9 science-backed signs you're smarter than average

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...