Intelligence: Measurement, Theories, and Development Across the Life Span

Descriptors for the WAIS-IV

Overview of the WAIS-IV

The Wechsler Adult Intelligence Scale – Fourth Edition (WAIS-IV) is a widely used test for measuring adult intelligence. It provides a standardized score (IQ) based on performance across several cognitive domains.

• 130 and above: Very superior

• 120–129: Superior

• 110–119: High average

• 90–109: Average

• 80–89: Low average

• 70–79: Borderline

• 69 and below: Extremely low

Example: An individual scoring 115 on the WAIS-IV would be classified as having "High average" intelligence.

Intelligence Quotient (IQ)

Definition and Calculation

Intelligence Quotient (IQ) is a standardized score used to evaluate intelligence relative to age-matched peers. It is calculated using the following formula:

• Formula:

$IQ = \frac{\text{Mental age}}{\text{Chronological age}} \times 100$

• Mental age: The age at which an individual performs intellectually.

• Chronological age: The actual age of the individual.

Example: If a 10-year-old child performs at the level of a 13-year-old, their IQ would be $\frac{13}{10} \times 100 = 130$.

Spearman's g

General Intelligence Theory

Spearman's g refers to the general intelligence factor proposed by Charles Spearman. It represents the underlying ability to learn, reason, and solve problems across a variety of domains.

• General ability: The capacity to acquire and retain information from experience.

• Argument: Those who excel at one type of intellectual task are likely to excel at others.

Example: A person who performs well in verbal reasoning may also show high performance in mathematical reasoning, supporting the existence of a general intelligence factor.

Concept of Intelligence

Theories of Multiple Intelligence

Modern theories of intelligence propose that intelligence is not a single entity but consists of multiple abilities. These include:

• Breaking intelligence down into multiple abilities: For example, Howard Gardner's theory of multiple intelligences includes linguistic, logical-mathematical, spatial, musical, bodily-kinesthetic, interpersonal, intrapersonal, and naturalistic intelligences.

Example: An individual may excel in musical intelligence but have average logical-mathematical intelligence.

Fluid and Crystallized Intellectual Development Across the Life Span

Fluid vs. Crystallized Intelligence

Intellectual abilities change across the life span, and psychologists distinguish between two major types of intelligence:

• Fluid Intelligence: The ability to reason abstractly, solve novel problems, and adapt to new situations. It tends to decline from middle adulthood onward.

• Crystallized Intelligence: Accumulated knowledge and verbal skills, which increase with age and experience.

Example: Solving a new type of puzzle relies on fluid intelligence, while using vocabulary knowledge relies on crystallized intelligence.

Developmental Trends

• Fluid intelligence peaks in early adulthood and gradually declines in later life.

• Crystallized intelligence continues to grow or remains stable into late adulthood.

• Longitudinal studies show that intellectual abilities are less likely to decline and may even improve in middle adulthood compared to cross-sectional studies.

Seattle Longitudinal Study (Schaie)

• Studied over 500 adult subjects.

• Findings: Intellectual abilities are less likely to decline and may improve in middle adulthood when assessed longitudinally.

• Parent generation cognitive decline: 60–67 years.

• Intergenerational stability or modest increase in cognitive functioning: 60–67 years.

Mechanics and Pragmatics of Intelligence

• Cognitive mechanics: Hardware of the mind (biology of the brain), speed and accuracy of processes involved in sensory input, more biologically influenced, relates to fluid intelligence.

• Cognitive pragmatics: Culture-based knowledge, reading and writing skills, language comprehension, professional skills, relates to crystallized intelligence.

Table: Comparison of Fluid and Crystallized Intelligence

Type of Intelligence	Description	Developmental Trend	Example
Fluid Intelligence	Ability to reason, solve novel problems, adapt to new situations	Peaks in early adulthood, declines in later life	Solving unfamiliar puzzles
Crystallized Intelligence	Accumulated knowledge, verbal skills, experience-based	Increases or remains stable with age	Vocabulary tests, general knowledge

Additional info: The notes infer the inclusion of Gardner's multiple intelligences and the distinction between cognitive mechanics and pragmatics for a more complete academic context.