Born First, Born Smarter? Zajonc, R.B., & Markus, G.B. (1975) Birth order and intellectual development. Psychological Review,

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

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

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

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

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

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

Methods and Results Used a hypothetical family with ten children

Methods and Results

Their hypothesis was mostly supported

Exceptions The only-child effect The last-child effect

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

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

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

By the Way Don’t be depressed... –Downsides to being first –Advantages to being later

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?