Intelligence and Aptitude
This domain combines theories of intelligence, the psychometric formula for IQ, and the distinction between aptitude and achievement. Numerical questions on mental age and IQ are common, so practise the arithmetic until it is automatic.
Theories
- Spearman: general factor g plus specific factors s.
- Thurstone: seven primary mental abilities.
- Guilford: structure of intellect - operations × contents × products.
- Gardner: multiple intelligences - linguistic, logical-mathematical, spatial, musical, bodily-kinaesthetic, interpersonal, intrapersonal, naturalistic (existential added later).
- Sternberg: triarchic - analytical, creative, practical.
- Cattell–Horn: fluid intelligence declines with age; crystallised grows with experience.
- PASS model (Das, Naglieri, Kirby): Planning, Attention, Simultaneous, Successive - an Indian contribution.
Measurement
- Binet–Simon led to the Stanford–Binet; Stern's formula: IQ = (MA / CA) × 100.
- Wechsler: deviation IQ, mean 100, SD 15, verbal and performance scales.
- Indian and adapted tests: Bhatia's battery, Raven's Progressive Matrices (relatively culture-fair), Cattell's Culture Fair tests.
- Normal curve: about 68% score between 85 and 115; about 95% between 70 and 130.
Aptitude
- Aptitude is potential to acquire a skill with training; achievement is what has already been learned; interest is preference.
- Tests such as the DAT and GATB are used in selection and guidance; their predictions are probabilistic, not certain.
Worked example
A 10-year-old earns a mental age of 12. IQ = (12 / 10) × 100 = 120, above average and in the superior band, because mental age exceeds chronological age. Caution: one score summarises performance on one test on one day, not the whole person.
Traps
- IQ 100 is average, not perfect or maximum.
- Gardner's intelligences are not measured by a single IQ score.
- Aptitude predicts; achievement reports what is already learned.