AnimalSentience2016.X:CommentaryonKeyonFishPain
Fishlackthebrainsandthepsychologyforpain
CommentaryonKeyonFishPain
StuartW.G.Derbyshire
DepartmentofPsychology
NationalUniversityofSingapore
Abstract:Debateaboutthepossibilityoffishpainfocuseslargelyonthefish’slackof
thecortexconsiderednecessaryforgeneratingpain.Thatviewisappealingbecause
it avoids relatively abstract debate about the nature of pain experience and
subjectivity. Unfortunately, however, that debate cannot be entirely avoided.
Subcorticalcircuitsinthefishmightsupportanimmediate,raw,“pain”experience.
The necessity of the cortex only becomes obvious when considering pain as an
explicitlyfeltsubjectiveexperience.Attributingpaintofishonlyseemsabsurdwhen
painisconsideredasastateofexplicitknowing.
[email protected]
Professor at the National University of Singapore in the
Department of Psychology and the A*STAR-NUS Clinical
Imaging Research Centre. His main research interest is the
neurobiology of pain, especially as it relates to issues of
consciousness, subjectivity and ongoing pain in the absence
ofinjury.http://www.fas.nus.edu.sg/psy/_people/derbyshire.htm
Thepasttwentyyearshaveseenincreasingdiscussionofwhatorganismsmayor
maynotfeelpainwitharticlesaddressingthepotentialpainofcrustaceans(Elwood,
2011),fetuses(Loweryetal.,2007)andfish(Braithwaite,2007).Ineachcasethe
argumentfollowsasimilartrajectory.First,thereisthediscoveryofsomepartofthe
neuralsystemforpain:opioidreceptorsinthelobster(Caseresetal.,2005),theHPA
axisinthefetus(Giannakoulopoulosetal.,1994),andC-fibresinfish(Sneddonetal.,
2003a).Thatdiscoveryisintegratedintoalargerframeworksupportingthe
experienceofpain:avoidancelearningincrabs(AppelandElwood,2009),facial
grimacinginthefetus(Reisslandetal.,2013),andlossofneophobiainfish(Sneddon
etal.,2003b).Finally,thereisthesuggestionthatcertainpracticesshouldbe
stoppedtopreventpain:lobstersshouldnolongerbeboiledalive;abortionshould
berestrictedto20weeks;andfishshouldnotbehooked.Theseargumentsare
followedbyrebuttalsfrominvestigatorswhodonotacceptthatpainisrelevantto
suchpractices(Derbyshire,2006;Rose,2007).
Onthewhole,Iamonthesideofthosewhobelievethattheterm“pain”isbeing
usedtoocasuallyandsoIwelcomeKey’s(2016)contributiontotheargument
againstfishpain.Keycoverstheessentialliteratureexplainingwhypainrequiresa
cortexinordertobeexperiencedandwhyfish,whichlackacortex,cannot
experiencepain.Keydismissesthepossibilitythatpainmightbesubcorticalbecause
completeablationofthecortexresultsincompletelossofconscioussensory
AnimalSentience2016.X:CommentaryonKeyonFishPain
perceptionandlossofthalamicprojectionsintoS1preventpainsensation.Thus,
concludesKey,thecortexisnecessaryforpainexperience.
Thecaseagainstfishpain,therefore,appearsstraightforwardandcompelling:fish
cannotfeelpainbecausetheydonothavethebrainsforit.Anyonemaintainingthe
notionoffishpainiseitherignorantastothefactsoffishneurology,orisinthegrip
ofanunreasonableanthropomorphism,orboth.
Ihaveconsiderablesympathywiththatargumentandwiththesuggestionthatthe
cortexisnecessaryforpainsensation.Atthesametime,however,Key’sargumentis
largelysilentonthenatureofpainandsubjectiveexperiencemorebroadly.
Consequently,hisentirecaseagainstfishpainrestsonwhetheritisacceptedthat
thefishnervoussystemisinadequatetogeneratepain.Bluntlyput,thatcaseisnot
accepted.Thediscoveryoffishnociceptors,withfunctionalconnectionsintothefish
tegmentum(Sneddonetal.,2003a;DunlopandLaming,2005),combinedwith
adaptivechangesinbehaviorfollowingnoxiousstimulation(Sneddonetal.,2003b),
areinterpretedbysomeassupportinganexperienceofpaininfish(Braithwaite,
2007;Sneddon,2009).
Othersalsosuggestthatbrainstemcircuitscangeneratepain,whichlikewise
supportsthecaseforfishpain(Devoretal.,2014).Evidencethatthebrainstem
mightsupportpainincludesexperienceswithanencephalicinfantswhoexpress
emotiondespitemissinglargeportionsoftheircortex(Merker,2007),activation
studiesdemonstratingbrainstem-mediatedfeelingsinnormalvolunteers(Damasio
andCarvalho,2013),andfetalwithdrawalandstressresponsestonoxious
stimulationbeforecorticaldevelopment(Giannakoulopoulosetal.,1994).
Fishmaynothavethecomplexbrainsofthehighermammals,buttheydohavea
nervoussystemthatcandetectnoxiousstimulation,andtheydemonstratea
behaviouralresponsetonoxiousstimulation.Somecallthatpainbecausethey
understandpainasanawarenessofanobjectivebodilystate—theimmediate
sensoryrepresentationoftissuedamage(Grahek,2007).Suchanexperiencedoes
notneedacortexbecausetheexperienceisraw,tieddirectlytotheimmediate
damage,andisanobjectiveextensionofthatdamage,whichdrivestheaversive
behaviouralresponses.
Thustheargumentforfishpainreliesonadistinction,notalwaysacknowledged,
betweentheimmediatestateofbeinginpainandtheexplicitknowledgethatoneis
inpain(Tallis,2005).DamasioandCarvalho(2013)makeasimilardistinction
betweenfeelings,astheexpressionofabodilystate,andemotions,asthatsame
stateinthecontextoftheperson’senvironmentandunderstanding.
Thedistinctionbetween“beingthat”and“knowingthat”soundslikeonethatcan
work.Thatdistinctionallowsforpaininthefishtobesubstantiallydifferentfrom
painasfeltbyanadultperson.Fishpainwillnotinvolveexplicitlyidentifiable
negativesensations,generatingfear,concern,andconsciouslyorganizedprotective
behavior.Fishpainwillbemuchlesselaborate,involvingsomethingapprehended,
AnimalSentience2016.X:CommentaryonKeyonFishPain
asanimmediacy,butnotcomprehended,asanunwelcomeintrusionintothe
subjectivebeingoffish(Derbyshire&Anand,2011).
Anapprehendedimmediacyisnotasubjectiveexperienceandwillnotbefeltinany
mannerapproachingwhatisusuallymeantbytheterm“felt.”Therearemany
apprehendedimmediaciesthatwillfloatinandoutofthefishnervoussystem:
changesintemperature,ambientmotion,lightandsoon,constantlyarrivingand
disappearingandvyingfordominance.Anyfishexperiencewillbepartofa
fragment,unconnectedtoapsychologicalself,andthusquiteunlikeour
experiences.Anyimmediateapprehensionthatmightaccompanynoxious
stimulationinthefish,therefore,shouldnotbecalledpainbecauseitisclearlyfar
fromthetypicalpainexperiencethatweknow.Useoftheterm“pain”is
mischievous;itunreasonablyinvitesequivalencebetweenwhatwewouldexpectto
feelwhenhookedandwhatafishwillfeelwhenhooked.
Tofeelpain,oranythingelse,asanexplicitsubjectivestate,requiresaconceptual
psychologicalsubjecttodothefeeling.Fishlackthebrainsandthepsychological
developmentnecessarytobecomesubjectivebeings,andthatiswhyfishdonotfeel
pain.
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