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//-->Allisonet al.– Social perceptionReview71DuBrul, E.L. (1976) Biomechanics of speech sounds.Ann. New YorkAcad. Sci.280, 631–64272Ohala, J.J. (1984) An ethological perspective on common cross-language utilization of Fø of voice.Phonetica41, 1–1673Fitch, W.T. (1999) Acoustic exaggeration of size in birds by trachealelongation: comparative and theoretical analyses.J. Zool.248, 31–4974Pocock, R.I. (1916) On the hyoidean apparatus of the lion (F.leo)andrelated species of Felidae.Ann. Mag. Nat. Hist.8, 222–22975Hast, M. (1989) The larynx of roaring and non-roaring cats.J. Anat.163, 117–12176Krebs, J.R. (1977) The significance of song repertoires: the Beau Gestehypothesis.Anim. Behav.25, 475–47877Sayigh, L.S.et al.(1990) Signature whistles of free-ranging bottlenosedolphins,Tursiops truncatus:stability and mother-offspring comparisons.Behav. Ecol. Sociobiol.26, 247–26078Ford, J.K.B. 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(1998)Principles of AnimalCommunication,SinauerSocial perception fromvisual cues: role ofthe STS regionTruett Allison, Aina Puce and Gregory McCarthySocial perception refers to initial stages in the processing of information thatculminates in the accurate analysis of the dispositions and intentions of otherindividuals. Single-cell recordings in monkeys, and neurophysiological andneuroimaging studies in humans, reveal that cerebral cortex in and near the superiortemporal sulcus (STS) region is an important component of this perceptual system. Inmonkeys and humans, the STS region is activated by movements of the eyes, mouth,hands and body, suggesting that it is involved in analysis of biological motion.However, it is also activated by static images of the face and body, suggesting that it issensitive to implied motion and more generally to stimuli that signal the actions ofanother individual. Subsequent analysis of socially relevant stimuli is carried out in theamygdala and orbitofrontal cortex, which supports a three-structure model proposedby Brothers. The homology of human and monkey areas involved in social perception,and the functional interrelationships between the STS region and the ventral face area,are unresolved issues.T. Allison is at theNeuropsychologyLaboratory, VAMedical Center, WestHaven, CT 06516and the Departmentof Neurology, YaleUniversity School ofMedicine, NewHaven, CT 06510,USA.tel: +1 203 932 5711fax: +1 203 937 3474e-mail:truett.allison@yale.eduA. Puce is at theBrain SciencesInstitute, SwinburneUniversity ofTechnology, PO Box218, Hawthorn,Victoria 3122,Australia.e-mail:puce@bsi.swin.edu.auonsider the predicament of Barbara Ehrenreich, who isconsidering a vacation out West1:It would be nice to go on a vacation where I didn’thave to worry about being ripped limb from limbby some big ursine slob…All right, I know theecologically correct line: ‘They won’t bother youif you don’t bother them.’ But who knows whatbothers a bear?…So instead of communing withthe majestic peaks and flower-studded meadows, Ispend my hikes going over all the helpful tips forCsurviving an Encounter. Look them in the eye?No, that was mountain lions. Bears just hate itwhen you stare at them, so keep your gaze fixeddreamily on the scenery. Play dead? Let’s see, thatworks for grizzlies but not for black bears. So doyou take off the backpack, get out the wildlifeguidebook, do a quick taxonomic determinationandthenplay dead?If it is difficult to infer the intentions of other humans fromtheir facial gestures and body language, it is even harder,PII: S1364-6613(00)01501-1G. McCarthy is at theBrain Imaging andAnalysis Center, Box3808, DukeUniversity MedicalCenter, Durham,NC 27710, USA.e-mail: gregory.mccarthy@duke.edu1364-6613/00/$ – see front matter © 2000 Elsevier Science Ltd. All rights reserved.267ReviewEye contactAllisonet al.– Social perception(a)60are related to the perception of facial expression, we will notaddress this important topic (see Refs 2–4 for reviews). Norwill we discuss the related question of whether individ-uals perceive the actions of other individuals using thesame neural mechanisms used to produce the same actionthemselves; this topic has recently been reviewed5.Direction of gazeEyes coveredEyes covered40SpontaneousactivityEyes avertedEyes avertedEye contactI saw her at church last SundayShe passed me on byI could tell her mind was changingBy the roving of her eye(American version of the English folk songHandsomeMolly)Response (spikes per second)20(b)80604020FaceFaceProfileProfileFaceProfiletrends in Cognitive SciencesStimulusFig. 1. Sensitivity to gaze direction of two cells in the superior temporal sulcus.CellM047(a)responded maximally when face and eyes were directed at the monkey and lesswhen the eyes or head were averted. Cell A027(b)responded more to averted eyes than toeye contact both for the full face and for the profile face. With the eyes covered both cellscontinued to show an effect of head orientation. (Reproduced, with permission, from Ref. 13.)Ehrenreich surmises, to communicate with, and infer theintentions of, animals who might have different ways ofconveying and interpreting social signals. Most such mis-perceptions are inconsequential, but in the interaction sheconsiders they could be disastrous. Bears, humans andmany other mammals depend on the correct productionand perception of facial and bodily gestures to signal threat,submission and other information.This article deals with the neuronal activity involved inthe perception of movements of the eyes, face, hands andbody of other individuals that provide information abouttheir actions and intentions. Single-cell recordings in mon-keys and, more recently, neuroimaging and neurophysio-logical studies in humans, suggest that early stages in theanalysis of bodily movement are instantiated in specificbrain regions in and near the superior temporal sulcus(STS) of both hemispheres. Although the issues discussedThe despondent narrator of this song has concluded that hislove is now unrequited. He came to this conclusion becausehis beloved avoided his gaze. He might have been wrong(she might not have seen him, or she might have beencoy), but for better or worse his judgement was based oninformation derived from the eyes.Of the objects that we routinely see in the course of aday, the human face is perhaps the most frequent and im-portant. In addition to the person’s identity, we determinesuch things as age, sex, ethnicity, emotional state and at-tractiveness; our interactions with that person are modifiedaccordingly. Of the internal facial features, the eyes are tra-ditionally thought to provide important information.Direction of gaze is thought to be particularly important inguiding our interactions with humans or, in Ehrenreich’scase, bears. Among other things, the direction of gaze isthought to provide information in social situations, expressintimacy and exercise social control (for a review see Ref. 6).Sensitivity to gaze direction occurs early in human develop-ment; infants as young as three months of age can detect thedirection of perceived gaze, which influences their own di-rection of attention7,8. Behavioral studies of the perceptionof gaze direction and other cues to the direction of socialattention have been reviewed recently9.In monkeys, gaze direction is an important componentof facial expressions, particularly those related to dominanceand submission10–12. Perrett and colleagues13,14have studiedthe responsiveness of monkey STS cells to gaze and head di-rection. The results summarized in Fig. 1 are representative.In general, cells that were most responsive to the full facepreferred eye contact, and cells that were tuned to the pro-file view of a face preferred averted gaze, but some cellsshowed independent sensitivity to head and eye direction.Such cells appear to have a role in ‘social attention’; thatis, cells that signal the direction of another individual’s at-tention14,15. Perrettet al.note ‘In many cases, the directionin which another person’s head is pointing is not a goodindex of where his or her attention lies. Gaze direction is amuch better guide to the focus of another’s attention.’ Adramatic example is illustrated in Fig. 2. A young womanfaces the viewer (a), but her gaze is directed to her right. Thereason for her averted gaze becomes clear when we viewmore of the scene (b) and see that she is carefully but sur-reptitiously attending to the dupe on her right and stealinghis jewelry while his attention is captured by the youngwoman’s confederate, a fortune teller. Such deceptive268Allisonet al.– Social perceptionReview(a)(b)Calvertet al.43Lip-reading (STG)Calvertet al.43Lip-reading (AG)Puceet al.21Mouth movementPuce and Allison92MouthmovementHowardet al.59Body movementBondaet al.52Body movementSenioret al.62Body movementKourtzi and Kanwisher61Body movementGrossmanet al.60Body movementFig. 2. An example of social attention. (a)Why are thiswoman’s eyes averted?(b)Because she is paying careful atten-tion to the direction of gaze of the man on her right, while heis paying attention to the old woman to their left. The man’sgullibility and misdirected attention will cost him dearly.(Reproduced, with permission, from Georges de La Tour’s ‘TheFortune-Teller’, ca. 1630.)Puceet al.21Eye gazeWickeret al.17Eye gazeHoffman and Haxby22Eye gazeNevilleet al.56ASLBondaet al.52Hand actionGrèzeset al.50Hand actionGrèzeset al.57Hand movementGraftonet al.49Hand graspRizolattiet al.48Hand grasptrends in Cognitive Sciencesbehavior is not limited to humans. A young gorilla has beenobserved hugging and looking into the eyes of a humanwhile surreptitiously stealing his watch16.Three neuroimaging studies in humans have examinedthe activity evoked by viewing eye movements or directionof gaze. In a PET study17, subjects viewed videos of actorslooking towards the subject (mutual gaze condition) orlooking away (averted gaze condition). Compared with acondition in which the actor looked down such that theeyes appeared to be closed (no-gaze condition), severalregions of activation were found, including parts of themiddle temporal gyri (Fig. 3). The activated regions wereFig. 3. Activation of the superior temporal sulcus (STS) region in the left hemi-sphere (a) and right hemisphere (b) during the perception of biological motion.All activations are to moving stimuli except for three studies of implied motion22,61,62.Activations are shown in the coordinate system of Talairach and Tournoux95. There is vari-ability in the location and configuration of sulci and gyri between individuals, hence thecenters of activation (circles) are only approximately correct in relation to brain structures.The centers of activation during the perception of American Sign Language (ASL) by expertdeaf signers are correct but misleading, as the entire STS region is activated bilaterally. Insome cases activations in different conditions or experiments of a study have beencombined. Some centers have been moved slightly to allow visualization of overlappingcenters. Activations of other brain regions are not shown. Abbreviations: AG, angulargyrus; STG, superior temporal gyrus. (Centers of activation are taken from Refs17,21,22,43,48–50,52,56,57,59–62,92.)anterior to area MT/V5, a motion-sensitive region locatedat the lateral occipitotemporal border18–20. It is likely thatsome of the activation was in the STS itself, but the rela-tively poor spatial resolution of PET and the consequentuse of across-subject averaging to detect activation mighthave obscured possible activity within the STS. In any269ReviewAllisonet al.– Social perceptionFig. 4. A direction-of-gaze experiment in normal and autistic children. (a)Exampleof a display. When asked which candy ‘Charlie’ prefers, most normal children point to thePolo Mints, but autistic children are less likely to do so.(b)Example of schematic faces.When asked ‘which one is looking at you?’, autistic children score as well as normal children.(Reproduced, with permission, from Ref. 33.)case, a region of cortex near and perhaps partly within theSTS was activated during perception of gaze. We will usethe term ‘STS region’ to refer to cortex within the STS, toadjacent cortex on the surface of the superior and middletemporal gyri (near the straight segment of the STS), andto adjacent cortex on the surface of the angular gyrus(near the ascending limb of the STS). Similar results havebeen obtained in a functional MRI (fMRI) study in whichsubjects viewed a face in which the eyes averted to the leftor right21. Alternations of eye aversion and eyes looking atthe observer activated portions of the STS region (Fig. 3).These regions were anterior to area MT/V5, as deter-mined by the activation produced by nonbiological mo-tion in the same parts of the visual field. Another fMRIstudy found that the perception of eye gaze in static facialimages activated similar portions of the STS region22(Fig. 3).In scalp recordings23, event-related potentials (ERPs)were recorded while subjects viewed the same stimuli used inthe fMRI study described above21. An N170 ERP, previouslyshown to be responsive to face and eye stimuli24–26, was largerin response to eye aversion than to eyes returning to gaze atthe observer. This effect occurred whether the eyes wereviewed in isolation or in the context of a full face. The ERPeffects evoked by eye movement were not produced bymovementper se.The exact regions of cortex that generateN170 cannot be determined from scalp recordings, but theresults suggest that regions of posterior temporal cortex arepart of a system sensitive to eye movement and directionof gaze.The results reviewed above suggest that the STS regionhas a role in the perception of gaze. If so, a lesion of the re-gion should impair judgements of gaze direction, as indeedoccurs in monkeys following lesions restricted to the STS(Refs 27,28). Three prosopagnosic individuals also exhib-ited deficits in the perception of gaze direction27,29, but thelocation and extent of the abnormality is unknown in a de-velopmental prosopagnosic (patient A.B.) and might in-volve, but is not limited to, the STS region in the other two(patients R.B. and K.D.). It will be important to study theperception of gaze direction in individuals with lesionsrestricted mainly to the STS region and who are notprosopagnosic, as it is likely that perception of gaze direc-tion and perception of facial identity can be dissociated27.Of the behavioral deficits seen in autistic children30–32,two are in the use of gaze direction and the comprehensionof mental states. Baron-Cohen and colleagues askedwhether these two abnormalities might be related33. Two ofthe experiments they carried out are summarized in Fig. 4.When normal or mentally retarded children are shown pic-tures like the one illustrated in Fig. 4a, and asked whichcandy ‘Charlie’ prefers, they typically point to the PoloMints. By contrast, autistic children were significantly lesslikely to point to the Polo Mints. This deficit was not duesimply to an inability to perceive the direction of gaze;autistic children scored as well as normal or mentally re-tarded children when shown faces like those illustrated inFig. 4b and asked, ‘Which one is looking at you?’. In otherwords, they were able to perceive the direction of gaze, butwere unable to use such information to infer the mentalstate of another person. Anatomical abnormalities havebeen described in the temporal lobes of autistic individuals,but no studies have yet specifically implicated the STSregion (for a review see Ref. 34).Head movementHead movements convey several types of information11.Rolls and colleagues studied the responsiveness of STS cellsas monkeys viewed human head movements35. The respon-siveness of a cell located in the lower bank of the STS(Fig. 5d) is particularly interesting in this context. This cellfired vigorously during ventral flexion of the head (move-ment towards the chest), but responded poorly during dor-sal flexion of the head (movement away from the chest) orto a static face (Fig. 5a). The responsiveness of the cell tohead movements performed in different orientations isshown in Fig. 5b. The cell responded strongly to ventralflexion whether the head was viewed full face, inverted, inprofile or from behind. The response of the cell to the in-verted head is informative, because in this case the direc-tion of movement on the retina is the opposite of that to270 [ Pobierz całość w formacie PDF ]