Alliesthesia (from – be changed, and (''aísthēsis'') – sensation, perception; thus "changed sensation"; , ) 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 w ...

phenomenon A phenomenon ( phenomena), sometimes spelled phaenomenon, is an observable Event (philosophy), event. The term came into its modern Philosophy, philosophical usage through Immanuel Kant, who contrasted it with the noumenon, which ''cannot'' be ...

(not to be confused with the pathologic

symptom Signs and symptoms are diagnostic indications of an illness, injury, or condition. Signs are objective and externally observable; symptoms are a person's reported subjective experiences. A sign for example may be a higher or lower temperature ...

of allesthesia) that describes the dependence of perceived pleasure or displeasure of

stimuli A stimulus is something that causes a physiological response. It may refer to: *Stimulation **Stimulus (physiology), something external that influences an activity **Stimulus (psychology), a concept in behaviorism and perception *Stimulus (economi ...

on the internal state of an organism. 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. 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 neurite structure that, on receiving environmental stimuli, produces an informative nerve impulse *Receptor (biochemistry), in biochemistry, a protein molecule that receives and responds ...

. The relationship between the perceptual system and

physiology Physiology (; ) is the science, scientific study of function (biology), functions and mechanism (biology), mechanisms in a life, living system. As a branches of science, subdiscipline of biology, physiology focuses on how organisms, organ syst ...

is subjective and studied by

psychophysics Psychophysics is the field of psychology which quantitatively investigates the relationship between physical stimulus (physiology), stimuli and the sensation (psychology), sensations and perceptions they produce. Psychophysics has been described ...

Forms

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

homeostatic In biology, homeostasis (British also homoeostasis; ) is the state of steady internal physical and chemical conditions maintained by living systems. This is the condition of optimal functioning for the organism and includes many variables, su ...

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 temperature ...

. It is an aspect of

thermal comfort Thermal comfort is the condition of mind that expresses subjective satisfaction with the thermal environment.ANSI/ASHRAE Standard 55-2017, Thermal Environmental Conditions for Human Occupancy The human body can be viewed as a heat engine where ...

. * ''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. Taste is the perception stimulated when a substance in the mouth biochemistry, reacts chemically with taste receptor cells l ...

– 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. In biology, this is typically done to provide a heterotrophic organism with energy and nutrients and to allow for growth. Animals and other heterotrophs must eat in order to survive – ...

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

Nature Nature is an inherent character or constitution, particularly of the Ecosphere (planetary), ecosphere or the universe as a whole. In this general sense nature refers to the Scientific law, laws, elements and phenomenon, phenomena of the physic ...

'' and 1971 in ''

Science Science is a systematic discipline that builds and organises knowledge in the form of testable hypotheses and predictions about the universe. Modern science is typically divided into twoor threemajor branches: the natural sciences, which stu ...

''. 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. 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