Here is an article about this topic: http://www.cnn.com/2014/05/04/living/screen-free-week-schools-susan-linn/index.html?hpt=hp_bn11
Personally, we do not allow our 3 or 1 year old to use our devices. The reason why: We are scared they will break them. They do watch TV so I cannot say that is any better or worse than the tablet. Having said that, neither of our kids show any interest in our devices either. If they were interested it might be a different story but at this point they do not use them. My advice to parents is that technology can be good or bad – you just need to set limits and know what your children are doing. And this goes for everything, not just technology.