Look at this picture. Who do you think is the smartest? That's my big brother on the left and my little bro on the right (and my adorable mom next to me!)
According to a new study of 5000 children out of the UK, there's a measurable IQ difference between firstborns and their siblings, and it shows up as early as age 1!
They say this is because parents tend to spend more time with their firstborn on games and tasks that develop thinking skills. Kids who come along later get a parent who's more strapped for time.