Slot is a gambling machine that accepts coins or tokens, spins a reel or series of reels, and pays off winnings when the symbols line up. The reels can be one to three or more and are marked into horizontal segments by varying symbols, including stars, card suits, bars, numbers (7 is a favourite), various pictured fruits (cherries, plums, oranges, lemons), and the word jackpot. The machine also features a lever that, when pressed, activates the reels.

The machine’s graphical representation of jackpots and their associated probabilities of success are designed to encourage gamblers to make consistent, persistent investments in the game, which are then repaid with large monetary wins on a random basis. These characteristics combine to form a hedonic cycle that is highly addictive.

Gamblers’ in-game reward reactivity is measured by two psychophysiological measures: a volt signal recorded using a force transducer fixed underneath the spin buttons on the slot-machine simulator and an in-game measure of positive affect. Unlike other psychophysiological measures requiring cumbersome electrodes and wires to be used on participants, these measures are unobtrusive, ecologically valid, and directly relate to the subjective enjoyment of slots play.

These new measures indicate that gamblers’ enjoyment of slots is primarily a function of their exogenous reining in of attention by the machine. Thus, despite their problems with mindfulness outside of the slot-machine context, their mind-wandering during play induces an experience similar to flow. In fact, Dixon and colleagues showed that ratings of dark flow predicted the degree to which gamblers experienced this state during their slots sessions – and the greater the rating of dark flow, the more they enjoyed playing.