The iPhone has both revolutionized telecommunications and become the most effective tool in human history to mollify a fussy toddler. It's a phenomenon that is attracting the attention of childhood development specialists. Kathy Hirsh-Pasek, a Temple psychology professor who specializes in early language development, sides with those who suggest keeping the phone out of a child's reach. Research shows that children learn best through active engagement that helps them adapt, she said, and interacting with a screen doesn't qualify.