In this ted, talk gilberts talk about the surprising science of happiness he talks about how the humans, grown over the course of evolution because we grew the frontal lobe prefrontal cortex. wich allows humans, to simulate experiences. meaning that we can experience something before it happens. we are able to make decisions that way. humans also have a psychological immune system that allows people change how we perceive something. this immune system works best if we don't have choices. also overthinking is a big part of why people are unhappy.