What makes someone smart?
Scientists have been investigating that question for decades, and the research suggests that everything from your mother's breast milk to the size of your waistline can influence your intelligence.
Additional reporting by Chelsea Harvey.
You don't smoke.
A 2010 Israeli study compared the IQ and smoking status of 20,000 young men.
As the Daily Mail reported, the results were stark:
• The average 18- to 21-year smoker had an IQ of 94, and the non-smoker had an IQ of 101.
• Those who smoked more than a pack a day had an average IQ of 90.
• In sibling sets, nonsmoking brothers were smarter than smokers.
You took music lessons.
Research suggests that music helps kids' minds develop in a few ways:
• A 2011 study found that the verbal intelligence of 4- to 6-year-olds rose after only a month of music lessons.
• A 2004 study found that 6-year-olds who took nine months of piano lessons had an IQ boost compared with kids who took drama lessons or no classes at all.
But the researchers may be getting it backward: A 2013 study suggested high-achieving kids were the ones most likely to take music lessons.
You're the oldest child.
Oldest siblings are usually smarter, but it's not because of genetics.
The New York Times reports, "The new findings, from a landmark study published [in June 2007], showed that eldest children had a slight but significant edge in IQ — an average of three points over the closest sibling. And it found that the difference was not because of biological factors but the psychological interplay of parents and children."
For this and other reasons, firstborns tend to be more successful than their siblings.
See the rest of the story at Business Insider