Intermittent Reward
While talking about the growth of VLTs, Nelson says the following:
I’m always fascinated when people get addicted to virtual things, which often times seem to boil down to a game that involves risk and intermittent reward — where does this tendency come from?
There is a large class of human behaviours which fall under this structure. Consider an action like checking e-mail throughout the day. There is a risk that your checking of e-mail will return nothing (except your disrupted focus), while there is an intermittent reward of getting an interesting or exciting e-mail. Finding food for many animals might be a similar sort of situation. I would guess that the tendency is probably rooted deeply in human (and other animals’) psychology, and serves very useful functions as well as not-so-useful ones.