An expert is a person who has the special knowledge, judgement, experience, and skills to put his or her knowledge in action to provide sound advice and to solve complex problems in a narrowly defined aread.
Typically, human experts are capable of doing the following:
Recognizing and formulating a problem
Solving a problem quickly and correctly
Learning from experience
Restructing knowledge
Breaking rules (i.e., going outside the general norms), if necessary
Determining relevance and associations
Declining gracefully