“…The person who most determinedly took up the challenge to refine and further develop the concept was Kenneth R. Hammond. Hammond, a student of Brunswik at Berkeley, extended Brunswik's ideas to the study of higher cognition, namely, judgment and decision making (e.g., Hammond, 1955;Hammond, Stewart, Brehmer, & Steinmann, 1975). Over the past 50 years, Hammond has used the notion of external validity and the requirements of representative design to critically evaluate the merits of psychological research in general and research on the normative analysis of rational behavior in particular (Hammond, 1948(Hammond, , 1951(Hammond, , 1954(Hammond, , 1955(Hammond, , 1978(Hammond, , 1986(Hammond, , 1990(Hammond, , 1996a(Hammond, , 2000Hammond, Hamm, & Grassia, 1986;Hammond & Wascoe, 1980).…”