oped for determining the separate factors that define the structure of intellect (Carroll, 1993).
At the core of this approach to studying the mind is the concept that individuals differ in their mental capacities and that these differences define stable mental traits—aspects of knowledge, skill, and intellectual competence—that can be measured. It is presumed that different individuals possess these traits in differing amounts, as measured by their performance on sample tasks that make up a test. Specific traits or mental abilities are inferred when the pattern of scores shows consistent relationships across different situations.
The differential perspective was developed largely to assess aspects of intelligence or cognitive ability that were separate from the processes and content of academic learning. However, the methods used in devising aptitude tests and ranking individuals were adopted directly in the design of “standardized” academic achievement tests that were initially developed during the first half of the century. In fact, the logic of measurement was quite compatible with assumptions about knowing and learning that existed within the behaviorist perspective that came to dominate much of research and theory on learning during the middle of the century.
Behaviorist theories became popular during the 1930s (e.g., Hull, 1943; Skinner, 1938), about the same time that theories of individual differences in intellectual abilities and the mental testing movement were maturing. In some ways the two perspectives are complementary. In the behaviorist view, knowledge is the organized accumulation of stimulus-response associations that serve as the components of skills. Learning is the process by which one acquires those associations and skills (Thorndike, 1931). People learn by acquiring simple components of a skill, then acquiring more complicated units that combine or differentiate the simpler ones. Stimulus-response associations can be strengthened by reinforcement or weakened by inattention. When people are motivated by rewards, punishments, or other (mainly extrinsic) factors, they attend to relevant aspects of a situation, and this favors the formation of new associations and skills.
A rich and detailed body of research and theory on learning and performance has arisen within the behaviorist perspective, including important work on the strengthening of stimulus-response associations as a consequence of reinforcement or feedback. Many behavioral laws and principles that apply to human learning and performance are derived from work within this perspective. In fact, many of the elements of current cognitive theories of knowledge and skill acquisition are more elaborate versions of stimulusresponse associative theory. Missing from this perspective, however, is any