A new research has debunked previous beliefs that eldest children are significantly better than those born later when it comes to smartness, competitiveness and achievements. The study showed that the eldest ones do have different personality traits to those born later and their IQ is also slightly better, but these factors are not big enough to make any meaningful sense.

Birth order does not mean significant differences as they are actually equal to a correlation of just 0.02, said Brent Roberts, the University of Illinois psychology professor behind the study.

"In some cases, if a drug saves 10 out of 10,000 lives, for example, small effects can be profound. But in terms of personality traits and how you rate them, a 0.02 correlation doesn't get you anything of note", he said.

Conclusion from a previous study was first-borns are more likely to get allergies, last borns are promiscuous, middle children are more rebellious and men with older sisters are not competent enough.

However, Rodica Damian, the psychology professor who co-authored the paper, has to say that the results of that study are flawed and based on small sample sizes and non-representative participant pools.

Roberts said chances are always high for making mistakes while comparing children's developments, because firstborns are older, therefore have a better sense of responsibility and are more focused because of their relative age.

Roberts said order of birth in the family does not affect personality development by any means.