Categorization is one of the main mental processes by which perception and conception develop. Nevertheless, categorization receives little attention with the development of critical thinking in Taiwan elementary schools. Thus, the present study investigates the effect that individual differences have on performing categorization tasks. Same-object and Different-object identification and categorizing activities were conducted with students asked to perceive various chemical properties by comparing touch before and after washing hands with laundry soap and cosmetic soap. 135 fourth and sixth-grade elementary students from a Taipei County elementary school participated in this experiment. For the purposes of this study, students completed worksheets describing their perception and categorization activities. We then used a scoring rubric to convert data on the learning sheets into quantitated data, which we plotted on a mapping tree. The results of this study indicated that firstly, overall perception performance by female students was significantly superior to that of the male students. Secondly, students who had achieved higher scores in prior science activities displayed better overall categorization performance than those students with low prior science scores did. Teachers could apply our method to cultivate elementary student cognitive processing in science by assigning practice categorization practice to students. (Contains 2 tables.)