What is the allure of slot machines? What can make a simple game as addictive as a drug?
Slot games have developed from simple 3 reels with only one way to win, to the modern multiple line ones with multitude of combinations to wager on: up, down, diagonal, etc. As a result, one spin in multi-line game can wager on 20 play lines while single-line game only one line.
Researchers have recently discovered a potential explanation for the multi-line machine addictiveness. The single-line machines celebrate wins when a gain is more than the wager. However, multi-line machines also celebrate a loss disguised as a win (LDW). When a player wins 5 on the total 20 play lines, which is a net loss, the machine still celebrates the “win” with sounds and animation. As a result of LDWs, players “win” more often and believe they have better competency on multi-line slot machines.
Mike J. Dixon’s team made this discovery by having 102 gamblers play both a 20-line game and single-line game for 250 spins.  They found that in both games, the pleasure increases when there is a 2-credit gain. 2 credits are an actual win in the single-line game, yet a LDW in the 20-line game, but unaware of LDWs, gamblers associate the sole animation with winning.
In the questionnaire after the game, players significantly overestimated the number of wins in multi-line game with many LDWs (by approximately 15 spins), yet had a fairly accurate estimate in the single-line game with no LDWs. Besides, participants considered the 20-line game to be more arousing. Problem gamblers, in particular, reported they “forgot everything around me”, and “felt completely absorbed”. This is a kind of feeling found in a variety of addictive activities such as Internet compulsion, and believed to be indicator of addiction.  K. Finlay’s team found this feeling is stronger when there is “a concurrent presence of lighting and sound”, which appears to be another reason for the game’s addictiveness. 
Despite interesting findings, the sample Dixon’s team chose is exclusively old gamblers (around 60 years old). Will the younger generation do better at discerning LDWs? Unfortunately, Jensen C.’s team’s answer is no. They found that college students, novices or gamblers, mostly overestimated their wins in the game with more LDWs (the multi-line slot machines), too.  The “power” of LDWs makes it very hard to keep the score clear in your mind.
Gambling technologies have made slot machines not only pleasurable, but addictive, by lying to its players. Players have a significant preference, and a higher win estimate on multi-line game than single-line game, because they miscategorized the LDWs as actual wins. However, what is the game doing to prevent us from realizing LDWs? What’s the role of sound and animation, and the number of wager? And ultimately, what could we do to stop gamblers’ addiction? To reveal the allure of multi-line slot machines, there are still studies to be done.
- Mike J. Dixon, Candice Graydon, Kevin A. Harrigan, Lisa Wojtowicz, Vivian Siu & Jonathan A. Fugelsang. The allure of multi-line games in modern slot machines. Addiction(2014): 1920-928. Print.
- Griffiths, M.D., Wood, R.T.A., Parke, J. & Parke, A. (2006). Dissociative states in problem gambling. In C. Allcock (Ed.). Current Issues Related To Dissociation. pp.27-37. Melbourne: Australian Gaming Council.
- Jensen C., Dixon M. J., Harrigan K. A., Sheepy E., Fugelsang J. A., Jarick M. Misinterpreting ‘winning’ in multi-line slot machine games. Int Gambl Stud 2013; 13: 112–26.
- Finlay K., Marmurek H. H. C., Kanetkar V., Londerville J. (University of Guelph, Guelph, Ontario). Effects of slot machine characteristics on problem gambling behaviour. Final report 30 July 2009. Contract No.: 2386.Guelph: Ontario Problem Gambling Research Centre: 2010.