Cited by 239Human-Animal Interaction StudiesAnimal Behavior and Welfare StudiesVeterinary Practice and Education Studies

Current Perspectives on Therapy Dog Welfare in Animal-Assisted Interventions

Open access
Glenk, Lisa·2017·Animals

Abstract

Research into the effects of animal-assisted interventions (AAIs) has primarily addressed human health outcomes. In contrast, only few publications deal with the therapy dog experience of AAIs. This paper provides an overview on potential welfare threats that therapy dogs may encounter and presents the results of a review of available studies on welfare indicators for therapy dogs during AAIs. Previous investigations used physiological and behavioral welfare indicators and dog handler surveys to identify work-related stress. Research outcomes are discussed in the light of strengths and weaknesses of the methods used. Study results suggest that frequency and duration of AAI sessions, novelty of the environment, controllability, age and familiarity of recipients modulate animal welfare indicators. However, this review reveals that currently, clear conclusions on how the well-being of dogs is influenced by the performance in AAIs are lacking due to the heterogeneity of programs, recipient and session characteristics, small dog sample sizes and methodological limitations. This paper further aimed to identify unresolved difficulties in previous research to pave the way for future investigations supporting the applicability of scientific findings in practice.

The claims and statistics of this paper haven’t been checked yet.

Run the check — free, no account needed. It reads the open-access text and checks the sources it cites.

A few free checks a day · papers already verified open instantly · results are public

Integrity signals

Registry

Crossref · 10.3390/ani7020007

Cites

Statistics

Claims the paper makes

The claims and statistics of this paper haven’t been checked yet.

Run the check — free, no account needed. It reads the open-access text and checks the sources it cites.

A few free checks a day · papers already verified open instantly · results are public

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

The self-check needs the paper’s full text.

The citation lists haven’t been fetched yet

References 88 · Cited by 239

Research works printed but not linked: 81

  1. [1]Wang G.D. Zhai W. Yang H.C. Wang L. Zhong L. Liu Y.H. Fan R.X. Yin T.T. Zhu C.L. Poyarkov A.D. Out of southern East Asia: The natural history of domestic dogs across the world Cell Res. 2016 26 21 33 10.1038/cr.2015.147 26667385 PMC4816135 · DOI
  2. [2]Hare B. Tomasello M. Human-like social skills in dogs? Trends Cogn. Sci. 2005 9 439 444 10.1016/j.tics.2005.07.003 16061417 · DOI · Paper page
  3. [3]Gueguen N. Ciccotti S. Domestic dogs as facilitators in social interaction: An evaluation of helping and courtship behaviors Anthrozoös 2008 21 339 349 10.2752/175303708X371564 · DOI · Paper page
  4. [4]Wells D.L. The facilitation of social interactions by domestic dogs Anthrozoös 2004 17 340 352 10.2752/089279304785643203 · DOI · Paper page
  5. [5]Beck A.M. Katcher A.H. Future directions in human-animal bond research Am. Behav. Sci. 2003 47 79 93 10.1177/0002764203255214 · DOI · Paper page
  6. [6]O’Haire M. Companion animals and human health: Benefits, challenges, and the road ahead J. Vet. Behav. 2010 5 226 234 10.1016/j.jveb.2010.02.002 · DOI
  7. [8]Kruger K.A. Serpell J.A. Animal-assisted interventions in mental health: Definitions and theoretical foundations Handbook on Animal-Assisted Therapy. Theoretical Foundations and Guidelines for Practice 2nd ed. Fine A.H. Academic Press San Diego, CA, USA 2006 21 38
  8. [9]Palley L.S. O’Rourke P.P. Niemi S.M. Mainstreaming animal-assisted therapy ILAR J. 2010 51 199 207 10.1093/ilar.51.3.199 21131720 · DOI
  9. [10]Jorgenson J. Therapeutic use of companion animals in health J. Nurs. Scholarsh. 1997 29 249 254 10.1111/j.1547-5069.1997.tb00993.x 9378480 · DOI
  10. [11]Wohlfarth R. Mutschler B. Beetz A. Kreuser F. Korsten-Reck U. Dogs motivate obese children for physical activity: Key elements of a motivational theory of animal-assisted interventions Front. Psychol. 2013 4 796 10.3389/fpsyg.2013.00796 24194726 PMC3810595 · DOI
  11. [12]Vagnoli L. Caprilli S. Vernucci C. Zagni S. Mugnai F. Messeri A. Can presence of a dog reduce pain and distress in children during venipuncture? Pain Manag. Nurs. 2015 16 89 95 10.1016/j.pmn.2014.04.004 25439114 · DOI
  12. [13]Beetz A. Kotrschal K. Turner D. Hediger K. Uvnäs-Moberg K. Julius H. The effect of a real dog, toy dog and friendly person on insecurely attached children in a stressful task: An exploratory study Anthrozoös 2011 24 349 368 10.2752/175303711X13159027359746 · DOI
  13. [14]Harper C.M. Dong Y. Thornhill T.S. Wright J. Ready J. Brick G.W. Dyer G. Can therapy dogs improve pain and satisfaction after total joint arthroplasty? A randomized controlled trial Clin. Orthop. Relat. Res. 2015 473 372 379 10.1007/s11999-014-3931-0 25201095 PMC4390934 · DOI
  14. [15]Calcaterra V. Veggiotti P. Palestrini C. De Giorgis V. Raschetti R. Tumminelli M. Mencherini S. Papotti F. Klersy C. Albertini R. Post-operative benefits of animal-assisted therapy in pediatric surgery: A randomised study PLoS ONE 2016 10 e0125813 10.1371/journal.pone.0125813 26039494 PMC4454536 · DOI
  15. [16]Garcia L.S.G. Zaine I. Domeniconi C. Influence of dog presence on the tolerance and evaluation of aversive stimulation Pet Behav. Sci. 2016 2 16 23 10.21071/pbs.v0i2.4002 · DOI
  16. [18]Stafford K. The Welfare of Dogs 1st ed. Springer Dordrecht, The Netherlands 2006 23
  17. [20]Hatch A. The view from all fours: A look at an animal-assisted activity program from the animals’ perspective Anthrozoös 2007 20 37 50 10.2752/089279307780216632 · DOI
  18. [21]Ehrén E. How Do Educated Therapy Dogs (Canis Lupus Familiaris) Get Affected by Their Work in Human Care? Bachelor’s Thesis University of Agricultural Sciences Uppsala, Sweden 2014
  19. [22]The IAHAIO definitions for animal-assisted intervention and guidelines for wellness of animals involved Handbook on Animal-Assisted Therapy: Foundations and Guidelines for Animal-Assisted Interventions 4th ed. Fine A.H. Elsevier San Diego, CA, USA 2015 415
  20. [25]Ng Z. Albright J. Fine A.H. Peralta J. Our ethical and moral responsibility: Ensuring the welfare of therapy animals Handbook on Animal-Assisted Therapy: Foundations and Guidelines for Animal-Assisted Interventions 4th ed. Fine A.H. Elsevier San Diego, CA, USA 2015 357 377
  21. [26]Zamir T. The moral basis of animal-assisted therapy Soc. Anim. 2006 14 179 199 10.1163/156853006776778770 16862727 · DOI
  22. [27]Iannuzzi D. Rowan A.N. Ethical issues in animal-assisted therapy programs Anthrozoös 1991 4 154 163 10.2752/089279391787057116 · DOI
  23. [28]Piva E. Welfare in a shelter dog rehomed with Alzheimer patients J. Vet. Behav. 2008 3 87 94 10.1016/j.jveb.2007.08.004 · DOI
  24. [29]Viau R. Arsenault-Lapierre G. Fecteau S. Champagne N. Walker C. Lupien S. Effect of service dogs on salivary cortisol secretion in autistic children Psychoneuroendocrinology 2010 35 1187 1193 10.1016/j.psyneuen.2010.02.004 20189722 · DOI
  25. [30]Serpell J.A. Coppinger R. Fine A.H. Peralta J.M. Welfare considerations in therapy and assistance animals Handbook on Animal-Assisted Therapy: Theoretical Foundations and Guidelines for Practice 3rd ed. Fine A.H. Academic Press San Diego, CA, USA 2010 453 474
  26. [31]Mongillo P. Pitteri E. Adamelli S. Bonichini S. Farina L. Marinelli L. Validation of a selection protocol of dogs involved in animal assisted intervention J. Vet. Behav. 2015 10 103 110 10.1016/j.jveb.2014.11.005 · DOI
  27. [32]Hennessy M. Morris A. Linden F. Evaluation of the effects of a socialization program in a prison on behavior and pituitary-adrenal hormone levels of shelter dogs Appl. Anim. Behav. Sci. 2006 99 157 171 10.1016/j.applanim.2005.09.011 · DOI
  28. [33]Odendaal J.S.J. Meintjes R.A. Neurophysiological correlates of affiliative behaviour between humans and dogs Vet. J. 2003 165 296 301 10.1016/S1090-0233(02)00237-X 12672376 · DOI · Paper page
  29. [34]Pop D. Rusu A.S. Pop-Vancia V. Papuc L. Constantinescu R. Miresan V. Physiological effects of human-animal positive interaction in dogs—Review of the literature Bull. UASVM Anim. Sci. Biotechnol. 2014 71 102 109 10.15835/buasvmcn-asb:10398 · DOI
  30. [35]Willen R.M. Mutwill A. MacDonald L.J. Schiml P.A. Hennessy M.B. Factors determining the effects of human interaction on the cortisol levels of shelter dogs Appl. Anim. Behav. Sci. 2017 186 41 48 10.1016/j.applanim.2016.11.002 · DOI · Paper page
  31. [36]Horváth Z. Igyártó B.-Z. Magyar A. Miklósi Á. Affiliative and disciplinary behavior of human handlers during play with their dog affects cortisol concentrations in opposite directions Horm. Behav. 2007 54 107 114 10.1016/j.yhbeh.2008.02.002 18353328 · DOI
  32. [37]Schalamon J. Ainoedhofer H. Singer G. Petnehazy T. Mayr J. Kiss K. Höllwarth M. Analysis of dog bites in children who are younger than 17 years Pediatrics 2006 117 e374 e379 10.1542/peds.2005-1451 16510617 · DOI
  33. [39]Kuhne F. Hößler J. Struwe R. Affective behavioural responses by dogs to tactile human-dog interactions Berl. Munchener Tierarztliche Wochenschr. 2012 125 371 378 23045798
  34. [40]Kuhne F. Hößler J. Struwe R. Effects of human dog familiarity on dogs’ behavioural responses to petting Appl. Anim. Behav. Sci. 2012 142 176 181 10.1016/j.applanim.2012.10.003 · DOI
  35. [41]Kuhne F. Hößler J. Struwe R. Behavioral and cardiac responses by dogs to physical human-dog contact Vet. Behav. 2014 9 93 97 10.1016/j.jveb.2014.02.006 · DOI
  36. [42]Hydbring-Sandberg E. von Walter L.W. Höglund K. Svartberg K. Swenson L. Forkman B. Physiological reactions to fear provocation in dogs J. Endocrinol. 2004 180 439 448 10.1677/joe.0.1800439 15012598 · DOI
  37. [43]Bert F. Gualano M.R. Camussi E. Pieve G. Voglino G. Siliquini R. Animal assisted intervention: A systematic review of benefits and risks Eur. J. Integr. Med. 2016 8 695 706 10.1016/j.eujim.2016.05.005 PMC7185850 32362955 · DOI · Paper page
  38. [44]Lefebvre S.L. Waltner-Toews D. Peregrine A.S. Reid-Smith R. Hodge L. Arroyo L.G. Weese J.S. Prevalence of zoonotic agents in dogs visiting hospitalized people in Ontario: Implications for infection control J. Hosp. Infect. 2006 62 458 466 10.1016/j.jhin.2005.09.025 16466831 · DOI
  39. [45]Broom D.M. Indicators of poor welfare Br. Vet. J. 1986 142 524 526 10.1016/0007-1935(86)90109-0 3594185 · DOI
  40. [46]Wechsler B. Coping and coping strategies: A behavioural view Appl. Anim. Behav. Sci. 1995 43 123 134 10.1016/0168-1591(95)00557-9 · DOI
  41. [47]Veissier I. Boissy A. Stress and welfare: Two complementary concepts that are intrinsically related to the animal’s point of view Physiol. Behav. 2007 92 429 433 10.1016/j.physbeh.2006.11.008 17182067 · DOI
  42. [49]Houpt K.A. Goodwin D. Uchida Y. Baranyiova E. Fatjo J. Kakuma Y. Proceedings of a workshop to identify dog welfare issues in the U.S., Japan, Czech Republic, Spain and the UK Appl. Anim. Behav. Sci. 2007 106 221 233 10.1016/j.applanim.2007.01.005 · DOI
  43. [50]Lind A.-K. Hydbring-Sandberg E. Forkman B. Keeling L.J. Assessing stress in dogs during a visit to the veterinary clinic: Correlations between dog behavior in standardized tests and assessments by veterinary staff and owners J. Vet. Behav. 2017 17 24 31 10.1016/j.jveb.2016.10.003 · DOI
  44. [54]Marinelli L. Normando S. Siliprandi C. Salvadoretti M. Mongillo P. Dog assisted interventions in a specialized centre and potential concerns for animal welfare Vet. Res. Commun. 2009 33 93 95 10.1007/s11259-009-9256-x 19578960 · DOI
  45. [55]King C. Watters J. Mungre S. Effect of a time-out session with working animal-assisted therapy dogs J. Vet. Behav. 2011 6 232 238 10.1016/j.jveb.2011.01.007 · DOI
  46. [56]Glenk L.M. Kothgassner O.D. Stetina B.U. Palme R. Kepplinger B. Baran H. Therapy dogs’ salivary cortisol levels vary during animal-assisted interventions Anim. Welf. 2013 22 369 378 10.7120/09627286.22.3.369 · DOI
  47. [57]Barstad B.N. Evaluation of Animal Welfare in Dogs Working with Animal Assisted Interventions for Elderly People with Dementia Master’s Thesis Norwegian University of Life Sciences Ås, Norway 2014
  48. [58]Glenk L.M. Kothgassner O.D. Stetina B.U. Palme R. Kepplinger B. Baran H. Salivary cortisol and behavior in therapy dogs during animal-assisted interventions: A pilot study J. Vet. Behav. 2014 9 98 106 10.1016/j.jveb.2014.02.005 · DOI
  49. [59]Ng Z.Y. Pierce B.J. Otto C.M. Buechner-Maxwell V.A. Siracusa C. Werre S.R. The effect of dog-human interaction on cortisol and behavior in registered animal-assisted activity dogs Appl. Anim. Behav. Sci. 2014 159 69 81 10.1016/j.applanim.2014.07.009 · DOI
  50. [60]Palestrini C. Calcaterra V. Cannas S. Talamonti Z. Papotti F. Buttram D. Pelizzo G. Stress level evaluation in a dog during animal-assisted therapy in pediatric surgery J. Vet. Behav. 2017 17 44 49 10.1016/j.jveb.2016.09.003 · DOI
  51. [61]Handlin L. Hydbring-Sandberg E. Nilsson A. Ejdebäck M. Jannson A. Uvnäs-Moberg K. Short-term interaction between dogs and their owners: Effects on oxytocin, cortisol, insulin and heart rate—An exploratory study Anthrozoös 2011 24 301 315 10.2752/175303711X13045914865385 · DOI · Paper page
  52. [63]Thodberg K. Berget B. Lidfors L. Research in the use of animals as a treatment for humans Anim. Front. 2014 4 43 48 10.2527/af.2014-0021 · DOI
  53. [64]Glenk L.M. Kothgassner O.D. Life out of balance: Stress-related disorders in animals and humans Comparative Medicine 2: Disorders Linking Humans with Their Animals 1st ed. Jensen-Jarolim E. Springer International Publishing Cham, Switzerland 2017
  54. [65]McEwen B.S. Stellar E. Stress and the individual: Mechanisms leading to disease Arch. Intern. Med. 1993 153 2093 2101 10.1001/archinte.1993.00410180039004 8379800 · DOI · Paper page
  55. [66]Cobb M.L. Iskandarani K. Chinchilli V.M. Dreschel N.A. A systematic review and meta-analysis of salivary cortisol measurement in domestic canines Domest. Anim. Endocrinol. 2016 57 31 42 10.1016/j.domaniend.2016.04.003 27315597 · DOI
  56. [67]Bennet A. Hayssen V. Measuring cortisol in hair and saliva from dogs: Coat color and pigment differences Domest. Anim. Endocrinol. 2010 39 171 180 10.1016/j.domaniend.2010.04.003 20705413 · DOI
  57. [69]Sandri M. Colussi A. Perrotta M.G. Stefanon B. Salivary cortisol concentration in healthy dogs is affected by size, sex, and housing context J. Vet. Behav. 2015 10 302 306 10.1016/j.jveb.2015.03.011 · DOI
  58. [70]Starling M.J. Branson N.J. Cody D. McGreevy P.D. Conceptualising the impact of arousal and affective state on training outcomes of operant conditioning Animals 2013 3 300 317 10.3390/ani3020300 26487403 PMC4494394 · DOI
  59. [73]Protopopova A. Effects of sheltering on physiology, immune function, behavior, and the welfare of dogs Physiol. Behav. 2016 159 95 103 10.1016/j.physbeh.2016.03.020 26996275 · DOI
  60. [75]Kikkawa A. Uchida Y. Nakade T. Taguchi K. Salivary secretory IgA concentrations in beagle dogs J. Vet. Med. Sci. 2003 65 689 693 10.1292/jvms.65.689 12867728 · DOI
  61. [76]Svobodová I. Chaloupková H. Končel R. Bartoš L. Hradecká L. Jebavý L. Cortisol and secretory immunoglobulin a response to stress in German shepherd dogs PLoS ONE 2014 9 e90820 10.1371/journal.pone.0090820 24637917 PMC3956493 · DOI
  62. [77]Minton J.E. Function of the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system in models of acute stress in domestic farm animals J. Anim. Sci. 1994 72 1891 1898 7928769
  63. [78]Beerda B. Schilder M.B. Van Hoff J.A. De Vries H.W. Mol J.A. Behavioural, saliva cortisol and heart rate responses to different types of stimuli in dogs Appl. Anim. Behav. Sci. 1998 58 365 381 10.1016/S0168-1591(97)00145-7 · DOI
  64. [79]Bergamasco L. Osella M.C. Savarino P. Larosa G. Ozella L. Manassero M. Badino P. Odore R. Barbero R. Re G. Heart rate variability and saliva cortisol assessment in shelter dog: Human-animal interaction effects Appl. Anim. Behav. Sci. 2010 125 56 68 10.1016/j.applanim.2010.03.002 · DOI
  65. [80]Gehrke E.K. Baldwin A. Schiltz P.M. Heart rate variability in horses engaged in equine-assisted activities J. Equine Vet. Sci. 2011 31 78 84 10.1016/j.jevs.2010.12.007 · DOI
  66. [82]Dreschel N.A. Granger D.A. Physiological and behavioral reactivity to stress in thunderstorm-phobic dogs and their caregivers Appl. Anim. Behav. Sci. 2005 95 153 168 10.1016/j.applanim.2005.04.009 · DOI
  67. [83]Beerda B. Schilder M.B. Van Hoff J.A. De Vries H.W. Mol J.A. Chronic stress in dogs subjected to social and spatial restriction. II. Hormonal and immunological responses Physiol. Behav. 1999 66 243 254 10.1016/S0031-9384(98)00290-X 10336150 · DOI
  68. [85]Schilder M.B.H. van der Borg J.A.M. Training dogs with help of the shock collar: Short and long term behavioural effects Appl. Anim. Behav. Sci. 2004 85 319 334 10.1016/j.applanim.2003.10.004 · DOI
  69. [86]Tomkins L.M. Thomson P.C. McGreevy P.D. Behavioral and physiological predictors of guide dog success J. Vet. Behav. 2011 6 178 187 10.1016/j.jveb.2010.12.002 · DOI
  70. [87]Rehn T. Keeling L.J. The effect of time left alone at home on dog welfare Appl. Anim. Behav. Sci. 2011 129 129 135 10.1016/j.applanim.2010.11.015 · DOI
  71. [88]Shiverdecker M.D. Schiml P.A. Hennessy M.B. Human interaction moderates plasma cortisol and behavioral responses of dogs to shelter housing Physiol. Behav. 2013 109 75 79 10.1016/j.physbeh.2012.12.002 23234768 · DOI · Paper page
  72. [89]Martin P. Bateson P. Measuring Behaviour: An Introductory Guide Cambridge University Press Cambridge, UK 2010
  73. [90]Payne E. Bennett P.C. McGreevy P.D. Current perspectives on attachment and bonding in the dog-human dyad Psychol. Res. Behav. Manag. 2015 8 71 79 10.2147/PRBM.S74972 25750549 PMC4348122 · DOI
  74. [91]Beck A.M. The biology of the human-animal bond Anim. Front. 2014 4 32 36 10.2527/af.2014-0019 · DOI
  75. [92]Topál J. Miklósi A. Csányi V. Dóka A. Attachment behavior in dogs (Canis familiaris): A new application of Ainsworth’s (1969) Strange Situation Test J. Comp. Psychol. 1998 112 219 229 10.1037/0735-7036.112.3.219 9770312 · DOI
  76. [93]Mariti C. Gazzano A. Moore J.L. Baragli P. Chelli L. Sighieri C. Perception of dogs' stress by their owners J. Vet. Behav. 2012 7 213 219 10.1016/j.jveb.2011.09.004 · DOI
  77. [94]Mongillo P. Pitteri E. Carnier P. Gabai J. Adamelli S. Marinelli L. Does the attachment system towards owners change in aged dogs? Physiol. Behav. 2013 120 64 69 10.1016/j.physbeh.2013.07.011 23911691 · DOI
  78. [95]Beck A.M. Katcher A.H. A new look at pet-facilitated therapy J. Am. Vet. Med. Assoc. 1984 184 414 421 6365867
  79. [96]Stern C. Chur-Hansen A. Methodological considerations in designing and evaluating animal-assisted interventions Animals 2013 3 127 141 10.3390/ani3010127 26487313 PMC4495515 · DOI
  80. [97]Chur-Hansen A. McArthur M. Winefield H. Hanieh E. Hazel S. Animal-assisted interventions in children’s hospitals: A critical review of the literature Anthrozoös 2014 27 5 18 10.2752/175303714X13837396326251 · DOI
  81. [98]Herzog H. The research challenge: Threats to the validity of animal-assisted therapy studies and suggestions for improvement Handbook on Animal-Assisted Therapy: Foundations and Guidelines for Animal-Assisted Intervention 4th ed. Fine A.H. Elsevier San Diego, CA, USA 2015 402 407

Authors
Glenk, L.
Affiliations
University of Vienna (AT)
Corresponding author
Glenk, Lisa
Venue
Animals
Publisher
MDPI AG
Published
2017-02-01
Volume
7
Issue
2
Pages
7
ISSN
2076-2615 (ISSN-L)
OpenAlex
W2583431242
Cited by
239
References
88
Citations by year
2026: 25 · 2025: 21 · 2024: 31 · 2023: 23 · 2022: 42 · 2021: 33 · 2020: 29 · 2019: 26 · 2018: 5 · 2017: 4
FWCI
2.24
Type
journal article
Language
en
Open access
Locations
  • Animals (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
Messerli-Stiftung
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Human-Animal Interaction Studies
  • Health Sciences › Veterinary › Small Animals › Animal Behavior and Welfare Studies
  • Health Sciences › Health Professions › Speech and Hearing › Veterinary Practice and Education Studies
Keywords
therapy dogs, animal welfare, animal-assisted interventions, welfare indicators, physiological parameters, behavioral indicators, occupational stress, dog handlers, session duration, controllability

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

Are you an author, or do you see a problem with this page? Request a review