Temporal and Spatial Discounting are Distinct in Humans

Previous research on temporal and spatial discounting has largely focused on temporal discounting in which responses to reward stimuli are altered by the time taken to reach the reward. However, there is currently minimal research on the behavioral effects of spatial discounting. In addition, contrary to the current findings, previous research on reward discounting has suggested a correlation between temporal and spatial discounting. Here we present results from three studies, all of which employed a spatial and temporal discounting task in which subjects were immersed in a virtual reality environment and were presented with a choice between two monetary rewards, each reward varying in distance and duration. In addition, in experiments 2 and 3, the speed at which a subject could move within the virtual environment was manipulated. Our findings indicate some of the first evidence that space and time may in fact be estimated independently when discounting rewards.