The authors have been developing CTR (Concentration Time Ratio) index, a quantitative measurement index analyzing the answering time distribution of receipt classification task as a
cognitive task with uniform difficulty. However, the receipt classification task has some issues. In this paper, a new cognitive task, “comparison task” has been proposed. It has been developed based on the aspect of cognitive psychology and human information processing. Two experiments were conducted to assess the comparison task. One experiment was conducted by
using NIRS (Near-infrared spectroscopy) to investigate cerebral blood flow of prefrontal area and Broca’s area while conducting the task to confirm that it employs linguistic ability and numerical ability. The other experiment was an environmental evaluation experiment to confirm that the answering time distribution of the task was properly affected by the room environment. As the result, the calculated CTRs showed the difference of environmental conditions.