ABSTRACT
Curiously, very few of the studies of expertise in complex problem solving take seriously the question of just what is an expert. For the most part, investigators have taken a task selected for reasons that are not always altogether clear, and then defined expertise operationally in terms of outstanding performance on that task. Often, outstanding performance has been compared to nonoutstanding performance in order further to clarify the foundations of expertise. Such operational definitions are functionally useful, but do not come face to face with the question of just what constitutes an expert. That is the question I will address here.
