What is a Slot Machine?

A slot is a machine that pays out credits based on a paytable. A player inserts cash or, in “ticket-in, ticket-out” machines, a paper ticket with a barcode, into a slot on the machine and activates reels that spin to arrange symbols. When a winning combination appears, the player earns credits based on the paytable. The slot game may also have one or more bonus games, scatter symbols, wild symbols or other special symbols that can increase the chances of winning. Most slot games have a theme, and the symbols and other features are typically aligned with that theme.

The first electromechanical slot machines appeared in 1963, led by Bally’s Money Honey machine. These replaced mechanical springs and levers with electronic parts, and added lights, a hopper for coins, and the ability to play more than one coin per spin. They were a major hit, and soon they replaced reel machines as the dominant form of gambling in casinos and other establishments.

B.F. Skinner suggested in 1953 that near-miss events might reinforce continuing behavior on slot machines, and although numerous experimental studies have examined conditions such as acoustic or visual feedback that could possibly reinforce persistence, none has demonstrated the effect explicitly. Nonetheless, the belief that near-miss events reinforcingly prolong gambling behavior persists even today.