de Gelder, B.

Pourtois, G.R.C.

Vroomen, J.

Weiskrantz, L.

English

Tilburg University Repository

    Tilburg UniversityAffective blindsightde Gelder, B.; Pourtois, G.R.C.; Vroomen, J.; Weiskrantz, L.Published in:Trends in Cognitive SciencePublication date:2000Document VersionPublisher's PDF, also known as Version of recordLink to publication in Tilburg University Research PortalCitation for published version (APA):de Gelder, B., Pourtois, G. R. C., Vroomen, J., & Weiskrantz, L. (2000). Affective blindsight: are we blindly led byemotions? 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Jul. 2022facial expressions, whenever amygdalaactivation has been demonstrated inthe absence of conditioned fear, sub-jects have not been required to make aforced-choice response about the natureof the unseen expression. That is, theywere not engaged in the sort of guess-work undertaken by blindsight patients.It is plausible that GY, a much-practisedobserver, is able to monitor his auto-nomic responses and use them to medi-ate above-chance performance in thediscrimination of facial expression. How-ever, the differential responses of theamygdala to different facial expressions2is consistent with its role in the process-ing of at least some facial expressions.The rapidity with which the responsesto unmasked fear-conditioned stimulidesensitize12 leaves open the possibilitythat repeated presentation could miti-gate against GY’s performance. More-over, it remains an interesting possibilitythat an improvement in performancemight have been obtained had GY beenasked to make a reflexive response, suchas a key press, which is less likely thanverbalization to invoke reflective con-scious processes. The genuine guesses ofan uninformed conscious system mightpotentially interfere with the stimulus-driven responses of the putative col-licullar circuit. We will have to wait forfurther experiments to answer thisquestion.References1 Whalen, P.J. et al. (1998) Masked presentationof emotional facial expressions modulateamygdala activity without explicit knowledge.J. Neurosci. 18, 411–4182 Blair, R.J.R. et al. (1999) Dissociable neuralresponses to facial expressions of sadness andanger. Brain 122, 883–8933 de Gelder, B. et al. (1999) Non consciousrecognition of affect in the absence of striatecortex. NeuroReport 10, 3759–37634 Morris, J.S. et al. (1999) A subcortical pathwayto the right amygdala mediating ‘unseen’ fear.Proc. Natl. Acad. Sci. U. S. A. 96, 1680–16855 Weiskrantz, L. (1997) Consciousness Lost andFound, Oxford University Press6 Dehaene, S. et al. (1998) Imaging unconscioussemantic priming. Nature 395, 597–6007 Marcel, A.J. (1998) Blindsight and shapeperception: deficit of visual consciousness orof visual function? Brain 121, 1565–15888 Bassili, J.N. (1979) Emotion recognition: therole of facial movement and the relativeimportance of upper and lower areas of theface. J. Pers. Soc. Psychol. 37, 2049–20589 Soken, N.H. and Pick, A.D. (1992) Intermodalperception of happy and angry expressivebehaviors by 7-month-old infants. Child Dev.63, 787–79510 Adolphs, R. et al. (1994) Impaired recognitionof emotion in facial expressions followingbilateral damage to the human amygdala.Nature 372, 669–67211 Calder, A.J. et al. (1996) Facial emotionrecognition after bilateral amygdala damage.Cognit. Neuropsychol. 13, 699–74512 Büchel, C. et al. (1998) Brain systems mediatingaversive conditioning: an event-related fMRIstudy. Neuron 20, 947–957UpdateCommentH e y w o o d  a n d  K e n t r i d g e  –  A f f e c t i v e  b l i n d s i g h t126 1364-6613/00/$ – see front matter © 2000 Elsevier Science Ltd. All rights reserved.     PII: S1364-6613(00)01470-4T r e n d s  i n  C o g n i t i v e  S c i e n c e s  –  V o l .  4 ,  N o .  4 ,   A p r i l  2 0 0 0such as personal identity, gender andfacial speech are not observed2.This pattern is consistent with theexplanation suggested by Heywood andKentridge that the biological or eco-logical salience of a stimulus is more im-portant than the degree of visual com-plexity per se when deciding whether agiven stimulus will support blindsight.However, if this were the only criticalfactor one might expect facial speechto support blindsight. Indeed, naturallanguage, certainly when taken at thelevel of basic phoneme and syllable dis-crimination, is an integral part of ourbasic biological make-up. So it wassomething of a surprise that we wereunable to find any indication of a ca-pacity for discriminating or identifyingfacial speech in blindsight patients.One possible explanation rests uponthe size of the stimuli used. There is ev-idence that spatial resolution is poor inblindsight, and so stimulus size is likelyto be crucial. Perhaps discrimination offacial speech was not found because thelower part of the face contains relativelysmall stimulus features. It remains to beseen whether a very large lip-readingstimulus would support blindsight.More importantly though, this neg-ative result does seem to pose problemsfor Heywood and Kentridge’s suggestionthat movement might be one of the criti-cal factors in explaining the findings. Thissuggestion was based upon our earlierfinding that, although moving imagessupported affective blindsight, station-ary images did not. This is consistent withfindings that demonstrate that discrimi-nating between two patterns of biologi-cal movement can be done on the basisof very limited or very impoverishedinput. But if movement is important, whydoes facial speech not support blind-sight? In facial speech, one has a stimu-lus that is socially and biologically signifi-cant and for which discrimination can bedone on the basis of the same kind ofimpoverished information consisting ofa small number of moving dots3.Whatever the outcome of that par-ticular debate we do now have somepreliminary evidence suggesting thatstationary images of facial expressionscan support affective blindsight (deGelder et al., unpublished data). In ourexperiment, we measured the impactof a face presented to the blind fieldon the response to a facial stimuluspresented to the intact, seeing field.The results showed that incongruencybetween the expressions presented tothe two hemifields significantly delayedjudgement of the facial expression inthe seeing field.This is an illustrative example thatcovert processing can often only befound with an indirect rather than a di-rect method, in which subjects are re-quired to ‘guess’ the identity of stimulithey patently deny seeing. As Heywoodand Kentridge suggest – in line withsome recent findings about qualitativedifferences between overt and covertprocesses – the superior sensitivity ofindirect methods for uncovering covertprocessing or residual processing abili-ties might be due to an absence of con-flict between overt, reflexive answeringand covert responding. We addressedAffective blindsight: arewe blindly led by emotions?Response to Heywood and Kentridge (2000)Beatrice de Gelder, Jean Vroomen, Gilles Pourtois and Larry WeiskrantzThe recent findings that facial expres-sion can be recognized in the absence ofawareness by blindsight patients sug-gests that, as the saying goes, we mightindeed be blindly led by emotions.Although we are entirely in agreementwith the comments made by Heywoodand Kentridge [Heywood, C.A. andKentridge, R.W. (2000) Affective blind-sight? Trends Cognit. Sci. 4, 125–126]1we would like to take this opportunityto discuss some of the questions thatthey raised and to describe our most re-cent data that may clarify some of theimportant issues.As Heywood and Kentridge remark,the finding of covert discrimination by ablindsight subject of facial expressionspresented to his blind field (‘affectiveblindsight’) raises the question of howthis performance is achieved. An fMRIapproach should provide new evidencewith regard to the actual pathways sus-taining affective blindsight, but it isworth noting that behavioral experi-ments can also help to clarify theneural basis of this phenomenon; forexample, by determining which stimu-lus categories and attributes can beprocessed in the absence of striate cor-tex. Indeed, our most recent results in-dicate that blindsight is found only forfacial expression and that covert dis-crimination of other facial attributesB. de Gelder, J. Vroomen and G. Pourtois are at the Cognitive Sciences Laboratory, University of Tilburg, 5000 LE Tilburg, The Netherlands.tel: +31 13 466 2167fax: +31 13 466 2067e-mail: b.degelder@kub.nlB. de Gelder and G. Pourtois are also atthe Laboratory ofNeurophysiology,University of Louvain,Brussels, Belgium.L. Weiskrantz is atthe Department ofExperimentalPsychology, Universityof Oxford, Oxford, UK  OX1 3UD.just this issue by using false responselabels in one of our experiments(Experiment 4). The results came as abit of a surprise. One of us stubbornlyreasoned that as a test for implicitlearning of discriminative cues we shouldask GY to respond using false responselabels – that is, emotional labels thatdo not correspond to the emotions ex-pressed in the stimuli. This might yieldresults showing that affective stimuliwere labelled systematically and, thus,that associative learning had occurred.This was not found. Instead, when in-structed with non-veridical alternatives,GY’s performance was completely un-systematic and at chance level. Affec-tive blindsight therefore does not ap-pear to be explained by implicit learning.After all, it is unlikely that through un-tutored, unsupervised implicit learningGY would hit upon the correct solution– a solution that reflects a three-wayequation between the stimulus, its con-scious meaning and its non-consciousmeaning.The above considerations suggestthat the issue of the relative sensitivityof various testing methods is more thana quantitative matter, and in fact in-volves a qualitative capacity for stimulusidentification. Heywood and Kentridgeraise a very interesting issue when ask-ing whether key-press reponses couldhave strengthened the data further (infact, that is what we did use). They specu-late that with reflexive verbal responses,the response generated in the blind fieldvia dedicated routes could be inhibitedby mechanisms of awareness. The find-ing that non-veridical response alter-natives have a negative effect on theresults of guessing suggests, paradoxi-cally, that awareness plays a role incovert recognition. For example, the un-derlying mechanism might be one ofconscious processes monitoring autono-mous reactions, as indeed Heywood andKentridge suggest.But there might be other reasonswhy indirect paradigms are more sensi-tive than direct paradigms and why dif-ferent response modalities yield differ-ent results. Neuropsychological subjectsare, by definition, unaware of the ca-pacities that can be revealed by experi-ments on their implicit processes. ‘Direct’methods require them to engage in dis-criminations that they do not believethey can make. In such a counterintui-tive situation, subjects (and some experi-menters!) might be less than willing toaccept that there is any point in contin-ued vigilance with forced-choice guess-ing. Indirect methods completely removethis counterintuitive element.Further research is needed to dis-cover whether affective blindsight is re-stricted to emotions for which the amyg-dala is at present known to play a specialrole. But even if the amygdala’s role isspecific only to particular emotionalstimuli or states, and other emotionalstates depend critically on other targets,our results suggest that these too canbe assumed to be well-provided for interms of visual projections via the sub-cortical collicular–pulvinar route (amongothers) that bypass the primary visualcortex.References1 Heywood, C.A. and Kentridge, R.W. (2000)Affective blindsight? Trends Cognit. Sci. 4,125–1262 Rossion, B. et al. Early extrastriate activitywithout primary visual cortex. Neurosci. Lett.(in press)3 Rosenblum, L.D. et al. (1996) Point–light facialdisplays enhance comprehension of speech innoise. J. Speech Hear. Res. 39, 1159–1170d e  G e l d e r  e t  a l .  –  R e s p o n s e UpdateComment1271364-6613/00/$ – see front matter © 2000 Elsevier Science Ltd. All rights reserved.     PII: S1364-6613(00)01473-XT r e n d s  i n  C o g n i t i v e  S c i e n c e s  –  V o l .  4 ,  N o .  4 ,   A p r i l  2 0 0 0Homologies for numericalmemory span?Marc D. HauserFor some, the case of Clever Hansrepresents the kind of trap that animalresearchers often fall into when search-ing for human capacities in other crea-tures. Hans was certainly clever with re-spect to picking up on human cues, butwas unquestionably clueless when itcame to solving mathematical problems.Ever since the debunking of Clever Hans,however, an extraordinary amount ofevidence has accumulated1,2, showingbeyond a shadow of doubt, that weshare many of the core building blocksof our number capacity with other ani-mals. We know, for example, that sev-eral avian (pigeon, African gray parrot)and mammalian (rat, rhesus monkey,chimpanzee) species can be trained toclassify sets of objects with respect totheir ordinal relationships, appreciatethat number is property indifferent (i.e.as long as the object or event is an entitythat can be counted or individuated, its properties are irrelevant), and thatthere is a one-to-one correspondencebetween the numerical tag and the ob-ject counted. There is also evidence thatmonkeys show a certain level of nu-merical sophistication in the absence oftraining. Specifically, using techniquesthat are analogous to those used withhuman infants, cotton-top tamarins andrhesus monkeys have been shown tocompute simple arithmetical operationssuch as additions and subtractions. Now,in an exciting new report in Nature3,Kawai and Matsuzawa add to our grow-ing understanding of the evolutionaryorigins of the human capacity for num-ber by showing that a chimpanzee hasa numerical memory span that falls wellwithin the range of the ‘magic number7’, at least on some accounts4.Kawai and Matsuzawa worked withtheir star chimpanzee, a female by thename of ‘Ai’ with over 20 years of ex-perimental experience. Prior to conduct-ing the current study, Matsuzawa hadshown that Ai could learn the Arabicnumerals from 0 to 9. Specifically, basedon extensive training, Ai had learned torespond on a touch-sensitive monitorto the ordinal relationships betweennumbers. Thus, when shown a sequenceof four numbers, with inter-integer dif-ferences of either one or more, shewould touch each number from lowestto highest, and with remarkable speedand accuracy. Taking advantage of thisability, Kawai and Matsuzawa set up amemory span task. A set of numbers wasdisplayed on a monitor, such as 1,3,4,6,9.As soon as Ai pressed the first number inthe sequence (i.e. 1), all of the remain-ing numbers were masked by a whitesquare. Ai’s task was to press the remain-ing numbers (now masked) in order. Forset sizes of two to four numbers, herperformance was above 90% correct.Although her performance dropped to65% for set sizes of five, this was none-theless significantly above chance (i.e.4%; note that in the original manuscriptthis was incorrectly calculated as 6%). Ofconsiderable interest was her reactiontime to respond. Independent of set size,Ai was slowest on the first press, withreaction time remaining relatively con-stant for all subsequent responses. Thus,for example, mean reaction time for thefirst response to a set size of four was717 ms, and then 390, 432, and 437 re-spectively for the last three, masked,responses. This strongly suggests thatAi first explored the number space, cal-culating the ordinal relationships andspatial locations of each number, andthen used this stored information toguide her subsequent responses.As in all well-designed research withinteresting results, many questions remain. To understand better whetherAi’s capacity for calculating ordinal M.D. Hauser is atthe Department ofPsychology andProgram inNeurosciences,Harvard University,Cambridge, MA 02138, USA.tel: +1 617 496 7077fax: +1 617 496 7077e-mail: hauser@wjh.harvard.edu

Affective blindsight:are we blindly led by emotions?

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Affective blindsight:are we blindly led by emotions?

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