. >> mit anthropology professor natasha schull has studied gambling addiction for over 15 years.nterviewed gamblers, casino owners, and slot machine designers. do you think that most people would even think that a machine could addict you, that a machine can do the same thing that a drug could? >> what addiction really has to do is with the speed of rewards. and these machines, if they're packing 1,200 hands per hour into play, you're being exposed--you could see that as being exposed to a higher dose. >> a higher dose, says schull, because all that speed means more bets, and that means more excitement. and no machine is better for that than the penny slot, the most popular game on the casino floor. because the bets are small, you can place hundreds of them at a time. >> another core aspect of their addictiveness is their continuous nature. you're not interrupted by anything. you're not waiting for the horses to run. you're not waiting for the guy next to you to choose his card to put down. there's no roulette wheel spinning. it's just you and the machine. it's a continuous flow

that's not found's in cities elsewhere, or -- >> well, i would say this rural to urban migration is schull lay worldwide phenomenal. the explodesing cities of other parts of the world today are part of the same world to urban migration, but i don't disagree with the premise of the question. american cities felt very different in the 19th century and early 20th century than the european citizens that would have been their nearist analogs early on. partly because they were so koss ma tall pin, so polygloth, the religious faiths expressed on the lanscape, and could you say that although the concept of the melting pot is a very complicated and in some ways problematic way of thinking about the immigrant experience, it is one of the challenges that the united states. to grapple with. for decades and decades and decades. what does it mean to be an american. how does one become an american in this complicated, convergence of peoples from all over the world that made this nation, calmed it into being. >> back to your writing about abraham lincoln a little more. expand, if you will, some of the thi