Historically, studies have claimed that IQ lowers among siblings with decreasing age. According to the research, this was because of the increasing strain on parents’ time, energy and resources. Other studies claimed that because the firstborn was only around adults, they tended to mature faster.
However, more recent studies have proven these theories wrong. Instead, your intelligent relies more on your family environment and genetics. Some research says that only children tend to be more success oriented as they were raised in an adult environment. Children from larger families tend to be more successful in social situations.
Other studies have tried to prove characteristics of each birth order. The oldest children are seen as more ambitious and given more responsibility. However, when brothers or sisters are born, they feel vulnerable and uncertain in difficult situations. Middle children are thought to struggle with finding their place and gaining recognition. Finally, the youngest are thought to receive the most attention and misbehave if they feel ignored.
Unfortunately, for every study done, there are many factors that don’t add up. Instead, studies that are consistent involve family culture, family relationships and the age of the parents. So when you older sibling brags about getting an ‘A’ in a class, don’t fret, you have just as much chance to get the same grade.
For more information on the subject of birth order, check out this article from Little Tree.