Every generation likes to judge the new by the standards of the old (which have already been discarded by anyone who cares). "However, as for tablets and smartphones, I think these devices will definitely make a kid dumber. There's nothing intellectual about them, nothing that expands the mind, and it's depressing to walk around the mall and see 50 percent of people staring at their phones or talking on them."
Horseshit. These devices have replaced newspapers and magazines. They've cut into the amount of TV that kids (and adults) watch. That, in turn has put pressure on networks to make purchasing changes that resulted in this being referred to as "the golden age of television" an awful lot these days. These devices have democratized music, taking the power of success away from radio and payola and putting it in the hands of the listener. There's plenty of arguments that, at worse, they are zero sum.
My daughter, now 8, has spent most of her life using smartphones and tablets. She reads more books and with far greater sophistication than her classmates. As a toddler, she had a digital coloring book accessible whenever she was with us, now she uses our devices as stop motion animation studios. Our fight, as parents, is to get her to stop reading and launching creative projects - yeah, you can have too much of anything.
Do I think the devices had an impact? Maybe. Constant access to ability-appropriate reading material might have accelerated literacy. It's hard to say, given that we're fairly bookish people anyway. But I certainly have never seen any evidence that she'd have benefited from having her access to modern technology restricted.
I don't know, maybe there were people who thought Isaac Newton should've been outside kicking a fucking ball around instead of being a nerdy kid with a book. Whatever. I'm inclined to say if your kid sucks, maybe it's not the phone's fault. It could be you just got a bum kid.