Assessing learning and memory in pigs

Animal Cognition

Volumn 14, Issue 2, 2011, Pages 151-173

  Gieling, Elise Titia ^a,b   Nordquist, Rebecca Elizabeth ^a,b   van der Staay, Franz Josef ^a,b  

^a UTRECHT UNIVERSITY   (Netherlands)

^b UNIVERSITY MEDICAL CENTER UTRECHT   (Netherlands)

Author keywords

Cognition; Learning; Memory; Model animal; Pig; Welfare

Indexed keywords

ANIMALIA; SUIDAE; SUS SCROFA;

EID: 79951769860     PISSN: 14359448     EISSN: None     Source Type: Journal    
DOI: 10.1007/s10071-010-0364-3     Document Type: Review

References (143)

1. Albarella U, Dobney K, Ervynck K, Rowley-Conwy P (2007) Pigs and humans: 10. 000 years of interactions. Oxford University Press, Oxford.
2. Arndt SS, Laarakker MC, van Lith HA, van der Staay FJ, Gieling E, Salomons AR, van't Klooster J, Ohl F (2009) Individual housing of mice-impact on behaviour and stress responses. Physiol Behav 97: 385-393.
3. Arnfred SM, Lind NM, Hansen AK, Hemmingsen RP (2004) Pre-pulse inhibition of the acoustic startle eye-blink in the Göttingen minipig. Behav Brain Res 151: 295-301.
4. Arts JWM, van der Staay FJ, Ekkel ED (2009) Working and reference memory of pigs in the spatial holeboard discrimination task. Behav Brain Res 205: 303-306.
5. Ashby FG, Isen AM, Turken AU (1999) A neuropsychological theory of positive affect and its influence on cognition. Psychol Rev 106(3): 529-550.
6. Astur RS, Taylor LB, Mamelak AN, Philpott L, Sutherland RJ (2002) Humans with hippocampus damage display severe spatial memory impairments in a virtual Morris water task. Behav Brain Res 132: 77-84.
7. Baldwin BA (1969) The study of behaviour in pigs. Br Vet J 125: 281.
8. Baldwin BA (1979) Operant studies on the behaviour of pigs and sheep in relation to the physical environment. J Anim Sci 49.
9. Baldwin BA, Meese GB (1977) Sensory reinforcement and illumination preference in the domesticated pig. Anim Behav 25: 497-507.
10. Baldwin BA, Meese GB (1979) Social behaviour in pigs studied by means of operant conditioning. Anim Behav 27: 947-957.
11. Baldwin BA, Stephens DB (1973) The effects of conditioned behaviour and environmental factors on plasma corticosteroid levels in pigs. Physiol Behav 10: 267-274.
12. Barnes RH, Moore U, Pond WG (1969) Behavioural abnormalities in young adult pigs caused by malnutrition in early life. J Nutrition 100: 149-155.
13. Bartsch T, Schönfeld R, Müller FJ, Alfke K, Leplow B, Aldenhoff J, Deuschl G, Koch JM (2010) Focal lesions of human hippocampal CA1 neurons in transient global amnesia impair place memory. Science 328: 1412.
14. Bauer R, Brust P, Walter B, Vorwieger G, Bergmann R, Elhalag E, Fritz A, Steinbach J, Füchtner F, Hinz R, Zwiener U, Johannsen B (2002) Effect of hypoxia/hypercapnia on metabolism of 6-[F]fluoro-L-DOPA in newborn piglets. Brain Res 934: 23-33.
15. Bennett MK (1970) Aspects of the Pig. Agric Hist 44: 223-236.
16. Boissy A, Manteuffel G, Jensen MB, Moe RO, Spruijt B, Keeling LJ, Winckler C, Forkma B, Dimitrov I, Langbein J, Bakken M, Veissier I, Aubert A (2007) Assessment of positive emotion in animals to improve their welfare. Physiol Behav 92: 375-397.
17. Bolhuis JE, Schouten WGP, Leeuw de JA, Schrama JW, Wiegant VM (2004) Individual coping characteristics, rearing conditions and behavioural flexibility in pigs. Behav Brain Res 152: 351-360.
18. Bouger PC, van der Staay FJ (2005) Rats with scopolamine- or MK-801-induced spatial discrimination deficits in the cone field task: animal models for impaired spatial orientation performance. Neuropsychopharmacology 15: 331-346.
19. Breland K, Breland M (1915) A field of applied animal psychology. Am Psychol 6: 202-204.
20. Broom DM (2010) Cognitive ability and awareness in domestic animals and decisions about obligations to animals. Appl Anim Behav Sci 126: 1-11.
21. Broom DM, Zanella AJ (2004) Brain measures which tell us about animal welfare. Anim Welf 13: 41-45.
22. Broom DM, Sena H, Moynihan KL (2009) Pigs learn what a mirror image represents and use it to obtain information. Anim Behav 78: 1037-1041.
23. Cánovas R, Espínola M, Iribarne L, Cimadevilla JM (2008) A new virtual task to evaluate human place learning. Behav Brain Res 190: 112-118.
24. Chaput RL, Barron EL, Marrenfeltz JK, Dalton TK, Wolfe WW (1973) The miniature pig: a biomedical model for behavioural studies. Lab Anim Sci 23: 711-715.
25. Chen K, Baxter T, Muir WM, Groenen MA, Schook LB (2007) Genetic resources, genome mapping and evolutionary genomics of the pig (Sus scrofa). Int J Biol Sci 3: 153-165.
26. Choleris E, Kavaliers M (1999) Social learning in animals: sex differences and neurobiological analysis. Pharmacol Biochem Behav 64: 767-776.
27. Conrad CD (2010) A critical review of chronic stress effects on spatial learning and memory. Prog Neuro-Psychopharmacol Biol Psychiatry 34: 742-755.
28. Crannell CW (1942) The choice point behavior of rats in a multiple path elimination problem. J Psychol 13: 201-222.
29. Croney CC, Adams KM, WashingtonCG Stricklin WR (2003) A note on visual, olfactory and spatial cue use in foraging behaviour of pigs: indirectly assessing cognitive abilities. Appl Anim Behav Sci 83: 303-308.
30. Curtis SE, Stricklin WR (1991) The importance of animal cognition in agricultural animal production systems: an overview. J Anim Sci 69: 2001-2007.
31. Danielsen EH, Smith DF, Andersen F, Gee AD, Bender D, Hansen SB, Hermansen F, Østergaard L, Cumming P, Gjedde A (2001) FDOPA metabolism in the adult porcine brain: influence of tracer circulation time and VOI selection on estimates of striatal DOPA decarboxylation. J Neurosci Methods 111: 157-168.
32. de Groot J, Boersma W, van der Staay FJ, Niewold T, Stockhofe N, Koopmans SJ, van der Lende T, Schuurman T (2005) Development of domestic animal models for the study of the ontogeny of human disease. In: Coe DHC (ed) Perinatal programming: early life determinants of adult health & disease. Taylor & Francis, London, pp 117-128.
33. de Jong IC, Prelle IT, van d Burgwal JA, Lambooij E, Korte SM, Blokhuis HJ, Koolhaas JM (2000) Effects of environmental enrichment on behavioural responses to novelty, learning, and memory, and the circadian rhythm in cortisol in growing pigs. Physiol Behav 68: 571-578.
34. de Souza AS (2006) Social recognition in neonatal pigs and the effects of acute stressors on it. Dissertation, Michigan State University.
35. de Souza AS, Jansen J, Tempelman RJ, Mendl M, Zanella AJ (2006) A novel method for testing social recognition in young pigs and the modulating effects of relocation. Appl Anim Behav Sci 99: 77-87.
36. Duncan IJ, Petherick JC (1991) The implications of cognitive processes for animal welfare. J Anim Sci 69: 5017-5022.
37. Ennaceur A, Delacour J (1988) A new one-trial test for neurobiological studies of memory in rats I: Behavioral data. Behav Brain Res 31: 47-59.
38. Ennaceur A, Meliani K (1992) A new one-trial test for neurobiological studies of memory in rats III spatial vs non-spatial working memory. Behav Brain Res 51: 83-92.
39. Ennaceur AAC, Costa JC, Delacour J (1989) A new one-trial test for neurobiological studies of memory in rats II: effects of piracetam and pramiracetam. Behav Brain Res 33: 197-207.
40. Entsu S, Dohi H, Yamada A (1992) Visual acuity of cattle determined by the method of discrimination learning. Appl Anim Behav Sci 34: 1-10.
41. Fang M, Li J, Rudd JA, Wai SM, Yew JCC, Yew DT (2006) fMRI Mapping of cortical centers following visual stimulation in postnatal pigs of different ages. Life Sci 78.
42. Ferguson SA, Gopee NV, Paule MG, Howard PC (2009) Female Mini-pig performance of temporal response differentation, incremental repeated aquisition, progressive ration operant tasks. Behav Processes 80(1): 28-34.
43. Fraser D, Thompson BK (1991) Armed sibling rivalry among suckling piglets. Behav Ecol Sociobiol 29: 9-15.
44. Friess SH, Ichord RN, Owens K, Ralston J, Rizol R, Overall KL, Smith C, Helfaer MA, Margulies SS (2007) Neurobehavioural functional deficits following closed head injury in the neonatal pig. Exp Neurol 204: 234-243.
45. Gallup GG (1970) Chimpanzees: Self-Recognition. Science 167: 86-87.
46. Gifford AK (2005) Assessing object recognition memory in the domestic pig. MSc thesis, Washington State University.
47. Gifford AK, Cloutier S, Newberry RC (2007) Objects as enrichment: effect of object exposure time and delay interval on object recognition memory of the domestic pig. Appl Anim Behav Sci 107: 206-217.
48. Glaser D, Wanner M, Tinti JM, Nofre C (2000) Gustatory responses of pigs to various natural and artificial compounds known to be sweet in man. Food Chem 68: 375-385.
49. Graf R (1976) Das visuelle Orientierungsvermögen der Schweine in Abhängigkeit von der Beleuchtungsstärke. In: Instituut voor Veeteeltkundig Onderzoek, Zeist, pp 56.
50. Graves HB (1984) Behaviour and ecology of wild and feral swine (Sus Scrofa). J Anim Sci 58: 482-492.
51. Grön G, Wunderlich AP, Spitzer M, Tomczak R, Riepe MW (2000) Brain activation during human navigation: gender-different neural networks as substrate of performance. Nature Neurosci 3: 404-408.
52. Gustafsson M, Jensen P, de Jonge FH, Schuurman T (1999) Domestication effects on foraging strategies in pigs (Sus scrofa). Appl Anim Behav Sci 62: 305-317.
53. Hagl C, Weisz DJ, Khaladj N, Griepp MM, Spielvogel D, Yang B, de Asla RA, Bodian CA, Griepp RB (2005) Use of a maze to detect cognitive dysfunction in a porcine model of hypothermic circulatory arrest. Ann Thorac Surg 79: 1307-1315.
54. Hammell DL, Kratzer DD, Bramble WJ (1975) Avoidance and maze learning in pigs. J Anim Sci 40: 573-579.
55. Heffner HE, Heffner AS (1992) Auditory perception in farm animals and the environment. In: Phillips C, Piggins D (eds) CAB International, Wallingford, pp 159-184.
56. Held S, Mendl M, Devereux C, Byrne RW (2000) Social tactics of pigs in a competitive foraging task: the 'informed forager' paradigm. Anim Behav 59: 569-576.
57. Held S, Mendl M, Devereux C, Byrne RW (2001a) Behaviour of domestic pigs in a visual perspective task. Behaviour 138: 1337-1354.
58. Held S, Mendl M, Devereux C, Byrne RW (2001b) Studies in social cognition: from primates to pigs. Anim Welf 10: 209-217.
59. Held S, Mendl M, Laughlin K, Byrne RW (2002) Cognition studies with pigs: livestock cognition and its implication for production. J Anim Sci 80: E10-E17.
60. Held S, Baumgartner J, Kilbride A, Byrne RW, Mendl F (2005) Foraging behaviour in domestic pigs (Sus scrofa): remembering and prioritizing food sites of different value. Anim Cogn 8: 114-121.
61. Held S, Cooper JJ, Mendl MT (2009) Advances in the study of cognition, behavioural priorities and emotions. In: Marchant-Forde JN (ed) The welfare of pigs. anim welf, vol 7. Springer, Heidelberg, pp 47-94.
62. Hemmer H (1990) Domestication-the decline of environmental appreciation. Cambridge University Press, Cambridge.
63. Hemsworth PH, Verge J, Coleman GJ (1996) Conditioned approach-avoidance responses to humans: the ability of pigs to associate feeding and aversive social experiences in the presence of humans with humans. Appl Anim Behav Sci 50: 71-82.
64. Hofman MA (1985) Size and shape of the cerebral cortex in mammals (Part 1 of 2) I. The cortical surface. Brain Behav Evol 27: 28-34.
65. Hoyte L, Kaur J, Buchan AM (2004) Lost in translation: taking neuroprotection from animal models to clinical trials. Exp Neurol 188: 200-204.
66. Jensen P (2003) The ethology of domestic animals. An introductory text, CAB International, Wallingford.
67. Kahana MJ, Sekuler R, Caplan JB, Kirschen M, Madsen JR (1999) Human theta oscillations exhibit task dependence during virtual maze navigation. Nature 399: 781-784.
68. Kennedy JM, Baldwin BA (1972) Taste preference in pigs for nutritive and non-nutritive sweet solutions. Anim Behav 20: 706-718.
69. Kirsch I, Lynn SJ, Vigorito M, Miller RR (2004) The role of cognition in classical and operant conditioning. J Clin Psychol 60: 369-392.
70. Koba Y, Tanida H (1999) How do miniature pigs discriminate between people? The effect of exchanging cues between a non-handler and their familiar handler on discrimination. Appl Anim Behav Sci 61: 239-252.
71. Köhn F, Sharifi AR, Simianer H (2007) Modeling of the growth of the Göttingen minipig. J Anim Sci 85: 84-92.
72. Koolhaas JM, de Boer de SF, Buwalda B (2006) Stress and adaptation-toward ecologically relevant animal models. Curr Dir Psychol Sci 15: 109-112.
73. Kornum BR, Thygesen KS, Nielsen TR, Knudsen GM, Lind NM (2007) The effect of the inter-phase delay interval in the spontaneous object recognition test for pigs. Behav Brain Res 181: 210-217.
74. Kratzer DD (1969) Effects of age on avoidance learning in pigs. J Anim Sci 28: 175-179.
75. Kratzer DD (1971) Learning in farm animals. J Anim Sci 32: 1268-1273.
76. Kristensen HH, Jones RB, Schofield CP, White RP, Wathes CM (2001) The use of olfactory and other cues for social recognition by juvenile pigs. Appl Anim Behav Sci 72: 321-333.
77. Lachman SJ, Brown CR (1957) Behavior in a free choice multiple path elimination problem. J Psychol 43: 27-40.
78. Larsen MO, Rolin B (2004) Use of the Göttingen minipig as a model of diabetes, with special focus on type 1 diabetes research. ILAR J 45.
79. Laughlin K, Mendl M (2000) Pigs shift too: foraging strategies and spatial memory in the domestic pig. Anim Behav 60: 403-410.
80. Laughlin K, Mendl M (2004) Costs of acquiring and forgetting information affect spatial memory and its susceptibility to interference. Anim Behav 68: 97-103.
81. Laughlin K, Huck M, Mendl M (1999) Disturbance effects of environmental stimuli on pig spatial memory. Appl Anim Behav Sci 64: 169-180.
82. Lewis PA, Critchley HD, Smith AP, Dolan RJ (2005) Brain mechanisms for mood congruent memory facilitation. NeuroImage 25: 1214-1223.
83. Lien J, Klopfer FD (1978) Some relations between stereotyped suckling in piglets and exploratory behaviour and discrimination reversal learning in adult swine. Appl Anim Ethol 4: 223-233.
84. Lind NM, Moustgaard A (2005) Response to novelty correlates with learning rate in a go/no-go task in Göttingen Minipigs. Neural Plast 12.
85. Lind NM, Arnfred SM, Hemmingsen RP, Hansen AK (2004) Prepulse inhibition of the acoustic startle reflex in pigs and its disruption by D-amphetamine. Behav Brain Res 155: 217-222.
86. Lind NM, Moustgaard A, Jelsing J, Vajta G, Cumming P, Hansen AK (2007) The use of pigs in neuroscience: modelling brain disorders. Neurosci Biobehav Rev 31: 728-751.
87. Lunney JK (2007) Advances in swine biomedical model genomics. Int J Biol Sci 3: 179-184.
88. Macellini S, Ferrari PF, Bonini L, Fogassi L, Paukner A (2010) A modified mark test for own-body recognition in pig-tailed macaques (Macaca nemestrina). Anim Cogn 13(4): 631-639.
89. Manteuffel G, Langbein J, Puppe B (2009) Increasing farm animal welfare by positively motivated instrumental behaviour. Appl Anim Behav Sci 118: 191-198.
90. Markou A, Chiamulera C, Geyer MA, Tricklebank M, Steckler T (2009) Removing obstacles in neuroscience drug discovery: The future path for animal models. Neuropsychopharmacology 34: 74-89.
91. Mauget R (1984) Rythme d'activité et budget-temps chez le sanglier européen (Sus scrofa L.). In: Spitz F, Pépin D (eds) Symposium International sur le Sanglier. INRA, Toulouse, pp 79-92.
92. McLeman MA, Mendl M, Jones RB, White R, Wathes CM (2005) Discrimination of conspecifics by juvenile domestic pigs, sus scrofa. Anim Behav 70: 451-461.
93. McLeman MA, Mendl MT, Jones RB, Wathes CM (2008) Social discrimination of familiar conspecifics by juvenile pigs, Sus scrofa: development of a non-invasive method to study the transmission of unimodal and bimodal cues between live stimuli. Appl Anim Behav Sci 115: 123-137.
94. Meehan CL, Mench JA (2007) The challenge of challenge: can problem solving opportunities enhance animal welfare? Appl Anim Behav Sci 102: 246-261.
95. Meese GB, Conner DJ, Baldwin BA (1975) Ability of the pig to distinguish between conspecific urine samples using olfaction. Physiol Behav 15: 121-125.
96. Mendl M (1999) Performing under pressure: stress and cognitive function. Appl Anim Behav Sci 65: 221-244.
97. Mendl M, Paul ES (2004) Consciousness, emotion and animal welfare: insights from cognitve science. Anim Welf 13: S17.
98. Mendl M, Laughlin K, Hitchcock D (1997) Pigs in space: spatial memory and its susceptibility to interference. Anim Behav 54: 1491-1508.
99. Mendl M, Randle K, Pope S (2002) Young female pigs can discriminate individual differences in odours from conspecific urine. Anim Behav 64: 97-101.
100. Mendl M, Burman OHP, Parker RMA, Paul ES (2009) Cognitive bias as an indicator of animal emotion and welfare: emerging evidence and underlying mechanisms. Appl Anim Behav Sci 118: 161-181.
101. Mikkelsen M, Moller A, Jensen LH, Pedersen A, Harajehi JB, Pakkenberg H (1999) MPTP-Induced parkinsonism in Minipigs: a behavioural, biochemical, and histological study. Neurotoxicol Teratol 21: 169-175.
102. Moore AU, Marcuse FL (1945) Salivary, cardiac and motor indices of conditioning in two sows. J Comp Psychol 38: 1-16.
103. Morris R (1984) Developments of a water-maze procedure for studying spatial learning in the rat. J Neurosci Methods 11: 47.
104. Moustgaard A, Lind NM, Hemmingsen R, Hansen AK (2002) Spontaneous object recognition in the Göttingen Minipig. Neural Plast 9(4): 255-259.
105. Moustgaard A, Arnfred SM, Lind NM, Hansen AK, Hemmingsen R (2004) Discriminations, reversals, and extra-dimensional shifts in the Göttingen minipig. Behav Processes 67: 27-37.
106. Moustgaard A, Arnfred SM, Lind NM, Hemmingsen R, Hansen AK (2005) Acquisition of visually guided conditional associative tasks in Göttingen minipigs. Behav Processes 68: 97-102.
107. Muma JR (1993) The need for replication. J Speech Hear Res 36: 927-930.
108. Nielsen TR, Kornum BR, Moustgaard A, Gade A, Lind NM, Knudsen GM (2009) A novel spatial delayed non-match to sample (DNMS) task in the Göttingen Minipig. Behav Brain Res 196: 93-98.
109. Noble M, Adams CK (1963) Conditioning in pigs as a function of the interval between CS and US. J Comp Physiol Psychol 56: 215-219.
110. Nofre C, Glaser D, J- Tinti, Wanner M (2002) Gustatory responses of pigs to sixty compounds tasting sweet to humans. J Anim Physiol Anim Nutr 86: 90-96.
111. Nunoya T, Shibuya K, Saitoh T, Yazawa H, Nakamura K, Yasuko Baba Y, Hirai T (2007) Use of miniature pig for biomedical research, with reference to toxicologic studies. JTP 20: 125-132.
112. Ohl F, Arndt SS, van der Staay FJ (2008) Pathological anxiety in animals. Vet J 175: 18-26.
113. Olton DS, Samuelson RJ (1976) Remembrance of places passed: spatial memory in rats. J Exp Psychol 2: 97-116.
114. Pacioni G (1986) Truffle hunting in Italy. Bull Br Mycol Soc 20: 50-51.
115. Paul ES, Harding EJ, Mendl M (2005) Measuring emotional processes in animal: the utility of a cognitive approach. Neurosci Bio Beh Rev 29: 469-491.
116. Petersen B, Carnwath JW, Niemann H (2008) The perspectives for porcine-to-human xenografts. Comp Immunol Microbiol Infect Dis 32: 91-105.
117. Puppe B, Ernst K, Schön PC, Manteuffel G (2007) Cognitive enrichment affects behavioural reactivity in domestic pigs. Appl Anim Behav Sci 105: 75-86.
118. Rehfeldt C, Kuhn G (2006) Consequences of birth weight for postnatal growth performance and carcass quality in pigs as related to myogenesis. J Anim Sci 84: E113.
119. Rescorla RA (1988) Behavioral studies of pavlovian conditioning. Ann Rev Neurosci 11: 329-352.
120. Sachs DH (1994) The pig as a potential xenograft donor. Vet Immunol Immunopathol 43: 185-191.
121. Schook L, Beattie C, Beever J, Donovan S, Jamison R, Zuckermann F, Niemi S, Rothschild M, Rutherford M, Smith D (2005) Swine in biomedical research: creating the building blocks of animal models. Anim Biotechnol 16: 183-190.
122. Schwabe L, Wolf OT (2010) Learning under stress impairs memory formation. Neurobiol Learn Mem 93: 183-188.
123. Siegford JM, Rucker G, Zanella AJ (2008) Effects of pre-weaning exposure to a maze on stress responses in pigs at weaning and on subsequent performance in spatial and fear-related tests. Appl Anim Behav Sci 110: 189-202.
124. Sik A, van Nieuwehuyzen P, Prickaerts J, Blokland A (2003) Performance of different mouse strains in an object recognition task. Behav Brain Res 14: 49-54.
125. Siswanto H, Hau J, Carlsson H, Goldkuhl R, Abelson KSP (2008) Corticosterone concentrations in blood and excretion in faeces after ACTH administration in male Sprague-Dawley rats. In Vivo 22: 435-440.
126. Sneddon IA, Beattie VE, Dunne L, Neil W (2000) The effect of environmental enrichment on learning in pigs. Anim Welf 9: 373-383.
127. Spinka M, Duncan IJH, Widowski TM (1998) Do domestic pigs prefer short-term to medium-term confinement? Appl Anim Behav Sci 58: 221-232.
128. Tanida H, Nagano Y (1998) The ability of miniature pigs to discriminate between a stranger and their familiar handler. Appl Anim Behav Sci 56: 149-159.
129. Tanida H, Senda K, Suzuki S, Tanaka T, Yoshimoto T (1991) Colour discrimination in weanling pigs. Anim Sci Technol 62: 1029-1034.
130. Thor DH, Holloway WR (1982) Social memory of the male laboratory rat. J Comp Physiol Psychol 69: 1000-1006.
131. Toates F (2004) Cognition, motivation, emotion and action: a dynamic and vulnerable interdependence. Appl Anim Behav Sci 86: 173-204.
132. van der Staay FJ (2002) Assessment of age-associated cognitive deficits in rats: a tricky business. Neurosci Biobehav Rev 26: 753-759.
133. van der Staay FJ (2006) Animal models of behavioral dysfunctions: basic concepts and classifications, and an evaluation strategy. Brain Res Rev 52(1): 131-159.
134. van der Staay FJ, Arndt SS, Nordquist RE (2009) Evaluation of animal models of neurobehavioral disorders. Behav Brain Funct 5: 11.
135. van der Staay FJ, Arndt SS, Nordquist RE (2010) The standardization-generalization dilemma: a way out. Genes Brain Behav 9: 849-855.
136. van Rooijen J (1982) Operant preference tests with pigs. Appl Anim Ethol 9: 87-88.
137. Vodička P, Smetana K, Dvořánková B, Emerick T, Xu YZ, Ourednik J, Ourednik V, Motlík J (2005) The miniature pig as an animal model in biomedical research. Ann N Y Acad Sci 1049: 161-171.
138. Wainwright PE, Colombo J (2006) Nutrition and the development of cognitive functions: interpretation of behavioural studies in animals and human infants. Am J Clin Nutr 84: 961-970.
139. Wang B, Yu B, Karim M, Hu H, Sun Y, McGreevy P, Petocz P, Held S, Brand-Miller J (2007) Dietary sialic acid supplementation improves learning and memory in piglets. Am J Clin Nutr 85: 561-569.
140. Wechsler B, Lea SEG (2007) Adaptation by learning: Its significance for farm animal husbandry. Appl Anim Behav Sci 108: 197-214.
141. Yerkes RM, Coburn CA (1915) A study of the behaviour of the pig sus crofa by the multiple choice method. J Anim Behav 5: 185-188, 188a, 189-225.
142. Zhang J, Groff RF, Chen X, Browne KD, Huang J, Schwartz ED, Meaney DF, Johnson VE, Stein SC, Rojkjaer R, Smith DH (2008) Hemostatic and neuroprotective effects of human recombinant activated factor VII therapy after traumatic brain injury in pigs. Exp Neurol 210: 645-655.
143. Zonderland JJ, Cornelissen L, Wolthuis-Fillerup M, Spoolder HAM (2008) Visual acuity of pigs at different light intensities. Appl Anim Behav 111: 28-37.