The Effects of the Presence of Others on Risky Betting in a Laboratory Gambling Task Among High-Risk Gamblers: A Cross-over Randomized Controlled Trial

We explored the effects of the presence of and cooperation with others on risky betting in a laboratory-based gambling task among high-risk gamblers. Specifically, we compared risky betting under solo, parallel, and cooperation conditions using a stratified randomized, cross-over design. Stratification was conducted according to participant age and gender. The participants were 40 Japanese adults (20 women, 20 men; mean age = 46, SD = 12.80). In the experiment, each participant conducted the Game of Dice Task (GDT) individually (solo condition), in parallel with another participant (parallel condition), and working together with another participant (cooperation condition). Linear mixed modeling results showed that when we controlled for previously specified covariates, there were no significant differences among the solo, parallel, and cooperation conditions regarding risky betting (parallel: estimates = 0.10, SE = 0.79, p = .900; cooperation: estimates = 0.95, SE = 0.79, p = .232). However, post-hoc analysis showed a significant difference between the solo and cooperation conditions regarding the number of times participants chose the riskiest bet (parallel: estimates = 0.18, SE = 0.52, p = .739; cooperation: estimates = 1.13, SE = 0.53, p = .035). Thus, we found that neither the presence of nor cooperation with others decreased risky betting in the GDT among high-risk gamblers. However, we did observe that participants displayed the riskiest betting behavior (i.e., selecting the single choice) in the GDT during the cooperation condition, compared with the solo condition.