A slot is a narrow opening in a machine or container, for example a hole where you put coins in to make a machine work. He dropped a coin into the slot and dialled the number.

Sixty-six years ago B.F. Skinner proposed that audio-visual stimuli correlated with winning on slot machines may acquire conditionally reinforcing properties that encourage continued play. This belief, referred to as the near-miss effect, continues to permeate the gambling literature. Several experimental studies, however, have not supported the claim that near-miss events contribute to increased frequency of gambling.

One concern is that conventional chained procedures (such as classical conditioning) that successfully produce conditional reinforcement rely on contingency between the putative conditional reinforcer and subsequent unconditional reinforcer. Classical slot machines, by contrast, provide random outcomes, and the occurrence of near-miss stimuli does not predict the appearance of a win. This difference may explain why Strickland and Grote’s (1967) study failed to reveal a near-miss effect. In addition, extinction tests have generally not been conducted with near misses in a typical slot machine. Despite these concerns, the results of some experiments suggest that near-miss stimuli may have a functionally valuable role in gambling behavior. In particular, they might facilitate a correct prediction of the probability of a future win, which could be used to reduce the cost of play. In such cases, near-miss feedback might be more useful than far-miss feedback, as in the case of a free throw in basketball.