The cognitive test on which Donald Trump received a perfect score is considered a good screening tool for mental decline in an otherwise healthy person, medical experts said.

The US president asked to be administered a mental test and was given the Montreal Cognitive Assessment (MoCA) as part of a medical exam by Dr. Ronny Jackson, the White House physician, who on Tuesday said he had absolutely no concerns about Mr Trump's neurological function. The president scored 30 out of 30.

Cognitive testing looks for signs of mild cognitive impairment and/or Alzheimer’s disease. It focuses on cognitive functions including memory, attention, language, abstraction, delayed recall and orientation.

Sample questions on the Montreal test include repeating a set of numbers in order both forwards and backwards and remembering a list of common words.

Test takers are asked to identify animals, and draw a clock face, putting in all of the numbers and setting the clock hands to a specific time. It takes about 10 minutes to administer.

One memory test involves memorising the words 'face', 'velvet', 'church', 'daisy', 'red' and recalling them after five minutes.

Another test challenges participants to name as many words as they can in one minute that begin with the letter F.