The University of Oslo in Norway has concluded through a study that first-born children tend to be smarter than their younger siblings in terms of IQ scores.

According to researcher Petter Kristensen who headed the study, records of 250,000 military draftees from 1985 to 2004 were examined, collated and processed and the results revealed that the IQ scores of first-borns were 2.3 points higher on average.

According to Frank Sulloway of the University of California, Berkeley, 2.3 points can be crucial. This means that chances of first-borns to have above-average IQ ratings are 1.3 percent higher than their brothers and sisters. A 2.3-point difference could also spell the outcome of entrance exams for top-tier universities in America.

The reason for first-born children having generally higher IQ's than their younger siblings is not in the genes, says Kristensen. Social factors actually play a bigger role in the development of a child's mind. The fact that parents tend to have spent more exclusive time with their eldest children could be one of the reasons. Another reason for better development could be because eldest children sometimes act as surrogate parents by helping rear the younger kids, thus raising their maturity level.

Kristensen, by the way, is the second in a family with five kids. He says the only person who believes him among his siblings is his older brother. All of his younger sisters completely disagree with his findings.