Duping delight is the positive feeling that some people experience when they lie, either before, during, or after lying. It can include a sense of excitement from taking a risk and getting away with it, and sometimes a feeling of contempt for the person being exploited.
Duping delight can be made visible to others through an inappropriate smile. A high intensity version of the Duchenne smile, which involves the cheek/eye and mouth muscles, is often associated with lying.