The Head Shake is a gesture in which the head is turned left and right along the transverse plane repeatedly in quick succession. In many cultures, it is most commonly, but not universally, used to indicate disagreement, denial, or rejection.
Shaking Head to indicate Rejection 
Different cultures assign different meanings to the gesture. Shaking to indicate "no" is widespread, and appears in a large number of diverse cultural and linguistic groups. Areas in which head shaking generally takes this meaning include Indian subcontinent, Middle East, Africa, Southeast Asia, Western Europe, and North America.
There are varying theories as to why head shake is so frequently used to mean "no". One simple theory is that it is most common form of expressing negative reaction, indicating that one disagrees with the other person. It has also been stated that babies, when hungry, search for their mother's milk by moving their heads vertically, but decline milk by turning their head from side to side.
An early survey of head shake and other gestures was The Expression of the Emotions in Man and Animals, written by Charles Darwin in 1872. Darwin wrote to missionaries in many parts of the world asking for information on local gestures, and concluded that shaking head for "no" was common to many different groups.
Types of Head Shake 
This gesture can be classified into two types based on the speed of delivery:
1. Fast: If the listener is shaking his or her head in quick succession, it implies that he or she disagrees with the speaker and wants to take the speaker's role.
2. Slow: A slow head shake implies that the listener does not agree with the speaker's message but does not want to interrupt the speaker.
See also 
- Darwin, Charles. The Expression of the Emotions in Man and Animals. New York: D. Appleton and Company, 1913; Page 272, accessed through Google Book Search.
- Kuhnke, Elizabeth. Body Language For Dummies. Page 49, accessed through Google Book Search
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