**5.1 Subjects**

Twenty-seven subjects from the same kindergarten initially participated in this experiment. The age of the subjects ranged from 4 years 7 months to 6 years 3 months, and the average was 5 years 5 months. All subjects were right handed and one subject wore glasses. Of these 27 subjects, the experimental data of only 20 subjects (8 males and 12 females) were used, as explained below.

Informed consent was obtained from all parents of the test subjects and from the kindergarten staff. The experiment was approved by the Research Ethics Committee of Tokyo Metropolitan University.
