Laughter is a rich experience and expression gifted to human beings. Thus there are several shades of smiling and laughing expressions. They involve elaborate neurological and physiological processes. Such laughter is not seen in animals. But one cannot deny occurrence of primitive laughter in animals. In fact, most mammals, from rats (chirps beyond the range of human hearing) to dogs (huffing and panting excitedly) can be shown to demonstrate laughter-like responses to certain stimuli, with laughter proving to be just as contagious between animals as it is between humans; when one dog laughs, another may be stimulated to do so.