100 years of psychology of concepts: the theoretical notion of concept and its operationalization.

The operationalization of scientific notions is instrumental in enabling experimental evidence to bear on scientific propositions. Conceptual change should thus translate into operationalization change. This article describes some important experimental works in the psychology of concepts since the beginning of the twentieth century. It is argued that since the early days of this field, psychologists' theoretical understanding of concepts has been modified several times. However, in all cases but one, these theoretical changes did not translate into changes in the operationalization of the notion of concept learning.