A student have been understand a concept, when he can show example and non-example of the concept has by giving excuses. Thinking process in order to gain example and non-example a concept would be different with others. Dimensions of individual differences, among others such as cognitive style.

This research is an explorative research based on qualitative approach. The subjects are two junior high school students, are a field independent (FI) and  field dependent (FD) cognitive-styled.

The research show that: 1) In determining non-example quadrilateral concept, FI builds her understanding through every quadrilateral features. Based on these characteristics, the subject argues that non-examples of a structure chosen is a shape which do not have appropriate feature, There is a tendency to choose the first non-example of a shape which has some similarities to the classified figure. 2) In determining non-example quadrilateral, FD builds her understanding through every quadrilateral features. Based on these features, the subject argues that non-examples of a structure chosen is a shape that does not have the suitable feature, the subject can choose non-examples of a structure by drawing the non-example shape in advance to facilitate her for giving the reason.