An article was published in the American Journal of Psychiatry in May 2007 and can be found at www.ajp.psychiatryonline.org.
Among other things, the article considered the common cognitive screening tests used by the medical profession to assess testamentary capacity.
By way of introduction, the article states:
Clinicians and legal experts must understand that cognitive tests are not diagnostic of dementia and cannot be used as a measure of capacity. Their value lies in the ability to screen for cognitive impairment and to reflect changes in cognition over time. The Mini Mental Examination (MMSE) and the clock-drawing test are the two most common used cognitive screening tests.
The MMSE is widely used and is generally regarded as a test of cognitive function, albeit with limitations. The MMSE canvasses seven cognitive functions with a possible total score of 30. Scores below 26 suggest that a person is impaired. However, there are a variety of outside biases that may affect the MMSE score, including education and language. The MMSE is therefore not necessarily determinative or diagnostic of incapacity, but simply instructive as to whether the person being assessed is cognitively impaired. It is a test that can be repeated over time with good results.
The clock-drawing test simply shows a circle. The person being assessed is then instructed to place numbers on the circle so that the circle looks like a clock. The patient is then asked to set the time to ten past eleven.
It is widely accepted that the clock-drawing test covers a wide range of intellectual and perceptual skills. According to the article, the clock-drawing test measures: comprehension; planning; visual memory and reconstruction of a graphic; motor programming and execution; numerical knowledge; abstract thinking; etc. While no specific score is given, the actual test provide a universal global assessment of cognitive function. For anyone with small children, they will know that telling time on a conventional clock is not necessary an easily acquired skill and takes some degree of cognitive proficiency on the part of a child. The value of the clock-drawing test in assessing cognitive function therefore becomes apparent when dealing with adults.