Economists at the University of Edinburgh and the University of Sydney have published a study that supports the hypothesis that first-born children are more intelligent than their younger siblings.
The study, published in the Journal of Human Resources and titled ‘The Early Origins of Birth Order Differences in Children’s Outcomes and Parental Behaviour’, says that although children receive equal amounts of emotional support from their parents, first-born children receive far more mental stimulation.
This comes in the form of intelligence-boosting activities such as music, reading and arts and crafts.
The study concludes that this leads to higher scores on IQ tests which suggest increased levels of intelligence.
According to the study, these differences in aptitude begin from a very early age and increase as the child gets older.
This theory was developed by the US Children of the National Longitudinal Survey of Youth, a dataset collected from the US Bureau of Labor Statistics, which included almost 5,000 children.
The data collection involved testing each child every two years from before birth until the age of 14.
Multiple types of intelligence tests were used, including reading words, vocabulary assessments, reading recognition and matching letters.
The survey also included environmental questions about family dynamics, parental behaviour and financial circumstances.
Parental behaviour was tested using the Home Observation Measurement of the Environment (HOME) at the pre-birth, pregnancy and after birth stages, allowing environmental factors to be considered in the results.
The study also discovered that parental behaviour during pregnancy changes from the first pregnancy to later pregnancies.
On average, mothers in their second or third pregnancies take more risks such as continuing to smoke or drink.
While the idea of a ‘birth order effect’ has existed for a while, this study provides concrete proof to the hypothesis.
This describes how earlier born children experience more success, financial and educational, than subsequent children, as well as older children being more likely to have leadership and organisational skills.
In a press release, Dr Ana Nuevo-Chiquero from the University of Edinburgh’s School of Economics said: “Our results suggest that broad shifts in parental behaviour are a plausible explanation for the observed birth order differences in education and labour market outcomes.”
Image: Neeta Lind