Intelligence and Its Measurement – Comprehensive Bullet-Point Notes

"Intelligence" = long-standing folk concept; no single precise meaning
- Folk concepts flexibly shaped by social context (cf. “cool”)
Cross-cultural core: rapid learning, problem-solving
- Variant emphases: humility, obedience (some societies) vs. distinct virtues (others)
Scientific stance (Neisser et al., 1996): capacity to
- understand complex ideas
- adapt effectively
- learn from experience
- reason
- overcome obstacles via thought
Debate on exact definition persists (Thorndike symposium 1921, Sternberg & Detterman 1986)
- Strategy: mark boundaries rather than fixate on immutable definition

Galton: sensory discrimination ⇒ intelligence; small positive correlations confirmed but weak; pioneered heritability studies
Binet & Simon: complex mental operations; memory, judgment, abstraction; designed tests for school placement—not pure IQ measurement; introduced mental age concept
Wechsler: intelligence = “aggregate or global capacity … to act purposefully, think rationally, deal effectively”; stressed non-intellective factors (drive, persistence)
Piaget: intelligence as biological adaptation; four invariant developmental stages; interaction of maturation & environment
Thurstone: Primary Mental Abilities (7 PMAs) e.g., verbal meaning, perceptual speed
Cattell & Horn: $Gf$ (fluid) vs $Gc$ (crystallized); later added $Gv, Ga, Gq, Gs, G{rw}, G{sm}, G_{lr}$ (vulnerable vs maintained abilities)
Carroll: Three-Stratum Model—Stratum III $g$ , Stratum II broad abilities (~8), Stratum I narrow abilities; re-analysed 461 data sets
Gardner: Multiple Intelligences (7→9); interpersonal & intrapersonal inspire Emotional Intelligence (Mayer et al.)
CHC Theory: synthesis of Cattell-Horn & Carroll; widely adopted for modern tests; emphasizes broad/narrow abilities without forcing consensus on $g$

Statistical method to uncover latent variables (factors) behind observed correlations
- Exploratory FA: discovers factor structure
- Confirmatory FA: tests specified models via path diagrams
Illustrations: independent abilities vs hierarchical vs general factor (Figure 1)
Key ideas: factor loadings, simple structure, higher-order factors (e.g., $g$ as 3rd-order)

Luria’s simultaneous (holistic) vs successive (sequential) processing
PASS Model: Planning, Attention/Arousal, Simultaneous, Successive; interventions effective for LD

Ratio IQ: $\text{IQ}=\frac{\text{Mental Age}}{\text{Chronological Age}}\times100$ (obsolete)
Deviation IQ: standard score $\mu=100, \sigma=15$ (SB from 3rd ed., Wechsler scales)
Floor / Ceiling: lowest & highest item difficulty; Basal & Ceiling rules govern start/stop
Routing test: directs examinee to optimal item level (adaptive logic)
Teaching items / prompts: ensure understanding; not scored
Adaptive Testing: item difficulty contingent on prior response; increases efficiency, rapport, reduces fatigue
Extra-test behaviour: qualitative observations enrich interpretation

1905 Binet-Simon → 1916 Terman’s Stanford-Binet (introduced detailed manual, alternate items, IQ)
1937 Forms L & M; extended preschool/adult items
1960 (L-M) introduced deviation IQ
1972 3rd ed.; criticised norms
1986 SB-4: point-scale, Gf-Gc theory basis
2003 SB-5
- Ages 2–85+; 10 subtests (5 verbal, 5 non-verbal)
- Factors ↔ CHC: Fluid Reasoning, Knowledge, Quantitative Reasoning, Visual-Spatial, Working Memory
- Composite scores: Full Scale IQ, Verbal IQ, Non-verbal IQ, Abbreviated Battery IQ
- Norms: $N=4{,}800$ representative (2000 census)
- $\alpha$ .97–.98 FS IQ; strong validity vs SB-4 & Wechsler

Wechsler-Bellevue I (1939): 6 Verbal + 5 Performance subtests, point scale
WAIS series (1955, 1981-R, 1997-III, 2008-IV)
- WAIS-IV core vs supplemental; 4 index scores: Verbal Comprehension, Perceptual Reasoning, Working Memory, Processing Speed; composites: Full Scale IQ, General Ability Index (GAI), Cognitive Proficiency Index (CPI)
- Extended norms to 90 yrs 11 mo; improved floors (40) & ceilings (160), enlarged stimuli for older adults
Child versions: WISC (1949→V 2014), WPPSI (1967→IV 2012)
Short Forms / Screeners: WASI & WASI-II (2- or 4-subtest; 15–30 min)
- Utility for quick screening; reliability good but reduced clinical accuracy—scores labelled "Est"

WWI Army Alpha (literate) & Beta (non-literate); >1.7 million recruits
WWII AGCT; OSS developed selection batteries
Modern armed forces: Officer Qualifying Test, Airman Qualifying Exam, ASVAB
- 10 subtests; includes AFQT (4 subtests) for enlistment; predicts training & technical school success
School Ability Tests: Otis-Lennon, California Test of Mental Maturity, Kuhlmann-Anderson, Henmon-Nelson, CogAT
Pros/Cons of traditional group testing (Table 9-4): efficient & cheap vs less adaptive, limited qualitative data, potential misuse

Creativity facets: originality, fluency, flexibility, elaboration; measured by Torrance Tests, Remote Associates Test (RAT)
Convergent ( $\rightarrow$ single correct answer) vs Divergent thinking (multiple novel answers)
Cognitive styles: field-(in)dependence, reflection vs impulsivity, visualizer vs verbalizer

Tests inevitably culture-loaded; efforts at culture-free tests unsuccessful; non-verbal items still require culture-based reasoning styles
Culture-fair strategies (Table 9-5): pictorial items, pantomime instructions, power vs speed, familiar content
Culture-specific measures (e.g., BITCH) highlight street-wiseness but lack predictive validity
Bias review: item analysis, differential prediction, examiner behaviour, referral criteria

Average IQ gains ≈ $3$ points/decade in industrial nations; larger in developing areas (Kenya ++)
Mostly on fluid reasoning tasks ⇒ raises questions for heredity vs environment debates
Practical impact: older norms over-inflate IQ (eligibility for services, legal death-penalty cases)

Factor structure should mirror test’s definition (Spearman → single $g$ ; Guilford → multiple; Thorndike → $g$ + 3 clusters)
Tests evaluated via correlations with external criteria, factor loadings, hierarchical models, predictive studies

High-stakes use (education, disability, employment, military, legal) demands competent administration & interpretation
Intelligence intertwined with socioeconomic outcomes; group mean differences smaller than individual variability; interpret scores person-by-person
Emphasis on environmental interventions to enhance intellectual development