The active foundations of the illusion of control: an experimental test of the Henslin effect

The mistaken belief that personal control can affect the outcomes of random events is seen as a core part of disordered gamblers’ irrational beliefs via the ‘illusion of control’. The present study tests the extent of action-based manifestation of the illusion of control in a dice-rolling game, which provides a novel controlled test of a claim first made by Henslin that craps gamblers tend to shake their dice harder when aiming for higher numbers. We also tested participants’ recent involvement in gambling games and rates of disordered gambling symptomology as two theoretically-informed potential moderators of any effect. An incentivized dice-rolling experiment was programmed for participants’ mobile devices, where device accelerometer data was used to animate the effects of their shaking and to record the dependent variable of shaking strength. 1,692 US-Based participants (Mean age 37.1; 60.7% male) completed 24 trials each, across which the target number that they would win a $1 bonus if rolled was varied from one to six. Participants rolled the dice 4.1% harder for the highest- (six) compared to lowest-number (one). However, the effect did not vary based on participants’ recent engagement with various gambling games, and also did not correlate with gamblers’ Problem Gambling Severity Index scores. These results uniquely demonstrate a small Henslin effect, but also challenge theoretical accounts that illusion of control effects should be higher in people with greater familiarity with a given situation (i.e. relevant gambling games), or who have higher levels of disordered gambling symptomatology.