Obviously I can’t devote an article to every Human Benchmark test so I’m limiting myself to the best ones. One of the best is number memory.

Digit Span is measured by the largest number of digits a person can repeat without error on two consecutive trials after the digits have been presented at the rate of one digit per second, either aurally or visually. Recalling the digits in the order of presentation is termed forward digit span (FDS); recalling the digits in the reverse order of presentation is termed backward digit span (BDS). Digit Span is part of the Stanford Binet and of the Wechsler scales. Digit Span increases with age, from early childhood to maturity. In adults the average FDS is about 7; average BDS is about 5. I have found that Berkley students, whose average IQ is about 120; have an average FDS of between 8 and 9 digits.

The g Factor by Arthur Jensen, page 262

It should be noted that the Human Benchmark version of digit span does NOT include the Backwards version and shows all the digits at once for several seconds, not each one at a rate of one per second, and it only has one trial per level so there’s no room for error. For this reason I suggest taking your best score on your first two attempts.

So important is this test that it is one of the 10 subtests handpicked by David Wechsler himself for his original Wechsler scale, published in the 1930s.

Perhaps no test has been so widely used in scales of intelligence as that of Memory Span for Digits. It forms part of the original Binet Scale and all the revisions of it. It has been used for a long time by psychiatrists as a test of retentiveness and by psychologists in all sorts of psychological studies. Its popularity is based on the fact that it is easy to administer, easy to score, and specific as to the type of ability it measures. Nevertheless, as a test of general intelligence it is among the poorest. Memory span, whether for digits forward or backward, generally correlates poorly with other tests of intelligence. The ability involved contains little of g, and, as Spearman has shown, is more or less independent of this general factor.

The Measurement and Appraisal of ADULT INTELLIGENCE 5th edition, David Wechsler, 1958, page 70 to 71

On page 221 of The g Factor, Jensen notes that FDS and BDS have g loadings of about 0.30 and 0.60 respectively.

Wechsler goes on to explain that despite being a poor measure of intelligence overall, he included it in part because in his eyes, it’s a great measure of low intelligence: “Except in cases of special defects or organic disease, adults who cannot retain 5 digits forward and 3 backward will be found, in 9 cases out of 10, to be feeble-minded or mentally disturbed.”

The other reason he included it is he viewed it as an excellent measure of dementia.

I’m not convinced the test is better at low levels than at high levels. For example, Charles Krauthhammer towered with a spectacular of BDS of 12, and his genius is validated by the enormous influence he had over U.S. foreign policy.

In the below poll your level corresponds to the highest number of digits you correctly remembered on at least one of your first two attempts: