EXPRESS: Post-Reinforcement Pauses During Slot Machine Gambling are Moderated by Immersion.

The Post-Reinforcement Pause (PRP) is an operant effect in which response latencies increase on trials following the receipt and consumption of reward. Human studies demonstrate analogous effects in electronic gambling machines that utilise variable ratio reinforcement schedules. We sought to identify moderators of the human PRP effect, hypothesizing that the magnitude of gamblers' PRPs is moderated by the type of reinforcing outcome (genuine wins vs. losses-disguised-as-wins vs. free-spin bonus features), and individuals' level of gambling immersion, a cognitive state linked to problem gambling. Experienced slot machine users (N = 53) played a real slot machine for 20 minutes. The dependent variable was defined as the time delay in the initiation of each bet ('Spin Initiation Latency'; SIL). Using 80% of trials, a linear model was fit regressing SIL on the independent variables (outcome type, immersion, and outcome-by-immersion interaction), and a larger group of covariates (participant ID, trial number, winnings, etc.) selected using double robust LASSO-regularized regression. The previously-unseen 20% of cases were used to validate the model. Positively-reinforcing outcome types showed significantly larger SILs than losses, indicating a PRP effect. Immersion did not predict response latencies, but win-by-immersion and LDW-by-immersion interactions indicated that pauses were greater among more immersed participants. The small number of free-spin bonus features showed similar trends that were not statistically significant. These results indicate that gamblers immersed in play remained sensitive to in-game reinforcement (contrary to prevailing accounts), and provide guidance for researchers bridging the gap between laboratory research and real-world behaviour.