CLASS 14
Chapter 10
Human Development
Babies are cute
But later on…..……not so much
Three types of development
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Physical

Intellectual
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Social
Developing physically – normal child
Developing intellectually
Jean Piaget
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1896 – 1980
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Stage theory of cognitive development
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Four stages
-highly influential
-the mind unfolds with age
-emphasis on normal child
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Critique:
Little concern with environmental
effects
Observations of his own children
Underestimated abilities
Learning theories
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It’s all conditioning
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Gradual accumulation of S-R links
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No systematic stages
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Allows for differences
Family Constellation Effects
The arrangement of siblings:
e.g. birth order, family size, etc.
examples
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FAMILY A
FAMILY B
FAMILY C
Charles
Anne
Andrew
Edward
Alec 9
Daniel 7
Bill 4
Stephen 1
Pierre 15
17
15
5
1
Intellectual Achievement (IA)
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Includes grades, IQ, SAT, etc.
Zajonc (1979) collected large datasets on
families
Noticed effects of arrangement of
children:
eg birth order, family size, spacing, etc.
Six facts to be explained:
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1.
2.
3.
4.
5.
6.
IA declines with birth order
IA declines with greater family size.
IA declines with close-spacing
IA declines with multiple births
IA declines with only children
Last-borns show extra decline
Confluence Model:
Two propositions
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Proposition I.
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Mental stimulation of the child leads
to permanent improvement in ability
Explains facts 1-4
Zajonc says do the math:
- Estimate degree of mental
stimulation by average level of
mental age in family
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Childless couple:

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At birth of first-born:
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MS = (16+16)/2 = 16
MS = (16+16+0)/3 = 10.67
At birth of second born:
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MS = (16+16+2+0)/4 = 8.5
How to explain facts 5 & 6 ?
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Proposition II: The Teaching Effect
Last-borns don’t get to teach
 Teaching aids the teacher
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Consistent with research on memory,
peer-tutoring, etc.
Followup study by
Paulhus and Shaffer
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data on 20, 000 students
SAT scores
 Number of younger siblings
 Number of older siblings
 gender
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Results
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Boys
more older sibs reduces SAT
 more younger sibs reduces SAT
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Girls
more older sibs reduces SAT
 More younger sibs increases SAT
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Interpretation
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Teaching effect is more than all-or-none
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But only works for girls
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Sex roles must have an impact
Kristensen & Bjerkedal (2007)
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All Norwegian males have their IQ tested
by the military
N = 250, 000
First borns > second borns
Confirmed effect of birth order
Actually effect of raising order
Summary
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Confluence Model is parsimonious
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Explains 6 facts with two propositions
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Entirely environmental
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Effects are small -- but interesting