What is a reward?

When we talk about liking something, like food friendship or even a nice car, we are talking about an important part of our lives Appreciation and pleasure are complex emotions. And have been studied by psychologists, neuroscientists and philosophers such as Aristoteles or John Stuart Mill.

This is not surprising: Desiring something, being motivated to get it and then enjoying it are states of mind that are responsible for large parts of our behaviors and they drive crucial phenomena, such as learning. When neuroscientists and psychologist investigate this mechanisms they often use the words reward and reward systems. The definition of this words is not defined on some chemical, physical or sensory property of an object. Instead, a reward is something that is sought and consumed by an individual and that has the potential to have that person, or animal, come back for more. The core concept of reward is therefore not based on what something is, but on what something

does: Attracting an individual, causing him to reach and consume it. So why are some stimuli rewarding while others are not? Can we imagine a universal reward? Eating when you are hungry, drinking when you are thirsty or seeking shade on a scorching day will keep you alive. More in general, maintaining homeostasis is one of the primary goals of the reward system. Mating, producing offspring and caring for it will increase the probability of survival of a given species and of gene propagation. These, too, are primary functions of the reward system, and it’s likely that maintaining homeostasis and ensuring reproduction are responsible for the evolution of the reward system in our brain. There is another class of rewards, called intrinsic.

This includes all the activities that we perceive as pleasurable in themselves, such as listening to beautiful songs or walking in a park at sunset. Sometimes, we are able to connect an intrinsic reward to an increased probability of survival, or of transmitting our genes. For instance, finding pleasure in exploring new places or trying new foods could lead to the discovery of valuable resources. In other cases the link is more tenuous, especially when the reward is non-material and not immediately beneficial for survival and reproduction. Lastly, there are secondary, or learned, rewards. They include things such as money. Even if they do not have biological significance in themselves, our brain associated them with primary or intrinsic rewards.

Regardless of categorization, all rewarding stimuli are processed by the same systems in the brain. In this sense, food, a primary reward, is not different from social interaction or even drugs. In the next lecture, we will see what happens when you eat something and how this might activate the reward system.