Breast-Feeding Linked to IQ Gain

The basic results of this study don't surprise me. It makes perfect sense that a million years of evolution would have callibrated the nutrients necessary for healthy development better than 50 years of formula company testing. What interests me (being an incurable sociologist) is this:

"Today, the practice is most common among white and wealthier women and least common among minority and poorer women."

It seems like poor people would have the most to gain from breastfeeding. They can't afford formula as easily, and their kids need all the intelligence they can get to help them succeed.