1. A cognitive capacity measurement device comprising: an image display unit that has a function to display to a subject a degraded image that is an image in which degradation of the data for recognizing a significant photographic object has been caused by conducting a specified process on an original image having the aforementioned subject; a receiving unit to receive from the subject the fact that the aforementioned photographic object has been recognized, and to output the reception signals; a recognition time calculator that receives the aforementioned reception signals from this receiving unit and calculates the recognition time, which is the time the subject requires to recognize the aforementioned photographic object; a challenge level data memory unit that memorizes the challenge level data, which is data related to the challenge level of the aforementioned degraded image in conjunction with recognition of the photographic object; and a cognitive capacity calculator that conducts specified operations using the aforementioned recognition time calculated by the aforementioned recognition time calculator and the aforementioned challenge level data memorized in the aforementioned challenge level data memory unit, and that calculates the cognitive capacity score, which is an index that digitizes the cognitive capacity of each subject.