At one time the German Shepherd was the breed chosen almost exclusively to be used as a guide dog for the visually impaired. When formal guide dog training began in Switzerland in the 1920s under the leadership of Dorothy Eustis, all of the dogs trained were German Shepherd females. An experiment in temperament testing of a group of Labrador Retrievers and German Shepherds showed that the Retrievers scored higher on average in emotional stability and ability to recover promptly from frightening situations, cooperative behavior and friendliness; while the German Shepherds were superior in aggression and defensive behavior. These results suggested that Labrador Retrievers were more suited to guide dog work while German Shepherds were more suited to police work.