Delay Discounting, Probability Discounting, Reward Contrast and Gambling: A Cross-Cultural Study
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
Problem and pathological gambling has become an increasing public health concern worldwide in recent years, and individuals from China and East Asian countries may be especially vulnerable. Knowledge of how individuals make choices between outcomes that are delayed or uncertain, and of potential differences in decision making across cultures, may contribute to our understanding of factors which increase the risk of problem gambling. Our research is based on a discounting perspective in which the value of a delayed or uncertain reward decreases according to the time until or the odds against its receipt, respectively. We use experimental procedures in which individuals make a series of hypothetical choices so as to estimate an indifference point – an amount of money available immediately or with certainty – that is equal in subjective value to a delayed or uncertain reward. Our starting point is the hypothesis that reward contrast – in which the subjective value of a reward varies inversely with amount of a prior reward – plays a role in choice between delayed or probabilistic outcomes and might contribute to problem gambling. This thesis describes four experiments which investigate these ideas. Experiments 1 and 2 establish that reward contrast is a reliable phenomenon in choice. Indifference points for an intermediate reward ($475/$525) varied as predicted if its subjective value was larger when the individual had previously been making choices with a smaller amount ($50) and smaller when previously making choices with a larger amount ($5,000). Reward contrast was obtained for both delayed and probabilistic choice, using between-subjects (Experiment 1) and within-subjects (Experiment 2) designs. Experiment 3 used a computerized Card Playing Game (CPG) as an analogue gambling task and also measured delay discounting using the same task as Experiment 2. Participants began with an initial stake and could win or lose 10% of the stake with each card that they played. The critical aspect of the procedure was that the probability of winning for each card decreased as more cards were played. Participants played the CPG four times with stakes of $50, $500, $5,000 and $500 (order of $50 and $5,000 was counterbalanced). Results showed that performance on the CPG improved over successive trials, suggesting that participants learned the contingencies in the task. Although this confounded our attempt to measure reward contrast within-subjects, participants who had a $50 stake in the first deck performed better in the second deck with a $500 stake than those who had a $5,000 stake in the first deck, consistent with reward contrast. Results from the delay discounting task were correlated with CPG performance, showing that participants who had lower reward contrast and discounting rates, and greater magnitude effects won more money on the CPG task. Experiment 4 used a larger sample (N = 182) with both Chinese and Caucasian (New Zealand European) participants and recruited individuals with gambling histories, and compared performance on delay and probability discounting tasks and the CPG. Results showed that Chinese participants had higher delay discounting rates and lower probability discounting rates when data were analyzed according to the area under the discounting curve (AUC). Gamblers (those participants with scores on the South Oaks Gambling Screen [SOGS; Lesieur & Blume, 1987] > 1) were less risk averse in probability discounting and had reduced magnitude effects in delay discounting and performed more poorly on the CPG. Closer analysis of the probability discounting data showed that compared with Caucasians, Chinese were more risk averse for high probabilities of reward outcome, and less risk averse for low probabilities. Although results do not suggest that individual differences in reward contrast, as measured using our within-subjects delay discounting task, play a significant role in the maintenance of gambling behavior, the cross-cultural differences in delay and probability discounting in Experiment 4 suggest some factors that might contribute to gambling. In the General Discussion, we propose an account of the probability discounting results in terms of a tendency toward dialectical thinking and emotions in Chinese culture. Based on this result and previous research, we propose a framework for the cross-cultural analysis of risky decision making, and consider some of its broader implications for both research in decision making and issues of globalization.