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Licking refers to passing the tongue over a (solid or liquid) surface, typically either to deposit saliva onto the surface or to collect liquid onto the tongue for ingestion. Many animals both groom themselves and drink by licking.
Licking in animals
Licking is a common way for animals to clean themselves. In mammals, licking helps keep the fur clean and untangled. The tongues of many mammals have a rough upper surface that acts like a brush when the animal licks its fur. Certain reptiles, such as geckos, clean their eyes by licking them.
Mammals typically lick their offspring clean immediately after birth; in many species this is necessary to free the newborn from the amniotic sac. The licking not only cleans and dries the offspring's fur, but also stimulates its breathing and digestive processes.
Many animals also drink by licking. While young mammals drink milk from their mothers' nipples by sucking, the typical method of drinking for adult mammals involves dipping the tongue repeatedly into water and using it to scoop water into the mouth. This method of drinking relies in part on the water adhering to the surface of the tongue and in part on muscular control of the tongue to form it into a spoonlike shape.
Hummingbirds are often said to "sip" nectar, but in fact they lap up nectar on their long tongues. Their tongues have fringed edges, which help in both nectar eating and in catching tiny insects. Mother hummingbirds also lick their chicks after a rainstorm, ironically, to dry them by licking water droplets from the coats of the chicks to avoid chill.
Animals also use their tongue to enhance their sense of smell. By licking a surface, molecules on it are transferred via the tongue to the olfactory receptors in the nose and in the vomeronasal organ.
Dogs and cats use licking both to clean, and to show affection.
Licking in humans
Compared to most other mammals, licking has a relatively minor role for humans . The human tongue is relatively short and inflexible, and is not well adapted for either grooming or drinking. Instead, humans prefer to wash themselves using their hands and drink by sucking fluid into their mouth. Humans have much less hair over their skin than most other mammals, and much of that hair is in places which they cannot reach with their own mouth. The presence of sweat glands all over the human body makes licking as a cooling method unnecessary.
Nonetheless, licking does play a role for humans. Even though humans cannot effectively drink water by licking, the human tongue is quite sufficient for licking more viscous fluids. The practice of licking dishware and cutlery clean, though often considered uncivilized, is nonetheless quite common. Some foods are sold in a form intended to be consumed mainly by licking, e.g. an ice cream cone and a lollipop.
There are a number of other uses for licking in humans. For example, licking can be used to moisten the adhesive surfaces of stamps or envelopes. In sewing, thread ends are commonly wet by licking to make the fibres stick together and thus make threading them through the eye of a needle easier. Another practice considered uncivilized is licking one's hand and using it to groom one's hair.
Licking, like other forms of oral contact, can also be an important element of human sexuality (see oral sex). In a less sexual way, licking can be part of physical intimacy, for example with the French kiss or necking.
- Ring-tailed lemurs use licking as a social function, licking each other's babies within the community.
- Macaques and other primates lick leaves for water in addition to dipping their arms into tree crevices and licking the water off.
- Chimpanzees use licking in a variety of ways:
- Gorillas use licking in addition other senses to determine the nature of an object
- Grooming in cats
- Hummingbird Licking Behavior
- Mice Licking Responses to Sweeteners
- The Stages of Canine Labor When Your Dog Gives Birth
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