AnimalSentience2016.X:CommentaryonKeyonFishPain
Paininparallel
CommentaryonKeyonFishPain
PeterGodfrey-Smith
Philosophy
CUNYGraduateCenter&UniversityofSydney
Abstract: Brian Key's arguments against the view that fish feel pain can be
shown to be fallacious by considering some damage-related behaviors in
invertebrates. Pain may have different neural bases in different organisms, so
the absence in fish of the cortical structures that might underlie pain in
mammalsdoesnotsettlethequestionoffishpain.
Peter Godfrey-Smith [email protected] is
Distinguished Professor of Philosophy, Graduate
Center,CUNY,andProfessorofHistoryandPhilosophy
of Science, University of Sydney. His main research
interests are philosophy of biology and philosophy of
mind. His books include Complexity and the Function
of Mind in Nature (Cambridge, 1996), Darwinian
Populations and Natural Selection (Oxford, 2009) and Philosophy of
Biology(Princeton,2014)http://petergodfreysmith.com/biographical
BrianKeyholdsthatonceweworkouttheneuralbasisforpaininmammals,some
questionsaboutpaininotheranimalscanbefairlyreadilyanswered:
“If“fishpain”existeditwouldneedtobeconsciouslyprocessedusingat
leasttheminimalneuralarchitecturedescribedabove.Thus,intheabsence
ofthisarchitecture,fishcannotfeelanysortofpain”(Key2016).
Iwillaccept,forthesakeofargument,alltheclaimsKeymakesaboutmammals.To
assesshowtheseclaimsbearonfish,I'llputonthetablesomeotheranimalsfrom
furtherafield.Ina2012studyofhermitcrabs,RobertElwoodfoundthattheycouldbe
inducedtoleavetheirshellsbyelectricshock,butweresurprisinglyparticularinhow
theydidthis,tradingoffthequalityoftheirpresentshellwiththeintensityofshock,
alongwithwhetherolfactorycuessuggestedthatpredatorswereabout:"[I]tisclear
thathermitcrabstrade-offcompetingdemandsintheirresponsestoelectricshockina
waythatcannotbeexplainedbyanociceptivereflexresponse."Healsoreports
"prolongedabdominalgroomingatthesiteofashockinhermitcrabsthatevacuate
theirshells"–groomingofakindnotseenwhencrabsareremovedfromtheirshellby
otherprocesses.ArecentstudybyJeanAlupayandherco-authors(2014)showedthata
crushofanarmintheoctopusAbdopusaculeatusledtoafamilyofwound-directed
AnimalSentience2016.X:CommentaryonKeyonFishPain
responses,someofwhicharefamiliar–groomingandprotectingthedamagedsite,
sensitization,long-termdecreasedthresholdsforescaperesponses–andsomemore
unusual:amputationofthearm.
Didtheseexperiencesfeellikeanythingfortheoctopusesandcrabs?It'svery
hardtoknow.ElwoodandAlupayetal.arecautious.Theynotethatinstudiesofother
animals,long-termtendingandgroomingbehaviorsareoftentakentobesomewhat
indicativeofpain.Setthatissueasideforamoment,though,assomeconclusionscan
bedrawnfromthisworkwithoutconsideringquestionsaboutthefeelofpain.
Thenervoussystemsofoctopuses,crabs,andmammalsallhavedifferent
architectures.Themostrecentcommonancestorofallthreeofthese(the
protostome/deuterostomecommonancestor)probablylivedover600millionyearsago
(Petersonetal.2008).Thisanimalisunknown,butprobablyhadaworm-likebody-plan
andasimplenervoussystem.Complexnervoussystemshaveseenparallelevolutionin
severallinessincethen.Whatevertheneuralarchitectureunderlyingwound-tending
andflexibleprotectionofinjuredareasinmammalsmightbe,itisalmostcertainlynot
homologoustothearchitecturesubservingthatfunctioninoctopuses.(Alupay'spaper
doesnotofferaviewonwhattheneuralbasismightbe,andnotesthataplausible
candidate,theverticallobe,doesnotseemtobetherelevantplace).Neurons
themselvesarepresentinalltheseanimals,andalmostcertainlyexistedintheir
commonancestor,buttheorganizationoftheseneuronsintocomplexnervoussystems
occurredindependently.Theseanimalsshareflexiblewound-tendingbehaviors,butdo
notsharetheneuralorganizationthatmakesthosebehaviorspossible.(Thecommon
ancestorprobablyhadnothingresemblinglimbs,either.)Soevenbeforeweconsider
subjectiveexperience,wehavelearnedthatflexible,non-reflexive,andadaptive
responsestodamageandothernoxiousstimulidonotrequirethe"neuralarchitecture"
(inKey'swords)foundinmammals.Theydonotrequireabrainwithamammalian
architectureatall.
Let'snowturntothemoredifficultquestionsaboutsubjectiveexperience.How
doesthisrelatetoKey'sargumentthatfishdonotfeelpain?LikeElwoodandAlupayet
al.,Idon'tprofesstoknowwhethercrabsandoctopusesfeelpain.Asacandidate
hypothesis,though,supposethatthecapacitytofeelpainispresentwhenananimal
hasaneuralorganizationthatmediatesadaptiveresponsestodamage-relatedstimuliin
aflexibleandnon-reflexiveway,includinglong-termmodificationofbehaviorinthe
lightofthestimulus,perhapsalsowithsomeoftheintegrationofinformation
exemplifiedbythetrade-offsinElwood'scrabs.Thattheoryisaone-sentenceplaceholder(seealsoKlein2015),butitwilldoformypurposeshere.Weknowthatthissort
ofcapacitycanbeachievedbymeansofdifferentneuralarchitectures.Itis"multiply
realizable,"asphilosopherssay.Ifso,thenfindingthatthearchitecturethatsubserves
thesefunctionsandhenceunderliespaininanimalXisnotpresentinanimalYdoesnot
tellyouthatanimalYdoesnotfeelpain.Itmighthavedifferentmechanismssubserving
thatfunction,andpainmightresultbothways.PerhapsanimalYdoesnotfeelpain,
becauseofsubtledifferences.Thatquestionwillbehardtoanswer.Butitisnot
answeredbysimplynotingthattheneuralbasisforpaininanimalXisnotfoundin
animalY.Key,however,wantstomakeaninferenceofthatsimpleforminthecaseof
AnimalSentience2016.X:CommentaryonKeyonFishPain
fish.Eveniftherightstoryaboutpainisquitedifferentfromtheplace-holderIused
above,thesamequestionswillariseandtheinvertebrateworkshowsthattheneural
basesforquitecomplicatedresponsestobodilydamagecanexistwithindifferent
architectures.
SomeonelikeKeymightobjecttoallthisasfollows:"Fisharevertebrates,as
mammalsare.Evenifsomearthropodsandmolluscshaveadifferentneuralbasisfor
pain,fishlackthestructuresthatarerelevantinvertebrates.Ifyouareavertebrate,
theninordertofeelpainyouneedtohavethesamesortofthingthatmammalshave.
Clearlyyouwon'thavetheneuralbasisforpainseeninarthropods."Butthose
considerationsshownothingaboutwhethertheremightbeasomewhatdifferent
neuralarchitectureunderlyingpaininfish.Thecategory"vertebrate"isnotsacred.
Mightfishhavepainviadifferentmechanisms?ThatisaninterestingquestionandI
don'tknowtheanswer.ButthisisthesortofquestionthatKeyrefusestoevenaddress;
hesimplydismissesit.
IemphasizeagainthatKey'sclaimsaboutthecorticalbasisofmammalianpain
wereacceptedhereonlyforthesakeofargument;othercommentatorsaremore
qualifiedthanItoassessthisissue.Lastly,Keydrawsananalogybetweenerringonthe
sideofgenerosityinourviewsaboutfishpainandanerrormadeinadifferentcontext.
"[A]scientificresearcharticlewaspublishedthatpurportedlylinkedmeaslesmumps-rubella(MMR)vaccinationcausallytoautism.Althoughthislinkwas
subsequentlydisproven,manypeoplecontinuedtoacceptat‘facevalue’the
causalassociationbetweenMMRvaccinationandthedevelopmentofautismin
children....Thiscausedparentsnottohavetheirchildrenvaccinatedand
subsequentlyledtoapublichealthcrisis.Thus,whileinitiallyacceptingtheidea
thatMMRvaccinationcausesautismmaybeconsideredasafewaytoproceed
(evenifitisnottrue),itcancausecatastrophiceffects"(Key2016).
Theirrelevanceofthiscomparisonistotal.OnecouldaswellsaythatKey'spositionis
akintotheviewsofthosewhoweretardyinrecognizingthedangersofthalidomide(a
drugthatcausesbirthdefectswhentakenbypregnantwomen)asittookawhileforits
dangerstobecomecompletelyclear.Keymightreplythatanycomparisonbetweenhis
stanceandthatofadilatorydrugcompanyisoutrageous,andsoitis,buthisanalogy
withtheMMRvaccinecaseisentirelyonapar.
References
Alupay,J.,Hadjisolomou,S.,andCrook,R.J.(2014).Arminjuryproduceslong-term
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Elwood,R.(2012).Evidenceforpainindecapodcrustaceans.AnimalWelfare21(S2):
23-27.doi:10.7120/096272812X13353700593365
AnimalSentience2016.X:CommentaryonKeyonFishPain
Key,B.(2016).Whyfishdonotfeelpain.AnimalSentience2016.3
Klein,C.(2015).WhattheBodyCommands:TheImperativeTheoryofPain.Cambridge
MA:MITPress.
Peterson,K.,Cotton,J.,Gehling,J.andPisani,D.(2008).TheEdiacaranEmergenceof
Bilaterians:CongruenceBetweentheGeneticandtheGeologicalFossilRecords.
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