Remembering passwords and usernames over the span of like what? 12-17 years is not at all difficult.
I guess you could say we are all smart since we know over 1000 words and the letters they are composed of, the sounds they make, and even more that's around 20+ pieces of information per word(Probably way more than that, more like 40. But I'll say 20 to be safe). So basically that's 20,000+ pieces of information you have to learn in order to function in society.