I believe games that don't require skill but only luck are more likely to lead to addiction, because in the specific case of slot machines, the sounds, the colors, the small wins, and the hope of a bigger one force your will to continue and hope.
Furthermore, since they're so relaxing from a gaming perspective, you don't even notice the loss you're incurring because your mind keeps repeating itself (I'm recovering now).
I confess that I play them every now and then, but I don't play for longer than 10 minutes. If I win or lose within 10 minutes, I quit the game.
Yes, most likely, in games where there is only chance and the gambler cannot influence the outcome in any way, addiction will most likely appear.
Because I've never heard of addiction to poker or blackjack, because the guys there are always tense, and they think, and the brain is designed in such a way that it's unlikely that it can get addicted to something where you have to constantly think and analyze and be tense.
