Kiss

A kiss is the act of pressing one's lips against the lips or other body parts of another. Cultural connotations of kissing vary widely. A kiss may be used to express sentiments of love, passion, affection, respect, greeting, friendship, and good luck, among many others. The word came from Old English cyssan "to kiss", in turn from coss "a kiss". The act of kissing has become a common expression of affection among many cultures worldwide. Yet in certain cultures, kissing was introduced only through European settlement; prior to this, kissing was not a routine occurrence. Examples of this include certain indigenous peoples of Australia, the Tahitians, and many tribes in Africa.[1]
Kissing is a physical expression of affection or love between two people, in which the sensations of touch, taste, and smell are involved.[2] According to psychologist Menachem Brayer, although many "mammals, birds, and insects exchange caresses" which appear to be kisses of affection, i.e. "love birds," they are not kisses as humans consider them. Psychologist William Cane notes that kissing in Western society is most often a romantic act and describes a few of its attributes:

Nature and history of the kiss

The origins of the kiss were studied in the early 20th century by natural historian Ernest Crawley. He wrote that kissing was "a universal expression in the social life of the higher civilizations of the feelings of affection, love (sexual, parental, and filial), and veneration." According to Crawley, touch is 'the mother of the senses,' and the kiss was a tactile and specialized form of intimate contact.[4]:113 However, he notes that the act of kissing was very rare among the "lower and semi-civilized races," but was "fully established as instinctive in the higher societies." Yet even among higher civilizations Crawley saw differences: while the kiss seems to have been unknown to ancient Egypt, it was well established in early Greece, Assyria, and India.[4]:113

Romeo and Juliet kissing in a painting by Sir Frank Dicksee.
The kiss of lovers, according to 19th century anthropologist Cesare Lombroso, originated and evolved from the maternal kiss.[5] Crawley supports this view by noting that Japanese society, before the 20th century, was "ignorant of the kiss except as applied by a mother to her infant," while in Africa and "other uncivilized regions," it was commonly observed that neither husbands and wives, or lovers, kissed one another.[4]:117 However, kissing was common among the Greeks and Latins as when parents kissed their children, or when lovers and married persons kissed. The kiss in Western societies was also used in various religious and ceremonial acts, as where the kiss had a sacramental value. Crawley concludes that generally, although kissing was prevalent in some form since primitive times, it "received its chief development in Western culture."[4]:119
In modern times, scientists have done brain scans on people when a romantic relationship progresses. Some studies found that after that "first magical meeting or perfect first date," a complex system in the brain is activated that is essentially "the same thing that happens when a person takes cocaine." In studies of affection between lovers, when participants viewed images of their partners, their brains' ventral tegmental area, which houses the reward and motivation systems, was flooded with dopamine, an internal chemical that is "released when you're doing something highly pleasurable . . ."[6]
Within the natural world of animals there are numerous analogies, notes Crawley, such as "the billing of birds, the cataglottism of pigeons and the antennal play of some insects." Even among higher animals such as the dog, cat and bear, similar behavior is noted.[4]:114 See also Biology and evolution, below