Alliesthesia (from grc, , translit=alloios – be changed, and (''aísthēsis'') – sensation, perception; thus "changed sensation"; french: alliesthésie, links=no, german: Alliästhesie, links=no) is a

psychophysiological Psychophysiology (from Greek , ''psȳkhē'', "breath, life, soul"; , ''physis'', "nature, origin"; and , ''-logia'') is the branch of psychology that is concerned with the physiological bases of psychological processes. While psychophysiology ...

phenomenon A phenomenon ( : phenomena) is an observable event. The term came into its modern philosophical usage through Immanuel Kant, who contrasted it with the noumenon, which ''cannot'' be directly observed. Kant was heavily influenced by Gottfrie ...

(not to be confused with the pathologic

symptom Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormality showi ...

allesthesia Allochiria is a neurological disorder in which the patient responds to stimuli presented to one side of their body as if the stimuli had been presented at the opposite side. It is associated with spatial transpositions, usually symmetrical, of s ...

) that describes the dependent relationship between the internal state of an organism and the perceived pleasure or displeasure of stimuli. The internal state of an organism is in constant change, and any stimulus that can help to correct an error or to satisfy a need will be pleasantly perceived. For example, food will be more pleasant when hungry compared to when an organism is

satiated Satiation may refer to: * Satiety, feeling "full" and satisfied after eating; the cessation of hunger * Economic satiation, where increasing the amount of a good reduces the worth of each individual unit of it * Predator satiation, an anti-predato ...

. The sensation aroused therefore depends not only on the quality or on the intensity of the stimulus, but also on the internal state of the organism as sensed by internal

receptors Receptor may refer to: *Sensory receptor, in physiology, any structure which, on receiving environmental stimuli, produces an informative nerve impulse *Receptor (biochemistry), in biochemistry, a protein molecule that receives and responds to a n ...

. The relationship between the

perceptual system A perceptual system is a computational system (biological or artificial) designed to make inferences about properties of a physical environment based on senses. Other definitions may exist. In this context, a scene is defined as information that c ...

and

physiology Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemic ...

is subjective and studied by

psychophysics Psychophysics quantitatively investigates the relationship between physical stimuli and the sensations and perceptions they produce. Psychophysics has been described as "the scientific study of the relation between stimulus and sensation" or, ...

Forms

* ''thermal'' alliesthesia: alliesthesia of the thermic perception (heat and cold), which contributes fundamentally to

homeostatic In biology, homeostasis (British also homoeostasis) (/hɒmɪə(ʊ)ˈsteɪsɪs/) is the state of steady internal, physical, and chemical conditions maintained by living systems. This is the condition of optimal functioning for the organism an ...

thermoregulation Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperatur ...

. It is an aspect of

thermal comfort Thermal comfort is the condition of mind that expresses satisfaction with the thermal environment and is assessed by subjective evaluation ( ANSI/ASHRAE Standard 55).ANSI/ASHRAE Standard 55-2017, Thermal Environmental Conditions for Human Occupan ...

. * ''olfactory'' alliesthesia: alliesthesia of

olfaction The sense of smell, or olfaction, is the special sense through which smells (or odors) are perceived. The sense of smell has many functions, including detecting desirable foods, hazards, and pheromones, and plays a role in taste. In humans, ...

(sense of smell) * ''gustatory'' alliesthesia: alliesthesia of

taste The gustatory system or sense of taste is the sensory system that is partially responsible for the perception of taste (flavor). Taste is the perception produced or stimulated when a substance in the mouth reacts chemically with taste receptor ...

– described for certain primary tastes (sweet and salty) * olfacto-gustatory alliesthesia or alimentary alliesthesia: alliesthesia of tastes/flavors pertaining to

food intake Eating (also known as consuming) is the ingestion of food, typically to provide a heterotrophic organism with energy and to allow for growth. Animals and other heterotrophs must eat in order to survive — carnivores eat other animals, herbi ...

* ''visual''/optic alliesthesia: alliesthesia of

vision Vision, Visions, or The Vision may refer to: Perception Optical perception * Visual perception, the sense of sight * Visual system, the physical mechanism of eyesight * Computer vision, a field dealing with how computers can be made to gain und ...

* ''auditory'' alliesthesia: alliesthesia of the

sense of hearing A sense is a biological system used by an organism for sensation, the process of gathering information about the world through the detection of stimuli. (For example, in the human body, the brain which is part of the central nervous system re ...

Each of these forms of alliesthesia exists in two opposite tendencies: * ''negative'' alliesthesia: shift of sensation from pleasure to displeasure. * ''positive'' alliesthesia: shift of sensation from displeasure to pleasure.

Evidence

The phenomenon of ''alliesthesia'' was first described by the French physiologist

Michel Cabanac Michel may refer to: * Michel (name), a given name or surname of French origin (and list of people with the name) * Míchel (nickname), a nickname (a list of people with the nickname, mainly Spanish footballers) * Míchel (footballer, born 1963), ...

. The first scientific publication from 1968 was succeeded by over 40 publications in international journals, for example: 1970 in ''

Nature Nature, in the broadest sense, is the physical world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans are ...

'' and 1971 in ''

Science Science is a systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earliest archeological evidence ...

''. The term ''alliesthesia'' was first mentioned in the annex of ''Physiological Role of Pleasure'' and was further elaborated in collaboration with the coauthor

Stylianos Nicolaïdis Stylianos of Paphlagonia (Latin: ''Stylianus'', Greek: ''Στυλιανός'', English: ''Stylian''), also known as Stylianos the Hermit, is venerated as a saint from Adrianopolis in the province of Paphlagonia (modern Turkey). Life Stylian ...

. Originally, alliesthesia was demonstrated in

experiment An experiment is a procedure carried out to support or refute a hypothesis, or determine the efficacy or likelihood of something previously untried. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs whe ...

s with human subjects, and later confirmed in rats (''

Rattus norvegicus ''Rattus'' is a genus of muroid rodents, all typically called rats. However, the term rat can also be applied to rodent species outside of this genus. Species and description The best-known ''Rattus'' species are the black rat (''R. rattus'') ...

'').{{cite journal , last1 = Cabanac , first1 = M , last2 = Lafrance , first2 = L , year = 1990 , title = Postingestive alliesthesia: the rat tells the same story. , journal = Physiology & Behavior , volume = 47 , issue = 3, pages = 539–43 , doi=10.1016/0031-9384(90)90123-L, pmid = 2359766 , s2cid = 37735253

References

Nutrition Sensory systems Physiology