Cognitive ability (CA) or intelligence testing has been hailed "as the most practical contribution made to humanity by all of psychology" (Roberts, Markham, Matthews, & Zeidner, in press). Spearman's paper from 100 years ago, "General Intelligence, Objectively Determined and Measured," was the initial turning point in directing attention to the construct of CA. Fascinating, detailed historical reviews of CA testing may be found in Carroll (1993) and Roberts et al.
