Born First, Born Smarter

1
Born First, Born Smarter?

• Zajonc, R.B., Markus, G.B. (1975) Birth order
  and intellectual development. Psychological
  Review, 82 74-88

2
Studies have shown that first born children tend
to be

• More verbally articulate
• Less impulsive
• More active
• Better performers in school
• More likely to go to college
• Tend to have a greater need to achieve
• Score higher on tests of intelligence aptitude

3
Why?

• Genetic composition may change with birth order
• Due to age of mother
• Chemical alterations caused by previous births

4
However, social scientists have rejected these
nature explanations in favor of nurture,
environmental based theories

• Environment can have a strong influence on
  intellectual capacities and abilities

5
Birth order is an environmental factor present in
the development of all children

• The first-born child will usually experience a
  completely different environment (usually
  consisting of two parents) than the second-born
  child (consisting of two parents and one child)
• The resulting developmental situation for the
  second child is considerably different

6
Robert Zajonc and Gregory Markus

• Confluence Theory
• Developed a theory explaining the relationship
  between birth order and intelligence
• It was unique in that their theory was applied to
  other researchers data

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Theoretical Propositions

• Average intellectual climate
• An average of the combined intellectual
  influences of the family members
• Each parent is 100 points
• Infants start out with 0 points
• 5 intellectual points are added per year

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Methods and Results

• Used a hypothetical family with ten children

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Methods and Results
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Methods and Results

• Their hypothesis was mostly supported

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Exceptions

• The only-child effect
• The last-child effect

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Discussion

• The effect of gaps
• The contributions of older siblings
• Intellectual climate raises after the fifth child
• The last child effect

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Discussion

• Parents dilemma
• Intellectual climate is not the only determinant
  of intellectual ability
• ?

14
Criticisms

• Statistical Significance?
• Measured within instead of across families
• Low-IQ parents have been making large families
• Large families do not make low-IQ children
• Resource-dilution theory

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By the Way

• Dont be depressed . . .
• Downsides to being first
• Advantages to being later

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Class Discussion

• Would you use this study to plan your family?
• Does this apply to your family or other families
  that you know?
• What are your feelings on the nature-nurture
  interaction and intelligence?