I think it has a lot to do with it. I can't quote statistics, but here's how I understand it. Everytime a child is introduced to something new from birth to age 5, a dendrite connection is made in the brain. It's like a PO box. So, if you take your 6 month old to the zoo, several PO boxes might open: zoo, animals, drive time, stroller. Then, when she goes to the zoo again, she's already got a box to put that in and can add to the box. This happens over and over again. So, if you are at home with your child and go to museums and libraries and parks and stuff, you are building more boxes (dendrites). Then, later in life, maybe at 6, your child sees an ad for a zoo and her brain automatically goes to the zoo box for information. If she's never been to the zoo before age 6, the box isn't there. I think day-care kids don't get this kind of exposure unless it's a really good daycare. On the other hand, if you stay at home with your child and don't interact at all, those dendrites aren't built either. I've never put mine in daycare (just Mother's Day Out twice a week) so I certainly can't speak from that side. And, I certainly am not condemning or criticizing anyone who uses daycare.