"The first-borns scored higher on tests including reading and picture vocabulary, which according to the researchers, could reflect the 'birth order effect'. This means children born earlier in a family go on to have a better level of education and earn higher wages further down the line."

Is the first child the smartest?

A new study says the oldest child is the smartest. The study, which has been published in the Journal of Human Resources, found that parents generally spend more time and attention on their first child, which often results in higher intelligence than younger siblings.

Are the oldest siblings smarter?

A new study by researchers at the Universities of Houston, New South Wales and Sheffield have revealed that older siblings are smarter than younger ones – and even revealed why. ... Scientists found that the lower IQ in younger siblings could be down to differences in parental attention.