W

wavelength A measure of the physical distance between the crest of one light wave and the crest of the next. 4

Weber’s law Formulated by Gustav Fechner, a law stating that the amount by which a stimulus must be increased to produce a “just noticeable difference” in sensation is always a constant proportion of the initial stimulus intensity. 4

Wechsler scales The Wechsler Adult Intelligence Scale (WAIS), the Wechsler Intelligence Scale for Children (WISC), and the Wechsler Preschool and Primary Scale of Intelligence (WPPSI). Along with the Stanford-Binet, these are the most frequently used individual intelligence tests. They differ from the Stanford-Binet in several ways, primarily in yielding not a single IQ score but separate scores for each subtest. 14