Disordered gambling is the first-ever disorder classified as a behavioural addiction, offering a unique model to study addiction mechanisms in the absence of neurotoxic effects from substances. Previous research suggests that maladaptive reward processing and altered perceptions of control may be key drivers in the development and persistence of gambling behaviour. However, the mechanisms that underlie this association of reward processing and perception of control with gambling are not well understood. In this study, we tested 45 pathological and 45 recreational gamblers using a naturalistic slot machine task, which manipulated reward magnitude and illusion of control in a 2x2 factorial design. We also used a computational reinforcement learning model to examine differences in reward and control processing between addicted and recreational gamblers. Our findings suggest that reward and control have distinct effects on gambling behaviour, with reward magnitude primarily influencing bet behaviour, while illusions of control additionally influence the anticipation of winning. This distortion of expected odds due to an illusion of control may drive continued gambling despite unfavourable outcomes and enhanced risk-taking. Moreover, the illusion of control differentially affected pathological and recreational gamblers and may thus provide a window into the nature of risk-taking across gamblers
