The idea that there’s a single scalar value that measures anything like “general intelligence” (“g”), commonly known as “IQ” or “intelligence quotient”, has been pretty much blown out of the water by this comprehensive study by the University of Western Ontario’s Brain and Mind Institute.
Our attempt to answer [the question of how to quantify relative intelligence] dates back more than five years, when Roger [Highfield] encountered work that I had conducted with Adrian [Hampshire] at the Medical Research Council in Cambridge on a reliable way to carry out cognitive tests online so we could monitor rehabilitation after brain injury, the effect of smart drug trials and so on.
Roger wondered if we could use this test to carry out a mass intelligence test. Drawing on earlier data from brain scans, Adrian and I came up with a series of tests which we knew would trigger activity in as much of the brain’s anatomy as possible, combining the fewest tasks to cover the broadest range of cognitive skills.