The present claimed invention intends to provide a simple and superior means that is possible to express a tendency or a characteristic of a learner as scientific data by making use of a fact that a blood amount or/and a blood component amount in a predetermined region of brains causes a characteristic change when a learner acquires strategy to solve a work during a process of solving the work and that is effective for developing a new educational method from the scientific data. In case a subject conducts a predetermined work, a blood amount or/and a blood component amount in a predetermined measuring region of brains of the subject is measured chronologically by the use of a near-infrared spectroscopy, time change data as data showing time change of the blood amount or/and the blood component amount is produced and a state of strategy acquisition to solve the work for the subject is determined based on the time change data.