1. A method used in an interactive device and for recognizing a behavior of a user operating on the interactive device, and the method comprises: capturing a plurality of images; forming a plurality of polygon images of a first face-like contour shape and a plurality of polygon images of a second face-like contour shape corresponding to the plurality of captured images according to a skin-tone model, the first face-like contour shape and the second face-like contour shape occurring in one of the plurality of captured images; and recognizing the behavior of the user operating on the interactive device and performing a corresponding function to automatically pause, stop, or suspend a process/software application being currently operated by the user in response to the recognized behavior of the user by analyzing time variation of at least one characteristic parameter with respect to the plurality of polygon images of the first face-like contour shape and time variation of at least one characteristic parameter with respect to the plurality of polygon images of the second face-like contour shape, the at least one characteristic parameter comprising widths of the plurality of polygon images of the first face-like contour shape and widths of the plurality of polygon images of the second face-like contour shape.