Who proposed a hierarchical model of intelligence with g at the top and two second-order factors: Verbal/Educational Aptitudes and Spatial/Mechanical/Practical Aptitudes?

• A. McGrew
• B. Piaget
• C. Vernon
• D. Cattell

Answer: (C)

Intelligence can be viewed as a hierarchy where a general factor (g) sits at the top and influences broader ability domains. Vernon proposed a specific two-factor second layer under g: Verbal/Educational Aptitudes and Spatial/Mechanical/Practical Aptitudes. Verbal/Educational captures language-based skills, vocabulary, reading, and knowledge, while Spatial/Mechanical/Practical covers nonverbal reasoning, spatial visualization, and hands-on problem solving. This organization explains why certain tests cluster together—verbal tasks align with educational outcomes, and spatial/mechanical tasks form a distinct but related cluster that still ties back to g. Among the theorists listed, Vernon is the one who formulated this exact two-factor second-order structure. (Piaget focused on developmental stages; Cattell emphasized fluid and crystallized intelligence; McGrew contributes to broader CHC theory, not this two-factor model.)