Intelligence, dual coding theory, and the brain

The distinction between verbal and nonverbal cognitive abilities has been a defining feature of psychometric theories of intelligence for the past century. Despite their popularity, however, these theories have not included functional connections between verbal and nonverbal systems that are necessary if they are to explain performance in intellectual tasks involving interactions between language and nonverbal knowledge. This functional gap limits the capacity of psychometric theories to explain and predict fundamental aspects of individual differences in cognitive abilities that have long been studied experimentally. This article summarizes the history, nature, and possible causes of the problem, and then concludes with a neuroscientifically-enhanced, multimodal dual coding approach to intelligence that focuses on the synergistic interactivity of verbal and nonverbal systems.