Supernormal stimulus

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Venus of Willendorf, figurine exaggerating body and breast stimuli. Venus von Willendorf 01.jpg
Venus of Willendorf, figurine exaggerating body and breast stimuli.

A supernormal stimulus or superstimulus is an exaggerated version of a stimulus to which there is an existing response tendency, or any stimulus that elicits a response more strongly than the stimulus for which it evolved.

Contents

For example, it is possible to create artificial bird eggs which certain birds will prefer over their own eggs, [1] particularly evident in brood parasitism. Some speculate humans can be similarly exploited by junk food. [2] Organisms tend to show a preference for the stimulus properties (e.g. size, colour, etc.) that have evolved in nature, but when offered an artificial exaggerated stimulus, animals will show behaviour in favour of the artificial stimulus over the naturally occurring stimulus. [3] A variety of organisms display or are susceptible to supernormal stimuli, including insects, birds, and humans.

Supernormal stimuli are present in areas of biology and psychology, but are also studied within other fields like sociology and art.

British academic Nigel Spivey demonstrates the effect in the first episode of the 2005 BBC documentary series How Art Made the World to illustrate neuroscientist Vilayanur S. Ramachandran's speculation that this might be the reason for the exaggerated body image demonstrated in works of art from the Venus of Willendorf right up to the present day.

Causation

Animals exhibiting, or responding to, characteristics that represent a supernormal stimulus usually display them as a result of selective pressures. Co-evolution between animals displaying supernormal stimuli, and the organisms responding to the supernormal stimuli, rely on evolution and propagation of genetics, behavioral patterns, and other biological factors. [4] Supernormal stimuli such as emphasized color, size, patterns, or shapes, are often successful because an organism that exhibits them will often be selected by an organism that favors it. This will ensure survival and increased reproductive fitness of current and later generations.  

In biology

In the 1950s, Konrad Lorenz observed that birds would select brooding eggs that resembled those of their own species but which were larger. Niko Tinbergen, coined this term through his research, which discovered that experimenters could display an alternate target that attract an organism's attention more so than the naturally occurring target. [4] Tinbergen studied herring gulls, and found the chicks peck at the red spot located on their parent's bill. The offspring targets the red spot due to the contrast of color (stimulus). [4] They do this in order to receive food through regurgitation from the parent. [4] Tinbergen and colleagues developed an experiment that presented different models to chicks and determined their pecking rates. [4] They used different models including an adult herring gull's natural head, a standard wooden model of its head, the bill only, and a red stick with smaller white markings on it. [4] The pecking rate of the chicks were consistent with the natural head, standard head model, and the bill only model. [4] The pecking rate of the chicks increased when presented with the stick model. [4] This suggests that the chicks preferred the dramatic contrast of the red stick with the yellow markings, therefore the artificial stimulus of the stick model was favored over the basic herring gull head and bill models, proving that the artificial stimuli was favored over the naturally occurring stimuli. Following his extensive analysis of the stimulus features that elicited food-begging in the chick of the herring gull, he constructed an artificial stimulus consisting of a red knitting needle with three white bands painted around it; this elicited a stronger response than an accurate three-dimensional model of the parent's head (white) and bill (yellow with a red spot). [4]

Tinbergen and his students studied other variations of this effect. He experimented with dummy plaster eggs of various sizes and markings finding that most birds preferred ones with more exaggerated markings than their own, more saturated versions of their color, and a larger size than their own. Small songbirds which laid light blue grey-dappled eggs preferred to sit on a bright blue black polka-dotted dummy so large they slid off repeatedly. Territorial male stickleback fish would attack wooden floats with red undersides—attacking them more vigorously than invading male sticklebacks if the underside were redder. [1]

Lorenz and Tinbergen accounted for the supernormal stimulus effect in terms of the concept of the innate releasing mechanism; however this concept is no longer widely used.[ citation needed ] The core observation that simple features of stimuli may be sufficient to trigger a complex response remains valid, however.

In 1979, the term supernormal stimulus was used by Richard Dawkins and John Krebs to refer to the exaggeration of pre-existing signs induced by social parasites, noting the manipulation of baby birds (hosts) from these, to illustrate the effectiveness of those signals. [5]

In 1983, entomologists Darryl Gwynne and David Rentz reported on the beetle Julodimorpha bakewelli attempting to copulate with discarded brown stubbies (a type of beer bottles) studded with tubercules (flattened glass beads). [6] This work won them the 2011 Ig Nobel Prize in biology. [7]

Another example of this is the study made by Mauck and colleagues, where they evaluated the effects of a plant pathogen named cucumber mosaic virus or CMV. This study showed that the aphids preferred the healthy plants but are still attracted by the infected plants, because of the manipulation of volatile compounds used by plants to attract them. [8]

Insects

Pollinators, like butterflies, show behavioral response(s) to supernormal stimuli through intersexual communication. [9] Butterflies use olfactory cues, but primarily rely on visual forms of communication, due to wind and temperature affecting their sense of smell. [9] Sexually active butterflies will perch and wait for a mate. Once an object is detected, the butterfly can determine if the color and movement patterns are of a sexually receptive butterfly. [9] In certain species, like the silver-washed fritillary butterfly ( Argynnis paphia ), the male butterfly will exhibit high contrast sensitivity and well-developed visual acuity. [9] A more dramatic contrast of color (or movement pattern) resembling, but further emphasizing the traits of the female butterfly, could alter this usual behavior in males. [9] Studies show that the male silver-washed fritillary butterfly select a monochromatic orange paper model, over receptive female butterflies who portrayed their usual coloration/markings. [9]

Manipulation by parasites

In 2001, Holen et al., analyzed the evolutionary stability of hosts manipulation through exaggerated signals. Their model indicated that intensity of parasitic signals must be below a threshold to ensure acceptance from host. This threshold depends directly on the range of parasitism. [10]

Supernormal stimuli can be exhibited by brood parasites, for example, the parasitic cuckoo chick and parental care by reed warblers. [11] Brood parasites have evolved more dramatic colors, sizes, patterns, and/or shapes that lead to the parasite being interpreted as healthier or more preferable, in contrast to neighboring offspring. Cuckoo chicks are often successful because their begging calls, the supernormal stimulus, are representative of an entire reed warbler brood. [11] Due to the host parent's evolutionary instinct, elicited by selective pressures, they will select this exaggerated form of the stimulus. These calls will cause the host parent to primarily invest energy into the parasitic chick and provide it with additional food resources. [11] Studies show that the supernormal stimuli in cuckoo chicks alter the foraging behavior in parental reed warblers. [11]

For them, the only evolutionary stable strategy is when the host accepts all signs of the parasite with optimal intensity, which must be below the threshold; if this is not the case, the host can use these signals to identify the parasite. [10]

Maladaptive behavior

Maladaptive behaviors are shown by organisms that display a preference for supernormal stimuli over naturally occurring stimuli. This is often based on instinct to gather as many resources as possible in a resource-sparse environment. [12] It can also be instinctual for certain species to select the supernormal stimuli that will suggest the best energy investment of the individual, often parental investment. [11] The selection of the supernormal stimuli must also simultaneously outweigh the cost of the behavior in order for it to evolve. This is shown in the cuckoo chick and the effects on host reed warblers. [11] These parasitic chicks exhibit irresistible begging calls toward the parental host. [11] This occurs as a result of selective pressures. The reed warbler increases foraging efforts to feed the parasitic chick and its own offspring. [11] As a result, this shows a maladaptive behaviour of the host reed warbler as it is investing into a chick that is not biologically related, which does not provide reproductive fitness gain.

Biodiversity concerns

The significance of supernormal stimuli and brood parasitism or in various other species susceptible to environmental manipulation, is that this can drastically reduce the population numbers of the respective species. Brood parasitism can cause host parents to ignore their own offspring or display a higher parental investment into the parasite. [11] Animals that are at risk of extinction, extirpation, or vulnerability will be impacted by supernormal stimuli present in brood parasites.

In psychology

Harvard psychologist Deirdre Barrett argues that supernormal stimulation governs the behavior of humans as powerfully as that of other animals. In her 2010 book, Supernormal Stimuli: How Primal Urges Overran Their Evolutionary Purpose , [13] she examines the impact of supernormal stimuli on the diversion of impulses for nurturing, sexuality, romance, territoriality, defense, and the entertainment industry's hijacking of our social instincts. In her earlier book Waistland , [2] she explains junk food as an exaggerated stimulus to cravings for salt, sugar, and fats and television as an exaggeration of social cues of laughter, smiling faces and attention-grabbing action. Modern artifacts may activate instinctive responses which evolved prior to the modern world, where breast development was a sign of health and fertility in a prospective mate, and fat was a rare and vital nutrient.

In a cross-cultural study, Doyle and Pazhoohi showed that surgically augmented breasts are supernormal stimuli, and they are more attractive than natural breasts, regardless of their size. [14] Also in a theoretical paper, Doyle proposed that how women walk creates supernormal stimuli through continuously alternating motion of the waist and hips causing peak shifts in perceptions of physical attractiveness involving women's waist-to-hip ratio. [15] Furthermore, Pazhoohi et al. (2019) using eye tracking confirmed that lower than optimal waist-to-hip ratios are supernormal stimuli and they may generate peak shifts in responding. [16]

Pascal Boyer has suggested that music is a superstimulus targeting human affinity for speech, and that symmetrical textile and building patterns are superstimuli targeted to the visual cortex. [17]

In art

Costa and Corazza (2006), [18] examining 776 artistic portraits covering the whole history of art, showed that eye roundness, lip roundness, eye height, eye width, and lip height were significantly enhanced in artistic portraits compared to photographic ones matched for sex and age. In a second study, forty-two art academy students were requested to draw two self-portraits, one with a mirror and one without (from memory). Eye and lip size and roundness were greater in artistic self-portraits. These results show that the exaggeration and "supernormalization" of key features linked to attractiveness, such as eye and lip size, are frequently found in art. Pazhoohi et al. (2019) showed that classic contrapposto pose is considered more attractive and provided evidence and insight as to why, in artistic presentation, goddesses of beauty and love are often depicted in contrapposto pose. [16]

See also

Related Research Articles

<span class="mw-page-title-main">Nikolaas Tinbergen</span> Dutch zoologist and ethologist (1907–1988)

Nikolaas "Niko" Tinbergen was a Dutch biologist and ornithologist who shared the 1973 Nobel Prize in Physiology or Medicine with Karl von Frisch and Konrad Lorenz for their discoveries concerning the organization and elicitation of individual and social behavior patterns in animals. He is regarded as one of the founders of modern ethology, the study of animal behavior.

<span class="mw-page-title-main">Cuckoo</span> Family of birds

Cuckoos are birds in the Cuculidae family, the sole taxon in the order Cuculiformes. The cuckoo family includes the common or European cuckoo, roadrunners, koels, malkohas, couas, coucals, and anis. The coucals and anis are sometimes separated as distinct families, the Centropodidae and Crotophagidae, respectively. The cuckoo order Cuculiformes is one of three that make up the Otidimorphae, the other two being the turacos and the bustards. The family Cuculidae contains 150 species, which are divided into 33 genera.

<span class="mw-page-title-main">Common cuckoo</span> Species of bird

The common cuckoo is a member of the cuckoo order of birds, Cuculiformes, which includes the roadrunners, the anis and the coucals.

<span class="mw-page-title-main">Trophallaxis</span> Transfer of food between members of a community through stomodeal or proctodeal means

Trophallaxis is the transfer of food or other fluids among members of a community through mouth-to-mouth (stomodeal) or anus-to-mouth (proctodeal) feeding. Along with nutrients, trophallaxis can involve the transfer of molecules such as pheromones, organisms such as symbionts, and information to serve as a form of communication. Trophallaxis is used by some birds, gray wolves, vampire bats, and is most highly developed in eusocial insects such as ants, wasps, bees, and termites.

<span class="mw-page-title-main">Black-headed gull</span> Species of bird

The black-headed gull is a small gull that breeds in much of the Palearctic including Europe and also in coastal eastern Canada. Most of the population is migratory and winters further south, but some birds reside in the milder westernmost areas of Europe. Small numbers also occur in northeastern North America, where it was formerly known as the common black-headed gull. As is the case with many gulls, it was previously placed in the genus Larus.

<span class="mw-page-title-main">Behavioral ecology</span> Study of the evolutionary basis for animal behavior due to ecological pressures

Behavioral ecology, also spelled behavioural ecology, is the study of the evolutionary basis for animal behavior due to ecological pressures. Behavioral ecology emerged from ethology after Niko Tinbergen outlined four questions to address when studying animal behaviors: What are the proximate causes, ontogeny, survival value, and phylogeny of a behavior?

<span class="mw-page-title-main">American coot</span> Species of bird

The American coot, also known as a mud hen or pouldeau, is a bird of the family Rallidae. Though commonly mistaken for ducks, American coots are only distantly related to ducks, belonging to a separate order. Unlike the webbed feet of ducks, coots have broad, lobed scales on their lower legs and toes that fold back with each step which facilitates walking on dry land. Coots live near water, typically inhabiting wetlands and open water bodies in North America. Groups of coots are called covers or rafts. The oldest known coot lived to be 22 years old.

<span class="mw-page-title-main">Kleptoparasitism</span> Type of animal feeding strategy

Kleptoparasitism is a form of feeding in which one animal deliberately takes food from another. The strategy is evolutionarily stable when stealing is less costly than direct feeding, such as when food is scarce or when victims are abundant. Many kleptoparasites are arthropods, especially bees and wasps, but including some true flies, dung beetles, bugs, and spiders. Cuckoo bees are specialized kleptoparasites which lay their eggs either on the pollen masses made by other bees, or on the insect hosts of parasitoid wasps. They are an instance of Emery's rule, which states that insect social parasites tend to be closely related to their hosts. The behavior occurs, too, in vertebrates including birds such as skuas, which persistently chase other seabirds until they disgorge their food, and carnivorous mammals such as spotted hyenas and lions. Other species opportunistically indulge in kleptoparasitism.

<span class="mw-page-title-main">Brood parasitism</span> Subclass of parasitism, phenomenon that an animal relies on other inidivids to raise its young.

Brood parasitism is a subclass of parasitism and phenomenon and behavioural pattern of certain animals, brood parasites, that rely on others to raise their young. The strategy appears among birds, insects and fish. The brood parasite manipulates a host, either of the same or of another species, to raise its young as if it were its own, usually using egg mimicry, with eggs that resemble the host's.

<span class="mw-page-title-main">Shiny cowbird</span> Species of bird

The shiny cowbird is a passerine bird in the New World family Icteridae. It breeds in most of South America except for dense forests and areas of high altitude such as mountains. Since 1900 the shiny cowbird's range has shifted northward, and it was recorded in the Caribbean islands as well as the United States, where it is found breeding in southern Florida. It is a bird associated with open habitats, including disturbed land from agriculture and deforestation.

<span class="mw-page-title-main">Alloparenting</span> Parenting not done by the birth parents

Alloparenting is a term used to classify any form of parental care provided by an individual towards young that are not its own direct offspring. These are often referred to as "non-descendant" young, even though grandchildren can be among them. Among humans, alloparenting is often performed by a child's grandparents and older siblings. Individuals providing this care are referred to using the neutral term of alloparent.

"Fixed action pattern" is an ethological term describing an instinctive behavioral sequence that is highly stereotyped and species-characteristic. Fixed action patterns are said to be produced by the innate releasing mechanism, a "hard-wired" neural network, in response to a sign/key stimulus or releaser. Once released, a fixed action pattern runs to completion.

An obligate parasite or holoparasite is a parasitic organism that cannot complete its life-cycle without exploiting a suitable host. If an obligate parasite cannot obtain a host it will fail to reproduce. This is opposed to a facultative parasite, which can act as a parasite but does not rely on its host to continue its life-cycle. Obligate parasites have evolved a variety of parasitic strategies to exploit their hosts. Holoparasites and some hemiparasites are obligate.

<span class="mw-page-title-main">Horsfield's bronze cuckoo</span> Species of bird

Horsfield's bronze cuckoo is a small cuckoo in the family Cuculidae. Its size averages 22g and is distinguished by its green and bronze iridescent colouring on its back and incomplete brown barring from neck to tail. Horsfield's bronze cuckoo can be destiguished from other bronze cuckoos by its white eyebrow and brown eye stripe. The Horsfield's bronze cuckoo is common throughout Australia preferring the drier open woodlands away from forested areas.

<span class="mw-page-title-main">Pavonine cuckoo</span> Species of bird

The pavonine cuckoo is a Neotropical cuckoo with a long graduated tail and a short crest. It is one of three species of Neotropical cuckoo which are known to be brood parasites.

<span class="mw-page-title-main">Screaming cowbird</span> Species of bird

The screaming cowbird is an obligate brood parasite belonging to the family Icteridae and is found in South America. It is also known commonly as the short billed cowbird.

<span class="mw-page-title-main">Egg tossing (behavior)</span>

Egg tossing or egg destruction is a behavior observed in some species of birds where one individual removes an egg from the communal nest. This is related to infanticide, where parents kill their own or other's offspring. Egg tossing is observed in avian species, most commonly females, who are involved with cooperative breeding or brood parasitism. Among colonial non-co-nesting birds, egg-tossing is observed to be performed by an individual of the same species, and, in the case of brood parasites, this behavior is done by either the same or different species. The behavior of egg tossing offers its advantages and disadvantages to both the actor and recipient.

<span class="mw-page-title-main">Begging in animals</span>

Begging in animals is when an animal solicits being given resources by another animal. This is usually a young animal soliciting food from their parents, brood hosts or other adults. However, the resource is sometimes non-food related or may be solicited by adult animals. Begging behavior is most widely studied in birds, however, mammals, amphibians, and invertebrates perform begging displays. Generally in food solicitation, begging behavior is instinctive, although in some instances it is learned.

In evolutionary biology, mimicry in vertebrates is mimicry by a vertebrate of some model, deceiving some other animal, the dupe. Mimicry differs from camouflage as it is meant to be seen, while animals use camouflage to remain hidden. Visual, olfactory, auditory, biochemical, and behavioral modalities of mimicry have been documented in vertebrates.

The mafia hypothesis posits that brood parasite eggs are accepted by the host out of fear of retaliation from the brood parasite, in an example of coevolution.

References

  1. 1 2 Tinbergen, Niko (1951). The Study of Instinct . Oxford, Clarendon Press. ISBN   978-0198573432. Based on a series of lectures given in New York, 1947, under the auspices of the American Museum of Natural History and Columbia University
  2. 1 2 Barrett, Deirdre (2007). "Supernormal Stimuli – Why Birds Are Cuckoo". Waistland: The (R)Evolutionary Science Behind Our Weight and Fitness Crisis. New York, New York: W.W. Norton & Co. pp.  31–51. ISBN   978-0393062168.
  3. ↑ McFarland, David (2014-01-01). A Dictionary of Animal Behaviour. doi:10.1093/acref/9780191761577.001.0001. ISBN   978-0191761577.
  4. 1 2 3 4 5 6 7 8 9 Tinbergen, Niko, 1907–1988 (1953). The herring gull's world; a study of the social behaviour of birds. London: Collins. ISBN   0002194449. OCLC   1029697.{{cite book}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)[ page needed ]
  5. ↑ Dawkins R, Krebs JR (1979). Arms between and within species. Proc R Soc Lond B Biol Sci 205:489–511
  6. ↑ D. T. Gwynne; D. C. F. Rentz (February 1983). "Beetles on the Bottle: Male Buprestids Mistake Stubbies for Females (Coleoptera)". Australian Journal of Entomology . 22 (1): 79–80. doi: 10.1111/j.1440-6055.1983.tb01846.x .{{cite journal}}: CS1 maint: multiple names: authors list (link)
  7. ↑ Jonathan Amos (September 30, 2011). "Beetle's beer bottle sex wins Ig Nobel Prize". BBC News . Retrieved September 30, 2011.
  8. ↑ Mauck E, De Moraes C and Mescher M. 2010. Deceptive chemical signals induced by a plant virus attract insects vectors to inferior hosts. PNAS Vol. 107. No. 8. 3603.
  9. 1 2 3 4 5 6 KRAL, Karl (2016-08-09). "Implications of insect responses to supernormal visual releasing stimuli in intersexual communication and flower-visiting behaviour: A review". European Journal of Entomology. 113: 429–437. doi: 10.14411/eje.2016.056 . ISSN   1210-5759.
  10. 1 2 Òistein HH, Glenn-Peter S, Tore S and Nils C. "Parasites and supernormal manipulation". Proc. R. Soc. Lond. B 268, 2551–2558
  11. 1 2 3 4 5 6 7 8 9 Grim, T.; Honza, M. (2001-02-01). "Does supernormal stimulus influence parental behaviour of the cuckoo's host?". Behavioral Ecology and Sociobiology. 49 (4): 322–329. doi:10.1007/s002650000295. ISSN   0340-5443. S2CID   25768229.
  12. ↑ Goodwin, B. C.; Browne, M.; Rockloff, M. (2015-10-29). "Measuring Preference for Supernormal Over Natural Rewards". Evolutionary Psychology. 13 (4): 147470491561391. doi: 10.1177/1474704915613914 . ISSN   1474-7049. PMC   10480800 .
  13. ↑ Barrett, Deirdre (2010). Supernormal Stimuli: How Primal Urges Overran Their Evolutionary Purpose. W. W. Norton. ISBN   978-0-393-06848-1.
  14. ↑ Doyle, J. F.; Pazhoohi, F. (2012). "Natural and augmented breasts: Is what is not natural most attractive?". Human Ethology Bulletin. 27: 4–14.
  15. ↑ Doyle, J. F. (2009). "A woman's walk: Attractiveness in motion". Journal of Social, Evolutionary, and Cultural Psychology. 3 (2): 81–92. doi:10.1037/h0099329.
  16. 1 2 Pazhoohi, F.; Macedo, M. F.; Doyle, J. F.; Arantes, J. (2019). "Waist-to-Hip Ratio as Supernormal Stimuli: Effect of Contrapposto Pose and Viewing Angle". Archives of Sexual Behavior. 49 (3): 837–847. doi:10.1007/s10508-019-01486-z. PMID   31214904. S2CID   195066235.
  17. ↑ "Why Candy Crush Saga likes to play on your sweet tooth". the Guardian. 23 June 2014. Retrieved 12 February 2021.
  18. ↑ Costa, Marco (2006). "Aesthetic phenomena as supernormal stimuli: the case of eye, lip, and lower-face size and roundness in artistic portraits". Perception. 35 (2): 229–246. doi:10.1068/p3449. PMID   16583768. S2CID   41378568.
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