First Child to Arrive May Get a Smart Edge

First-born and only children enjoy an intellectual advantage over other children and younger siblings because they are exposed to more adult-level thought and speech, says University of Michigan psychologist Robert B. Zajonc.

He said a family’s intellectual atmosphere tends to decline as the family expands, and newer members are especially shortchanged. This theory is supported by Scholastic Aptitude Test scores, which began rebounding when the baby boom of 1945-1962 ended and family size began declining, Zajonc said.

Parents provide the primary intellectual influence during a first-born or only child’s formative years, but that influence becomes diluted by younger children, said Zajonc, director of the Research Center for Group Dynamics at the university’s Institute for Social Research.

“As families get larger, children’s intellectual development suffers, and the effect is accentuated by birth order,” he said. “The more older siblings a person has, the lower his or her intellectual level, because of the overall decline of the family’s intellectual environment. The pool of words surrounding the only child at age 5 is different from the pool surrounding the second-born child of the same age who has a 7-year-old sibling.”

Zajonc first cited his birth-order theory in 1976, when he accurately predicted an increase in national SAT scores after 1980. The average score that year was 445, down from 490 in 1963.

“Because there had been a steady increase in average family size for the students taking the SATs between 1963 and 1980, SATs were predicted to decline until 1980 and then to rise again when the birth rate, and therefore family size, began decreasing.

“The trend of continued decline in family size suggests a rise in SATs until the year 2000,” Zajonc continued. “A leveling off and a decline is expected thereafter.”