Abstract: Understanding human risk taking and decision making behavior poses a major challenge for psychological and economical research during the last decades. Although real or hypothetical monetary rewards are commonly used as reinforcers in previous studies, it remains controversial whether real and hypothetical rewards have the same effects to motivate risk taking and decision making behavior. The recently developed balloon analogue risk task (BART) is a laboratory-based risk taking paradigm and offers an ecologically valid model for objective measurement of risk taking propensity and behavior. In the present study, the authors used the BART paradigm in two experiments to compare the effects of real and hypothetical monetary rewards on risk taking behavior. We predicted that compared with hypothetical monetary reward, real monetary rewards will show stronger impacts on the risk taking behavior during the BART task. In Experiment 1, forty-four healthy young adults completed both real money and hypothetical monetary versions of the BART task, in which they were required to sequentially inflate a virtual balloon that can either grow larger or explode. The order of two tasks was counter-balanced between subjects. Paired t-tests and one-way Analysis of Variance (ANOVA) were conducted to compare the effects of real and hypothetical monetary rewards on the BART risk taking behavior, including the mean adjusted number of balloon inflations, the number of balloon explosions, and the number of balloon inflations after positive or negative feedbacks. Experiment 2 added a variable of reward magnitude and used a 2 (authenticity: real, hypothetical) × 2 (magnitude: small, large) factorial design. Thirty healthy young adults completed the experiment 2. The results from Experiment 1 showed that during the real monetary reward BART condition, subjects stopped inflating balloons earlier and were more risk averse for the current balloon trial if they lost the last balloon (i.e., the balloon exploded). This result suggests a significant learning effect from the negative feedback of real monetary reward. However, no such effect was observed for the BART condition with the hypothetical monetary reward. The results from Experiment 2 replicated the findings from Experiment 1 and revealed significant main effects of both reward authenticity and magnitude on risk taking propensity and behavior. Specifically, subjects were more risk averse during the BART condition with large real monetary reward compared with small real monetary reward. However, no differences were found between large and small hypothetical rewards. In addition, subjects were more risk averse for large real monetary reward comparing with hypothetical monetary reward, while no differences were found between small real and hypothetical monetary rewards. Finally, the effect of reward magnitude on risk taking was significant only in subjects with low sensation-seeking scores, whereas subjects with high sensation-seeking scores were insensitive to variation in reward magnitude. In conclusion, this study demonstrated that real and hypothetical monetary rewards modulate risk taking behavior during the BART task in a different way. The findings could be explained by the regret theory and/or the equate-to-differentiate model of risky decision making. Our results suggest that real and hypothetical monetary rewards may have different external validity, which will inform the utility of real and hypothetical rewards in future studies.

Key words: Balloon Analogue Risk Task, risk taking and decision making, real monetary reward, hypothetical monetary reward