What the task involves
In the clock drawing task the person draws a clock face with all the numbers and sets the hands to a given time. Doing that well needs comprehension of the instruction, planning the layout, placing numbers evenly, knowing which hand shows hours and which shows minutes, and translating a verbal time into hand positions. Because it involves so many abilities, the drawing can show quite different kinds of difficulty.
Shulman (2000) reviewed clock drawing as a cognitive screening task and the many scoring systems that have been proposed for it.
Administering the task
- Instruction. A common wording is: “Draw a clock, put in all the numbers, and set the hands to ten past eleven.” Ten past eleven is often used because the hands fall in different halves of the clock and “ten” can pull the minute hand towards the number 10.
- Pre-drawn circle or blank page. Some versions provide the circle, which removes the planning demand of drawing it. Note which version you used, because results are not directly comparable.
- Repetition. The instruction can be repeated, but how much help was given should be recorded.
- Materials. For people with tremor or weakness, a thicker pen and a stable surface make the drawing easier to read.
A 0–5 hierarchical score
Hierarchical scales assign one overall level to the drawing. A widely cited six-level version, associated with Shulman, runs from a perfect clock to no reasonable representation of a clock:
| Score | Description |
|---|---|
| 5 | Perfect clock |
| 4 | Minor visuospatial errors (for example slightly uneven spacing) |
| 3 | Inaccurate representation of the requested time, with good visuospatial organisation |
| 2 | Moderate visuospatial disorganisation, such that the requested time cannot be shown accurately |
| 1 | Severe visuospatial disorganisation |
| 0 | No reasonable representation of a clock |
A component checklist (contour, all numbers, number placement, two hands, correct hour, correct minute, hands joined at the centre) makes scoring more consistent and shows which parts went wrong. Note that scoring systems differ in direction and detail, so always state which one you used.
Errors worth noting
- Numbers crowded to one side or missing from one side, sometimes seen with unilateral neglect.
- Perseveration: numbers continuing past 12, or repeated numbers.
- “Stimulus-bound” errors: the minute hand pointing at the 10 for “ten past”.
- Hands of equal length or missing, or not meeting at the centre.
- Planning problems: numbers placed without regard to the space available, needing to squeeze the last numbers in.
- Writing the time in words or digits instead of drawing hands.
Repeating the task over time
Clock drawings are easy to compare side by side, which makes them a useful visual record of change. To make comparisons fair, keep the instruction, target time (or a set of equivalent times), circle condition and pen consistent, and keep the drawings themselves, not just the scores.
Clock drawing is a screening and practice task. A score on its own does not establish a diagnosis, and results should be interpreted alongside other assessments.