In a lot of baby books they talk about how infants don't have an understanding of object permanence. If something is out of sight for a baby it is really out of mind and they think it ceases to exist. From watching our baby even from a young age I think this theory is BS. So I was looking it up and some more recent studies seem to be placing a dent in this theory. Since baby studies are hard they're often wrong and back in the day they thought babies don't feel pain, which I think any normal mother would have easily been able to refute http://www.usatoday.com/news/health/2005-05-08-babies-pain_x.htm

So I was just wondering what everyone with babies thought about object permanence.