Theories of Intelligence
Lecture, Chapters 9 & 10
Assessment of Intelligence
In order to measure intelligence, we must first be able to define it. Unfortunately, of all the major concepts in the field of testing, intelligence is among the most elusive.
In order to make an assessment of intelligence, we must create some form of observable translation of an abstract construct
•Sir Francis Galton – first cousin of Charles Darwin
•Applied Darwin’s concepts of survival of the fittest and individual differences to humans.
•Postulated the existence of a “General Mental Ability”
•Based upon speed and refinement of sensory responses
•Includes measures of sensory discrimination, perceptual speed, and motor coordination
•Later discovered that these scores were not highly correlated with each other or with measures of common sense or other intuitively reasonable measures of intelligence
•Began theory development in the 1920s.
•Cognitive stages of development:
Sensorimotor (0-2) – reflexes and sensorimotor skills
Preoperational (2-7) – pretending and the use of symbols
Concrete operational (7-11) – logical, problem-solving operations
Formal operational (12+) – applying logic to abstract ideas, forming hypothetical thinking
•Began theory development in the 1930s.
•Stages of psychosocial development
Infancy (0-2) – trust vs. mistrust
Early childhood (2-3) – autonomy vs. shame/doubt
Play age (3-5) – initiative vs. guilt
School age (6-12) – industry vs. inferiority
Adolescence (13-18) – identity vs. identity confusion
Young adulthood (19-30) – intimacy vs. isolation
Adulthood (31-60) – generativity vs. stagnation
Old age (61+) – integrity vs. despair
Binet’s definition of Intelligence
According to Binet, intelligence is the capacity to…
•Find and maintain a definite direction or purpose
•Make necessary adaptations to achieve a purpose
•Engage in self-criticism so that necessary adjustments in strategy can be made.
Binet’s Principles of Test Construction
•Age Differentiation – the fact that with increasing age, children develop their abilities; older children thus have greater abilities than do younger children.
•General Mental Ability – initially developed by Spearman, the idea that a single general factor (g) underlies all intelligence
Fluid (gf) intelligence is the ability to reason, think, and acquire new knowledge.
Crystallized (gc) intelligence is intelligence which has already been acquired.
Binet’s Units of Measure
•Mental age is the unit of measure based on a participant’s performance compared with the average performance in a specified age group.
•Intelligence quotient (IQ) is the ratio of a participant’s mental age to chronological age, multiplied by 100 (ratio level of measurement).
•Deviation IQ – is the standardization of IQ scores among various age groups, with all groups having a mean of 100 and a standard deviation of 15.
2003 edition of the Binet Scale
•Age range spans 2 to 85+.
•Norms were based on a sample of 4800, stratified by gender, ethnicity, region, and education according to the 2001 census data.
•3000 additional individuals were included, encompassing gifted, mentally retarded, ADHD, and those with speech, language, and hearing problems.
•Reliability coefficients for overall IQ are .97 or .98 for all 23 age ranges.
•Reliability coefficients for nonverbal IQ subscale is .95 and for verbal is .96.
Wechsler Intelligence Scales: WAIS-III, WISC-IV, and WPPSI-III
•Motivated by the effort to construct a more appropriate intelligence scale that that of the 1937 Binet scale.
•Used a point scale, in which a specific number of credits or points is assigned to each item.
•Incorporated performance scales, which measure nonverbal intelligence, requiring participant to do something other than merely answer questions.
Content – 7 Verbal Subtests
vocabulary – level
similarities – abstract thinking
arithmetic – concentration
digit span – immediate memory, anxiety
information – range of knowledge
comprehension – judgment
letter- number sequencing – freedom from distractibility
Content – 7 Performance Subtests
•Picture completion – alertness to details
•Digit symbol-coding – visual-motor skills
•Block design – nonverbal reasoning
•Matrix reasoning – inductive reasoning
•Picture arrangement – planning ability
•Object assembly – analysis of part-whole relationships
•Symbol search – information-processing speed
Scoring of the WAIS-III
•The WAIS-III provides a verbal IQ, performance IQ, and full-scale IQ.
•Verbal and Performance IQ’s:
Convert raw scores of each subtest to a scaled score (age-corrected standard score of 10 with standard deviation of 15)
Adding the subtest scores within that group
Converting to IQ’s using a table (mean=100; std=15)
Add scaled scores for both groups.
Convert to IQ using table of norms
Measurements of Error
•WAIS-III has excellent reliability for verbal, performance, and full-scale IQ’s but varies with individual subtests.
•WAIS-III has high correlation with prior test, WAIS-R, providing evidence for validity.
WISC-IV & WPPSI-III
•WISC-IV is a revised form of the WAIS-III for the purpose of measuring children’s intelligence.
•WPPSI-III is a revised form of the WISC-IV for the purpose of measuring youngest children’s intelligence (ages 2.5 years to 7 years, 3 months).