Laughing is an involuntary reaction to certain external or internal stimuli. Laughter can arise from such activities as being tickled,[1] or from humorous stories or thoughts.[2] Most commonly, it is considered a visual expression of a number of positive emotional states, such as joy, mirth, happiness relief, etc. On some occasions, however, it may be caused by contrary emotional states such as embarrassment, apology, or confusion ("nervous laughter)" or courtesy laugh. Factors such as age, gender, education, language and culture are determinant factors[3] as to whether a person will experience laughter in a given situati