Animal welfare science

Last updated

Animal welfare science is the scientific study of the welfare of animals as pets, in zoos, laboratories, on farms and in the wild. Although animal welfare has been of great concern for many thousands of years in religion and culture, the investigation of animal welfare using rigorous scientific methods is a relatively recent development. The world's first Professor of Animal Welfare Science, Donald Broom, was appointed by Cambridge University (UK) in 1986.

Contents

Historical legislation and guidelines

Early legislation which formed the impetus for assessing animal welfare and the subsequent development of animal welfare science include the Ireland Parliament (Thomas Wentworth) "An Act against Plowing by the Tayle, and pulling the Wooll off living Sheep", 1635, and the Massachusetts Colony (Nathaniel Ward) "Off the Bruite Creatures" Liberty 92 and 93 in the "Massachusetts Body of Liberties" of 1641. [1]

Richard Martin's act, the "Cruel Treatment of Cattle Act 1822" is often considered to be the precursor of modern relevant legislation. One of the first national laws to protect animals was the UK "Cruelty to Animals Act 1835" followed by the "Protection of Animals Act 1911". In the US it was many years until there was a National law to protect animals—the "Animal Welfare Act of 1966"—although there were a number of states that passed anti-cruelty laws between 1828 and 1898. [2] In India, animals are protected by the "Prevention of Cruelty to Animals Act, 1960". In the UK, the "Animal Welfare Act 2006" consolidated many different forms of animal welfare legislation.

Animal welfare science can be considered as the assessment of welfare. The first publication to include the term "assessment" appears to be a 1965 appendix by William Homan Thorpe entitled The assessment of pain and distress in animals. [3] This was followed 20 years later by a highly influential paper on assessing pain and distress in laboratory animals by Morton and Griffiths. [4]

Methods of assessment

Animal welfare science uses a variety of behavioural or physiological measures or indicators. Integrated approaches to assess animal welfare include risk analysis and semantic modelling[ clarification needed ] of animal welfare. [5]

Animal behaviour

Animal physiology

Organisations

Organisations interested in animal welfare science were set up before the subject became recognised as a science. The Royal Society for the Prevention of Cruelty to Animals (RSPCA) was founded in 1824 by a group of twenty-two reformers led by Richard Martin MP (who would thereby earn the nickname Humanity Dick), William Wilberforce MP and the Reverend Arthur Broome. The Universities Federation for Animal Welfare (UFAW) history can be traced to the founding in 1926 of the University of London Animal Welfare Society (ULAWS) by Major Charles Hume. The name was changed to the Universities Federation for Animal Welfare in 1938, reflecting the increasingly wide range of people and institutions involved.

More recent organisations involved in animal welfare science include the Scientists Center for Animal Welfare (SCAW) and university departments specialising in this branch of science including the Animal Welfare and Anthrozoology Center at Cambridge University, the Animal Welfare Science Centre at The University of Melbourne in Australia and the Animal Welfare Science and Bioethics Centre at Massey University in New Zealand.

Although not limited to animal welfare science, many members of the International Society for Applied Ethology work and publish research in this subject.

Journals, articles and books

Veterinary journals carrying articles on animal welfare have been published for many years, for example, the Veterinary Record has been published weekly since 1888. Peer-reviewed scientific journals have been launched more recently, e.g. Applied Animal Behaviour Science in 1974, Animal Welfare in 1992, the Journal of Applied Animal Welfare Science in 1998, [32] and Frontiers in Veterinary Science—Animal Behavior and Welfare in 2014.

Many books on animal welfare science have been written, for example those by Professor Marian Stamp Dawkins, [33] Professor David Fraser, [34] Michael Appleby, Barry Hughes and Joy Mench, [35] John Webster, [36] and David Mellor et al. [37]

Teaching

In 2011 in an article on the history of animal welfare science, Donald Broom wrote "The numbers of animal welfare scientists is increasing rapidly. The subject is now being taught in all European countries and the number of university courses on animal welfare in Brazil has increased from one to over 60 in 15 years. The diversity of animal welfare science is increasing and the expansion is likely to continue. The decision by the American Veterinary Medical Association to promote the teaching of the subject in all American veterinary schools will have a substantial effect." [38]

See also

Related Research Articles

<span class="mw-page-title-main">Animal welfare</span> Well-being of non-human animals

Animal welfare is the well-being of non-human animals. Formal standards of animal welfare vary between contexts, but are debated mostly by animal welfare groups, legislators, and academics. Animal welfare science uses measures such as longevity, disease, immunosuppression, behavior, physiology, and reproduction, although there is debate about which of these best indicate animal welfare.

<span class="mw-page-title-main">Broiler</span> Chicken bred for meat

Breed broiler is any chicken that is bred and raised specifically for meat production. Most commercial broilers reach slaughter weight between four and six weeks of age, although slower growing breeds reach slaughter weight at approximately 14 weeks of age. Typical broilers have white feathers and yellowish skin. Broiler or sometimes broiler-fryer is also used sometimes to refer specifically to younger chickens under 2.0 kilograms, as compared with the larger roasters.

<span class="mw-page-title-main">Feather-plucking</span> Maladaptive, behavioural disorder commonly seen in captive birds

Feather-plucking, sometimes termed feather-picking, feather damaging behaviour or pterotillomania, is a maladaptive, behavioural disorder commonly seen in captive birds that chew, bite or pluck their own feathers with their beak, resulting in damage to the feathers and occasionally the skin. It is especially common among parrots, with an estimated 10% of captive parrots exhibiting the disorder. The areas of the body that are mainly pecked or plucked are the more accessible regions such as the neck, chest, flank, inner thigh and ventral wing area. Contour and down feathers are generally identified as the main target, although in some cases, tail and flight feathers are affected. Although feather-plucking shares characteristics with feather pecking commonly seen in commercial poultry, the two behaviours are currently considered to be distinct as in the latter, the birds peck at and pull out the feathers of other individuals.

An ethogram is a catalogue or inventory of behaviours or actions exhibited by an animal used in ethology.

<span class="mw-page-title-main">Cribbing (horse)</span> Stable vice in horses

Cribbing is a form of stereotypy, otherwise known as wind sucking or crib-biting. Cribbing is considered to be an abnormal, compulsive behavior seen in some horses, and is often labelled a stable vice. The major factors that cause cribbing include stress, stable management, genetic and gastrointestinal irritability.

<span class="mw-page-title-main">Emotion in animals</span> Research into similarities between non-human and human emotions

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.

<span class="mw-page-title-main">Behavioral enrichment</span> Techniques for stimulating captive animals

Behavioral enrichment is an animal husbandry principle that seeks to enhance the quality of captive animal care by identifying and providing the environmental stimuli necessary for optimal psychological and physiological well-being. Enrichment can either be active or passive, depending on whether it requires direct contact between the animal and the enrichment. A variety of enrichment techniques are used to create desired outcomes similar to an animal's individual and species' history. Each of the techniques used is intended to stimulate the animal's senses similarly to how they would be activated in the wild. Provided enrichment may be seen in the form of auditory, olfactory, habitat factors, food, research projects, training, and objects.

<span class="mw-page-title-main">Shock collar</span> Dog training device using electrical pain to change behavior

A shock collar or remote training collar, also known as an e-collar, Ecollar, or electronic collar, is a type of training collar that delivers shocks to the neck of a dog to change behavior. These collars incorporate a radio-controlled electronic device and are worn around the dog's neck. Many European and South American countries view shock collars as animal cruelty and have banned their use. The mechanism behind shock collars involve inflicting varying levels and duration of pain, which generates fear and serves as a deterrent for undesirable behaviors. Some models of shock collar models offer additional features such as a tone or vibrational setting that can be used as an alternative or in combination with the shock. Certain advanced collars include Internet mapping capabilities and GPS functionality to track the dog's location or notify the owner about its whereabouts.

Animal psychopathology is the study of mental or behavioral disorders in non-human animals.

<span class="mw-page-title-main">Pain in fish</span>

Fish fulfill several criteria proposed as indicating that non-human animals experience pain. These fulfilled criteria include a suitable nervous system and sensory receptors, opioid receptors and reduced responses to noxious stimuli when given analgesics and local anaesthetics, physiological changes to noxious stimuli, displaying protective motor reactions, exhibiting avoidance learning and making trade-offs between noxious stimulus avoidance and other motivational requirements.

<span class="mw-page-title-main">Pain in animals</span> Pain experienced by non-human animals

Pain negatively affects the health and welfare of animals. "Pain" is defined by the International Association for the Study of Pain as "an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage." Only the animal experiencing the pain can know the pain's quality and intensity, and the degree of suffering. It is harder, if even possible, for an observer to know whether an emotional experience has occurred, especially if the sufferer cannot communicate. Therefore, this concept is often excluded in definitions of pain in animals, such as that provided by Zimmerman: "an aversive sensory experience caused by actual or potential injury that elicits protective motor and vegetative reactions, results in learned avoidance and may modify species-specific behaviour, including social behaviour." Nonhuman animals cannot report their feelings to language-using humans in the same manner as human communication, but observation of their behaviour provides a reasonable indication as to the extent of their pain. Just as with doctors and medics who sometimes share no common language with their patients, the indicators of pain can still be understood.

<span class="mw-page-title-main">Pain in crustaceans</span> Ethical debate

There is a scientific debate which questions whether crustaceans experience pain. It is a complex mental state, with a distinct perceptual quality but also associated with suffering, which is an emotional state. Because of this complexity, the presence of pain in an animal, or another human for that matter, cannot be determined unambiguously using observational methods, but the conclusion that animals experience pain is often inferred on the basis of likely presence of phenomenal consciousness which is deduced from comparative brain physiology as well as physical and behavioural reactions.

<span class="mw-page-title-main">Stereotypy (non-human)</span> Non-pathological pattern of animal behavior which displays very low variability

In animal behaviour, stereotypy, stereotypic or stereotyped behaviour has several meanings, leading to ambiguity in the scientific literature. A stereotypy is a term for a group of phenotypic behaviours that are repetitive, morphologically identical and which possess no obvious goal or function. These behaviours have been defined as "abnormal", as they exhibit themselves solely in animals subjected to barren environments, scheduled or restricted feedings, social deprivation and other cases of frustration, but do not arise in "normal" animals in their natural environments. These behaviours may be maladaptive, involving self-injury or reduced reproductive success, and in laboratory animals can confound behavioural research. Stereotypical behaviours are thought to be caused ultimately by artificial environments that do not allow animals to satisfy their normal behavioural needs. Rather than refer to the behaviour as abnormal, it has been suggested that it be described as "behaviour indicative of an abnormal environment".

<span class="mw-page-title-main">Abnormal behaviour of birds in captivity</span>

Abnormal behavior of birds in captivity has been found to occur among both domesticated and wild birds. Abnormal behavior can be defined in several ways. Statistically, 'abnormal' is when the occurrence, frequency or intensity of a behaviour varies statistically significantly, either more or less, from the normal value. This means that theoretically, almost any behaviour could become 'abnormal' in an individual. Less formally, 'abnormal' includes any activity judged to be outside the normal behaviour pattern for captive birds of that particular class or age. For example, running rather than flying may be a normal behaviour and regularly observed in one species, however, in another species it might be normal but becomes 'abnormal' if it reaches a high frequency, or in another species it is rarely observed and any incidence is considered 'abnormal'. This article does not include 'one-off' behaviours performed by individual birds that might be considered abnormal for that individual, unless these are performed repeatedly by other individuals in the species and are recognised as part of the ethogram of that species.

<span class="mw-page-title-main">Preference test</span> Experiment in animal behavior

A preference test is an experiment in which animals are allowed free access to multiple environments which differ in one or more ways. Various aspects of the animal's behaviour can be measured with respect to the alternative environments, such as latency and frequency of entry, duration of time spent, range of activities observed, or relative consumption of a goal object in the environment. These measures can be recorded either by the experimenter or by motion detecting software. Strength of preference can be inferred by the magnitude of the difference in the response, but see "Advantages and disadvantages" below. Statistical testing is used to determine whether observed differences in such measures support the conclusion that preference or aversion has occurred. Prior to testing, the animals are usually given the opportunity to explore the environments to habituate and reduce the effects of novelty.

<span class="mw-page-title-main">Pain in amphibians</span> Ethical issue

Pain is an aversive sensation and feeling associated with actual, or potential, tissue damage. It is widely accepted by a broad spectrum of scientists and philosophers that non-human animals can perceive pain, including pain in amphibians.

<span class="mw-page-title-main">Grimace scale</span> Method of assessing pain in non-human animals

The grimace scale (GS), sometimes called the grimace score, is a method of assessing the occurrence or severity of pain experienced by non-human animals according to objective and blinded scoring of facial expressions, as is done routinely for the measurement of pain in non-verbal humans. Observers score the presence or prominence of "facial action units" (FAU), e.g. Orbital Tightening, Nose Bulge, Ear Position and Whisker Change. These are scored by observing the animal directly in real-time, or post hoc from photographs or screen-grabs from videos. The facial expression of the animals is sometimes referred to as the pain face.

<span class="mw-page-title-main">Pain in cephalopods</span> Contentious issue

Pain in cephalopods is a contentious issue. Pain is a complex mental state, with a distinct perceptual quality but also associated with suffering, which is an emotional state. Because of this complexity, the presence of pain in non-human animals, or another human for that matter, cannot be determined unambiguously using observational methods, but the conclusion that animals experience pain is often inferred on the basis of likely presence of phenomenal consciousness which is deduced from comparative brain physiology as well as physical and behavioural reactions.

<span class="mw-page-title-main">Chris Sherwin</span> English veterinary scientist (1962–2017)

Christopher M. Sherwin was an English veterinary scientist and senior research fellow at the University of Bristol Veterinary School in Lower Langford, Somerset. He specialised in applied ethology, the study of the behaviour of animals in the context of their interactions with humans, and of how to balance the animals' needs with the demands placed on them by humans.

References

  1. ↑ "Animal Rights History". Archived from the original on 1 October 2011. Retrieved 8 November 2011.
  2. ↑ "AWIC". Archived from the original on 2 March 2013. Retrieved 8 November 2011.
  3. ↑ Thorpe, W.H., (1965). The assessment of pain and distress in animals. Appendix III in the report of the technical committee to enquire into the welfare of animals kept under intensive husbandry conditions, F.W.R. Brambell (chairman). H.M.S.O., London
  4. ↑ Morton D.B.; Griffiths P.H.M. (1985). "Guidelines on the recognition of pain, distress and discomfort in experimental animals and an hypothesis for assessment". Veterinary Record. 116 (16): 431–436. doi:10.1136/vr.116.16.431. PMID   3923690. S2CID   34686008.
  5. ↑ Bracke M.B.M.; Edwards S.A.; Metz J.H.M.; Noordhuizen J.P.T.M.; Algers B. (2008). "Synthesis of semantic modelling and risk analysis methodology applied to animal welfare". Animal. 2 (7): 1061–1072. Bibcode:2008Anim....2.1061B. doi: 10.1017/S1751731108002139 . PMID   22443707.
  6. ↑ Mason G.J. (1991). "Stereotypies – A critical Review". Animal Behaviour. 41 (6): 1015–1037. doi:10.1016/S0003-3472(05)80640-2. hdl: 10214/4622 . S2CID   53187334.
  7. ↑ Claes A.; Attur Shanmugam A.; Jensen P. (2010). "Habituation to environmental enrichment in captive Sloth Bears-effect on stereotypies". Zoo Biology. 29 (6): 705–714. doi:10.1002/zoo.20301. PMID   20069629.
  8. 1 2 Sherwin C.M.; Richards G.J.; Nicol C.J. (2010). "Comparison of the welfare of layer hens in 4 housing systems in the UK". British Poultry Science. 51 (4): 488–499. doi:10.1080/00071668.2010.502518. PMID   20924842. S2CID   8968010.
  9. ↑ Brunberg E.; Wallenbeck A.; Keeling L.J. (2011). "Tail biting in fattening pigs: Associations between frequency of tail biting and other abnormal behaviours". Applied Animal Behaviour Science. 133 (1–2): 18–25. doi:10.1016/j.applanim.2011.04.019.
  10. ↑ Leach, M.C.; Klaus, K.; Miller, A.L.; Scotto di Perrotolo, M.; Sotocinal, S.G.; Flecknell, P.A. (2012). "The assessment of post-vasectomy pain in mice using behaviour and the Mouse Grimace Scale". PLOS ONE. 7 (4): e35656. Bibcode:2012PLoSO...735656L. doi: 10.1371/journal.pone.0035656 . PMC   3338444 . PMID   22558191.
  11. ↑ Dawkins M.S. (1989). "Time budgets in red junglefowl as a baseline for the assessment of welfare in domestic-fowl". Applied Animal Behaviour Science. 24: 77–80. doi:10.1016/0168-1591(89)90126-3.
  12. ↑ Mondol, Samrat; Fitzpatrick, Malcolm; Kadivar, Riyazahmed F.; Pandit, Shwetank J.; Malik, Pradeep K.; Tyagi, Praveen C.; Goswami, Sitendu (2019-01-19). "Effects of personality and life-history on the welfare of captive Asiatic lions (Panthera leo persica)". PeerJ Preprints. doi: 10.7287/peerj.preprints.27495v1 .
  13. ↑ McBride G.; Parer I.P.; Foenander F. (1969). "The social organization and behaviour of the feral domestic fowl". Animal Behaviour Monographs. 2: 125–181. doi:10.1016/s0066-1856(69)80003-8.
  14. ↑ Stolba A.; Wood-Gush D.G.M. (1989). "The behaviour of pigs in a semi-natural environment". Animal Production. 48 (2): 419–425. doi:10.1017/s0003356100040411.
  15. ↑ Sherwin C.M.; Glen E.F. (2003). "Cage colour preferences and effects of home-cage colour on anxiety in laboratory mice". Animal Behaviour. 66 (6): 1085–1092. doi:10.1006/anbe.2003.2286. S2CID   53191108.
  16. ↑ Sherwin C.M. (2004). "The motivation of group-housed laboratory mice, Mus musculus, for additional space". Animal Behaviour. 67 (4): 711–717. doi:10.1016/j.anbehav.2003.08.018. S2CID   53181481.
  17. ↑ Mendl M.; Burman O.H.P.; Parker R.M.A.; Paul E.S. (2009). "Cognitive bias as an indicator of animal emotion and welfare: Emerging evidence and underlying mechanisms". Applied Animal Behaviour Science. 118 (3–4): 161–181. doi:10.1016/j.applanim.2009.02.023.
  18. ↑ Sherwin C.M.; Olsson I.A.S. (2004). "Housing conditions affect self-administration of anxiolytic by laboratory mice". Animal Welfare. 13: 33–38. doi:10.1017/S0962728600026634. S2CID   56915273.
  19. ↑ Duncan I.J.H.; Wood-Gush D.G.M. (1971). "Frustration and aggression in the domestic fowl". Animal Behaviour. 19 (3): 500–504. doi:10.1016/s0003-3472(71)80104-5. PMID   5167834.
  20. ↑ Zimmerman P.H.; Lundberg A.; Keeling L.J.; Koene P. (2003). "The effect of an audience on the gakel-call and other frustration behaviours in the laying hen (Gallus gallus domesticus)". Animal Welfare. 12 (3): 315–326. doi:10.1017/S0962728600025823. S2CID   145114602.
  21. ↑ Kemppinen N.; Hau J.; Meller A.; Mauranen K.; Kohila T.; Nevalainen T. (2010). "Impact of aspen furniture and restricted feeding on activity, blood pressure, heart rate and faecal corticosterone and immunoglobulin A excretion in rats (Rattus norvegicus) housed in individually ventilated cages". Laboratory Animals. 44 (2): 104–112. doi: 10.1258/la.2009.009058 . PMID   19854757. S2CID   17743686.
  22. ↑ Von Borrell E.; Langbein J.; Despres G.; Hansen S.; Leterrier C.; Marchant-Forde J.N.; Marchant-Forde R.M.; Minero M.; Mohr E.; Prunier A.; Valance D.; Veissier I. (2007). "Heart rate variability as a measure of autonomic regulation of cardiac activity for assessing stress and welfare in farm animals – a review" (PDF). Physiology & Behavior. 92 (3): 293–316. doi:10.1016/j.physbeh.2007.01.007. hdl: 2434/35886 . PMID   17320122. S2CID   6135941.
  23. ↑ Laws N.; Ganswindt A.; Heistermann M.; Harris M.; Harris S.; Sherwin C. (2007). "A case study: fecal corticosteroid and behavior as indicators of welfare during relocation of an asian elephant". Journal of Applied Animal Wlfare Science. 10 (4): 349–358. doi:10.1080/10888700701555600. PMID   17970634. S2CID   46617133.
  24. ↑ Accorsi P.A.; Carloni E.; Valsecchi P.; Viggiani R.; Garnberoni M.; Tarnanini C.; Seren E. (2008). "Cortisol determination in hair and faeces from domestic cats and dogs". General and Comparative Endocrinology. 155 (2): 392–402. doi:10.1016/j.ygcen.2007.07.002. PMID   17727851.
  25. ↑ Bortolotti G.R.; Marchant T.A.; Blas J.; German T. (2008). "Corticosterone in feathers is a long-term, integrated measure of avian stress physiology". Functional Ecology. 22 (3): 494–500. Bibcode:2008FuEco..22..494B. doi:10.1111/j.1365-2435.2008.01387.x. hdl: 10261/36997 .
  26. ↑ Royo F.; Mayo S.; Carlsson H.E.; Hau J. (2008). "Egg corticosterone: A noninvasive measure of stress in egg-laying birds". Journal of Avian Medicine and Surgery. 22 (4): 310–314. doi:10.1647/2008-001.1. PMID   19216258. S2CID   21155214.
  27. ↑ Martin L.B.; Kidd L.; Liebl A.L.; Coon C.A.C. (2011). "Captivity induces hyper-inflammation in the house sparrow (Passer domesticus)". Journal of Experimental Biology. 214 (15): 2579–2585. doi: 10.1242/jeb.057216 . PMID   21753052.
  28. ↑ Lewis M.H., Presti M.F., Lewis J.B. and Turner, C.A. (2006). The neurobiology of stereotypy I: Environmental complexity. In Stereotypic Animal Behaviour: Fundamentals and Applications to Welfare, G. Mason and J. Rushen (Editors). CABI pp. 190-226. doi : 10.1079/9780851990040.0190
  29. ↑ Hughes B.O.; Gilbert A.B.; Brown M.F. (1986). "Categorisation and causes of abnormal egg shells: relationship with stress". British Poultry Science. 27 (2): 325–337. doi:10.1080/00071668608416885. PMID   3742268.
  30. ↑ Wilcox C.S.; Patterson J.; Cheng H.W. (2009). "Use of thermography to screen for subclinical bumblefoot in poultry". Poultry Science. 88 (6): 1176–1180. doi: 10.3382/ps.2008-00446 . PMID   19439627.
  31. ↑ Ikkatai Y.; Watanabe S. (2015). "Eye surface temperature detects stress response in budgerigars (Melopsittacus undulatus)". NeuroReport. 26 (11): 642–646. doi:10.1097/wnr.0000000000000403. PMID   26103119. S2CID   31058405.
  32. ↑ "JAAWS" . Retrieved 8 November 2011.
  33. ↑ Dawkins, M.S., (1980). Animal Suffering: The Science of Animal Welfare. Chapman and Hall, London
  34. ↑ Fraser, D., (2008) Understanding Animal Welfare: The Science In Its Cultural Context. John Wiley and Sons
  35. ↑ Linda J. Keeling, Jeff Rushen and Ian Duncan. Understanding animal welfare. Animal Welfare. 2011 Page 13. edited by Michael C. Appleby, Barry O. Hughes, Joy A. Mench
  36. ↑ Webster, J (2008). Animal Welfare: Limping Towards Eden. John Wiley and Sons. p. 6.
  37. ↑ Mellor, D., Patterson-Kane, E. and Stafford, K.J., (2009). The Sciences of Animal Welfare. UFAW/Wiley-Blackwell
  38. ↑ Broom D.M. (2011). "A History of Animal Welfare Science". Acta Biotheoretica. 59 (2): 121–137. doi:10.1007/s10441-011-9123-3. PMID   21347723. S2CID   5959851.

Further references

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.