first-born children had slightly higher IQs. Researchers from the University of Leipzig studied the birth order of 20,000 people from the United States, the United Kingdom, and Germany.
ADVERTISEMENT They assessed intelligence based on verbal ability and general IQ tests. Researchers also gave personality tests to the participants in adulthood, which measured the “Big Five” personality traits.
These include extroversion, emotional stability, agreeableness, conscientiousness, and openness. ADVERTISEMENT The researchers determined that the first born children had, on average, an IQ of 1.5 points higher than second-born children.
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