ABSTRACT Aims Players can wager on multiple lines of modern slot machines. When they spin and fail to gain any credits, the machine goes into a state of relative quiet. By contrast, when they spin and win, these spins are accompanied by reinforcing sights and sounds. Such reinforcement also occurs when the amount won is less than the spin wager. We sought to show that these ‘losses disguised as wins’, or LDWs, would be as arousing as wins, and more arousing than regular losses. Measurement and participants We measured skin conductance response (SCR) amplitudes and heart-rate changes following wins, LDWs and losses for 40 novices playing a multi-line slot machine. Findings SCR amplitudes were similar for wins and LDWs—both were significantly larger than for regular losses. Conclusions For novice players, the reinforcing sights and sounds of the slot machine triggered arousal on wins, where the number of credits gained was greater than the spin wager, but also on ‘losses disguised as wins’ where the amount ‘won’ was less than the spin wager. Despite the fact that players lost money on these spins, these outcomes were more arousing than regular losses where no credits were gained. Although these findings involve novice players, the heightened arousal associated with these losses may have implications for the development of problem gambling, as arousal has been viewed as a key reinforcer in gambling behaviour.