When most people think of gambling, they probably picture blackjack or roulette — high-stakes bouts of chance where fortunes can be won or lost in seconds. But these days, slot machines are dominating the industry, accounting for as much as 85 percent of casino profits. And they’re also becoming increasingly addictive. In this article, cultural anthropologist Nicole Schull describes how slots have become less about the randomness of the outcome (which can still be very exciting) and more about casinos’ dizzying array of strategies for making them as addictive as possible.

One crucial advance was technological. Whereas old-fashioned slot machines were all-or-nothing affairs where you yanked the lever and either all cherries or lucky 7s lined up to win some money, new computer technology allowed casinos to tweak the odds and payouts to maximize profits. For example, a quarter machine might pay out 10 credits for a 777 outcome when you play just one coin, but will give you four times that amount if you play three coins.

Another strategy is to use audio-visual stimuli correlated with winning outcomes to conditionally reinforce behavior. Research suggests that, just like the tally up on a basketball free throw that tells you whether you made or missed, near-miss feedback can have similar reinforcement properties for gamblers. In one study, researchers manipulated the frequency of near miss presentations on a three-reel slot machine to give participants a 15%, 30% or 45% chance of receiving a win. The results showed that participants persisted the longest with a 45% frequency, although they didn’t show any greater willingness to continue gambling after extinction.