The Bottom Line: Why Are Slot Machines So Addictive?

In a casino, almost nothing is more carefully engineered to get gamblers to spend more money than its slot machines. From the pattern on the carpet to the position of the armrests, virtually everything about a modern-day slot machine is designed to make it more seductive and more likely that players will keep betting. This week on The Bottom Line, we speak with MIT anthropologist and gambling expert Schull, who has spent years in casinos studying these machines. He reveals that while slots are still only a minor part of casino revenues, they remain a significant temptation to people with gambling problems and even to those who do not have them.

In the early days of the game, all-or-nothing slot machines ruled the gaming landscape. When a player yanked the lever, all cherries or lucky 7s lined up on the screen and the machine paid out cash — or did not. But advances in computer technology gave casinos the ability to manipulate odds and percentage paybacks to attract more gamblers and boost profits.

Schull explains that one major reason why slot machines are so addictive is the way they exploit certain learning processes, most notably conditional reinforcement. In the classic experiment by Strickland and Grote, near misses were manipulated to have a greater probability of occurring than wins, but participants whose experiences with near misses were more frequent opted to continue playing longer than those who saw more wins. A series of subsequent studies including two systematic replications by Ghezzi et al., however, have found that near-miss stimuli do not produce reinforcing effects in a typical slot machine.