Problem gamblers often have distorted beliefs about gambling, including illusion of control and gambler's fallacy. Most multiline slots games allow players to adjust the number of wagered paylines and the amount bet per line, and over time this control may support incorrect conclusions and promote distorted gambling beliefs. We created software to run simulations of a popular multiline slots game and examined the effects of betting on single versus multiple paylines. Simultaneous multiline betting tends to produce a less varied gambling experience because it increases the frequency of legitimate wins and ‘losses disguised as wins’, while decreasing the occurrence of ‘big wins’. It also shortens consecutive series of losing spins and it prolongs the time a typical player takes to exhaust funds. Indirect control over losing streaks may give some players the false impression that they can play skilfully and predict the occurrence of wins. However, applying five different wagering strategies in our simulations showed that none had any real effect on the average percentage of wagers that would be ‘paid back’ to players as prizes. Player control over multiline slots games may lead frequent gamblers to incorrect conclusions that sustain excessive play despite recurring losses.