The brown rat, also known as the common rat, street rat, sewer rat, wharf rat, Hanover rat, Norway rat and Norwegian rat, is a widespread species of common rat. One of the largest muroids, it is a brown or grey rodent with a body length of up to 28 cm (11 in) long, and a tail slightly shorter than that. It weighs between 140 and 500 g. Thought to have originated in northern China and neighbouring areas, this rodent has now spread to all continents except Antarctica, and is the dominant rat in Europe and much of North America. With rare exceptions, the brown rat lives wherever humans live, particularly in urban areas.
Laughter is a pleasant physical reaction and emotion consisting usually of rhythmical, often audible contractions of the diaphragm and other parts of the respiratory system. It is a response to certain external or internal stimuli. Laughter can rise from such activities as being tickled, or from humorous stories, imagery, videos or thoughts. Most commonly, it is considered an auditory expression of a number of positive emotional states, such as joy, mirth, happiness, or relief. On some occasions, however, it may be caused by contrary emotional states such as embarrassment, surprise, or confusion such as nervous laughter or courtesy laugh. Age, gender, education, language, and culture are all indicators as to whether a person will experience laughter in a given situation. Other than humans, some other species of primate show laughter-like vocalizations in response to physical contact such as wrestling, play chasing or tickling.
Tickling is the act of touching a part of a body in a way that causes involuntary twitching movements or laughter. The word evolved from the Middle English tikelen, perhaps frequentative of ticken, to touch lightly.
An erogenous zone is an area of the human body that has heightened sensitivity, the stimulation of which may generate a sexual response such as relaxation, sexual fantasies, sexual arousal, and orgasm.
An itch is a sensation that causes a strong desire or reflex to scratch. Itches have resisted many attempts to be classified as any one type of sensory experience. Itches have many similarities to pain, and while both are unpleasant sensory experiences, their behavioral response patterns are different. Pain creates a withdrawal reflex, whereas itches leads to a scratch reflex.
A mechanoreceptor, also called mechanoceptor, is a sensory receptor that responds to mechanical pressure or distortion. Mechanoreceptors are innervated by sensory neurons that convert mechanical pressure into electrical signals that, in animals, are sent to the central nervous system.
Death from laughter is an extremely rare form of death, usually resulting from either cardiac arrest or asphyxiation, that has itself been caused by a fit of laughter. Though uncommon, death by laughter has been recorded from the times of ancient Greece to modern times.
Tickle torture is the prolonged use of tickling to abuse, dominate, harass, humiliate, or interrogate an individual. While laughter is popularly thought of as a pleasure response, in tickle torture, the one being tickled may laugh whether or not they find the experience pleasant. In a tickling situation, laughter can indicate a panic reflex rather than a pleasure response, and the tickling may be a consensual activity or one that is forced, depending on the circumstances. In a consensual form, tickling may be part of a mutually fulfilling, physically intimate act between partners. However, tickle torture can cause real physical and mental distress in a victim, which is why it has been used as an interrogation method or to simply show dominance over another person.
The medial forebrain bundle (MFB) is a neural pathway containing fibers from the basal olfactory regions, the periamygdaloid region and the septal nuclei, as well as fibers from brainstem regions, including the ventral tegmental area and nigrostriatal pathway.
Emotion is defined as any mental experience with high intensity and high hedonic content. The existence and nature of emotions in non-human animals are believed to be correlated with those of humans and to have evolved from the same mechanisms. Charles Darwin was one of the first scientists to write about the subject, and his observational approach has since developed into a more robust, hypothesis-driven, scientific approach. Cognitive bias tests and learned helplessness models have shown feelings of optimism and pessimism in a wide range of species, including rats, dogs, cats, rhesus macaques, sheep, chicks, starlings, pigs, and honeybees. Jaak Panksepp played a large role in the study of animal emotion, basing his research on the neurological aspect. Mentioning seven core emotional feelings reflected through a variety of neuro-dynamic limbic emotional action systems, including seeking, fear, rage, lust, care, panic and play. Through brain stimulation and pharmacological challenges, such emotional responses can be effectively monitored.
Referred itch or mitempfindung is the phenomenon in which a stimulus applied in one region of the body is felt as an itch or irritation in a different part of the body. The syndrome is relatively harmless, though it can be irritating, and healthy individuals can express symptoms. Stimuli range from a firm pressure applied to the skin—a scratch—to irritation or pulling on a hair follicle on the skin. The referred sensation itself should not be painful; it is more of an irritating prickle leading to the compulsion to scratch the area. The stimulus and referred itch are ipsilateral. Also, because scratching or putting pressure on the referred itch does not cause the stimulus area to itch, the relationship between the stimulus and the referred itch is unidirectional. The itching sensation is spontaneous and can cease with continued stimulation.
The preoptic area is a region of the hypothalamus. MeSH classifies it as part of the anterior hypothalamus. TA lists four nuclei in this region,.
A cold chill is described by David Huron as, "a pleasant tingling feeling, associated with the flexing of hair follicles resulting in goose bumps, accompanied by a cold sensation, and sometimes producing a shudder or shiver." Dimpled skin is often visible due to cold chills especially on the back of the neck or upper spine. Unlike shivering, however, it is not caused by temperature, but rather is an emotionally triggered response when one is deeply affected by things such as music, speech, or recollection. It is similar to autonomous sensory meridian response; both sensations consist of a pleasant tingling feeling that affects the skin on the back of the neck and spine.
Although humor is a phenomenon experienced by most humans, its exact cause is a topic of heavy debate. There are many theories of humor which attempt to explain what it is, what social functions it serves, and what would be considered humorous. Although various classical theories of humor and laughter may be found, in contemporary academic literature, three theories of humor appear repeatedly: relief theory, superiority theory, and incongruity theory. These theories are used as building blocks for the rest of the theories. Among current humor researchers, there has yet to be a consensus about which of these three theories of humor is most viable. Some proponents of each theory originally claimed that theirs, and theirs alone, explained all cases of humor. However, they now acknowledge that although each theory generally covers its area of focus, many instances of humor can be explained by more than one theory. Similarly, one view holds that theories have a combinative effect; Jeroen Vandaele claims that incongruity and superiority theories describe complementary mechanisms that together create humor.
Jaak Panksepp was an Estonian-American neuroscientist and psychobiologist who coined the term "affective neuroscience", the name for the field that studies the neural mechanisms of emotion. He was the Baily Endowed Chair of Animal Well-Being Science for the Department of Veterinary and Comparative Anatomy, Pharmacology, and Physiology at Washington State University's College of Veterinary Medicine, and Emeritus Professor of the Department of Psychology at Bowling Green State University. He was known in the popular press for his research on laughter in non-human animals.
Laughter in animals other than humans describes animal behavior which resembles human laughter.
Sham rage is behavior such as biting, clawing, hissing, arching the back, and "violent alternating limb movements" produced in animal experiments by removing the cerebral cortex, which are claimed to occur in the absence of any sort of inner experience of rage. These behavioral changes are reversed with small lesions in hypothalamus.
Tactile hallucination is the false perception of tactile sensory input that creates a hallucinatory sensation of physical contact with an imaginary object. It is caused by the faulty integration of the tactile sensory neural signals generated in the spinal cord and the thalamus and sent to the primary somatosensory cortex (SI) and secondary somatosensory cortex (SII). Tactile hallucinations are recurrent symptoms of neurological diseases such as schizophrenia, Parkinson's disease, Ekbom's syndrome and delirium tremens. Patients who experience phantom limb pains also experience a type of tactile hallucination. Tactile hallucinations are also caused by drugs such as cocaine and alcohol.
Cognitive bias in animals is a pattern of deviation in judgment, whereby inferences about other animals and situations may be affected by irrelevant information or emotional states. It is sometimes said that animals create their own "subjective social reality" from their perception of the input. In humans, for example, an optimistic or pessimistic bias might affect one's answer to the question "Is the glass half empty or half full?"
Ultrasonic vocalizations (USVs) occur at frequencies ranging from approximately 20–100 kHz. They are emitted by animals such as bats and rodents, and have been extensively studied in rats and mice. As opposed to sonic vocalizations, ultrasonic vocalizations cannot be detected by the human ear. USVs serve as social signals, and are categorized according to their frequency. Different categories of USVs are elicited in response to different situations and varying affective states. The behavioural functions of USVs vary as a rat or mouse pup reaches the juvenile/adult stage of their development. The brain mechanisms behind calling behaviour have also been studied, and some studies have used pharmacological manipulation.
