Scientists started to study the link between the birth order and personality a long time ago. Earlier, people could assume that the two factors are related as all siblings share the same genes, nevertheless, develop different character and personality traits. This evidence can be explained by some inborn characteristics which are not properly researched yet and environmental factors such as parenting and education.
In 2007, Norwegian epidemiologists published the study in which they concluded that the level of IQ in children declines with every next child in the family. In fact, scientists have not yet detected any hidden factor which appears to be higher in the first-born child and lower in the baby of the family so that suggestions in this area remains rather hypothetical.
In 2009 psychologists concluded that birth order predetermines person’s choice of friends: first-born children usually choose first-borns to communicate. And most people resemble their spouses in terms of personality so that the choice of spouses must be affected by the birth order as well. Nevertheless, this evidence proves that individuals resemble their peers born in the same succession as they were.
Talking about the effect of birth order it is more important to mention the roles ingrained to every particular child by their parents. The oldest children always tend to be more responsible, ambitious and successful than their younger siblings just because they were taught to be so by their parents. First-borns also can be more ruling and dominant because they used to be always in charge.
Birth order is a potent factor which determines personality. However, there is no evidence that a baby of the family will grow up irresponsible and careless just because they are the youngest of their siblings. If parents divide duties and expectations more or less equally, all children can be same ambitious and responsible.