5. Young children who were breastfed as infants scored higher on intelligence tests than formula-fed kids, and the longer and more exclusively they were breastfed, the greater the difference, say Harvard University researchers in a study published today in J AMA Pediatrics. According to the NBC story: \"The Harvard study, unlike most past studies, controlled for these and other variables, including the mother's intelligence, education level, and any postpartum depression; family income and home environment; and the child's race, ethnicity, sex, and birth weight. \"As a result, we felt we were able to get a reasonable estimate of what the relationship is between the length of breastfeeding and the IQ of the child at school age,\" says Dr. Mandy Belfort, lead author and assistant professor of pediatrics at Harvard Medical School.\" The language above should provide a big clue that the researchers used multiple regression in their analyses, because it says, \"controlle for." Why would the researchers want to control for mother's intelligence when they look for the association between breastfeeding and child's