Electrophysiological evidence for attentional capture by irrelevant angry facial expressions

12 Pages·2016·1.47 MB·English

by  Nicolas Burra

BiologicalPsychology120(2016)69–80

ContentslistsavailableatScienceDirect

Biological Psychology

journal homepage: www.elsevier.com/locate/biopsycho

Electrophysiological evidence for attentional capture by irrelevant

angry facial expressions

NicolasBurra∗,CarolineBarras,SélimYahiaColl,DirkKerzel

FacultédePsychologieetdesSciencesdel’Education,UniversitédeGenève,Switzerland

a r t i c l e i n f o a b s t r a c t

Articlehistory: Attentionisbelievedtobebiasedtowardthreateningobjectsorfaces.Therefore,wetestedwhetherangry
Receiv ed6January2016 facestimu li wouldca pt ure atten tioneve nwhenthey areirre le vantt othetask. Obs ervers searched fora
AReccceepivteedd i2n 3 rAevuigsueds t f2o0rm16 12 August 2016 neut ral face with a tilted n ose. On so me t rials, t he ta rget was show n toge ther with an irr elevant a ngr y
orhappyfaceandwemeasuredtheN2pc(anelectrophysiologicalmarkerofattentionalselectivity)to
Availableonline24August2016
thedistractorexpression.WefoundthatangrydistractorstriggeredanN2pc,whereashappydistractors

didnot.Follow-upexperimentsexploredthereliabilityoftheN2pctoangrydistractorsusinguprightor
Keywords:
invertedangryfaces,theeyeormouthregionofangryfacesandface-likestimuli.Weconcludethata
N2pc
threateningexpressionhasahighattentionalpriorityduetoitsemotionalcontentandcapturesattention
Attentionalcapture
Angry faces despite being irrelevant for the task. ©2016ElsevierB.V.Allrightsreserved.

1. Introduction Smilek,&Merikle,2001;Foxetal.,2000;Hansen&Hansen,1988;

Öhman,Lundqvist,&Esteves,2001;Sawada&Sato,2015)thatare

Facialexpressions,especiallythreateningfaces,areimportant easily recognizable and are created with lines representing eye-

to our survival, and are assumed to be preferentially detected. browsandmouthsurroundedbyacircleoranoval.Typically,they

Fromanevolutionaryperspective,preferentialdetectionofthreat- share the same attributes as real faces, i.e. furrowed brows and

eningstimuliisadaptivelybeneficial(Lang,Davis,&Öhman,2000), acompressedmouth(Darwin,1872;Ekman&Friesen,1976)and

because a threat detection system would allow the attentional receivesimilarevaluationsintermsofvalenceandintensity(Calvo

system to uncover possible threats with minimal allocation of &Nummenmaa,2008;Coelho,Cloete,&Wallis,2010).

attentiontothesurroundingenvironment(LeDoux,1996).Some However, the interpretation of the anger superiority effect is

models of early emotional and attentional processing have pro- controversial.Anumberofstudiessuggestedthatattentionalcap-

posedthatthreateningstimuliareprocessedpriortotheoperation ture by angry faces does not result from preferential attentional

of selective attention, with a specialized “threat-detection sys- selectionofthreateningexpressions,butfromsalientperceptual

tem”(Öhman&Mineka,2001).Thus,thethreat-capturehypothesis featuresassociatedwithangryfacesthatvarystronglyasafunc-

predicts automatic attentional capture by threatening stimuli to tion of stimulus set (i.e. Horstmann, 2007; Horstmann, Lipp, &

facilitatefurtherprocessing. Becker, 2012; Lipp, Price, & Tellegen, 2009; Savage, Becker, &

Preferential attentional selection of threatening stimuli like Lipp, 2016; Savage & Lipp, 2015; Savage, Lipp, Craig, Becker, &

angry faces has been observed in visual search of facial expres- Horstmann, 2013). In addition, intentions or working memory

sionsandhasbeencalledtheangersuperiorityeffect(Hansen& havealsobeenestablishedaspartiallydrivingtheangersuperior-

Hansen,1988).Whenparticipantswererequiredtodetectthepres- ityeffectbecausetheypromoteanattentionalsettothreatening

ence of an angry face among happy faces or the presence of a content (Hahn & Gronlund, 2007; Moriya, Koster, & De Raedt,

happyfaceamongangryfaces,itwasobservedthatparticipants 2014; Todd, Cunningham, Anderson, & Thompson, 2012; Vogt,

arefastertodetectangryfacesthanhappyfaces.Interestingly,the De Houwer, Crombez, & Van Damme, 2013). Consequently, the

angersuperiorityeffectpersistswithschematicfaces(Eastwood, advantageofangryfacesmightbetheconsequenceofgoal-driven

attentionmorethaninvoluntaryattentionalcapture.

Infact,bottom-upattentionalcaptureistypicallyobservedin

responsetoirrelevant,buthighlysalientstimulithatcompetewith
∗ Correspondingauthorat:FacultédePsychologieetdesSciencesdel’Education, task-relev an tstimulis oth atatten tionm ovesto the irrelevant dis-

UniversitédeGenève,40bdduPontd’Arve,Geneva,Switzerland. tractorbeforeitreachesthetarget(Theeuwes,1992,2010).Atthe
E-mail add ress:nic ola s.b urr a@un ige.ch( N.Burra) .

http://dx.doi.org/10.1016/j.biopsycho.2016.08.008
0301-0511/©2016ElsevierB.V.Allrightsreserved.
70 N.Burraetal./BiologicalPsychology120(2016)69–80

levelofsimplefeatures,ithasbeenestablishedthatcolor,shape,

size,luminanceandonsetsmaycaptureattention(Schreij,Owens,

&Theeuwes,2008).However,evidencefortheinvoluntarycapture

of attention by complex features, like the human face and facial

expressions,hasbeenrelativelyscarce.

Some have addressed the threat-capture hypothesis by ask-

ing participants to search for a singleton target in competition

withanirrelevantfacialexpression(Hodsoll,Viding,&Lavie,2011;

Huang, Chang, & Chen, 2011). Despite establishing that irrele-

vantfacialexpressionsresultedinlongerRTs,theseexperiments

failed to establish a significant difference in paired comparisons

between angry and happy distractors. However, it may be that

behavioralmeasures(reactiontimes,RTs)arenotsensitiveenough

todetectstrongerattentionalcapturebyangryfacescomparedto

happyfaces.Inparticular,thethreat-capturehypothesisstatesthat

threateningexpressionsaredetectedearlyinthevisualprocessing

chainandleadtoearlyattentionalselection,butRTsaretheresult

ofamultitudeofprocessingstages.Thus,differencesinRTsmay

reflectearlyattentionalselectionorlateresponse-relatedbiases.

Also,itmaybethatRTsincreasebecausedisplayswithanemo-

tional distractor are visually more complex, which may lead to

spatiallyunspecificfilteringcosts(Kahneman,Treisman,&Burkell,

1983). To ascertain that facial expressions result in early atten-

tionalcapture(vs.lateresponse-relatedbiases),wemeasuredan

electrophysiologicalcorrelateofattention,theN2pc,whichoccurs

only200–300msafterstimulusonsetandindicatestheattended

hemifield,whichmakesitaspatiallyspecificmeasure(vs.spatially

unspecificfilteringcosts).

Ingeneral,attentionalselectivityinvisualsearchtaskshasbeen

investigatedusinglateralizedevent-relatedpotentials(ERPs).The

N2pcisanegativedeflectioninelectrodescontralateraltothetar-

getatposteriorsitesintheN2latencyrange,about200–300ms

afterstimulusonset(Eimer,1996;Luck&Hillyard,1994).Function-

ally,theN2pccomponentisusuallyassociatedwiththeattentional

selectionoftask-relevantstimuli(Eimer,1996)orwiththeinhi-

bitionofdistractors(Luck&Hillyard,1994).Morerecentstudies

suggest that the N2pc consists of two subcomponents, a target

negativity(N )thatreflectsenhancementofrelevantinformation
T

andadistractorpositivity(P )thatreflectsinhibitionofdistrac-
D

tors(e.g.,Feldmann-Wüstefeld,Uengoer,&Schubö,2015;Hickey,

DiLollo,&McDonald,2009;Kiss,Grubert,Petersen,&Eimer,2012;

Sawaki & Luck, 2013). In addition, the N2pc component reflects

involuntaryattentionalcapturewhenthedistractorisshownata

lateralpositionandthetargetisontheverticalmidline,sothatany

lateralizedcomponenthastobeascribedtothedistractor(Burra
Fig.1. Visualsearchtaskandspatialconfigurations.Sixfaceswerepresentedon
&et Kael.r,z2el0, 1220)1.3F,u 2rt0h1e4r;m Hoircek,etyh, eMsceDnosnitailvdit, y& oTfhteheeuwNe2sp, c20to06a;t tKeinss- ao nveir otuf atwl coirbcule t taotn 6s◦acf rcoomrd itnhge tc oenthteero. r Piaennetal tAio snhoofwths et hliante praerptirce ispeanntti sn ghathde ton opsre eossf

tionalcapturemaybegreaterthanthesensitivityofRTs(Ansorge, thetarget.ThespatialconfigurationsinExperiment1areshowninpanelB.Inthe
Horstm ann,& Wors ch ech,201 0;Eim er &Kiss,200 8; Hub er-Huber, nod istract orco ndition ,thetargetwa so nalateralp os itio nandt he distra cto rw as

absent(1/3oftrials).Inthelateraldistractorcondition,thetargetwasonthevertical
Grubert,Ansorge,&Eimer,2015).
midlineandthedistractorwasonalateralposition(1/3oftrials).Inthecontralateral
Withrespecttothedetectionofangrytargetfaces,somestud- distracto rco ndi tion,thet arge tw a sonal ateralpo sitio n andthe d istr actorwason
iesrepor tfacilit ate dd etectiono fa ngryt argetfa cesco mpar edto theoppos iteside(1 /6o ftrials ).In the i psilate raldistra ctor con dition,the tar get

happyfacesusingRTsandtheN2pc,thatis,alargerN2pcforangry waslateralandthedistractorwasonthesameside(1/6oftrials).Thelateralized
than h appy targe t fac es ( Feld mann -Wü ste fe ld, Sch midt -Da ffy, & even t-relat ed po ten tial was on ly an aly zed for th e lat eral d ist ractor cond ition.

Schubö,2011;Weymar,Löw,Öhman,&Hamm,2011;Yao,Ding,Qi,

&Yang,2013,Yao,Ding,Qi,&Yang,2014),butstudiesinvestigat- (Burra&Kerzel,2013,2014;Hickeyetal.,2006;Kissetal.,2012)

ingtheelectrophysiologicalcorrelatesofangryorhappydistractor onlypicksupresponsestolateralizedstimuli.Therefore,wewere

facesaremissing.Attentionalcapturebythreateningfacedistrac- particularly interested in a spatial configuration where the dis-

tors would support the initial assumption of preferential threat tractor was on a lateral position, whereas the target was on the

detectionthatoperatesindependentlyoftheobserver’svolition. verticalmidline,aboveorbelowfixation.Importantly,thisspatial

Inthepresentresearch,weinvestigateattentionalcaptureby configurationallowsustocompareattentionalcapturebylateral

anirrelevantdistractorinvisualsearch.Thatis,weusedanarrayof positive(happy)andthreatening(angry)distractorexpressions.To

neutralexpressionsandasingledistractorexpression(Eastwood controlforlow-leveldifferencesamongourstimulithatmightoth-

et al., 2001). Participants were asked to indicate the orientation erwisecompromiselateralizedERPs,weusedschematicfaces.At

of a tilted bar (the nose) inside a neutral face in an array of six thebehaviorallevel,weexpectadelayinRTswhencomparingthe

faces(seeFig.1).TheN2pcasamarkerofattentionalselectivity distractor-present and distractor-absent conditions without any
N.Burraetal./BiologicalPsychology120(2016)69–80 71

differencebetweenfacialexpressions(Hodsolletal.,2011;Huang respondasquicklyaspossiblewhilemaintainingaccuracyabove

etal.,2011). 90%.Responsesweregivenwiththerighthand,usingtwokeysof

astandardkeyboard.Incorrectresponseswereindicatedbyames-

2. Experiment1a sagedisplayedatthecenterofthescreen.Beforetheexperiment,

participants completed 48 trials of the task in which they were

2.1. Method trainedtoavoidmovingtheireyesindirectionofthetarget.Each

participantperformed24blocksof48experimentaltrials,eachfor

2.1.1. Participants atotalof1152trials.

Twenty-one students of the University of Geneva (8 male)

without any neurological or psychiatric indications participated 2.1.4. Electrophysiologicalrecordingandanalysis

in this experiment for class credit. Participants were naive as to A Biosemi (Amsterdam, The Netherlands) ActiveTwo ampli-

the purpose of the experiment. The local ethics committee had fiersystemAD-Boxwith64activeAG/AgCLelectrodessampledat

approved the study and informed consent was obtained from 1024Hzwasused.Weusedthevoltagedifferenceoftwohorizon-

participants prior to the experiment. The data of three partici- talelectro-oculogram(HEOG)electrodes,fixedattheoutercanthi

pantswereremovedbecauselessthan60%ofthetrialsremained oftheeyes,todetecthorizontalandverticaleyemovements.The

afterartifactrejection.Thedataoftwofurtherparticipantswere twoearlobeswereusedasonlineandofflineReferences.

removedbecauseofmeanEOGtracesoutsidetheacceptablerange Data were filtered online with a 0.01Hz high pass filter

(seebelow).Thus,thefollowinganalyseswereconductedonthe and a 100Hz low-pass filter. Using BrainVision Analyzer 2.1

sixteenremainingparticipants(7male). (Brain Products GmbH., Munich, Germany), we filtered the data

with a zero-phase-shift, low-pass Butterworth filter (40Hz with

2.1.2. Stimuli 24dB/oct.).Inordertoremoveocularartifacts(blinksorsaccades),

We used the Cogent toolbox (www.vislab.ucl.ac.uk/ weusedindependentcomponentanalysis.Trialscorrespondingto

Cogent2000) for Matlab to display the stimuli. Six stimuli were incorrectbehavioralperformance,trialswithresponsetimeshorter
presentedat 6◦o feccentr ici tyonafl at-p anelscre en. Thegray used than 200 ms and lon ger than 200 0ms were eliminat ed fr om the
todrawth eo utlin eshadanap pr ox imatelum inance of1 1.6c d/m2 analy sis. The n,a baselin ecorr ection (− 100m stostimul uson set)

andthebackgroundwasblack.Luminancewasmeasuredwitha wasperformedbeforetheartifactexclusion.Weexcludedblinks
Colo rCA L MKII Colo rime ter (Ca mbridge Re sear ch System s) tha t (VEO G±60(cid:2)V) , vertic al o r horizo ntal ocular mo vements (HEOG
was place d dir ectly on a ce ntral rectan gle filled with the s ame orVEO G ±4 0(cid:2)V )andal lot herartifact s(alle lectrodes±1 00(cid:2)V).
gray usedfo rtheou tlin es ofthe schematic faces. Ano valo f1.8◦ Ifi ndoub t abo utt hesi gna l,epo chswere ma nuallychec ke d.T hen,
horiz ontal by 2◦ v ertical w as sho wn as the conto ur o f the fa ces. ac co rdingt othep roc edured escribe dbyL uck(2005 ),inorder tobe

Insideeachoval,aschematicfacewascreated(seeFig.1A)with surethatourparticipantdidnotmovetheireyes,wecomputedthe

twodotsrepresentingtheeyes.Moreover,fortheneutralfaces,two averageHEOGforleftandrighttargetconditionsseparatelyand

horizontalbarswereshownaseyebrowsandasinglehorizontal rejected two subjects whose HEOG from 0 to 350ms was larger
bar as mou th. T o cre ate hap py and angry faci al expre ssions, the than±3 (cid:2)V. Thereby, particip ants d id no t m o ve th eir eyes more
eye bro wswer eti ltedat ±40◦ f rom horizo ntala ndacurvedl ine, than ∼ 0. 4◦fr omthefi xationpoint thro ugh outthe artif actfre etri-

uprightforhappyandinvertedforangry,replacedthehorizontal als.Onaverage,18%ofthetrialswereremoved.Thesameprocedure

lineforthemouth.Thesizeofthelineswasscrupulouslycontrolled ofartifactrejectionwasusedinallofthefollowingexperiments.

tobeequalamongfacialexpressions,particularlyforthemouth, Epochs started at 100ms before the onset of the display and

inordertoavoidanylow-levelconfound.Thetargetconsistedof endedat350msafter,foratotaltimewindowof450ms.When
ab ar,th en ose,i nthe centero fthefacea ndt ilteda t±45◦ fro m necess ary ,we cor rected for t heno n-sph ericityof ou rdat aby using

verticalwhile the remainingnosesconsistedof a verticalbar. In theGreenhouse-Geissercorrectionofthedegreesoffreedom.To

1/3ofthetrials,nodistractorexpressionwasshown(seeFig.1B). maximizetheamplitudeoftheN2pcandthedifferencesbetween
Con sis tent with our previous studies(Bur ra& Kerzel, 2013 ,20 14), conditions ,we measured the N2 pcfro m23 0to 300ms1att heP7/P8

the main condition to isolate the distractor-related N2pc was a electrodes,ratherthanatthemostcommonPO7/PO8electrodes.

displaywiththetargetontheverticalmidlineandthedistractor Behavioral analyses were conducted on median RTs for each

onalateralposition(1/3oftrials),whichelicitedanN2pctothe condition and participant. We compared distractor-absent and

distractor, but not to the target. To make target and distractor distractor-presenttrialsacrossspatialconfigurationsoftargetand

positions unpredictable, the distractor also occurred ipsilateral distractor. The results did not differ significantly when we only

(1/6oftrials)andcontralateral(1/6oftrials)tothetarget.Asthe analyzed RTs from distractor-present displays with the target at

latterconditionsdonotdirectlytestourexperimentalhypothesis, amidlinepositionandthedistractoratalateralposition.Thesame

they will not be analyzed any further. The distractor expression procedure of artifact rejection was used in all of the following

wasrandomlyhappyorangry.Furthermore,theschematicfaces experiments.Thet-testswerealwaystwo-tailed.

were validated by a group of 18 independent participants (see

supplementaryFigureA).Resultswereconsistentwiththevalence 2.2. Results
and intensity o f other pi cture se ts (Ö hman et a l., 20 01; Coelho

et al., 2010; Weymar et al., 2011). Angry stimuli were rated as 2.2.1. Behavior
m ore negativ eandint ens eth anhap pystim uli. A one-wayrepeated-measureANOVA(distractortype:absent,

happy, angry) revealed that RTs increased with happy (631ms)
2.1.3. Procedure andan gry(633 ms)dist racto rsco mparedto distr actora bsent tri-
tooCkoa nbdoiutito2nm orindetro wcoams rpalnetdeo.mEaizchedt rwiailthbieng abnlowckitsh oaf 4g8ra tyrifiaxlsa tthioant als ( 606 m s), F(2 ,30) = 9.31, p < 0 .001, (cid:3)p2= 0.3 9. The two distrac tor

crossonablackbackgroundforarandomintervalbetween600and

1600ms.Thestimulusremainedonthescreenuntilaresponsewas
1 This time window matches other studies using the additional singleton
given.Participantswereaskedtoperforma2-AFCtaskbasedon
paradigm:230–290msinHickeyetal.(2006);200–280msinBurraandKerzel
lineorientation.Theyjudgedwhethertheonlynosethatwasnot
(2013,2014);225–325msinMcDonaldetal.(2013);220–300msinKissetal.
vert icalwastilte dto theleft orright. Part icipa ntsw ere asked to (2012) .
72 N.Burraetal./BiologicalPsychology120(2016)69–80

Table1

Meanreactiontimes(inms)andbetween-subjectstandarddeviations(inparenthesis)fromExperiments1–4.Therewaseithernodistractor(absent),ahappy,oranangry

distractorexpression.InExperiment2,thefaceswereeitheruprightorinvertedandinExperiment3,eithertheeyesorthemouthregionwasshown.InExperiment4,

face-likestimuliwereused.

Absent Happy Angry

Exp.1a 606(71) 631(78) 633(81)

Exp.1b 676(129) 728(168) 754(158)

Upright Inverted Upright Inverted

Exp.2 622(89) 624(100) 669(112) 664(119)

Eyes Mouth Eyes Mouth

Exp.3 578(47) 569(47) 603(48) 594(50)

Exp.4 592(81) 613(86) 621(82)

conditionswerenotsignificantlydifferent(p=0.82).Wesubjected 3.3. Discussion

proportioncorrecttothesameANOVA,butnosignificanteffectwas

observed.Overall,theproportionofcorrectresponseswas0.97(see InExperiment1a,weestablishedbehavioralinterferencefrom

Table1). bothangryandhappydistractors.However,weobservedanN2pc

onlytoangry,butnottohappydistractorexpressions.Similarly,

the N2pc to face targets was found to be larger for angry than
2.2.2. ERPstolateralizeddistractors
happy expressions, suggesting a preferential selection of angry
Averagecontra-andipsilateralERPstohappyandangrydistrac-
faces (Feldmann-Wüstefeld et al., 2011; Weymar et al., 2011;
torsareshowninFig.2.Apaired-samplest-testshowedthatthe
volta ge differen ce toa ng ry distractors(-0.6 2(cid:2)V) wassign ifican tly Yao et al., 2013). As in prior studies, Experiment 1a confirmed
increasedRTsforemotionalexpressionswithoutsignificantdiffer-
more negative than the voltage difference to happy distractors
(0.18 (cid:2)V), t(15 )=3.7 2, p =0.002, d=0.92. M ore over, o ne-sample ences between angry and happy faces (Hodsoll et al., 2011; Huang
et al., 2011). However, when we reduced the presentation time
t-testsagainstzeroconfirmedasignificantN2pctotheangrydis-
bymaskingthefacialfeaturesafter200msinExperiment1b,we
tractor, t(15)=3.23, p=0.006, d=0.83, but the lateralized ERP to
observedstrongerinterferencefromangrythanhappydistractors.
happydistractorsdidnotreachthelevelofsignificance,p=0.3.
Thus,processesoccurringafter200msmayobscuretheinitialdif-

ferencebetweenangryandhappydistractorsthatisvisibleinthe

3. Experiment1b ERPs. We have no precise idea of what these processes may be,
but w e su spect th at respo nse sel ection and t op-down scann ing

In Experiment 1a, we did not observe behavioral differences strategiesmayplayarole.
betwe en angry an d h app y di strac tor faces while the N2pc com- Thus,w eha ved em onstratedthatatask-irrelevantangrydis-
ponentsw ered iffere nt.Pos sibly,thed ifferen cebet wee nangr yand tractor p rod uced electrophysio logica l evidence for attenti onal
happyw aslos tinproce ssingstag es succeeding theN2p c-inter val. capture . That is, w hen searching for a tilted bar insid e a neutral
To iso late early p rocessing s tages, we masked th e stimuli after face,onl yang ry facesr esultedin anN 2 pc.Int eres tingly, th eN2pc
20 0msan dmea suredRTs. towa rdth eirrele vant facialdist ra cto rwasd ifferentbetwe en angry
andhap pye xpression sdesp itethesim ilar RTs.Insu m,ERPsr eflect

involuntaryattentionalselectionofthreateningbutnothappydis-
3.1. Methods tractorexpr essionsdesp iteequal RT swhenfaces we res hownu ntil

response.
Twentyparticipants(4male)participated.Thisexperimentwas Unfortunately,theangersuperiorityeffectmaybeaffectedbya
similar to Experiment 1a excep t that the m outh , the eyes, and perceptualconfou nd( Horstm ann,2007) .Acco rding to thisacco un t,
the eye bro ws disappea red and w ere r epla ced by a ma sk 20 0ms facilitated detection of angry face s mig ht be stron gl y as sociated
afte rtheonse tofthevisua lsea rchdi splay.The m as kcons isted of withthein teraction of interna lfacia lfeatu res (i.e.the mouthand
250d ots thatw er esp readi nsideth efacec onto urwi thoutcove r- eyeb row s)andthec on tourofth eface .Particu larly ,an gryexp res-
ing then ose. Mask andnos ewere dis play eduntil arespon sewas sionsmayb epr efer entially de tect eddu etoclosure( eyebro wsand
give n.T hus,th ecen tralb ars(i .e.,the noses),in cludin g therespo nse- upper out line of the face, mouth an d lo we r outlin e of the fa ce).
releva nttilt edn ose,re main edv isib leunti larespon sew asgiven, Inorde rtorule o utth ispos sibility ,we ranthr eeaddit ion ale xperi-
whichm adesu reth attheresp onsere quire m entsdid notc hange m ents.In E xper ime nt2, weinvestig ate dth eeffec tofpresen tingthe
withre spect toEx perim en t1a.There wasatotalof 192 tria ls. angryf ace upside-dow n .In Experiment 3,w eexam i nedtherol eof

internalfacialfeatures(eye/mouth)oftheangrydistractorexpres-

sioninthecaptureeffect.Finally,inExperiment4,wequantified
3.2. Results
theimpactofpuresaliency-drivencapturebyusingface-likestim-

ulithatsharefeatureswithfacialexpressions(Coelhoetal.,2010).
Aone-wayrepeated-measureANOVA(distractortype:absent,
WepredictthattheN2pcwillbepresentandsignificantlylarger
happy, angry) revealed that RTs increased with happy (728ms)
foruprightthaninvertedangryexpressionsandfortheeyethan
andangry(754ms)distractorscomparedtodistractorabsenttri-
als( 676m s),F(2 ,38) =23.96,p< 0.001,(cid:3)p2 =0 .55.Impo rtantly, the the mouth region. Finally, we expect the difference between angry
andhappyfacialexpressionstobeabsentforface-likestimuli.
twodistractorconditionsweresignificantlydifferent,t(19)=2.36,

p=0.029,d=0.56.Thesebehavioraleffectsareconsistentwiththe

electrophysiologicalevidenceforattentionalcapturebyangry,but 4. Experiment2
nothappydistractor expressio ns. Themaskm ayhave iso latede arly

processingstagesbecausetheinformationaboutfacialfeatureswas Thefaceliteraturesuggeststhatfacesareprocessedholistically.
onlyavaila blefor 200ms. Furt her,wesubj ected propo rtioncor rect Thus,th eya reperceiv edandc harac teriz eda sawhole, ratherthan
toth esameAN OV A,b utn osignific ant effectwas observed.O verall, based onth esu mofthei ndiv idualfeatures (Ta n aka&F arah,1 993).
th epr oport ionofco rrec tre sponsesw as0.97 (se eTable1). Inreco gn itio noff aci ale xpressions ,features areimp or tant(T anaka,
N.Burraetal./BiologicalPsychology120(2016)69–80 73

Fig.2. Top:SampledisplaysfromExperiment1.Bottom:ResultsfromExperiment1.WeevaluatedtheN2pcintheintervalfrom230to290ms.Note:**=p<0.01and

n.s.=notsignificant.

Kaiser,Butler,&LeGrand,2012),butholisticprocessingpermits 4.1.2. Stimuli

integrationoffacialfeaturesintoameaningfulcoherentrepresen- ThepresentexperimentwassimilartoExperiment1aexceptfor

tationofafacialexpression(Calder&Jansen,2005;Calder,Young, thedistractors.Onlytheangryfacewaskeptanditwaspresented

Keane,&Dean,2000). inanuprightorinvertedcondition.

Moreover,holisticprocessingiscentraltotheemergenceofthe

angersuperiorityeffect.Consequently,theangersuperiorityeffect
4.1.3. Procedure
doesnotoccurinvisualsearchwithupside-downfaces(Foxetal.,
TheprocedurewassimilartoExperiment1a.However,inhalf
2000;butseeÖhmanetal.,2001forotherresults).Infact,inversion
ofthetrials(512trials)thestimuliwereuprightandintheother
offacesdisruptstheintegrationofconfiguralrelationshipsamong
half,inverted.Theirappearancewasrandomlymixed.
facial features (Farah, Tanaka, & Drain, 1995; Tanaka & Sengco,

1997;Valentine,1988;Yin,1969),butatthesametime,inversion
allows keepingth eindi vidu alperc eptu al feat uresu nchan ged. 4.1.4. EEGrecordingandanalysis
Usin g the in ver sion effect to our ben efit, we presented only Us ingt hesamec rite riaasinExperiment1a,29%ofthetrials
angry dis trac tor expres sions t ha t we re either up right or up side- wererem ove d.

down.Thus,inversionenablesustoruleoutthattheN2pctoward

the angry distractor expression is related to low-level percep- 4.2. Results
tual confo unds,likea preferentia ld etection of tiltedbars thatare

presentintheeyebrowsofbothhappyandangryexpression,but 4.2.1. Behavior
whichm ig htb emoreper ce ptible inang ryex pressi ons.Iflow-le vel A2 (distractor:absence,presence)x2(faceorientation:upright,
accoun tswer et rue,w eshouldob tai nanN 2pctothean gr ydistrac- inver te d)repeated -measur eANOVAr ev e aledt hattheprese nceofa
torofthe same amp litu deinu pright an dinve rt edo rienta tions.If distractor increasedRTs(623 vs.667 ms),F(1, 16)= 33. 58,p<0.0 01 ,
otshhfeoa wnNg 2 trhpyacf ta o acctectsuenrar nteidodn tohanle lciyra pteomtu torhete i w ounapasrl irgceholant ttaeendng t tro.y t dhies throalc itsotirc, pthriosc wesosuin ldg (cid:3)ainppgp2tr=ho 0aat.c2th1he .e dId nsivisgetnrrasificiotcona r nhecafefd ,e Fcn(t1ow, 1 ea6fsf)es =cli t4g .h(2p t5 l=y, p0s .t= 7r 07on.90)g5,e 6br,u i (cid:3)nt put2hp=er i 0gin.h2 tt1e (,r 4 sa7hctomiwosn-)

thanininvertedorientation(40ms).Theanalysisofproportioncor-

4.1. Method rectdidnotyieldanysignificantresults.Overall,theproportionof
corr ectr esp onses was 0.97(seeT able1) .

4.1.1. Participants

Twenty-threenewparticipants(10male)fromthesamepool 4.2.2. ERPstolateralizeddistractors
as above took pa rt. T he data of fi ve p articip ants wer e rem oved Av erage co ntra- and ipsilateral ERPs to inverted and upright
be cause l ess th an 6 0% o f the tri als re mained afte r artif act rejec- distractors are show n in Fig. 3. A p aired -sa mples t-t est r evealed
tion.The dat afrom one fu rthe rpar ticipantwa srem ovedbe cause a larger N 2pc for upr igh t (- 0.3 8 (cid:2)V) than invert ed thr eatening
them ean EOG trac esw ereouts idetheacc epta blerange ,leaving d istracto rs (0.1 7(cid:2) V), t(16) =2.63, p=0 .018, d=0.66. One-sample
sev enteen part icipant s(8m ale)inth efi nalsample. t-tests sho wed th at t he N2 p c to t he lateral an g ry di stractor was
74 N.Burraetal./BiologicalPsychology120(2016)69–80

Fig.3. Top:SampledisplaysfromExperiment2withinvertedfaces.Bottom:ResultsfromExperiment2.Note:**=p<0.01andn.s.=notsignificant.

significant when the face was upright, t(16)=3.31, p=0.004, lower part, due to the presence of the eyes (Haxby, Hoffman, &

d=0.80,butnotwhenitwasinverted,p=0.351. Gobbini,2000;Schyns,Bonnar,&Gosselin,2002;Schyns&Oliva,

1999)andpreferentiallytriggersshiftsofattentioncomparedtothe

4.3. Discussion lowerpartoftheface,especiallyforthreateningfaces(Foxetal.,
2000; Tipp les , At kinso n, & Youn g, 2 002). Moreo ver, t he g rea ter

TheresultsconfirmedanN2pctoanangrydistractorexpression importanceoftheupperfeaturesofthefacerelativetothelower
whenit wasup right,butn ot when it wa sinver ted.Thus, attentional featureshas be end emons tratedin re cogn ition offacia lex pre ssions
captur e bya nangry dis trac torca nn otb edueto bette rdetection (Baron-C ohe n,19 97).Theeyes see mtobecru ci alfor recognizing
ofobliq uel ine sinsc hematican gryeye bro ws, be causet heselines angryorfearfu lfaces but less sofor ha pp yfaces (Bo mbarietal.,
ar esimilar inup rig htandinv ertedo rientation s.Wethi nktha tthe 2013; Fo xetal., 2000; Sch yns, Pe tro, &Smit h,200 7;Tanaka et al.,
hol isticpro ce ssingof face s,whicht ypicallyfacili tate sthea ccur ate 2012) .Ins um ,if theey eregion wassu ffi cientt ocapt ureatte nti on,
recogni tionoffacia le xpres sions, precedes attentiona lca ptureby wesho ul dobt ai nan N2 pctoth eey eregion,b ut nottot hemouth
uprightface s. Conseq uently,thea ttentiona lpriorityof thethre at- reg ion.

eningstimulusafterrecognitionandappreciationofitsemotional

contentislikelytoexplainattentionalcapture.
5.1. Method

5. Experiment3
5.1.1. Participants

TwentystudentsoftheUniversityofGeneva(8male)partici-
Another possible confound is the “closure” feature (Wolfe &
pated.Thedatafromthreeparticipantswereremovedbecauseless
Horowitz,2004)causedbytheangrymouthneighboringthelower
than 60% of the trials remained after artifact rejection. The data
edge of the schematic face, which may pop out in visual search
fromonefurtherparticipantwereremovedbecauseofmeanEOGs
(Elder&Zucker,1993,1994;Wolfe&Horowitz,2004).Thisfeature
outsidetheacceptablerange,leavingsixteenparticipants(6male)
ispartofanangryexpression,butnotpresentinneutralorhappy
foranalysis.
faces.Thus,duringvisualsearchforanangrytargetexpression,the

presenceofclosuremayconferbothspeedandefficiencyadvan-

tages(Mak-Fan,Thompson,&Green,2011).Whilethiseffecthas
5.1.2. Stimuli
notbeeninvestigatedwithangryfacesasdistractors,onemayargue

TheexperimentwassimilartoExperiment1awiththefollowing
thatclosureexplainsthecapturebyangrydistractors.Toisolatethe

exceptions.Wedividedthefacesinmouthregion(lowerpart)and
closurefeature,wesplitourstimuliintomouthandeyeregion,but

eyeregion(upperpart).Onlyangryfaceswereused.
kept the outline of the face. If closure explains the N2pc toward

angryfacedistractors,anN2pcisexpectedtothemouthregion,

butnottotheeyeregion.
M or eov er, this manipulationallowedustotestwhethertheeye 5.1.3. Procedure
regionhasala rge rimportancet hanthe mo ut hre gion.Ith asb een Th e procedure was similar to Experiment 1a. Mouth and eye
claime dth at theup perpartoft hefa ceis morei mporta nt tha nthe display swererand oml ymixed .
N.Burraetal./BiologicalPsychology120(2016)69–80 75

5.1.4. EEGrecordingandanalysis & Strobel, 2014), which has been linked to affective processing.

WeusedthesamesettingsasinExperiment1a.Onaverage,16% Consequently, we wondered whether geometrical shapes would

ofthetrialswereremoved. produceacaptureeffectsimilartotheoneweobservedforangry

faces.
5.2. Results Therefore,wereplicatedtheprocedureofExperiment1a,but

usedface-likestimulisimilartoCoelhoetal.(2010).Iflow-level

5.2.1. Behavior featuresexplaintheN2pctowardthreateningdistractors,alarger

A2(distractor:absence,presence)x2(faceregion:eye,mouth) N2pc to face-like threatening than to face-like happy stimuli is

ANOVA revealed that the presence of a distractor increased RTs expected.Ifonlytheemotionalcontentofangryfacesexplainsthe
(573vs. 599ms), F(1,1 5)= 63.44,p< 0.0 01 ,(cid:3)p2=0.8 0.Thedist rac- attentiona l captu reb yangrydis tractor fac es,the N2pc toface- like

tor effect was similar for both face regions, as evident in the threateningandface-likehappystimuliisnotexpectedtodiffer.

non-significant interaction, p=0.96. No significant effects were

observedintheanalysisofproportioncorrect.Overall,proportion 6.1. Participants

correctwas0.97(seeTable1).

SeventeenstudentsoftheUniversityofGeneva(6male)partici-

5.2.2. ERPstolateralizeddistractors pated.Dataofonefemaleparticipantwasrejectedbecauselessthan

Average contra- and ipsilateral ERPs to the mouth and eye 60%ofthetrialsremainedafterartifactrejection,leavingsixteen

regionofangrydistractorsareshowninFig.4.Apaired-samples participantsinthefinalanalyses.

t-testsshowedthattheN2pcwasmorenegativetolateraldistrac-
torssh owingth eey ere gion (-0.4 0(cid:2)V) thantol ate raldis tractors 6.2. Stimuli
show ingthem out hre gion(0. 19(cid:2)V) ,t(1 5)=2. 26 ,p=0.0 39,d=0.57.

One-samplet-testsagainstzerorevealedasignificantN2pcforthe Weusedshapessharinginternalfeatureswithfaces,butwhich

eye region, t(15)=2.32, p=0.035, d=0.58, but not for the mouth werenotfaces(Coelhoetal.,2010).Thesestimuliwerecreatedby

region,p=0.37. replacingthemouthbyinvertedeyebrows.Inadditiontothetwo

pairsofeyebrows,thenosewasshown(seeFig.5).

5.3. Discussion

6.3. Procedure

ThisexperimentestablishesanN2pctotheeyeregionofirrel-

evant angry faces, but not to the mouth region, ruling out the TheprocedurewassimilartoExperiment1a.Weavoidedcon-

possibilitythattheN2pctoangrydistractorexpressionswasdriven textualeffectsbynotspeakingaboutfaces.Thereby,participants

bythemouthregion,whichmaybereducedtothelow-leveleffect wouldnotbeencouragedtoseethesestimuliasfaces.Asinthe

ofclosure.Moreover,theresultsareinlinewithpreviousresearch preceding experiments, participants were required to search for

showingthattheeyeregioncontainstheelementsofathreatening thetiltedbar.

facethatcaptureattention(Fox&Damjanovic,2006).Itislikely

thata“face”contourmightenhanceholisticprocessingandmight 6.4. EEGrecordingandanalysis

lead to a filling-in effect (Bentin, Sagiv, Mecklinger, Friederici, &

von Cramon, 2002; Righart, Burra, & Vuilleumier, 2011), so that WeusedthesamesettingsandstatisticsasinExperiment1a.

theeyeregioninisolationmightbesufficienttoresultintheper- Onaverage,13%ofthetrialswereremovedfromtheEEGdata.

ception of a whole schematic face, whereas the mouth region is

insufficient. However, when the contour of the face is removed, 6.5. Results

theN2pctoangryeyesoreyebrowsinisolationdoesnotreachthe

level of significance (Weymar et al., 2011; Experiment 2 and 3), 6.5.1. Behavior

underliningtheimportanceofthefaceoutlineandthefacecon- Aone-wayrepeated-measuresANOVA(distractortype:absent,

textintheangersuperiorityeffect(Schubö,Gendolla,Meinecke,& face-like happy, face-like angry) revealed that the presence of a

Abele,2006).Thus,ourdatasupporttheideathattheeyeregion distractorincreasedRTsfrom592mswithoutdistractorto613ms

ispreferentiallyprocessedintheperceptionofangryfaces(Schyns withaface-likehappyand621mswithaface-likeangrydistrac-
et al.,2007;Vine tte,Gossel in ,&S chyns,2004 )a ndmi ghtth erefore tor, F (2 ,30)=11 .27, p< 0.00 1, (cid:3) p2= 0.42. H owever, the di stractor

driveattentionalcapturetoangryfaces. conditionswerenotsignificantlydifferent(p=0.23).Nosignificant

effects were observed in the accuracy analysis. Overall accuracy

6. Experiment4 was0.97(seeTable1).

Finally, even if schematic faces reduce the likelihood of low- 6.5.2. ERPstolateralizeddistractors

levelconfounds,differentstudieshaveestablishedthattheydonot Averagecontra-andipsilateralERPstohappy-likeandangry-

completelyrulethemout(Horstmann&Bauland,2006;Purcell& likedistractorsareshowninFig.5.Apaired-samplest-testshowed

Stewart,2010).Besidestheclosureeffect,linescrossingtheface that the N2pc components in the two distractor conditions did

outlinehavebeensuggestedasapossibleexplanationfortheanger not differ, p=0.77. One-sample t-tests against zero showed that
superio rity e ffect . Indeed, w h en the fac e outline is rem ov ed or the N2pc w as neit her significa nt for f ace-like happ y (−0.3 (cid:2)V),
manipulate dinthe display ,thean ger super iorityef fec tdisappe ars t(15 )=1.5 5,p= 0.141,n orforface-li kea ngrydistr actors( −0.23 (cid:2)V),

(Horstmann&Bauland,2006;Schuböetal.,2006).Furthermore, t(15)=1.54,p=0.144.

it has been demonstrated that even meaningless face-like stim-

ulicangenerateanangersuperiorityeffect(Coelhoetal.,2010). 6.6. Discussion

Inthesamevein,geometricalshapes,suchasinvertedtriangles,

might be seen as emotional (Larson, Aronoff, & Stearns, 2007; Face-like angry and happy distractors sharing basic features

Watson,Blagrove,&Selwood,2011)andwerefoundtoactivatethe with facial expressions did not capture attention differen-

amygdala(Larson,Aronoff,Sarinopoulos,&Zhu,2009)andincrease tially, as indexed by the non-significant difference in the N2pc.

peripheralphysiologicalresponses(Armbruster,Suchert,Gärtner, Therefore,weconcludethatthecontributionoflow-levelfactors
76 N.Burraetal./BiologicalPsychology120(2016)69–80

Fig.4. Top:SampledisplaysfromExperiment3inwhicheithertheeyeregionorthemouthregionwasshown.Bottom:ResultsfromExperiment3.Note:*=p<0.05and

n.s.=notsignificant.

Fig.5. Top:SampledisplaysfromExperiment4thatwereface-likefigurescomposedofthesamelinesasinthepreviousexperiments.Bottom:ResultsfromExperiment3.

Note:n.s.=notsignificant.
N.Burraetal./BiologicalPsychology120(2016)69–80 77

tothedifferenceinattentionalcapturebetweenangryandhappy Wykowska&Schubö,2011).Inconclusion,ourresultsareinline

faces that we observed in Experiment 1a is rather minor. Con- witha“threat-detectionsystem”,implyingthatthreateningstimuli

sequently, we claim that the emotional content of angry faces affectattentionalselection(Öhman&Mineka,2001).

underliesattentionalcaptureandnottheassociatedlow-levelfea- Furthermore, attentional capture by angry distractor expres-

tures. sions only occurred when faces were shown in an upright

orientation, which shows that the effect was largely due to the

emotionalcontentofangryfacesratherthantolow-levelfactors
7. Generaldiscussion
contributingtotheirsaliency(Horstmann,2007)ortotop-down

attentionalsetsforangryfaces(Mohanty&Sussman,2013;Moriya
Weinvestigatedattentionalcapturebythreateningdistractors.
etal.,2014;Toddetal.,2012).Thus,holisticprocessing(i.e.,the
Inavisualsearchtask,weusedschematicfacialexpressionsnotas
perceptionandcharacterizationofafaceasawhole)ratherthan
atargetbutasanirrelevantdistractorthatcompetedforselection.
processingthesumofitsindividualfeaturesisatthecoreofatten-
Toourknowledge,previouselectrophysiologicalresearchhasonly
tionalcapturebyangrydistractorfacesinourstudy.Infact,holistic
confirmed facilitated attentional selection of angry target faces.
processingoffacesmayoccurbeforeattentionalselection(Towler,
Forinstance,whenfacialexpressionswereusedassearchtargets
Kelly,&Eimer,2015).Thus,wethinkthatanangryfacialexpression
(Eastwoodetal.,2001;Foxetal.,2000;Hansen&Hansen,1988;
resultsinattentionalcapturebecauseofitsemotionalcontent.
Sawada&Sato,2015),therewasnocompetitionbetweenrelevant

and salient-but-irrelevant elements. Therefore, we pitted search

for a relevant facial feature (the nose) against distraction from
7.2. Importanceoftheeyeareainattentionalcaptureby
irrelevantfacialfeatures(theeyesandmouth).Wedemonstrated
threateningstimuli
thatattentionwascapturedbyangrydistractorexpressions,but

notbyhappydistractorexpressions.Thisresultsupportstheview
Interestingly,theeyeregionofangryfacesisessentialtopro-
thatthreateningstimulioverridecurrentattentionalcontrolset-
duceattentionalcapture.Thisclaimissupportedbythepresenceof
tingsbyaspecialized“threat-detectionsystem”(Öhman&Mineka,
anN2pctotheeyeregionanditsabsencetothemouthregion.Ithas
2001).Attentionalcapturewasindexedbyanelectrophysiological
beenreportedthattheeyeregion(oreyebrows)withoutthecon-
marker of attentional selection, the N2pc component. As shown
tourofthefacedoesnotleadtopreferentialattentionalselection
in Fig. 6, attentional capture by angry distractors occurred with
(Weymar et al., 2011). Thus, the anger superiority effect disap-
upright faces, but not with inverted faces (Experiment 2). Addi-
peared when faces lack external contours (Schubö et al., 2006).
tionally, when angry faces were split in eye and mouth regions,
WeshowedinExperiment4thatcapturebytheeyeregiondoes
attentionalcapturewasonlyobservedfortheeyeregion(Exper-
notresultfromlow-levelfeatures,suchasspecificorientationsor
iment 3). Finally, shapes that shared the basic internal features
angles,becauseface-likeversionsofthreateningfacesdidnotshow
ofemotionalfacialexpressionsdidnotresultindifferentialatten-
moreattentionalcapturewithface-likeangrycomparedtoface-
tionalcaptureforangry-likefaces(Experiment4).
likehappystimuli.Experiment3suggeststhattop-downprocesses

enabletheperceptualsystemtoperceivetheeyeareaascontained

7.1. Attentionalcapturebythreateningdistractorsandholistic withinawholeface(Bentinetal.,2002;Righartetal.,2011).Thus,

processing theangryeyesinafacecontexttriggerattention.Takentogether,

ourdatasuggestthattheeyeregionunderliesattentionalcapture

We have demonstrated that attentional capture by threaten- byangrydistractorexpressions.

ing faces occurs when faces are upright. Previously, it has been

reportedthattargetdiscriminationwasdelayedbyfacialexpres-

sionsthatwereirrelevantforthetaskwithoutadifferencebetween 7.3. Face-likestimuliarenotsufficienttocaptureattention

angry and happy distractors (Hodsoll et al., 2011; Huang et al.,

2011). However, previous studies beg the question whether the Finally,stimulicreatedwithfeaturessharingtheirbasicorgani-

effectoriginatedatanearlyperceptual/attentionalstageoratalate zationwithfacialexpressionsdidnotprovideevidenceforstronger

response-relatedstage.Infact,someauthorsconcludedthatangry attentionalcapturebyangrycomparedtohappyfaces.Somepre-

facesmisguideattentionratherthancaptureattention(Horstmann viousresultsquestionedtheangersuperiorityeffectbysuggesting

&Becker,2008).Whereastheinitialshiftofinvoluntaryattentionis that the anger superiority effect was mainly the consequence

directedtoadistractorinattentionalcapture,voluntaryattention of a low-level difference between stimuli (Becker, Horstmann,&

issupposedtobebiasedtowardthesalientdistractorinattentional Remington,2011;Horstmann&Bauland,2006;Koster,Crombez,

misguidance.Thatis,anaffectivesingletonfacemayreceivesome Van Damme, Verschuere, & De Houwer, 2004), such as the clo-

attentionalpriorityandweaklyattractattentiontothetarget(Todd sureofthemouthregionortheeyebrowswiththecontour.Indeed,

&Kramer,1994). theangersuperiorityeffecthasrecentlybeenobservedusingsim-

Nevertheless,ourresultsconfirmanN2pctoangryfacialexpres- ilar face-like stimuli (Coelho et al., 2010; Dickins & Lipp, 2014).

sions, showing that threatening stimuli attract attention at an Moreover,face-likestimuliareprocessedinthesamewayasfacial

earlystageofvisualprocessing.Incontrast,noN2pcoccurredto expressions (Armbruster et al., 2014; Larson et al., 2007; Larson

happy facial expressions. Therefore, the present results support et al., 2009; Watson et al., 2011). Overall, these results suggest

theattentionalcapturehypothesis.Whenprocessingtimewaslim- thatlow-levelperceptualfactorsaccountfortheangersuperior-

itedbyamasktoonly200ms,strongerdistractionbyangrythan ityeffect.Whileourresultsdonotquestionthevalidityofprevious

happy expressions was also visible in RTs (see Experiment 1b). studies,theynonethelessshowthatangryexpressionsmaycap-

Withunlimitedviewingtime,however,RTsdidnotdifferbetween ture attention more strongly even when perceptual factors are

angryandhappydistractorexpressions,suggestingthatattentional controlledfor.

capture by angry expressions was lost in late processing stages. Importantly,wedemonstratedthatface-likeangrystimulido

Another interpretation may be that both angry and happy dis- nottriggerattentionalcapturemorestronglythanface-likehappy

tractorsinducedsimilarnon-spatialfilteringcoststhatresultedin faces,suggestingalackofattentionalcapturebymeaninglessstim-

similar RTs, but that a spatial measure of attentional selectivity, ulidespitetheirsimilaritywithangryfaces.Therefore,onlyfacial

theN2pc,broughtdifferencestothefore(Folk&Remington,1998; features seen in the context of faces (whole faces or segmented
78 N.Burraetal./BiologicalPsychology120(2016)69–80

Fig.6. SummaryofdistractorN2pcamplitudes(Experiment1–4).Note:*=p<0.05,**=p<0.01,andn.s.=notsignificant.

faces)permitangryfacestogaintheiremotionalcontent,which speaksagainstthescanninghypothesis.However,moreresearchis

contributescruciallytotheirattentionalpriority. clearlyneededtoconfirmthisconclusion.

7.5. Summary

7.4. Caveats

Insum,weproposethattheemotionalcontentassociatedwith

Themaingoalwhencreatingourstimuliwastoremovephysical angrydistractorexpressionsmaycauseattentionalcapture.Indeed,

differencesbetweenschematicfaces.Tothisend,webasicallyonly angry schematic faces were associated with negative emotional

mirroredtheeyebrowsandthemouthtocreatehappyandangry valence,whilehappyschematicfaceswereassociatedwithpositive

faces.Therefore,low-levelvisualdifferencescannotaccountforthe valence(seeAppendixA).Instudiesonreward,ithasbeenshown

larger N2pc to angry distractors. On the flip side, the control of thatincreasingtheintrinsicvalueofastimulusleadstoanincrease

visualstimuluspropertiesmayhaveinduceddifferencesinjudged ofattentionalcapture(Hickey,Chelazzi,&Theeuwes,2010;Mine

valenceandintensity(seeAppendixA).Thus,thecurrentstudyis & Saiki, 2015), which modulates the N2pc (Qi, Zeng, Ding, & Li,

certainlylimitedinthatwecannotentirelyruleoutconfounding 2013).Further,angryfacesaremorerelevantforoursurvivalthan

effectsofintensity.However,animportantpointisthatthevalence happyfacesbecausetheyindicatepotentiallyharmfulencounters.

andintensityofourstimuliwerecomparabletoCoelhoetal.(2010) Consequently,thethreateningandnegativeemotionalcontentof

whoclaimedthatlow-levelfeaturesprobablyunderliethebetter angryfacesmightexplainattentionaldeploymenttoangryexpres-

detectionofangryfaces.Incontrast,weprovideevidencethateven sions even when they are irrelevant. However, the preferential

perceptuallybalancedstimulishowan“angersuperiority”effect. attentionalselectionofangrydistractorsmightbeattenuatedafter

Infuturestudies,valenceandintensityshouldbebettercontrolled, conditioning,whichchangesthenegativevalenceassociatedwith

possiblybyusingnaturalstimuli.However,thiswouldnecessarily thefacialexpression(Yaoetal.,2014).Ingeneral,wethinkthatthe

come at the cost of re-introducing physical differences between attentionalpriorityofastimulusintermsofitsintrinsicreward-or

stimuli. The purpose of the present study, however, was to find task-relatedvalue(Awh,Belopolsky,&Theeuwes,2012)isessen-

evidenceforstrongerattentionalcapturebyangryexpressionswith tialtoelicitattentionalcaptureandmightextendthehypothesisof

perceptuallybalancedstimuli. a“threat-detectionsystem”(Öhman&Mineka,2001).

Additionally, we have implied that our task relied on config- Taken together, our experiments demonstrate that irrelevant

ural face processing. Alternatively, participants may have used angryexpressionscapturespatialattentionwhencompetingwith

a feature-based strategy without processing individual face con- thetarget.Inaseriesofcontrolexperiments,weruledoutalter-

figurations. Possibly, participants scanned the faces from top to native explanations in terms of low-level factors that have been

bottom to find the response-relevant feature (the nose), which showntorenderangryexpressionssalient.Weconcludethatthe

wouldexplainwhytheeyesplaysuchadominantrole.Infact,the emotionalcontentofangryexpressionsmayoverrulethecurrent

eyeswouldbeencounteredfirstwhereastheyareencounteredlast taskset,resultingininvoluntaryattentionalcapture.

whenthefacesareturnedupside-down.Consequently,attentional

capturewouldbereducedwithupside-downfaces,asobservedin Acknowledgements

Experiment2.However,iftheupperpartsarecrucialandtherestis

not,weshouldhaveobservedanangersuperiorityeffectalsowith TheauthorsweresupportedbytheSwissNationalFoundation

face-likegeometricalfiguresinExperiment4.Thefactthatwedid 100014152684.WethankLaureFreydefontforherconstructive

notobserveadifferencebetweenangry-likeandhappy-likefaces comments.