When you become a dad, it's like a plate has been set spinning in your brain (or two in my case) – suddenly, no matter where you are, or what you're doing, you have this restless vigilance for your fragile offspring. And then there's the time spent playing and feeding, when you're alert to every flicker of emotion on their little face, every tiny hiccup or cry. It would be incredible if these new responsibilities and ways of interacting didn't have a profound effect on the brain.