"Indifference of the indicator"

Over 100 years ago, Charles Spearman made discoveries about human intelligence. One is that the general factor of intelligence (g-factor) conforms to the principle of the "indifference of the indicator," meaning that regardless of what test of intelligence you use, as long as the intelligence test is difficult and long enough, you can reliably measure a person's intelligence.

A new study suggests the same principle applies to human malignancy. The General Dark Factor of Personality (D-factor) conforms to the principle of "indifference of the indicator."