A new study carried out by Leipzig University suggests that the IQ of first-borns increases because they have to teach their younger siblings how things work. The fact that first-borns have their parents’ attention all to themselves also boosts their IQ. It is said that the variations in intelligence are a result of how a child is raised and nurtured, not of biology.
The study evaluates a 1.5 IQ drop per sibling. In families with two children, however, the first-born isn’t necessarily the most intelligent since they only have a 60% chance of having a higher IQ. In this equation, there is still a good chance that the younger sibling will surpass them later on life.
Apart from boosted intelligence, first-born children also show a heightened perception of their brain capabilities. The data for this study was accumulated from personality and IQ tests from three different national studies, one of which was carried out in the UK and involved more than 20,000 participants.