Many philosophers, AI researchers, and even psychologists have taken emotions to be peripheral to cognition. Most philosophers and AI researchers have believed that emotional thought is inferior to rational thought.
Emotions involve feelings and conscious, which are hard to study scientifically.
Thinking can have emotional outputs, e.g. thinking that you've won the lottery can make you happy. Thinking can have emotional inputs, e.g. being happy at the thought of going to a hockey game may make you decide to go to the game. Empathy is an important part of understanding other people. Model reasoning about emotions. Model the interactions of emotion and cognition.