Sentiment Analysis - Columbia University · • Social Media Features *Apoorv Agarwal, Fadi Biadsy, and Kathleen R. McKeown. 2009. Contextual phrase-level polarity analysis using

SentimentAnalysis

Announcements•  HW1isduetodayat11:59pm•  HW2willcomeoutMonday•  IfyouuselatedaysforHW1,MUSTSTATEITINYOURSUBMISSION.•  Reading:Today:C4.2NLP• Monday:C8.1-8.3SpeechandLanguage,

8.1NLP•  RecommendreadingchaptersinYoavGoldbergonneuralnetsandJurafskyandMarVnaswell.•  BotharemoreintuiVve

Today• SenVmentanalysistasks:definiVon• SenVmentresources• TradiVonalsupervisedapproach• Neuralnetapproach

Whatissentiment?• ExpressionofposiVveornegaVveopinions• ..Towardsatopic,person,event,enVty• ..Towardsanaspect(e.g.,service,foodorambienceinarestaurant)

Whysentimentanalysis?• SenVmentiscommoninonlinepla[orms• Peoplewriteabouttheirpersonalviewpoints

• UsefultounderstandwhatpeoplethinkaboutpoliVcalissues,poliVcalcandidates,importanteventsoftheday• UsefulforgeneraVngsummariesofreviews:restaurants,products,movies

Thesentimentanalysistask(s)• SubjecVvevsobjecVve• Polarity:PosiVve,negaVveorneutral• DowehavesenVmenttowardsatarget?OraspectbasedsenVment?• What/whoisthesenVmentsource?

SubjectivevsObjective• �Atseveraldifferentlayers,it’safascina3ngtale.[“Who’sSpyingonOurComputers”,GeorgeMelloanWallStJournal.(Bookreview)• BellIndustriesIncincreaseditsquarterlyto10centsfrom7centsashare.

ExamplesfromWeibeetal2004

Positive/Negative/Neutral•  FromUseNet:

• NegaVve:Ihadinmindyourfacts,Buddy,nothers.•  PosiVve:Nicetouch.“Alleges”whateverfactspostedarenotinyourpersonaofwhatis“real”• Neutral:Marchappearstobeanes3matewhileearlieradmissioncannotbeen3relyruledout,"accordingtoChen,alsoTaiwan'schiefWTOnego3ator

ExamplesfromWeibeetal2004andRosenthal2014

SubjectivePhrases• TheforeignministrysaidThursdaythatitwas“surprised,toputitmildly”bytheU.S.StateDepartment’scri0cismofRussia’shumanrightsrecordandobjectedinparVculartothe“odious”secVononChechnya.[MoscowTimes,03/08/2002]• Subjec3vityanalysisiden3fiestextthatrevealsanauthor’sthoughts,beliefsorotherprivatestates.


SubjectivePhrasesandSources• TheforeignministrysaidThursdaythatitwas“surprised,toputitmildly”bytheU.S.StateDepartment’scri0cismofRussia’shumanrightsrecordandobjectedinparVculartothe“odious”secVononChechnya.[MoscowTimes,03/08/2002]• Whowassurprised?• WhowascriVcal?


SentimenttowardsTarget•  IpreUymuchenjoyedthewholemovie.Target=wholemovie,senVment=posiVve.•  Bulgariaiscri3cizedbytheEUbecauseofslowreformsinthejudiciarybranch,thenewspapernotes.Target=Bulgaria,senVment=negaVve•  Stanishevwaselectedprimeministerin2005.Sincethen,hehasbeenaprominentsupporterofhiscountry’saccessiontotheEU.Target=country’saccesstotheEU,senVment=posiVve

ExamplesfromBreck&Cardie

Datasets(Sem-evaldatasetsalsoused)

2000sentencesineachcorpus

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Corpus AverageWordCount

AverageCharacterCount

Subjec6vePhrases

Objec6vePhrases

VocabularySize

CharacterLengthRestric6ons

LiveJournal 14.67 66.47 3035(39%) 4747(61%) 4747 30-120

MPQA 31.64 176.68 3325(41%) 4754(59%) 7614 none

Twimer 25.22 118.55 2091(36%) 3640(64%) 8385 0-140

Wikipedia 15.57 77.20 2643(37%) 4496(63%) 4342 30-120

MPQA:extensivelyannotateddatasetbyStoyanav,CardieandWeibe2004.15opinionorientedqusVons,15factorientedquesVons.Alongwithtextspansfrom252arVcles.

RosenthalandMcKeown2013)

ExampleSentences

LiveJournal iwillhavetosVcktomycanonfilmslrunVlinafewyearsicanaffordtoupgradeagain:)

MPQA ThesaleinfuriatedBeijingwhichregardsTaiwananintegralpartofitsterritoryawaiVngreunificaVon,byforceifnecessary.

Twimer RT@tashjade:That’sreallysad,CharlieRT“UnVltonightIneverrealisedhowfuckedupIwas”-CharlieSheen#sheenroast

Wikipedia PerhapsifreportedcriVcallybyawesternsourcebutcertainlynotbyanIsraelisource.

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SubjecVve ObjecVve

SentimentLexicons• GeneralInquirer• SenVWordNet• DicVonaryofAffect(DAL)

DictionaryofAffectinLanguage• DicVonaryof8742wordsbuilttomeasuretheemoVonalmeaningoftexts• Eachwordisgiventhreescores(scaleof1to3)•  pleasantness-alsocalledevaluaVon(ee)•  acVveness(aa)•  andimagery(ii)

C.M.Whissel.1989.Thedic6onaryofaffectinlanguage.InR.PlutchikandH.Kellerman,editors,EmoVon:theoryresearchandexperience,volume4,London.Acad.Press.

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Emoticons• 1000emoVconsweregatheredfromseverallistsavailableontheinternet• Wekeptthe192emoVconsthatappearedatleastonceandmappedeachemoVcontoasingleworddefiniVon

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Methods• Pre-processingsteps•  EmoVconkeysandcontracVonexpansion• Chunkerandtagger*• LexicalFeatures*• SyntacVcFeatures*• SocialMediaFeatures

*ApoorvAgarwal,FadiBiadsy,andKathleenR.McKeown.2009.Contextualphrase-levelpolarityanalysisusinglexicalaffectscoringandsyntac6cn-grams.InProceedingsofEACL’09

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PreprocessingLiveJournal [i]/NPsub[willhavetos6ck]/VPobj[to]/PPobj[mycanonfilmslr]/NPobj[unVl]/

PPobj[in]/PPobj[afewyears]/NPsub[i]/NPsub[canaffordtoupgrade]/VPobj[again:)]/NPsub

MPQA [Thesale]/NPsub[infuriated]/VPobj[Beijing]/NPobj[which]/NPsub[regards]/VPsub[Taiwan]/NPobj[anintegralpart]/NPsub[of]/PPobj[itsterritoryawaiVngreunificaVon,]/NPobj[by]/PPobj[force]/NPsub[if]/obj[necessary.]/sub

Twimer [RT@tashjade:]/NPobj [That]/Npobj[is]/VPsub[really]/sub[sad,]/sub[CharlieRT]/NPobj[”]/NPobj[UnVl]/PPobj[tonight]/NPsub[I]/NPsub[never]/sub[realised]/VPsub[how]/sub[fucked]/VPsub[up]/PPobj[I]/NPsub[was]/VPsub[”]/obj[-CharlieSheen#sheenroast]/NPobj

Wikipedia [Perhaps]/sub[if]/obj[reported]/VPsub[cri6cally]/sub[by]/PPobj[awesternsourcebut]/NPsub[certainlynot]/sub[by]/PPobj[anIsraelisource.]/NPsub

18Xuan-HieuPhan,CRFChunker:CRFEnglishPhraseChunkerhmp://crfchunker.sourceforge.net/,2006

LexicalFeatures• POSTags*• N-grams*• Performedchi-squarefeatureselecVononthen-grams


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SyntacticFeatures• Usethemarkedupchunkstoextractthefollowing:*• n-grams:1-3words• POS:NP,VP,PP,JJ,other• PosiVon:target,right,lev•  SubjecVvity:subjecVve,objecVve• Minandmaxpleasantness


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SocialMediaFeatures

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SingleCorpusClassiLication

BalancedUnbalanced

•  LogisVcRegressioni

•  10runsof10-foldcross-validaVon

•  StaVsVcalsignificanceusingthet-testwithp=.001

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Experiment LiveJournal MPQA Twimer Wikipedia

n-gramsize 100 2000 none none

majority 58% 59% 64% 63%

JustDAL 76.5% 75.7% 83.6% 80.4%

DicVonaries+SM 77.1% 76.1% 84% 81.4%

Wordnet 76.7% 75.6% 84% 80.7%

Wordnet+SM 77.1% 76.1% 84.2% 81.4%

DicVonaries 76.6% 75.7% 83.9% 80.7%

SM 77% 76.1% 83.7% 81.2%

Experiment LiveJournal MPQA Twimer Wikipedia

n-gramsize 100 200 none none

majority 50% 50% 50% 50%

JustDAL 74.7% 75.7% 81.9% 79.3%

DicVonaries+SM 76.7% 76.2% 82.6% 80.2%

Wordnet 75.1% 75.8% 82.4% 79.1%

Wordnet+SM 76.6% 75.3% 82.6% 80.3%

DicVonaries 75.3% 75.8% 82.4% 79.1%

SM 76.2% 76.3% 82.2% 80.4%

SocialMediaErrorAnalysis• Wikipedia• PunctuaVonwasusefulasafeaturefordeterminingthataphraseisobjecVveifitisasmallphrase.However,severalsubjecVvephraseswereincorrectlyclassifiedbecauseofthis 23

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SocialMediaErrorAnalysis• Twimer•  EllipseshelpindicatethatasentenceisobjecVve.Theaccuracyimprovedfrom82%to92%forsentenceswiththisfeature•  AllothersocialmediafeatureswereincorrectlyclassifiedasobjecVve/subjecVvedependingonthesocialmediapreference. 24

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SocialMediaErrorAnalysis• LiveJournal•  OutofVocabularywordsandpunctuaVonwerethemostusefulsocialmediafeatures.•  InalldatasetsthepunctuaVonfeaturecausedcloseto50/50exchangebutthefeaturewasbestinLiveJournal. 25

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NeuralNetworkApproachestoSentiment•  TakeastandardRNN•  Takealabeleddataset(e.g.,IMDBsenVmentdataset)•  IniValizewithpre-trainedwordembeddings(wordtovecorglove)• UsesigmoidtopredictbinarysenVmentlabels:posiVvevsnegaVve.

Languageismadeupofsequences• Sofarwehaveseenembeddingsforwords•  (andmethodsforcombiningthroughvectorconcatenaVonandarithmeVc)

• Buthowcanweaccountforsequences?• Wordsassequencesoflemers•  Sentencesassequencesofwords• Documentsassequencesofsentences

RecurrentNeuralNetworks• Representarbitrarilysizedsequencesinfixed-sizevector• GoodatcapturingstaVsVcalregulariVesinsequences(ordermamers)• IncludesimpleRNNs,Longshort-termmemory(LSTMs),GatedRecurrentUnit(GRUs)

[Thangetal.2013] [Bowmanetal.2014]

Learningwordmeaning Logicalentailmentfromtheirmorphsusingcompositional

semanticsviaRNNs

MachineTranslation(Sequences)

• Sequence-to-sequence•  Sutskeveretal.2014

RNNAbstraction• RNNisafuncVonthattakesanarbitrarylengthsequenceasinputandreturnsasingledoutdimensionalvectorasoutput•  Input:x1:n=x1x2…xn(xiεRd-in)•  Output:ynεRd-out

OOutputvectoryusedforfurtherpredicVon

RNNCharacteristics• CancondiVonontheenVresequencewithoutresorVngtotheMarkovassumpVon• Cangetverygoodlanguagemodelsaswellasgoodperformanceonmanyothertasks

RNNsaredeLinedrecursively• BymeansofafuncVonRtakingasinputastatevectorhi-1andaninputvectorxi• Returnsanewstatevectorhi• ThestatevectorcanbemappedtoanoutputvectoryiusingasimpledeterminisVcfuncVon• AndfedthroughsovmaxforclassificaVon.

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UpdatingParametersofanRNN

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BackpropagaVonthroughVme

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Example• Foreachsentenceinthetrainingcorpus,classify,comparetogoldstandardandcomputeloss,backpropagate.• Recallthatwemayusemini-batchessothatwe’renotback-propagaVngforeachexample

•  Ihadinmindyourfacts,Buddy,nothers.

RNN–Ihadinmindyourfacts,buddy,nothers.

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Inthisoverview,wreferstotheweightsButtherearedifferentkindsofweightsLet’sbemorespecific


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Y=posiVve?Y=negaVve?Finalembeddingrunthroughthesigmoid

funcVon->[0,1]1=posiVve0=negaVveOvenfinalhisusedaswordembeddingforthesentence

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BackpropagaVonthroughVmeGoldlabel=0(negaVve)AdjustweightsusinggradientRepeatmanyVmeswithallexamples

SlidefromRadev

I had in

ProblemwithRNN• Vanishinggradients• BytheVmeweback-propogateallthewaythroughthenetwork,theweightsapproachzero->vanishinggradient• Errorsignals(gradients)inlaterstepsdiminishquicklyanddonotreachearlierinputsignals•  ->Hardtocapturelong-distancedependencies

Whatisalongdistancedependency?• ThestudentswerelisteningtoKathyMcKeownspeak.• Thestudentsin451CSBuildingwerelisteningtoKathyMcKeownspeak

GatedArchitectures• RNN:ateachstateofthearchitecture,theenVrememorystate(h)isreadandwrimen• Gate=binaryvectorgε{0,1}•  Controlsaccesston-dimensionalvectorx�g

• Consider•  Readsentriesfromxspecifiedbyg•  Copiesremainingentriesfroms(orhaswe’vebeenlabelingthehiddenstate)

Example:gatecopiesfromposiVons2and5intheinputRemainingelementscopiedfrommemory

LSTMSolution§ UsememorycelltostoreinformaVonateachVmestep.

§ Use“gates”tocontroltheflowofinformaVonthroughthenetwork.§ Inputgate:protectthecurrentstepfromirrelevantinputs

§ Outputgate:preventthecurrentstepfrompassingirrelevantoutputstolatersteps

§ Forgetgate:limitinformaVonpassedfromonecelltothenext

[slidesfromCatherineFinegan-Dollak]

TransformingRNNtoLSTM

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LSTMforSequences

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Bi-LSTM for sentiment!•  Pre-trained Word Embeddings !!

Word Embeddings

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Bi-LSTM enriched with sentiment!word embeddings !!

Sentiment Word Embeddings

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Vsentiment(x1)Bilingual Sentiment Scores

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RecursiveDeepModelsforSemanticCompositionalityoveraSentimentTreebank•  Socheretal,Stanford2013hmps://nlp.stanford.edu/~socherr/EMNLP2013_RNTN.pdf•  Problemwithpreviouswork:difficultyexpressingthemeaningoflongerphrases• Goal•  TopredictsenVmentatthesentenceorphraselevel•  CaptureeffectofnegaVonandconjuncVons•  SenVmentTreebank•  RecursiveNeuralTensorNetwork

SentimentTreebank• Moviereviewexcerptsfromromentomatoes.com(Pang&Lee2005)•  10,662sentences• ParsedbyStanfordParser(Klein&Manning2003)•  215,154phrases• EachphraselabeledforsenVmentusingAmazonMechanicalTurk(AMT)•  5classesemerge:negaVve,somewhatnegaVve,neutral,somewhatposiVve,posiVve

Example--verynegaVve++veryposiVve-  NegaVve+posiVve0neutral

RecursiveNeuralModels

RNN:RecursiveNeuralNetwork

WaretheweightstolearnWεf=tanh

MV-RNNMatrixvectorRNN• Introduceweightmatrixassociatedwitheachnon-terminal(P2foradjP)andterminal(Afora)• a=not,b=very,c=good

RNTN:RecursiveNeuralTensorNetwork•  TheMV-RNNhastoomanyparameterstolearn(sizeofvocabulary)•  CanwegetcomposiVonalitywithreducedparameters?•  P1=f([ab]u1u2a)u3u4b=f([ab]u1a+u2b)u3a+u4b

=f(u1aa+u2ab+u3ab+u4bb)

Results

Positive–“mostcompelling”

Negative–“leastcompelling”

HandlingConjunctions