Often associated with flashing lights and jackpot prizes, slot machines are a staple in casinos around the world. With their simple structure and easy-to-use controls, these machines offer the promise of riches for those who have the right combination of luck and skill. However, despite the allure of big wins, most players lose money in the long run. While some people may enjoy gambling as a harmless pastime, others develop severe problem-gambling behaviors that can lead to financial ruin, emotional distress, and even criminal activity.

Unlike many other types of casino games, slots have no storyline or action and are purely a game of chance. Yet, there is little doubt that slots are highly addictive. One explanation for the phenomenon of slot addiction is that slots are particularly effective at activating arousal in their players. The current study aimed to test this hypothesis by measuring the psychophysical and psychological responses of participants to different configurations of slot machine sounds. Results showed that sounds elicited arousal both in the players’ minds and bodies, and they found that they preferred playing sessions in which wins were accompanied by sound. This suggests that, for these players at least, the sounds of a slot machine contribute to the enjoyment derived from dark flow.

The experiment was conducted using three separate slot-machine simulators housed in cabinets with force transducers fixed underneath the spin buttons. Each time a button was depressed to initiate a spin, the amount of force applied was translated to a volt signal that was recorded by AD Instruments PowerLabs and saved in LabChart software (Colorado Springs, CO, USA). The stimuli for each condition were identical: 301 consecutive spins of a randomly assigned slot machine.

When the sounds of a slot machine were played, the results demonstrated that players overestimated the number of times they had won during the session. This effect was more pronounced when the sounds of losing spins were disguised as winning ones, suggesting that sound enhances the illusory nature of slot-machine play.

The current study’s results support Dixon et al.’s claim that dark flow is a unique route to slots enjoyment, distinct from other aspects of enjoyment. Specifically, the two measures of reward reactivity (PRP and force as a function of win size) were independently associated with dark-flow ratings, but not with the enjoyment attributed to positive affect or depression scores. In contrast, the PRP measure was negatively correlated with the CPGI gambling-severity scale and positively correlated with the DASS depression score. This suggests that the distinctive arousal generated by modern multiline slots play leads to a distinct psychological response that is a powerful contributor to the enjoyable experience of dark flow. Moreover, it also highlights the importance of studying the context in which arousal-inducing stimuli are used to drive gambling behaviour. Currently, most research on the psychology of slots is done in isolation of other sensory modalities, but these studies fail to capture the full complexity of the interaction between sight and sound in the gaming environment.