The two-level theory of mental abilities posits two broad classes of ability: level I (learning and memory) and level II (the "g" factor of intelligence tests, reasoning, abstraction, and problem solving). Levels I and II are hypothesized to interact with SES and/or race such that: (l) SES differences are greater for level II than for I,…

An entire elementary school system with 60 percent white and 40 percent black children was given several ability tests administered by 12 white and eight black examiners. The tests measured verbal and nonverbal IQ, perceptual-motor cognitive development, "speed and persistence" under neutral and motivating instructions, listening attention, and…