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.
Semantic networks Add nodes to the network for happy, sad, etc.
Use associations as retrieval cues, as in Gordon Bower's idea of mood-dependent memory. No inhibition between nodes. No production of emotions. THEN x is happy. IF x is happy THEN x sings.