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Research basis of consciousness and embedded processes in working memory

Co�an(1988,1995,1999,2005)su��arize����iverseevi��encerelevanttothe

consciousversusunconsciousstatusofinfor�ationinactivate���e�or��ver-susthefocusofattention.Whatiscriticalisthatsensor��featuresfro��ulti�le

sti�ulicanbeco�eactivate��in�e�or��atthesa�eti�e,�ithoutevi��encethat

the��entera�areness.Ho�ever,��ee�er�rocessin��see�storequirea�areness,

�a�in��thes��ste��oreli�ethatofBroa��bent(1958).Co�an(1988)�asnon-co��ittalabout�hethertheauto�aticall��activate��infor�ationcoul��inclu��e

se�anticinfor�ation.Unli�eBroa��bent�estillassu�ethatit�a��but,li�e

Broa��bent,�e��onotbelievethatauto�aticactivationofse�anticfeaturesca�-turesattention.Theevi��enceco�esfro�se�arateau��itor��an��visualstu��ies.

1.2.1 Au��itor��stu��iesrelate��toconsciousnessan���or�in���e�or��

Broa��bent(1958)su��arize���or�ofthist���eb��severalinvesti��ators.Inso�e

ofthe�or�,a��ichoticlistenin���etho���asuse��in�hich��ifferent�essa��es

�ere�resente��inthet�oearsusin��ata�erecor��in��.The�essa��einoneear

�astobeatten��e��an��re�eate��(sha��o�e��)�hereasa��ifferent�essa��einthe

otherear�astobei��nore��.Occasionall��,theta�e�assto��e��an��theresearch

�artici�ant�astore�eatas�uchas�ossiblefro�theear�iththe�essa��etobe

i��nore��.Onl��the�ostrecentinfor�ationfro�that�essa��ecoul��bere�e�-bere��;thelastfe�secon��satbest.Man��versionsof��ichoticlistenin��ex�eri�ent

��iel��e��infor�ationconsistent�iththeconclusionthatinfor�ationishel��ina

sensor��for�an��isfor��otten�ithinafe�secon��sunlessitisentere��intoatten-tionan��consciousness.

Johnstonan��Heinz(1978)�ereabletoverif��theassu��tionthatattention

an��a�areness��oto��etheran��arefoun��foronechannelinselectivelistenin��.

The���resente��t�oau��itor��channelsthat�ere��istin��uishe��eitherinter�sof

�h��sicalcuesli�elocationan��voicequalit��,asin�ostofthestu��ies��escribe��b��

Broa��bent(1958),or�ere�resente��in�h��sicall��i��entical�eans,��ifferin��onl��

inthese�anticto�icofthe�essa��e.The�e���ani�ulation�asthat,ina����ition

tosha��o�in��onechannel,�artici�antsalso�eretocarr��outathesubsi��iar��

tas�of�ressin��a�e��asquic�l��as�ossible�henavisualsi��nala��eare��.The

subsi��iar��tas�reactionti�e�as�no�nfro�other�or�tobea��oo���easure

ofho��uchattentionisfree��es�itetheselectivelistenin��tas�.It�asfoun��that

thesubsi��iar��tas�reactionti�e�as�uchfaster�henthe�essa��es�ere�h��si- call��se�arate��than�henthe���ereonl��se�anticall��se�arate��.Withinthee�-be����e��-�rocesses�o��el,thisin��icatesthatthefocusofattentioncanbe��irecte��

atone�h��sicalstrea�ofinfor�ation�ithlittle��ifficult��.Thiscannotbe��one

�henthe�essa��es��ifferonl��intheirse�antic�eanin��sbecausetheanal��sisof

se�anticsisnotauto�atic;itrequiresattentionan��effort.Itsee�s�ostli�el��

thatboth�essa��esarehel��inthefocusofattentionuntilthe�ortionsrelate��toa

se�anticall��coherent�essa��ecanbeextracte��.Giventhenee��tohol��so�uch

aneffortful�rocessthatleaveslittleattentiontobeuse��forthesubsi��iar��tas�.

Boththee�be����e��-�rocesses�o��el(Co�an1988,1999)an��theBroa��bent

(1958)�o��elareconsistent�iththesefin��in��sin��icatin��thatnot�uchauto-�aticse�antic�rocessin��contributestosha��o�in���erfor�ance.One�a��in

�hichthe����ifferisinthe�annerofthecontrolofattention.Broa��bent�osits

anattentionalfilteran��one�i��htthin�thatthe�orechannelstherearetobe

rejecte��,thehar��erthefilter�ust�or�.InCo�an’s�o��el,incontrast,thereis

nofilterin��an��thefocusofattention�ustselectonechanneltobe�rocesse��

se�anticall��,a�rocessthatnee��not��e�en��onho��an��channelsthereareto

berejecte��.Afurtherex�eri�entofJohnstonan��Heinz(1978)see�stosu��ort

thisa����itional�re��iction.Acon��itionin�hichthere�ereonl��t�o�h��sicall��

��ifferent�essa��es,onetobeatten��e��an��onetobei��nore��,�asco��are��to

acon��itionin�hichthere�erethree�h��sicall����ifferent�essa��es,onetobe

atten��e��(afe�alevoice)an��t�otobei��nore��(t�o��ifferent�alevoices).The

subsi��iar��tas�reactionti�e�asthesa�eno�atter�hetherit�asnecessar��

toi��noreoneort�ochannels,asex�ecte��accor��in��tothee�be����e���rocesses

�o��elin�hichthereisnorealfilterin��outofirrelevantsti�uli,justaccentuation

oftherelevantchannelor�essa��ehel��inthefocusofattention.

Atoneti�ethere�asani��ortant�ove�entto�ar���o��elsin�hichinfor-�ationlea�sthrou��htheattentionalfilter,suchastheattenuatin��filter�o��elof

Treis�an(1964).The�ainreasonforit�asthatthere�ereanu�berofstu��ies

su����estin��thatinfor�ation��i����etthrou��h.The�ostfa�ousofthose�as�hen

the�artici�ant’so�nna�e�as�resente��intheunatten��e��channelinselective

listenin��(Mora��1959).Thefin��in���asthat�artici�antsso�eti�escoul��reco��-nizean��re�e�berhearin��theiro�nna�es.Woo��an��Co�an(1995a,1995b)

confir�e��that�artici�antscoul��noticesubtlechan��esintheunatten��e��chan-nel,inclu��in��theiro�nna�es.It�asabout1/3ofthe�artici�ants�honotice��

theirna�es,aboutthesa�e�ro�ortionobtaine��inthes�allerstu����b��Mora��.

Ho�ever,thereare��ifferent�a��sthatthiscoul��co�eabout.Itcoul��bethatin-for�ationaboutthena�ein��ee��lea�e��throu��hthefilter(or,inthee�be����e��

�rocesses�o��el,thatacousticco��onentsofthena�e�a��econtact�iththe

lon��-ter��e�or��re�resentationofthena�ean��thereb��attracte��attention).

Alternativel��,itcoul��bethatattentionoften�an��ere��fro�theassi��ne���essa��e

overtotheunatten��e���essa��e,or�ass�litbet�een�essa��es,an��thereforethat

thena�e�asalrea����atten��e���henit�ashear��.Ita��earsthatthatisthecase

inas�uchasonestu����(Con�a��,Co�an,an��Buntin��2001)sho�e��that65%of

in��ivi��ualsinthelo�estquartileof�or�in���e�or��notice��theirna�es,�here-asonl��20%ofin��ivi��ualsinthehi��hestquartileof�or�in���e�or��notice��their

na�es.The�oststrai��htfor�ar��inter�retationisthatthehi��hs�ans�ereontas�

�oreoftenthanthelo�s�ans.Colfleshan��Con�a��(2007)sho�e��that�henthe

tas��astotr��to�onitorboth�essa��esatonce,hi��h-s�anin��ivi��ualsnotice��

theirna�es�oreoftenthanlo�s�ans.

1.2.2 Visualstu��iesrelate��toconsciousnessan���or�in���e�or��

S�erlin��(1960)carrie��outase�inalstu����thatcanbeconsi��ere��thebasisof

thevisual�or�relatin���or�in���e�or��toconsciousness,�uchasthe�or�

revie�e��b��Broa��bent(1958)canbeconsi��ere��thebasisofthecorres�on��-in��au��itor���or�.S�erlin���resente��anarra��ofcharacters(�rinte��lettersan��

nu�bers)onaco��uterscreen,so�eti�esfollo�e��shortl��after�ar��b��atone

cuein��icatin���hethertheto�,�i����le,orbotto�ro�ofcharacters�astobe

re�orte��.Withnotonecue,�artici�antscoul��recallabout4ite�sfro�thearra��.

Whenthetonecuefollo�e��closel��afterthearra��,the��coul��recallabout4ite�s

fro�theselecte��ro�.Thisin��icate��thattherearet�oli�itsinrecall.First,there

isali�itofabout4ite�sinho��uchinfor�ationcanbeextracte��into�or�-in���e�or��.Secon��,thereisali�itinho��an��ite�scanbeenco��e��fro�the

arra��butitisnotnearl��assevereas4ite�s.Instea��,ita��earsthat�ostorallof

thearra��ite�sareenco��e��,��iventhatthe�artici�ants��i��not�no�ina��vance

�hichro��oul��becue��butstillcoul��successfull��recall4ite�sfro�thatro�.

Theretentionof�ostofthearra���assai��tobeinthefor�ofsensor���e�or��,

usableifattentionisturne��toitbutnotre�ortableinan��thin��nearitsentiret��.

Thissensor���e�or��thereforesee�stobehel��outsi��eofthefocusofattention

an��a�areness.Incontrast,thes�alla�ountof�or�in���e�or��thatisre�ort-able(about4ite�s)isinattentionan��a�areness.

Luc�an��Vo��el(1997)create��acleanerversionofS�erlin��’s�roce��urethat

�asinten��e��toquantif��visual�or�in���e�or��.The��use��colore��nonverbal

sha�esratherthanverbalcharacterstosho�that�or�in���e�or��forevennon- verbalinfor�ationisli�ite��toabout4ite�s.Thearra��ofobjectstobere�e�-bere���asfollo�e��b��a�robethatcoul��evenbeasin��leite�,thetas�bein��to

in��icate�hethertheite�chan��e��fro�thecorres�on��in��ite�intheori��inal

arra��.Perfor�ance�asnearl���erfect�henthere�ere3or4ite�sinthearra��,

an����ecline��asthearra��sizeincrease��.Co�an(2001)��erive��asi��lefor�ula

toesti�atethenu�berofarra��ite�sin�or�in���e�or��forthesin��le-ite�

�robecase,an��Rou��eretal.(2008)foun��a��oo���athe�aticalfitof��etaile��

��atatothefor�ula.

Thet���eof�e�or��observe��b��Luc�an��Vo��el(1997)isoftenconsi��ere��

tobevisual�or�in���e�or��,�hichcoul���a�eitaratherauto�aticstoreli�e

thevisuos�atialbufferofAlanBa����ele��’s�o��els,�otentiall��o�eratin���ithout

to��o�iththefocusofattentionan��consciousness.More��an��Co�an(2004)

sho�e��thatinterferenceoccursfro�as�o�enverbal�e�or��loa��(sevenran-��o���i��its),butnotfro�as�o�enseriesthatbloc�sarticulationbut��oesnot

loa���e�or��(a�no�nseven-��i��ittele�honenu�ber).Saultsan��Co�an(2007)

use����i��its�resente��in��ifferentvoicesfro�fourlou��s�ea�ersto�reventre-hearsalan��foun��thatthe�e�or��forthe��i��itstra��e��off�ith�e�or��forthe

colore��visualobjects;�artici�antscoul��re�e�berabout3.5visualobjectsor,

ifas�e��tore�e�berboth�o��alities,the��coul��re�e�berfe�ervisualobjects

butabout3.5objectstotal,visual�lusau��itor��.Co�anan��More��(2007)sho�e��

thatthisinterferencebet�eenvisuos�atialan��au��itor��-verbalite�soccurre��in

the�or�in���e�or��retention�hase,notjustintheenco��in��ofthesti�uli.It

see�s,therefore,that�eare��ealin���ithacentral�or�in���e�or��storethatis

li�ite��to3or4ite�sina��ults.Notsur�risin��l��,thiscentralstore�oul��bethe

sa�ethatS�erlin��(1960)observe���ith�rinte��verbalcharacters.Thisli�ite��-ca�acit��store�atchestheconsciousinfor�ationthatthee�be����e��-�rocesses

�o��elconceivesasthefocusofattentionan��a�areness.

Stu��iesrevie�e��b��Co�an(2001)sho�e��thatin��ivi��ualsvar��quiteabit

intheir�or�in���e�or��ca�acit��;a��ultsvar��fro�2to6�ith�ostin��ivi��uals

intheran��eof3to5ite�s,an��chil��renan��ol��era��ults�oret���icall��about1

ite�fe�er.Thereareatleastt�o�echanis�sb���hichthevisualstorein��exe��

b��thetas�ofLuc�an��Vo��el(1997)coul��var��a�on��a��e��rou�san��in��ivi��u-als.First,itcoul��bethatso�ein��ivi��ualsare�ore��istractiblean��thereforeare

lessli�el��toenco��ethecorrectinfor�ationinto�or�in���e�or��.Thiscanbe

teste��b��inclu��in��so�eobjectsthataretobei��nore��(e.��.,re��bars)an��others

thataretobeatten��e��(e.��.,��reenbars;atten��totheirorientations).A��istract-iblein��ivi��ual�oul��incorrectl��treatthere��barsasifthe���ererelevantan��

therefore�oul��actasiftheir�or�in���e�or���ereheavil��loa��e��.Incontrast,

aless��istractiblein��ivi��ual�oul��exclu��ethere��barsan��therefore�oul��act

asiftheir�or�in���e�or���asnotsoheavil��loa��e��.Vo��eletal.(2005)use��an

event-relate���otential�easureof�or�in���e�or��loa��an��foun��thatin��ivi��-uals�hore�e�bere���oreite�s�ereless��istractible.McNaban��Klin��ber��

(2008) ��u�licate�� this result in an fMRI stu����, sho�in�� in��ivi��ual ��ifferences

insubcorticalcentersinvolve��inexclu��in��irrelevantobjects.Ofcourse,either

enco��in��ofinfor�ationintoanunconsciousstoreorenco��in��ofinfor�ation

intoaconsciousstorecoul��beinfluence��b��theabilit��tofilteroutorexclu��e

irrelevantite�s.Thist���eof�echanis�alsoa��rees�ell�iththenotionthat

in��ivi��uals�ithbetters�anarethose�hoarebetterabletoexclu��eorinhibit

irrelevantinfor�ation(Lusti��etal.2007).

Thereisotherevi��ence,thou��h,ofanother�echanis��hereb��in��ivi��uals

��ifferinca�acit��.This�echanis�isnot�ellun��erstoo��butitisa��ifferencein

stora��eabilit���erse.Gol��etal.(2006)exa�ine��thisinabehavioralstu����of

in��ivi��uals�ithschizo�hreniaan��health��controlsusin��arra��sofobjectstobe

atten��e��an��i��nore��.The��usuall���robe��objectstobeatten��e��butoccasion-all���robe��objectstobei��nore��.Thesu�oftheatten��e��an��i��nore��ite�s

in�or�in���e�or����aveanesti�ateofthetotala�ountin�or�in���e�or��,

�hereasthe��ifferencebet�eenatten��e��an��i��nore��ite�s,favorin��theatten��e��

ones,��aveanesti�ateoftheefficienc��oftheattentionalfilterin���rocess.Sur�ris-in��l��,itturne��outthatthe��ifferencebet�eenthe��rou�s�asal�ostentirel��in

thetotala�ountin�or�in���e�or��,�ithver��little��ifferenceinthefilterin��

efficienc��.Co�anetal.(2010)re�licate��thisfin��in��for��oun��chil��ren(7to8

��earsol��)inco��arisontool��erchil��ren(12to13��earsol��)ora��ults,�hen

thearra��sinclu��e��2relevantite�s(e.��.,circles;atten��totheircolors)an��2ir-relevantite�s(e.��.,trian��les).Ho�ever,�henthearra��sinclu��e��3relevantan��

3irrelevantite�s,thelar��ea��e��ifferenceinca�acit��(as�easure��b��thesu�of

�e�or��forrelevantan��irrelevantite�s)�asno�su��le�ente��b��as�allera��e

��ifferenceintheabilit��tofilteroutorexclu��eirrelevantite�s(as�easure��b��

the��ifferencebet�een�e�or��forrelevantversusirrelevantite�s).Thisfin��in��

su����eststhattheabilit��tofilteroutorexclu��eirrelevantite�sisco��ro�ise��

�hen�or�in���e�or��isoverloa��e��.Thatistobeex�ecte��onl��ifthe�or�in��

�e�or��storeinquestionisacentralstorethatisattention-relate��initself,asis

thefocusofattentionasastora��e��evice.

So�econtrovers��hasarisenre��ar��in��thenatureof�e�or��intheLuc�

an��Vo��el(1997)arra��tas�base��onthe�ro�ertiesofbin��in��bet�een��ifferent

featuresofobjects.Anexa��leisre�e�berin���hichsha�e�ent�ith�hich

color,an��/or�hichcolor�asfoun��at�hichlocationinthearra��.Ourinitial

ex�ectationafe���earsa��o�asthatintro��ucin��anattentional��istraction�oul��

��ifferentiall�� i��air the abilit�� to re�e�ber bin��in�� infor�ation as o��ose��

tofeatureinfor�ation.Thatisbecausethefocusofattention�asvie�e��asthe

vehiclefortheretentionofne�bin��in��sbet�eenfeatures(Co�an1995,1999,

2001).Theactivationofinfor�ationfro�lon��-ter��e�or��coul��notinclu��e

ne�bin��in��sbet�eenfeatures,asonefin��s�henne�or�eanin��lessobjects

are�resente��.Itcoul��inclu��etheinfor�ationthatana��leisre��,forexa��le,

butnottheinfor�ationthatanabstractcirclethathasbeen�resente��is�ur�le.

Si�ilarl��,�erce�tualtheor���o�ularinthefiel��ha��lon��hel��thatitta�esatten-tiontofor�bin��in��sbet�eenfeatures(Treis�anan��Gela��e1980).T�ostu��ies,

ho�ever,sho�e��thatthis�asnotthecase.A��istractin��tas���urin��thearra��

retentiontas��asjustashar�fulforbin��in��infor�ationasit�asforthefeature

infor�ation(Allenetal.2006;Co�anetal.2006).

inthistas�isattention-relate��,asinthefocusofattention?Notnecessaril��.One

�a��toun��erstan��thisfin��in��isthatbrin��in��anite�intothefocusofattention

necessaril��entailsitsfeaturesbein��boun��.Ifthefocusofattention�erethe�ain

facult��in�hichinfor�ationisstore��inthetas�,intro��ucin����istraction�oul��

interfere�ithstora��eoftheite�san��therefore�oul��affectboth�e�or��for

�e�or��forfeaturesan���e�or��forthebin��in��bet�eenthesefeatures.

1.2.3 Unitsof�or�in���e�or��an��consciousness

Miller(1956)e��hasize��that�or�in���e�or����e�en��sontheabilit��to��rou�

ite�sto��ethertofor��eanin��fulchun�s.ThelettersPRF�a��for�3chun�sif

the��for�no�no�nacron���;thelettersUSA�a��for�asin��lechun�iftheac-ron���Unite��StatesofA�ericais�no�ntothe�artici�ant.In�an���roce��ures,

theabilit��to��rou�ite�sto��etherisli�ite��(becausetheite�sare�resente��

quic�l��an��un�re��ictabl��,asinthevisualarra��tas�orinrunnin���e�or��s�an;

orbecauseverbalre�etitionofa�or��orshort�hrasetoeli�inateverbalrehears-alisrequire��)an��theusualresultisthatabout3to5ite�sarerecalle��b��a��ults

(Co�an2001).Itre�ainsunclearfro�thisresearch,thou��h,ho���eneralisthis

ans�erre��ar��in��thenu�berofite�sthatcanbehel��inthefocusofattention.

Theite�li�ita��earstohol��even�henite�sare��rou�e��to��ether.Chen

an�� Co�an (2009b) sho� this �ost clearl��. The�� tau��ht �artici�ants �airs of

�or��sto100%correctcue��recall,an��also�resente��un�aire���or��sin��letons.

Thus,there�ere1-an��2-�or��chun�s.Durin��therecalloflistsof�or��sof

variouslen��thsran��in��fro�4to12�or��s,the��sho�e��thattherecallli�it�as

narro�l����efine��inchun�s.In��ivi��ualscoul��recallabout3sin��letonsfro�a

listofthoseite�s,orthe��coul��recallabout3�airsfro�alistofthoseite�s,

re��ar��lessofthelistlen��th.Thusit��oesnota��earthattheli�itinthefocusof

attentionisinho��an���or��scanbehel��,butratherinho��an���eanin��-fulunitscanbehel��.Si�ilarl��,Gilchristetal.(2008)�resente��listsofunrelate��

attentionisinho��an���or��scanbehel��,butratherinho��an���eanin��-fulunitscanbehel��.Si�ilarl��,Gilchristetal.(2008)�resente��listsofunrelate��