Birth order has nothing to do with the personality type of different siblings, according to a new study from the University of Mainz and Leipzig in Germany.

Lead researcher Julia Rohrer pointed out that the order of birth does not affect the sibling's "big five" personality traits - agreeableness, conscientiousness, extroversion, emotional stability, and openness to experience.

The study was conducted by investigating the data of almost 20,000 adults coming from the United States, Great Britain and Germany. Rohrer together with his colleagues specifically studied the intelligence and personality data of about 5,240 Americans, 4,489 Britons, and 10,456 Germans.

The result shows that firstborns achieved a higher score in terms of intelligence but according to Rohrer, the cause for the said high score can be traced in the social family interactions and not on the birth order.

"A firstborn can 'tutor' their younger siblings, explaining how the world works and so on. Teaching other people has high cognitive demands - the children need to recall their own knowledge, structure it and think of a good way to explain it - which could be a boost to intelligence for some firstborns," stated by Rohrer who is a graduate student at the University of Leipzig in Germany.

The report also found out that firstborns have higher chance of having a rich vocabulary and will have less effort in understanding abstract ideas compared to those who are non-firstborns.

In terms of the effect of personalities, the researchers were unable to discover any link between birth order and the effect of personality traits.

Frank Sulloway of the University of California, Berkeley stated that the result is quite striking because the said outcomes contradict with the most established studies which showed that birth order differences is linked with the variation of personalities for siblings.

The study was published on October 19 and is now available in the journal Proceedings of The National Academy of Sciences of the United States of America.