Wechsler–Bellevue Intelligence Scale

The Wechsler-Bellevue Intelligence Scale, developed by psychologist David Wechsler in 1939, was a significant advancement in measuring adult intelligence. Unlike previous methods that relied on a "mental age," Wechsler defined normal intelligence as the average score for an age group, typically represented by 100 on a standard scale. This test became widely used in the United States and was later revised and adapted for children and younger age groups.1

The scale's structure, which includes verbal and performance subtests, influenced later intelligence tests like the Wechsler Adult Intelligence Scale (WAIS) and the Wechsler Intelligence Scale for Children (WISC). These tests provide an overall IQ score, as well as scores for different cognitive abilities.2