Class 28: Intelligence: Definitions and Notes on Measuring IQ (Outline)

What does it mean to say that someone is "intelligent"? What are the ways in which intelligence is demonstrated? Can "intelligence" be measured? "

Some Definitions and Models of Intelligence

There are multiple ways in which psychologists have defined or constructed models of how to understand human intelligence,

Charles Spearman (1863-1945) & the Two-Factor Theory *the general factor, or simply "g"* *expanded to include a limited number of specific abilities "s" (verbal, spatial, numerical, mechanical)*
David Wechsler (1943) “Intelligence is the aggregate or global capacity of the individual *to act purposefully, to think rationally, and to deal eﬀectively with his environment*” (emphasis added).
Anne Anastasi (1992) “Intelligence is not a single, unitary ability, but rather composite of several functions. The term denotes that combination of abilities required for survival and advancement within a particular culture.” (emphasis added) Consider how an Aboriginal person in Australia might be assessed compared to an Australian of European descent? How might the environment and cultural background of each sort of person affect how well they would do on an intelligence test? • YouTube Video: Intelligence and Culture
Raymond Cattell (1905-1998), John Horn (1928-2006) Fluid vs. Crystallized Intelligence Model
C-H-C Theory of Intelligence (Cattell-Horn-Carroll) John B. Carroll (UNC Chapel Hill) publishes *Human Cognitive Abilities: A Survey of Factor Analytic Studies (1993). 400 data sets of cognitive ability scores re-analyzed "Three Stratum Model of Intelligence"* Stratum I -- *the speciﬁc or narrow level* Stratum II -- *the broad level;* eight factors, including ﬂuid intelligence, crystallized intelligence, general memory and learning, broad visual perception, broad auditory perception, broad retrieval ability, broad cognitive speediness, and processing speed Stratum III -- *the general level;* general intellectual ability, similar to "g"

A Brief History of Intelligence Testing

A. Binet-Simon Scale of Intelligence (1905) Alfred Binet & Théodore Simon How to identify children needing alternative schooling Created test of 30 items of increasing difficulty Standardized against a group of 50 average students in 5 age groups Mental Age (MA): the level a testee can reach successfully as compared to age norms Chronological Age (CA): actual age of a testee Intelligence quotient (IQ) calculated as a simple problem in division MA/CA 8-year-old child who has a mental age of 8: 8/8 = 1 8-year-old child who has a mental age of 10: 10/8 = 1.25 8-year-old child who has a mental age of 6: 6/8 =0.75
B. Stanford-Binet Intelligence Scale (1916) Stanford University cognitive psychologist Lewis Terman Adaptation of the Simon-Binet Scale William Stern, German psychologist, suggested IQ be calculated as (MA/CA) x 100 to get rid of the decimals 8-year-old child who has a mental age of 8: (8/8)x100 = IQ of 100 8-year-old child who has a mental age of 10: 10/8 = IQ of 125 8-year-old child who has a mental age of 6: 6/8 = IQ of 75 Terman used the Stanford-Binet to identify very intelligent children in California for a longitudinal study of giftedness Terman is controversial today for his endorsement of eugenics and frank racism.
C. Wechsler Adult Intelligence Scale (WAIS, 1955) David Wechsler, Chief Psychologist at Bellevue Psychiatric Hospital, NYC Dissatisfied with Stanford-Binet: based on children, not adults and "mental age" made little sense with adults Authored the first scale for use with adults in 1939 which eventually became the WAIS Innovations: Deviation IQ and Multiple Scales of Intelligence WISC (Wechsler Intelligence Scale for Children): ages 5 to 16
Deviation IQ: use of normal curve with the average set at 100 with a standard deviation of 15
Multiple Scales of Intelligence WAIS: Full-Scale IQ (FSIQ), Verbal IQ (VIQ) & Performance IQ (PIQ) WAIS-IV (2008): FSIQ plus Verbal Comprehension, Perceptual Reasoning, Working Memory, and Processing Speed. A 5th edition, the WAIS-V, was published late in 2024. WISC: Full-Scale IQ (FSIQ), Verbal IQ (VIQ) & Performance IQ (PIQ) WISC-V (2014): FSIQ plus Verbal Comprehension, Visual Spatial Ability, Fluid Reasoning, Working Memory, and Processing Speed.