Not sure how it works, but seem to be extremely accurate test. It was used in a case study on stress level at St. Marys Hospital. Look at both dolphins jumping out of the water. The dolphins are identical. A closely monitored, scientific study of a group revealed if test person find differences in the two dolphins, means that the person is experiencing a great amount of stress. Now look at the photograph and if you find more than one or two differences you may want to take a vacation.