I don't really think they get their full brain as I say until they are a few years old! Unfortunately, they can be super distracted very easily. I generally work with my dogs at any age when I'm doing anything routine. If I'm in the kitchen, I call them in there and reward them - with praise or just a piece of kibble for paying attention to me. If they are in the yard, I call them where I am and do the same - or any time just whatever I'm doing to get them to focus on me - praise or a kibble. Sometimes a bigger treat if they have done something really spectacular like left that interesting thing and come right to me. It is all about them understanding that they need to do it - bit by bit, time by time - and the more you do that, the more they respond - and usually the more quickly they respond. It takes a long time to train a pup though and 4 months old is still very, very young!