We didn’t need Econ 101 to learn that a dollar in the future isn’t worth as much as a dollar today. Our brains knew that all along. And, as it turns out, monkey brains know it too. The Pure Pedantry blog has a lengthy post on research showing that monkeys have a high discount rate when comparing immediate rewards to those that occur in the near future. The author, Jake Young, translates some of the findings into refreshingly straightforward language:
They found that screwing with the quantity of the reward and the delay to receive it have equivalent effects on neuronal firing. If you decrease the value of the reward, the neuron fires less. If you increase the waiting time, the neuron fires less. This is exactly what you would expect if the neurons are encoding the temporally discounted magnitude of reward.
Other studies have shown that humans will take an immediate reward, such as an Amazon gift certificate, in preference to waiting for one that is higher in value – even when logic would dictate waiting to be more profitable. Apparently, this tendency runs in the primate family.