Interactive evolutionary computation (IEC) is one type of evolutionary computation which includes a human user as an evaluation system. Unlike a computer program in standard EC, an IEC user is expected to be aware of his/her tastes more clearly with iteration of evaluations. However, there has not been any research that tries to confirm it so far. If it is confirmed, IEC is desired to design based on that fact. In the paper we first propose an experimental way to investigate it and then conduct an experiment following the proposed way. In addition, we try to extract features of solutions which correspond to the awareness well. The results show that most subjects can be more aware of their tastes with iteration and the extracted features correspond to the awareness well.