Theories of Intelligence

Abstract

Some of the most robust phenomena in behavioral science relate to individual differences in intellectual functioning. This chapter provides an overview of historical and contemporary theories of human intelligence, especially highlighting how theoretical and psychometric developments have influenced clinical intellectual assessment. Definitions of intelligence are presented, highlighting the core debate between views of intelligence as a unitary, overarching capacity versus a composite of independent, lower-order abilities. The chapter then outlines the historical progression of theories in this area, beginning with early figures who established basic principles of intelligence research and intellectual assessment and discovered the positive manifold phenomenon and psychometric g. Subsequent work during the twentieth century was primarily directed at clarifying the status and significance of psychometric g, the key features of broad cognitive abilities, and the relation of these lower-order abilities to one another and to overall intellectual ability. These studies culminated in a group of hierarchical models that consolidated and refined the insights of the previous century and are well-represented in current intelligence batteries. Most recently, an alternative group of theories has emerged, which aims to reconcile classic psychometric findings on intelligence with a more process-oriented view informed by cognitive psychology, systems theory, and neuroscience. The chapter ends with a discussion of the connections between specific theories of intelligence and assessment batteries used to clinically assess intelligence. A hypothetical case example is presented to demonstrate how theory has shaped modern test batteries and their clinical interpretations.