In this chapter you have learned about the history of intelligence assessment. You have seen how the conceptualization and measurement of intelligence developed over time. Additionally, you have learned about the complex relationship of intelligence assessment and eugenics.

The history of intelligence assessment can be traced back to early attempts such as phrenology, which linked skull features to mental traits. Francis Galton and James McKeen Cattell contributed to the field’s development, though Cattell’s efforts fell short in correlating with achievement. A pivotal shift occurred with the Binet-Simon Intelligence Scale, introducing the assessment of complex abilities and standardized administration. Lewis Terman later refined this scale into the Stanford-Binet version, incorporating IQ and treating intelligence as a unified concept.

The significance of intelligence testing became evident during World War I when Walter Dill Scott and Robert M. Yerkes demonstrated its value in personnel selection for the U.S. Army. However, the post-war period revealed limitations in the Stanford-Binet Test, including bias and inadequate standardization for adults.

Addressing these shortcomings, psychologist David Wechsler recognized the need for a new adult intelligence test. He meticulously designed the Wechsler Adult Intelligence Scale (WAIS), amalgamating existing tests into an innovative, organized battery. The WAIS proved immensely successful, becoming the most widely used intelligence assessment tool to this day.

You also learned that, despite considerable effort, there is no consensus on the definition of intelligence. Throughout history, diverse viewpoints have emerged regarding the structure of intelligence. In this context, you’ve also discovered that the Cattell-Horn-Carroll Model of intelligence, which delineates Fluid and Crystallized Intelligence, stands out as a pivotal modern framework for understanding intelligence’s structure and hierarchy.

You discovered that most early intelligence authorities supported eugenics or belonged to eugenics-promoting groups. Furthermore, you recognize the potential misuse of intelligence test results to discriminate against particular individuals or groups of individuals.

To help you memorize important events, you can fill out this timeline.