This is the 101 explanation of the science at work. It's basically a conditioned response to dopamine caused by pulling the lever. At it's most basic level, if you are gambler, you pull the lever and get a neurotransmitter reward.
The moral of the story is that if there were no profit motive on the part of the casinos, eventually gamblers could be conditioned to sit at a slot machine that has had the payout slot removed, thus explaining the woman playing "no payout" slots on her phone. I've often joked that my dogs must ask themselves sometimes, "he tells me to sit and my butt just hits the ground. Why? What's wrong with me?" One might get the same response from the woman were she able to give you an honest answer. Like my dogs, she has probably long since forgotten why she even plays slots on her phone.
The training will probably come in handy for the human pup, too. As I watched the one set of friends who would tolerate a comparison between their offspring and dogs, and how they raised their kids, they probably got tired of me pointing out, "oh, so it's just like training dogs..". :-) I wish my old man was a little more into that whole "positive training" thing.