I used to not understand why anyone would play slots; I realized that playing a slot machine is EXACTLY like handing someone $100 and having them immediately hand back $90 (maybe with a little entertainment like making a funny face). Then you hand them back that $90 and they hand you $81. Repeat until broke.
There used to be a lot of chimp experiments. In one, a prominently displayed button would be put in their cage, and if they pressed it, they would get a small amount of food. They naturally figured this out pretty quickly and would press the button and eat the resultant food until satiated.
Then, the experimenters reconfigured the paytables. A button-press wouldn't always produce any food. They reduced it to half the time, then a third of the time, then a tenth of the time--always random. The chimps would still press the button over and over until they got something, but the truly fascinating part was that the less frequent the reward was, the more often they would push the button. When the payout was reduced to "never," they would still press the button over a hundred times, over multiple days, before they gave up.
You can see the parallel. Chimp and human brains are very similar (though chimps are smarter, because they usually don't play slots and never pay resort fees). Casinos milk slot players dry because their victims experience the same phenomenon that the chimps did: "intermittent gratification." Turns out, the more infrequent the reward, the more effort the chimp/human will expend to get it--even when it's nigh-hopeless.
So when you don't get anything after fifteen spins in a row, you're actually being conditioned to keep playing until you finally DO get that banana, or run out of time/energy/money to keep pressing the button.
