How the Clock-Drawing Test Screens for Dementia

The Clock Drawing Test Can Screen for Dementia
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The clock-drawing test is a simple tool that is used to screen people for signs of neurological problems, such as Alzheimer’s and other dementias. It is often used in combination with other, more thorough screening tests, but even when used by itself, it can provide helpful insight into a person’s cognitive ability.

How Is the Clock-Drawing Test Administered?

The clinician (often a doctor, psychologist, or social worker) gives the person being tested a piece of paper with a pre-drawn circle on it and asks him to draw the numbers on the clock.

She then tells him to draw the hands to show a specific time. There are several different times that people who administer this test may use, but many choose 10 minutes after 11.

Another method is to simply give the person a blank piece of paper and ask her to draw a clock that shows the time of 10 minutes after 11. Some clinicians also intentionally omit the word "hands" in their directions to avoid giving the test-taker a cue of what needs to be included in the drawing.

How Is the Clock-Drawing Test Scored?

There are as many as 15 different ways to score this test. Some are quite elaborate and involve awarding points for inclusion of every number, correctly ordered numbers, two clock hands, drawing the correct time, and for each of the correct numbers placed in the four quadrants. As many as five, 10, or 20 points can be involved in some of the different scoring methods.

However, a study published in the Danish Medical Journal outlines research that compared five of the most common ways to score the test.

Their conclusion? The easiest scoring method provided results that were just as accurate as the more complicated scoring methods.

This simplest scoring method consists of giving one point if the task was completed correctly and zero points if the clock was not completed correctly. The Alzheimer's Association also recommends this simple scoring method, concluding that a normal clock (or a score of one point) indicates the absence of dementia, while an abnormally completed clock is cause for further evaluation.

Critical Clock-Drawing Test Errors

Additional research identified six features in this test that were important in successfully identifying problems in cognition. These were described as critical clock-drawing errors and included the wrong time, no hands, missing numbers, number substitutions, repetition, and refusal. These researchers concluded that these six errors were predictive in identifying dementia based on the clock-drawing test. Notice that simply refusing to complete the test can be indicative of a problem.

Benefits of the Clock-Drawing Test

  • Fast screening tool: It is a very quick way to screen a person for possible dementia. It often requires only a minute or two for completion.
  • Easy to administer: It does not require much training to administer.
  • Well-tolerated: This test is easier to complete than the MMSE for people with short attention spans.
  • Free: Unlike some cognitive tests that require you to purchase a copy of the test and scoring tools, the clock-drawing test can be completed with only the cost of paper and a pen.
  • May be useful in developing countries: Because of the low cost and minimal training, this test can be used in countries with fewer resources.
  • Screening for delirium: This test can has also been administered to patients in the hospital to assess for signs of delirium. Delirium is a sudden deterioration in someone’s cognitive ability. It can follow the use of anesthesia for a surgery, for example, as well as be triggered by an infection or illness.

Clock-Drawing Test: Effective in Identifying Executive Functioning Problems

One other very helpful aspect of this test, as published in the Canadian Medical Journal Association, is that it can detect problems in executive functioning even when someone scores well on the MMSE, a common screening tool. Executive functioning can be impaired before any memory problems are evident, and identifying this early allows early treatment.

For example, your father could perform well on the MMSE, which would show that his memory still is quite intact, his language and calculation skills remain functional, and his orientation remains fairly normal. You, however, may notice that his decisions are not always appropriate. He may be able to get dressed, but not be able to determine that he should wear a warm coat out if it is cold outside.

Often, family members are the first to suspect a cognitive impairment because they will see that evidence of poor executive functioning, while an MMSE test in a doctor’s office might not catch this. Performing the clock-drawing test is one way to identify people who may be experiencing early signs of dementia, such as decreased executive functioning, but may not be displaying memory disturbances yet.

Why would this be helpful? The medications that are currently available to treat Alzheimer’s disease are generally more effective earlier in the disease process. It appears that they might preserve the current functioning for a time. So, if we can detect dementia in its earlier stages, we can treat it earlier and hopefully extend the amount of time the person functions well.

How Accurate Is the Clock Drawing Test In Detecting Alzheimer’s Disease or Another Dementia?

Several research studies indicate that this test is an excellent tool to screen for cognitive impairment. Its results are highly correlated with other mental status tests and with actual evidence of impairment. Also, as noted above, it appears to have the ability to detect problems with executive functioning that other tests may miss.

While the clock-drawing test is generally quite effective at identifying cognitive concerns, there is not a consensus in the research community that it can consistently identify mild cognitive impairment or help distinguish between different forms of dementia (such as Alzheimer's disease and vascular dementia).

The Importance of Professional Evaluation

If you suspect a loved one may be showing signs of Alzheimer’s or another dementia, it's important to seek an assessment by a qualified clinician. They can work to rule out other potentially reversible causes of dementia, such as vitamin B12 deficiency and normal pressure hydrocephalus, as well as determine an accurate diagnosis and treatment plan.


Alzheimer's Association. Cognitive Testing.

Aprahamian, I., Martinelli, J.E., Liberalesso Neri, A., Sanches Yassuda, M. Dementia & Neuropsychologia 2009 June;3(2):74-80. The Clock Drawing Test:A review of its accuracy in screening for dementia.

Aprahamian I, Martinelli JE, Neri AL, Sanches Yassuda, M. International Psychogeriatrics The accuracy of the Clock Drawing Test compared to that of standard screening tests for Alzheimer's disease: results from a study of Brazilian elderly with heterogeneous educational backgrounds.

Juby, A., Tench, S., and Baker, V. Canadian Medical Journal Association. The value of clock drawing in identifying executive cognitive dysfunction in people with a normal Mini-Mental State Examination score.

Lessig, M., Scanlan J., Nazemi, H., and Borson, S. International Psychogeriatrics. Time that tells: Critical clock-drawing errors for dementia screening.

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