I don't completely believe this. My formula fed (sadly my breast milk dried up when she was a month old) 3 month old is super smart. And she was mostly formula fed. Now I'm not saying that being breastfeeding has nothing to do with it but its mostly genetics. If a baby is not the brightest lightbulb in the lamp (I guess) breastfeeding will only do so much. So I thibk using the "breastfeeding will make your baby smarter" argument is dumb. My 3 month old can hold her bottle. Can't adequately bring it to her mouth yet but dammit she can hold it. And you know what she probably would've whether she was breast or bottle fed. So quit formula shaming! (Stemmed from jerky breast feeding mommas talking trash about her being bottle fed telling me breast is best and breastfeeding makes babies smarter. F you!) Rant over.