This is a part of the pleasure. The faculty of an organ to occupy a field of the conscience or to withdraw itself is a phenomenon related to a need, the impulse and its satisfaction. It is thus for the stomach and hunger, or erotic excitation. Without taste or odor, the carbon dioxide contained in sodas operates in the same way on the mucous membrane inside the mouth. The cold or the heat works in the same manner and beer is good with freshness, CO2 and alcohol.
Physiology explains the psychological effect.
The sensitivity of the mouth has as a role to guide the baby towards maternal nipple. At this age of communication without language, the attachment of the child to his mother find its power and its expression in the act of sucking and its repetition. The preponderance of an oral need for plenitude will remain a long time evident and always latent. And this vacant appetite will always express tenderness by the kiss in love and in oral sex. A food indistinguishable from love Man has other reasons to drink than his thirst and his need for water.