When someone can't draw a clock face it means that the person has issues with visuospatial skills, problems with memory, problems with their executive function or even cognitive impairment.
The CDT test also known as the clock drawing test is a quick and simple assessment test that is used for screening people with cognitive issues and most particularly in the context of dementia.
The clock drawing test helps to assess a persons ability to organize, plan and execute a task, which are also all part of a persons executive function.
Having difficulties with hand positioning, number placement or even drawing of a simple circle can suggest a person has problems in these areas.
Drawing of a clock also requires the ability to understand spatial relationships and to also translate a visual concept onto paper.
And having impairments in visuospatial skills can also result in errors in number placement, hand positioning or even the overall shape of the clock.
Remembering of the numbers of a clock face, their order and how to represent time using hands are all memory related tasks.
Having difficulty with these aspects of the clock drawing test can indicate that a person has problems with memory, including both long term memory and short term memory.
The clock drawing test also assesses indirectly a persons attention, abstract thinking and language comprehension.
The clock drawing test is also a common tool in the use of screening for dementia, including Alzheimer's disease as it can reveal subtle cognitive changes.
The clock drawing test is not a definitive test or diagnoses but it can help identify people that may require further tests and evaluation.
Having a single instance of difficulty in drawing a clock does not automatically mean that someone has dementia.