A lot of people have wondered over the years what character traits can be caused by birth order. Well in this topic you will see a short summary of the study done at the University of Leipzig on birth order and its influence.

20.000 people have participated in this study and the results were magnificent. The study shows that birth order can affect us greatly, whether older siblings can be smarter or younger siblings being healthier and/or more likely to be homosexual.

Older and smarter

Studies are showing that firstborns have a small difference in intelligence compared to the second born. This continued furthermore, showing that second born children also have slightly more intelligence than their younger siblings.

Firstborn children claimed that they are sharp, easy to comprehend tough topics, abstract ideas and have a richer vocabulary compared to their siblings.

This advantage has been associated with a biological change in the womb and the social status in the family. However, scientists believe that the social status is more contributive to the development rather than biological change. This leads to the conclusion that higher social ranking can contribute to this advantage or higher intelligence.


The same study showed that younger siblings were actually healthier than their older siblings.

There are few more studies that came to the same conclusion and one specifically performed at Queen’s University Belfast which stated that younger siblings had a reduced risk of becoming diabetic. According to the researchers, this could be contributed to changes in the womb or to delayed exposure to infections.

Being surrounded by older siblings exposes them to more health-threatening factors. This, in turn, stimulates the immune system and reduces the risk of getting a variety of diseases.

Sexual orientation

Another discovery was that men with more elder brothers are more likely to be gay. This effect is known to the society as the “older brother phenomenon”. Every extra brother increased the chance of younger siblings becoming interested in men.

Prof. Tony Bogaert explains that this is a biological effect in which every older brother changes the womb. He states that the cause could be the maternal immune response.

The more elaborate explanation is that every male fetus creates a particular protein in the womb which is needed to form male genitalia. As a response to this, the immune system creates different protein or antibodies. This process means that in every subsequent pregnancy, male fetuses will be more quickly exposed to these antibodies, which is his explanation of why this phenomenon occurs. This process is natural and safe for both the mother and the fetus

Finding the link

Finding the cause for all these changes or advantages is hard. Scientists claim that there are numerous factors that contribute to the sexuality or higher or lower intelligence.

The problem with finding the cause is that there aren’t enough researches on this topic. Without the researches, scientists can only speculate on what is the cause.

The Leipzig study is only the second largest research that has looked at what effects birth order has. This research has shown us that birth order can influence your intelligence or your sexuality.

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