Clock Drawing Test (CDT) — Free Online Dementia Screening-Style Check

The clock drawing test is a short task of placing numbers on a clock face and setting the hands to a given time; it calls on visuospatial construction, number concepts, attention, planning and executive function all at once. That is why it has long served as a cognitive screening tool, and Shulman and colleagues (1986) systematically reported the relationship between clock drawing performance and cognitive function in older adults.

Soundary's version is an in-house implementation that moves the task from paper and pen to a screen. In Part 1 you pick number tiles from 1 to 12 and tap them into place on a blank face; in Part 2 you drag the hour and minute hands, both starting at the 6 o'clock position, to 11:10. Placing numbers out of the 1 to 12 sequence is recorded as an order error.

11:10 is a time commonly used in the paper version as well, because errors such as putting the minute hand near the 10 instead of the 2, or confusing the length and role of the two hands, expose conceptual mistakes clearly. Numbers bunched to one side or unevenly spaced are taken to reflect visuospatial difficulty, while a scrambled order reflects lapses in planning and attention.

Four things are measured: placement error, the mean angular deviation of each number from its correct position in degrees; order errors, the number of placements outside the 1 to 12 sequence; hand error, how far the hour and minute hands deviate from their target angles in degrees; and total time taken. These combine into a composite score from 0 to 100.

The composite is weighted as follows: number placement 40 points, order 10, hour hand 20, minute hand 20 and speed 10. A placement error of 30 degrees, 6 order errors or a hand error of 45 degrees zeroes that component, and speed scores full marks at 60 seconds or less and zero at 240 seconds or more. A score of 85 or above is described as well-preserved clock concept and visuospatial construction, 60 to 84 as generally good with some error, and under 60 as a range where a retry is recommended.

The accompanying approximate Shulman grade (1 to 5) transfers the paper scoring scheme onto on-screen measurements. Placement within 12 degrees, zero order errors and both hands within 15 degrees gives 5 (perfect); placement within 20 degrees, up to 2 order errors and hands within 30 degrees gives 4 (minor visuospatial error); acceptable placement with hands far off gives 3 (error in time representation); placement within 35 degrees and up to 5 order errors gives 2; anything else is 1. The original 0 (no clock at all) cannot occur in this format.

The biggest variable in this test is not cognition but the mechanics. If tapping tiles into place and dragging hands is new to you, unfamiliarity alone enlarges the errors, and a small screen, unsteady hands or working without a stylus also inflate placement error. That is why a score under 60 first raises the possibility of unfamiliar controls and suggests trying once more.

Paper clock drawing starts with drawing the circle, whereas here the face is provided, and choosing tiles replaces handwriting numbers, so the task is easier in some respects and harder in others than the original. The result should therefore not be equated with a clock drawing score obtained in a clinic. Eyesight, hand tremor and musculoskeletal problems also feed into the result, so take them into account.

This is a screening-style self-check that does not diagnose dementia. However, if you repeatedly score under 60 or receive an approximate Shulman grade of 2 or below even after getting used to the controls, and you also notice recent memory decline, trouble finding your way or confusion about time, do not put off a comprehensive cognitive evaluation at a neurology or psychiatry clinic. Changes observed by family members are important information too.