The delay-reward heuristic: What do people expect in intertemporal choice tasks?

Recent research has shown that risk and reward are positively correlated in many environments, and that people have internalized this association as a "risk-reward heuristic": when making choices based on incomplete information, people infer probabilities from payoffs and vice-versa, and these inferences shape their decisions. We extend this work by examining people's expectations about another fundamental trade-off-that between monetary reward and delay. In 2 experiments (total N = 670), we adapted a paradigm previously used to demonstrate the risk-reward heuristic. We presented participants with intertemporal choice tasks in which either the delayed reward or the length of the delay was obscured. Participants inferred larger rewards for longer stated delays, and longer delays for larger stated rewards; these inferences also predicted people's willingness to take the delayed option. In exploratory analyses, we found that older participants inferred longer delays and smaller rewards than did younger ones. All of these results replicated in 2 large-scale pre-registered studies with participants from a different population (total N = 2138). Our results suggest that people expect intertemporal choice tasks to offer a trade-off between delay and reward, and differ in their expectations about this trade-off. This "delay-reward heuristic" offers a new perspective on existing models of intertemporal choice and provides new insights into unexplained and systematic individual differences in the willingness to delay gratification.

Multifunctional graphene oxide-bacteriophage based porous three-dimensional micro-nanocomposites.

Graphene, since its successful exfoliation and characterisation has been continuously drawing extensive research interests due to its potential for a broad range of applications ranging from energy, microelectronics, through polymer fillers and sensors to environmental and biomedical devices. Exploitation of its unique chemical and physical properties for the manufacturing of functional materials, requires careful structural control and scaling-up into three-dimensional morphologies. Here, a facile method is established to create and control the bottom-up self-assembly of graphene oxide nano-sheets via unprecedented integration with a highly versatile bio-ingredient, the filamentous bacteriophage M13, into hierarchical, three-dimensional, porous sponges of GraPhage13. This study explores the interplay of the GraPhage13 structure formation and studies the mechanisms that give rise to the controllable self-assembly. The straightforward fabrication of robust hierarchical micro-nano-architectures further lays a platform for applications in energy storage and conversion, catalysis and sensing.