recently, particularly with the goal of assessing executive functioning early in Alzheimer’s. Rather than continue the same set of directions throughout the test, the new version required the participants to switch back and forth between two different sets of directions.

For example, on one section of the test, they might have to identify the color the word is written in, and in another section of the test, they might have to read the word and ignore the color that the word is written in.

Other variations might include a written word that is not a color, such as the word "five" in a certain color ink.

How Accurate Is the Test?

In one study conducted by Hutchison, Balota, and Duchek, variations of the Stroop Test (which involved switching the directions as described above) were better than 18 other typical cognitive tests at differentiating between healthy older adults and those with early Alzheimer’s.

A Word From Verywell

While there are many screening tests that help identify symptoms of dementia, the Stroop test is one that is more effective at pointing out those with just the early, or mild, stages of dementia such as mild cognitive impairment. Its ability to test executive functioning sets it apart as an important component of a comprehensive assessment of cognition.

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  • Alzheimer’s Society. The Stroop Test. 
  • Dementia and Geriatric Cognitive Disorders EXTRA. 2011 Jan-Dec; 1(1): 190–201. Neural Correlates of Stroop Performance in Alzheimer's Disease: A FDG-PET Study.
  • National Institutes of Health. National Institute on Aging. Developing New Cognitive Tests.
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  • The Environmental Psychology Lab. School of Natural Resources and Environment, University of Michigan. Stroop Effect.

By Esther Heerema, MSW
Esther Heerema, MSW, shares practical tips gained from working with hundreds of people whose lives are touched by Alzheimer's disease and other kinds of dementia.