1. CLASS 12

2. Intelligence Tests (IQ)

3. HISTORY 1. Binet’s Mental age (MA) 2. Stern’s Ratio formula for IQ
3. Deviation formula for IQ

4. Ratio formula
IQ = (MA/CA) x 100
MA=mental age
CA=chronological age

5. PROS AND CONS
Can compare across ages
Average=100
Problem

6. Example: Martha’s two sons
Dieter
Wolfie
Mental age
Chronological age IQ

7. example
Dieter
Wolfie
Mental age 7
Chronological age 5 IQ

8. example
Dieter
Wolfie
Mental age 7
Chronological age 5 IQ
140

9. example
Dieter
Wolfie
Mental age 7 6
Chronological age 5 IQ
140

10. example
Dieter
Wolfie
Mental age 7 6
Chronological age 5 IQ
140
100

11. Deviation formula Separate calculations for each age group
Set average = 100 for each group
Similar to using percentiles to compare students from different schools

12. PROS AND CONS Can compare across ages
Drawback – hides real differences

13. Bell Curve of IQ scores
< 9.4>

14. Mental retardation -70 or below -morons, imbeciles, and idiots
Giftedness
-130 or above

15. Validity of intelligence tests
Some famous tests:
-Stanford-Binet
-WISC
-WAIS
Generally successful: reliable and valid

16. Representative views:
Nature vs. Nurture
Representative views:
1. Mostly genetic:
Rushton, Eysenck, Jensen
2. All environment: Kamin
3. It’s 50-50: Scarr

17. Nature: Genetic Influences on IQ
- estimating heritability
1. Twin studies
2. Adoption studies

18. Identical Twins

19. Fraternal Twins

20. Logic of Twin Studies Do twins match up on a trait?
e.g. same eye color; intelligence
Usually identical twins match up better than fraternal twins. Why?
- identical twins share 100% of genes
- fraternal twins share 50% of genes
Use heritability formula (see textbook)

21. Sample heritability values
Eye color (100%)
Shoe color (8%)
Personality (40-60%)
Intelligence (50-80%)

22. Nurture: Environmental influences
Twin & Adoption studies also confirm impact of nurture
1. Group differences
2. Economic differences
3. Test bias

23. Culture-Free Tests -- designed to avoid language handicap
-- e.g., Raven’s matrices

26. More examples
See course web site