Cognitive abilities, like all psychological traits, are invisible. To create measures of intelligence, researchers have to choose observable qualities that signal the presence of underlying aptitudes. In other words, since we cannot actually see a cognitive ability, we have to find some outward sign of its existence. It is like detecting the wind by observing wheat bending in a field. Although we cannot physically see a person’s intelligence, we can measure its presence and strength by observing activities that require it.
This task is complicated by the fact that there is little agreement about what specific activities denote intelligence. In fact, there still exists no universally accepted ...
