The Signaling Effects of Blood Glucose and Appetitive Stimuli on Delay Discounting: A Meta-Analysis

Studies have shown that people are sensitive to resource cues which signal body-energy budgets or resource availability. These signals adaptively shift their preferences when making intertemporal choices between a smaller but immediate reward and a larger but delayed alternative. Although recent research results are heterogeneous, there has been no article to date summarizing the effect of different types of resource cues on preference in intertemporal choice. Through a meta-analytic approach, we examined the putative signaling effects of two types of resource cues – blood glucose and appetitive stimuli – on delay discounting, which gauges the preference for intertemporal decision-making. We extracted 44 effect sizes from 26 articles, and these indicated that high levels of blood glucose (e.g., feeling satiated or less hungry) decrease delay discounting (d = 0.26, 95% CI [0.06, 0.46]) while exposure to appetitive stimuli increases delay discounting (d = -0.28, 95% CI [-0.51, -0.05]). In addition, the effect of blood glucose was moderated by the type of reward, showing that the signaling effect on delay discounting was stronger for food in contrast to nonfood rewards such as money. Overall, the results suggest that both internal signals and external cues about resource situations serve as forecasting signals for regulating resource budgets. Furthermore, the signaling effect is domain-specific, with its magnitude dependent on the relevance of rewards to individuals’ goals of resource acquisition and conservation.