A method for controlling a wearable device including a display, the method including changing a content currently displayed on an external device from a first content to a second content different from the first content; determining, via a controller, whether the changing the content is performed by a wearer of the wearable device; and displaying the first content on the display of the wearable device to be viewed by the wearer if it is determined that the changing the content is performed by a person other than the wearer of the wearable device, further during the displaying the first content on the display, the first content is displayed only on the display of the wearable device.