Even when rules are taught with case examples, learners sometimes do not pay attention to the information in the rule and instead engage in inductive learning, based solely on the case examples (Kudo, 2013, in Japanese).  Kudo (2013) suggested that this phenomenon might be caused by insufficient formation of rule representation after the learners are given the case examples.  However, why that results in insufficient formation of rule representation has not been investigated thus far.  Therefore, in the present research, 2 experiments were conducted.  The participants were university students (Study 1, N=42 ; Study 2, N=87).  The students were informed of the rule “metal conducts electricity”, and, at the same time, given information on a case example, “copper conducts electricity”.  The results suggested that participants with an insufficient framework of knowledge, i.e., general or individual, formed the representation that copper, which is a metal, conducts electricity.  In other words, the participants thought that the concept term of “metal” was a modifier for “copper”.  Consequently, they did not form a rule representation, and thus could not apply the rule to subsequent problems.  The phenomenon of concepts losing their abstractness and being regarded simply as modifiers of case examples can be described as the concepts becoming customary expressions without any specific meaning (in Japanese, makura kotoba ka).