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Clock Drawing Test (CDT)
Standard Instruction: Give the patient a blank piece of paper and say:
"Please draw a clock. Put in all the numbers, and set the time to 10 past 11."
Score the drawing (Shulman Qualitative Method)
Guidelines & Evidence
Clinical Details
Section 1
When to Use
When to Use
Brief cognitive screening for dementia in primary care or geriatric clinics.
Assessment of executive function, visuospatial ability, and semantic memory.
Identifying cognitive impairment in patients who score normally on the MMSE due to high premorbid intellect.
Included as a core component of the Mini-Cog and MoCA.
A Window into Executive Function
Drawing a clock requires complex cognitive interplay: verbal understanding (the instruction), semantic memory (what a clock looks like), visuospatial skills (planning the circle and numbers), and executive function/abstraction (placing the hands to represent a specific time).
Section 2
Formula & Logic
Scoring (Freedman 10-Point Scale)
Instruction: "Draw a clock, put in all the numbers, and set the time to 10 past 11."
Points awarded for specific elements:
Contour (1), Numbers present (1), Numbers correct sequence (1), Numbers correct position (1)
Hands present (1), Correct time indicated (1), etc.
Scoring system varies widely (e.g., 3-point, 5-point, 10-point). OpiCalc provides the qualitative 5-point Shulman or the binary Mini-Cog approach.
Common Errors
Stimulus-bound error
Drawing hands at 10 and 11 instead of 11 and 2.
Planning deficit
Numbers clustered on one side, running out of room.
Conceptual deficit
Writing "10 past 11" instead of drawing hands.
Perseveration
Continuing to write numbers past 12 (e.g., 13, 14).
Section 3
Pearls/Pitfalls
Language and Education Independence
The CDT is less influenced by language, culture, and educational level than the MMSE, making it a robust screening tool across diverse populations.
Section 4
Next Steps
Management
Section 5
Evidence Appraisal
Primary Reference
Clock-drawing: is it the ideal cognitive screening test?
Shulman KI. • Int J Geriatr Psychiatry.. 2000;15(6):548-561. Comprehensive review of the CDT's utility, validity, and various scoring systems.
Section 6
Origins
Historical Context
Originally used in the early 20th century to assess parietal lobe lesions (apraxia and agnosia), the CDT was popularised as a dementia screening tool in the 1980s and 1990s. Its elegance lies in its ability to quickly sample a wide range of cognitive domains with minimal equipment.
