The Journal of Deaf Studies and Deaf Educationlcn.salk.edu/publications/1997/Bettger - Facial discrimination ASL... · The Journal of Deaf Studies and Deaf Education J. Deaf Stud

The Journal of Deaf Studies and Deaf Education

2:223-233, 1997. J. Deaf Stud. Deaf Educ.Jeffrey G. Bettger, Karen Emmorey, Stephen H. McCullough and Ursula Bellugi Enhanced Facial Diserimination: Effects of Experience With American Sign Language

http://jdsde.oxfordjournals.orgThe full text of this article, along with updated information and services is available online at

Reprints http://www.oxfordjournals.org/corporate_services/reprints.html

Reprints of this article can be ordered at

Email and RSS alertinghttp://jdsde.oxfordjournals.org Sign up for email alerts, and subscribe to this journal’s RSS feeds at

image downloadsPowerPoint® Images from this journal can be downloaded with one click as a PowerPoint slide.

Journal informationto subscribe can be found at http://jdsde.oxfordjournals.org Additional information about The Journal of Deaf Studies and Deaf Education, including how

Published on behalf ofhttp://www.oxfordjournals.org Oxford University Press

at Salk Institute for Biol Studies on 5 September 2008 http://jdsde.oxfordjournals.orgDownloaded from

http://jdsde.oxfordjournals.org

http://jdsde.oxfordjournals.org

http://www.oxfordjournals.org/corporate_services/reprints.html

Enhanced Facial Discrimination: Effects of Experience WithAmerican Sign Language

Jeffrey G. BettgerSan Francisco State University

Karen EmmoreyStephen H. McCulloughUrsula BellugiThe Salk Institute for Biological Studies

On-line comprehension of American Sign Language (ASL)requires rapid discrimination of linguistic facial expressions.We hypothesized that ASL signers' experience discriminat-ing linguistic facial expressions might lead to enhanced per-formance for discriminating among different faces. Fiveexperiments are reported that investigate signers' and non-signers' ability to discriminate human faces photographedunder different conditions of orientation and lighting (theBenton Test of Facial Recognition). The results showed thatdeaf signers performed significantly better than hearing non-signers. Hearing native signers (born to deaf parents) alsoperformed better than hearing nonsigners, suggesting thatthe enhanced performance of deaf signers is linked to experi-ence with ASL rather than to auditory deprivation. Deafsigners who acquired ASL in early adulthood did not differfrom native signers, which suggests that there is no "criticalperiod" during which signers must be exposed to ASL in or-der to exhibit enhanced face discrimination abilities. Whenthe faces were inverted, signing and nonsigning groups didnot differ in performance. This pattern of results suggeststhat experience with sign language affects mechanisms spe-cific to face processing and does not produce a general en-hancement of visual discrimination. Finally, a similar patternof results was found with signing and nonsigning children,6-9 years old. Overall, the results suggest that the brain

This research was supported in part by NIDCD 00146, NICHD 13249,NIDCD 00201, and the March of Dimes. Experiment 2 is based on Bett-ger (1992), partially supported by NIDCD 00167 to E. Newport andT. Supalla We thank the students, staff, and administration at the Califor-nia School for the Deaf in Fremont, California, Gallaudet University inWashington, D C ; Lafayette Elementary School in San Diego, Califor-nia; and the National Technical Institute for the Deaf in Rochester, NewYork. We are grateful to Kevin dark , Bonita Ewan, Katliy Say, GeorgeZein, Edward S. Klima, Ila Parasnis, and Vincc Samar for their commentsand assistance. Correspondence should be sent to Jeffrey G. Bettger, Dcpt.of Special Education—Burk Hall, San Francisco State University, 1600Holloway Ave., San Francisco, CA 94132 (e-mail: [email protected]).

Copyright © 1997 Oxford University Press. CCC 1081-4159

mechanisms responsible for face processing are somewhatplastic and can be affected by experience. We discuss implica-tions of these results for the relation between language andcognition.

A common yet difficult task required of the visual sys-tem is discriminating between and recognizing humanfaces. For example, we often must pick out the face ofa friend in a crowd, a difficult task because all peoplehave the same general facial features and configura-tion—two eyes above a nose above a mouth. Somestudies have suggested that our expertise in human facerecognition is due to specialized brain mechanisms(e.g., Yin, 1969; Farah, 1996). In the studies presentedhere, we investigate whether experience can alter cer-tain face-processing abilities and whether such effectsare seen early in development or only in adulthood.Finding effects of experience will suggest that the brainmechanisms responsible for human face processing arerelatively plastic and can be affected by environmentalexperience with faces. But how do we test for dif-ferences in experience with human faces? Some re-searchers have even suggested that the uniqueness offace-processing mechanisms arises because we are allexperts at human face perception. However, there isreason to suspect that one group of people may acquireadditional "expertise" due to their particular experi-ence with the human face: deaf people who use Ameri-can Sign Language (ASL).

A unique and modality-specific aspect of ASLgrammar is the use of the face as a linguistic marker.

224 Journal of Deaf Studies and Deaf Education 2:4 Fall 1997

Different facial expressions serve to mark different lex-ical and syntactic structures, such as wh-questions(e.g., what, where, when), relative clauses, conditionals,adverbials, and topics (Baker-Shenk, 1983; Liddell,1980; Reilly, Mclntire, & Bellugi, 1990a). These facialexpressions differ from emotional expressions in theirscope and timing and in the facial muscles used (Reilly,Mclntire, & Bellugi, 1990b). Grammatical facial ex-pressions have a clear onset and offset and are coordi-nated with specific parts of the signed sentence. Theseexpressions are critical for interpreting the syntacticstructure of many ASL sentences. For example, restric-tive relative clauses are indicated by raised eyebrows, aslightly lifted upper lip, and a backward tilt of the head.When this combination of head and facial features oc-curs, the co-occurring lexical items are interpreted asconstituting a relative clause (Liddell, 1980). Condi-tional clauses are signaled by raised eyebrows, a headtilt to the side, and a slight forward movement of theshoulders. Again, the onset and offset of these featuressignal the scope of the conditional clause and distin-guish this clause type from a conjoined main clause.Facial behaviors also constitute adverbials that appearin predicates and carry different specific meanings.For example, the facial expression "mm" (lips pressedtogether and protruded) indicates an action done ef-fortlessly, whereas the facial expression "th" (tongueprotrudes between the teeth) means "awkwardly" or"carelessly." These two facial expressions accom-panying the same verb (e.g., DRIVE) convey quitedifferent meanings ("drive effortlessly" or "drive care-lessly"). Finally, facial expressions operate at a referen-tial discourse level to convey "shifted attribution ofexpressive elements" (Engberg-Pedersen, 1993) andfunction to convey character point of view. In this case,facial expressions convey affective information repre-senting the perspective of a particular discourse refer-ent, similar to the use of "free indirect style" in spo-ken languages.

It is clear from the preceding description that ASLsigners must be able to quickly identify and discrimi-nate between different linguistic and affective facial ex-pressions in order to process and interpret signed sen-tences. Facial expressions signal syntactic and semanticstructure at lexical, syntactic, and discourse levels. In

this article, we investigate how experience discriminat-ing linguistic facial expressions, as is necessary in ASL,affects the ability to discriminate faces in a nonlinguis-tic domain.

In the five experiments reported here, we used theBenton Test of Facial Recognition (Benton, Hamsher,Varney, & Spreen, 1983) For this test, subjects are re-quired to detect a target face from within a set of sixsimilar-looking faces (see Figure 1). We consider thistest to be actually a measure of face discrimination, notrecognition, because subjects must discriminate amonga group of faces presented on the same page rather thanrecognize a remembered target face. Therefore, we willrefer to this test as the "Benton Faces Test" rather thanby its formal name. We chose this test as a measure offace-processing ability because it is relatively difficult(and thus may be sensitive enough to reveal differencesbetween subject groups), and we hypothesized that theability to distinguish between different facial expressions(a task that ASL signers must do quickly and fre-quently) may lead to an enhancement in the ability todistinguish between the different faces. We predictedthat groups of deaf signers will perform better thangroups of hearing nonsigners. Experiments 1-3 com-pare the performance of adults, and experiments 4 and5 compare the performance of children.

Experiment 1: Method

In this experiment, we provide the foundation for ourstudies of the effects of experience on behavior. Westart with the basic question: do behavioral differenceson a facial discrimination test exist between deafpeople who use ASL and hearing people who do not?

Subjects. Sixteen hearing adults (mean age = 22 years)and sixteen deaf adults (mean age = 33 years) partici-pated in the experiment. The deaf subjects were eitherrecruited from the Fremont, California, communityand tested at the California School for the Deaf in Fre-mont or recruited and tested at a California Associationfor the Deaf meeting in San Diego. All deaf subjectswere born to deaf parents (DD for "deaf with deaf par-ents") and acquired ASL as their first language. Thesesubjects reported that ASL was their primary and pre-

Enhanced Facial Discrimination 225

ferred language. Hearing subjects (HH for "hearingwith hearing parents") were recruited from the River-side, California, community and were tested at theUniversity of California Riverside. This group had nosigning experience.

Materials and procedures. In the Benton Faces Test, abooklet of photographs is presented to the subject. Foreach of the 22 trials in the long-form version of thetest, a photograph of a target face is shown at the topof the page. Below this target photograph are six choicephotographs. To answer correctly, a subject must pointto the choice picture that is the same person as shownin the target photograph. The remaining choices aredistracter photographs of people who look similar tothe target person in overall appearance (see Figure 1).

The 22 trials are divided into three conditions. Forth.e first six test items (the front condition), all of thefaces are looking straight ahead. Subjects were in-formed that only one of the six choice photographs isthe same-person shown in the target photograph. Forthe second and third conditions of the test (the profileand shadow conditions), subjects were informed thatthree of the six choice photographs are the same personshown in the target photograph and that all three mustbe correctly identified. In the profile condition, all sixchoice photographs show the faces from a side view. Inthe shadow condition, all six choice photographs showthe faces looking forward but are taken under lighting

conditions that produce shadows across portions of thefaces. The 22 trials in the long-form version of the testconsists of six front trials (one answer each), followedby eight profile view trials (three answers each) inter-mixed with eight shadow trials (three answers each),producing a total of 54 possible correct answers. Sub-jects were informed that no time limit existed for thistask.-

Experiment 1: Results and Discussion

As suggested by Benton et al. (1983), each of the 54total responses produced from the 22 trials was scoredseparately as correct or incorrect. Percentage correctwas computed to be comparable with scores obtainedfrom the short-form version of the test (13 trials pro-ducing 27 possible correct) used in studies 4 and 5.

The average correct percentages for the deaf andhearing groups are shown in Table 1. We found thatdeaf ASL signers performed significantly better overallthan hearing nonsigning adults (see Table 1). Given theoverall group difference, we next computed plannedcomparisons for each of the three conditions of the test(front, profile, shadow) to determine whether any onestimulus condition most differentiates the groups.

Significant group differences were found for thosetrials in the shadow condition. Note that the primarydifference between the shadow condition and the othertwo conditions is that many individual features in the

Figure 1 Example stimulus from the Benton Faces Test. The model face is the same face as the top middle, bottom middle,and bottom right face. This example is from the profile condition.


Table 1 Mean percentage correct for deaf and hearing adults onthe Benton facial discrimination task

Subject groupConditions DD HH /"valueTotal 87.4 81.7 /"(1,30) = 5.29,/. < .05

Breakdown by viewFront 100Profile 91.6Shadow 73.3

99 F(l,30)< 1, ns86.5 F(\,30)< l,ns63.9 /"(1.30) = 5.98, p< .05

shadow stimuli are obscured. Even though the profileview provides a different perspective, each type of fea-ture of the face (e.g., eyes, eyebrows, ears) is visible.Apparently, all subjects were at ceiling on the frontcondition.

The results from this study provide the foundationand starting point for our exploration into the perfor-mance differences found when testing deaf adults andhearing adults on a facial discrimination task. Deafsigners were significantly more accurate in detecting atarget face from among a set of distracters, particularly,those faces partially obscured by shadows.

However, the two groups differ in two importantways: language modality (a visual-spatial languagecompared with an auditory-spoken language) and audi-tory experience (deafness compared to normal hear-ing). In experiment 2, we attempt to tease apart theeffects of language and sensory experience.

Experiment 2: Linguistic VersusSensory Experience

It is possible that the advantage of deaf subjects in ex-periment 1 is not due to experience processing facialexpressions in ASL, but rather to auditory deprivationfrom birth. Perhaps the lack of auditory input boostsface discrimination skills because deaf subjects de-pennd more on the visual sensory system for obtain-ing information. Exposure to a visual-spatial language,such as ASL, may be irrelevant. To investigate the de-gree to which language exposure versus auditory depriva-tion is associated with enhanced face discrimination, weconducted an experiment that included two additionalgroups of subjects: hearing subjects who have deaf par-

ents and who are native signers (HD subjects) and deafsubjects with hearing parents who acquired ASL late(DH subjects).

HD subjects acquire ASL as a first language fromtheir deaf parents, but crucially, these subjects canhear. If enhanced face discrimination is due to auditorydeprivation from birth, then hearing native signersshould show a pattern of results similar to those forhearing nonsigners. On the other hand, if this in-creased ability is due to experience processing ASL,then the hearing native signers should show the sameenhanced performance as do the deaf native signers.

DH subjects are deaf, have hearing parents, andwere not exposed to ASL until late childhood or earlyadulthood. By comparing the performance of thesesubjects with the DD and HD subjects, we can investi-gate whether there might be a "critical period" for theobserved enhancement. That is, if DH subjects per-form like hearing nonsigners, we can suggest that earlyexposure to ASL is necessary for the enhancementeffect.


Subjects. All subjects were tested at the National Tech-nical Institute for the Deaf (NTID) in Rochester, NewYork. All subjects were paid for their participation inthe experiment. Further group details are given below.

DD group (deaf subjects with deaf parents; native deafASL signers). Eight NTID students participated(mean age = 21 years). All subjects reported them-selves to be deaf from birth, with a current Pure ToneAverage (PTA) hearing level of above 90 dB. All sub-


jects learned ASL from their parents and relatives frombirth and were rated at the highest level on an ASLproficiency test administered upon entering NTID.

DHgroup (deaf subjects with hearing parents; late ASLsigners). Eight NTID students participated (meanage = 24 years). All subjects reported themselves to bedeaf from birth, with a current average PTA hearinglevel of above 87 dB, except for one subject at 83 dB.Because most of these subjects had previously attendedschools that emphasized lip-reading and oral skills,they reported having only minimal signing experiencebefore entering NTID. The. average reported amountof signing experience was three years.

HD group (hearing subjects with deaf parents; nativeASL signers). Eight hearing subjects who have deafparents participated in the experiment (mean age = 42years, ranging from 25 to 60 years old). All subjects hadnormal hearing. At the time of this experiment, threeof these subjects were employed as ASL interpreters,and the other five were employed as instructors or ad-ministrators at NTID. All eight subjects in this grouplearned ASL from birth from their deaf parents andother relatives.

HHgroup (hearing subjects with hearing parents; non-signers). Eight hearing monolingual students at theRochester Institute of Technology participated (meanage = 22 years). All subjects had normal hearing andhad no signing skills.

Materials and procedures. All materials and procedureswere identical to those used in experiment 1.


The mean percentage correct for each subject groupis presented in Table 2. Using a one-factor analysis ofvariance (ANOVA), we find that the groups were sig-nificantly different from each other. Based on the over-all group difference, multiple planned pairwise com-parisons show that both the DD and HD groups scoredsignificantly higher than the HH group (p < .02) andthe DH group scored higher than the HH group, al-

Table 2 Mean percentage correct for each adult group onthe Benton facial discrimination task

Subject group

Conditions DD HD DH HH lvalue

Total 90.4 89.6 87.3 79.3 F (3,31) = 5.01, p< .01

Breakdown by viewFront 95.8 100 100 100 ,P (3,31) = 2.33, nsProfile 96.9 94.3 91.7 85.4 ^(3,31) = 2.65, nsShadow 82.3 81.8 79.7 68.2 ^(3,31) = 4.40,p < .02

though the difference fell just short of significance(/"[1,15] = 4.46, p = .05). The DD, DH, and HD didnot significantly differ from each other.

Based on the findings of experiment 1, we foundthat the shadow condition once again provided thegreatest group difference. However, the same patternof group performance is found for the profile view (i.e.,DD highest, HH lowest), although this difference didnot Teach significance. All groups were at ceiling on thefront view condition.

This experiment replicates and extends the find-ings of experiment 1. As in experiment 1, deaf nativesigners performed significantly better on the BentonFaces Test than hearing subjects with no signing expe-rience. Furthermore, hearing subjects who were nativesigners'also performed significantly better than non-signing subjects, indicating that experience with ASL,rather than auditory deprivation, leads to an enhancedability to discriminate among faces. The performariceof deaf signers who acquired ASL in early adulthooddid not differ from that of native signers, and their per-formance was also better than that of the nonsigninghearing group. This result indicates that there is no"critical period" during which signers must be exposedto ASL in order to exhibit enhanced face discrimina-tion abilities. The observed enhancement effect doesnot appear to be tied to early exposure to ASL.

Experiment 3: Inverted Faces

It has long been known that inverting faces has a nega-tive effect on facial recognition tasks (Arnheim, 1954).Furthermore, while inversion does affect recognition ofother types of familiar mono-oriented objects (such as


houses, airplanes, or costumes), inversion dispropor-tionately impairs the recognition of faces (Yin 1969,1970). This "inversion effect" has been interpreted asindicating that unique mechanisms underlying faceprocessing are sensitive to changes in orientation.However, Diamond and Carey (1986) suggested thatthe inversion effect with face recognition is actually theresult of perceptual experience. To support their alter-native hypothesis, they presented inverted pictures ofdogs to two groups: dog breeders and nonexperts. Thedog breeders are assumed to have more extensive per-ceptual experience with a specific dog breed, and, ac-cording to the hypothesis, the experts should be moredisrupted in comparison to the nonexperts when theimages are presented in a noncanonical orientation.The data confirmed the hypothesis; dog breeders ex-hibited a larger inversion effect compared to subjectswho were not experts. That is, the group of dog breed-ers did more poorly recognizing inverted dog facesthan did the nonexperts, suggesting a relationship be-tween the inversion effect and expertise. These dataprovide the rationale for our next study: do ASL sign-ers, whose language requires extensive use of specific,facial expressions to convey linguistic information,have a larger inversion effect (i.e., perform more poorlywhen discriminating inverted faces compared to non-signers)?


Subjects. Seventeen deaf college students and 20 hear-ing nonsigning college students participated in the ex-periment. All deaf subjects had deaf parents and wereexposed to ASL from birth. Deaf subjects were paidfor their participation and were tested at GallaudetUniversity in Washington, DC. Hearing subjects fromthe University of California San Diego were either paidor received course credit for their participation andwere tested at the Salk Institute in La Jolla, California.

Materials and procedure. Each subject was given the up-right and the inverted version of the Benton FacesTest. As in experiments 1 and 2, the long form of eachtest was used. Half of the subjects in each group re-ceived the upright test first; the other half of the sub-jects received the inverted test first. For the inverted

form of the test, the target face was upright, and theresponse faces were all upside-down.


A repeated measures ANOVA with the total score re-vealed that all subjects performed better on the uprighttest than on the inverted test (^[1,35] = 65.38, p <.01). There was no main effect of subject group. Im-portantly, the interaction between test type and subjectgroup was significant (F[l,35] = 12.86, p < .01). Re-sults from the upright test are shown in Table 3. Simi-lar to experiments 1 and 2, DD subjects scored higherthan hearing nonsigners, although the difference in to-tal score did not reach significance this time. However,we did find that native signers scored significantlyhigher than hearing nonsigners on the critical shadowcondition.

Results from the inverted condition are shown inTable 4. In the inverted condition, for the first time, wefind that the deaf signers actually have a lower groupaverage than the hearing subjects oneach componentof the test, as well as on the overall score. Of particularinterest is the data from the front view component ofthe test. Whereas both groups were at ceiling on the

Table 3 Mean percentage correct for deaf and hearingadults on die Benton upright facial discrimination task

Subject group

Conditions DD H H F value

Total 83.55 80.09 F(l,35)< 1, ns

Breakdown by viewFront view 99Profile view 87.5Shadow view 75.75

98.33 F ( l , 3 5 ) < 1, ns86.25 7̂ (1,35) < 1, ns69.38 ^(1,35) = 4 . 5 9 , p < . 0 5

Table 4 Mean percentage correct for deaf and hearingadults on the Benton inverted facial discrimination task

Subject group

Condition DD HH F value

Total 71

Breakdown by viewFront view 85.3Profile view 78.9Shadow view 60.8

75.1 ^(1,35) = 2.267, ns

99.2 F(1,35) = 7 .76 ,p<.0181.5 / " (1 ,35)= 1.04, ns62.7 F ( l , 3 5 ) < l , n s


upright version of the front view, the deaf signers per-formed significantly lower than did the hearing non-signers when these stimuli were inverted.

The results provide some evidence for an expertiseeffect for ASL signers for face processing. When faceswere inverted and presented in the front view condi-tion, ASL signers scored significantly lower than hear-ing nonsigners. This pattern of results is similar to thatof Diamond and Carey (1986), who found that expertdog breeders showed worse performance under inver-sion than novices. Our finding of an expertise effect forASL signers supports the hypothesis that the enhancedperformance on discriminating canonical upright facesis due to signers' unique experience with the humanface.

In addition, Farah, Wilson, Drain, and Tanaka(1995) have recently suggested that the hypothesizedbrain mechanisms responsible for human face pro-cessing are not utilized when faces are turned upsidedown. Farah et al. propose that face perception systemsare specific to upright faces. Since ASL signers did notperform better than hearing nonsigners when faceswere inverted, we argue that experience with sign lan-guage affects only mechanisms specific to face pro-cessing. Experience with ASL does not produce a gen-eral enhancement of discrimination abilities (evenwhen the stimuli are faces).

Experiment 4: Children, Upright Faces

In this study, we begin to investigate how and whenfacial discrimination enhancement develops. By thetime native signing children are 9 or 10 years old, theyhave mastered many of the linguistic facial expressionsof ASL (Reilly et al., 1990a, 1990b). We investigatewhether children who have had exposure to ASL frombirth show the same enhancement as do adults. Havethese children had enough experience interpretingASL facial expressions to produce an effect on nonlin-guistic face discrimination skill? What about the deafchildren who have had delayed exposure to ASL? Deafchildren with hearing parents who are exposed to ASLlate may not have yet mastered these linguistic mark-ers since they generally show delays in the acquisitionof numerous ASL grammatical structures (Bettger,Klima, Ewan, & Smith, 1995; Galvan, 1989). To inves-

tigate these issues, the Benton Faces Test was given toDD (native signers), DH (late signers), and to HH(nonsigners).


Subjects. Thirty-six DD and 17 DH children from theCalifornia School for the Deaf in Fremont, California,were tested. Twenty HH children from Lafayette Ele-mentary school in San Diego, California, and from theRiverside, California, community were tested. All chil-dren were between the ages of 6 and 9 years old. Aver-age age for the three groups at time of test was 7;7, 7;2,and 7;5 years old for the DD, DH, and HH groups, re-spectively.

Materials and procedures. Subjects were given a reducedversion of the Benton Faces Test. The short-form ver-sion consists of the first 13 trials of the long-form ver-sion (i.e., six front, four profile, three shadow). Thiscombination of trials produces a total of 27 possiblecorrect answers (as opposed to 54 possible in the long-form version). All deaf children were tested by a deafresearcher (native signer) using ASL, and all hearingchildren were tested by a hearing researcher using En-glish.


The ANOVA results and test scores are shown in Table5. Planned pairwise comparisons revealed that the DDchildren scored significantly higher than both the DHand HH children for the total and profile scores. TheDD children scored significantly higher than only theHH children for the shadow scores. The DH and HH

Table 5 Children's mean percentage correct on theBenton upright facial discrimination task

Subject group

Condition DD DH HH F value

Total 75.31 65.14 66.85 F (2,70) = 8.66,/. < .01

Breakdown by viewFront 92.13 83.33 87.5 F (2,70) = 1.54, nsProfile 77.08 60.29 67.5 F (2,70) = 7.32, p< .01Shadow 61.73 59.48 52.22 F (2,70) = 3.84, p = .03


100

. . . . o . . . .

DD

DH

7 0 -

6 0 -

50

AgeFigure 2 Performance on the upright version of the Benton Faces Test by deaf children ex-posed to ASL from birth by deaf parents (DD), deaf children with hearing parents exposed toASL later in childhood (DH), and hearing children who have no signing experience (HH).

children did not differ significantly for total score orfor any of the component scores.

Figure 2 plots the total score for each group by age.Children tend to get better on the test with age. Im-portantly, at each age level, the DD children scoredabove both the HH and DH children.

These data show that the enhancement of facialdiscrimination we found with native adult signers isalso apparent in deaf children ages 6—9 years who havebeen exposed to ASL from birth. In contrast to experi-ment 2 (adults), we found that deaf children with hear-ing parents performed more like nonsigning childrenthan like native signing children. Differences betweenDD and DH children may be related to the fact that DDchildren are not only exposed to ASL from birth, but arealso more likely to be exposed to a richer and morecomplete version of ASL that more frequently includesthe use of linguistically meaningful facial expressions.DH children may not have been exposed to ASL longenough or with enough consistency to affect their non-linguistic face discrimination skills. However, the re-sults from experiment 2 suggest that by adulthood,these children will have been exposed to ASL longenough to produce enhanced face-processing abilities.

Experiment 5: Children, Inverted Faces

In this experiment, we investigated the inversion effectfor faces with DD and DH and HH children. Ex-periment 4 showed that native signing children weresuperior on the Benton Faces Test when the faces werepresented in their canonical orientation. If this en-hancement is due to face-specific processing mecha-nisms and if DD children's enhancement is due to theirexperience with ASL, then we predict that under in-version, DD children will perform similarly to DH andHH children, or perform more poorly under inversiondue to the expertise effect.


Subjects. Thirty-one DD and 27 DH children from theCalifornia School for the Deaf at Fremont, California,were tested. Forty-two HH children from Lafayette El-ementary School in San Diego, California, were like-wise tested. All subjects were between the ages of 6 and9 years old. Average age for the three groups at time oftest was 7;8, 7; 10, and 7;7 years old for the DD, DH,and HH groups, respectively.


Procedures. All procedures for the inverted version ofthis test were the same as for the upright version givento children in experiment 4.


The ANOVA results and test scores are shown in Table6. The total score data are plotted by age in Figure 3.The three groups did not differ significantly from eachother on total score or on any of the three components(i.e., front, profile, or shadow) of the inverted faces test.

All three groups had very similar scores. As withthe adults in experiment 3, the DD children had gener-ally lower scores than the HH children, but the differ-ences in scores did not reach significance on any corn-

Table 6 Children's mean percentage correct on theBenton inverted facial discrimination task

Condition

Total

BreakdownFrontProfileShadow

Subject

DD

57.88

by view59.1462.950.53

group

DH

58.67

61.7362.8651.13

HH

58.47

59.1261.7753.70

F value

f(2,97)

F (2,97)/" (2,97)f(2,9?)

< 1

< 1< 1< 1

, ns

, ns,ns, ns

100

9 0 -

508

parison. The DD children may not have had enoughexposure to ASL to exhibit an expertise effect (i.e.,worse performance under inversion compared to non-signers). Nevertheless, these results again suggest thatenhanced discrimination ability is specific to face pro-cessing since face-processing mechanisms are arguedto operate only for the recognition of canonically ori-ented faces (Farah et al., 1995). Since these mecha-nisms are not called into play for inverted faces, nativesigning children and adults are not superior to non-signing subjects.

General Discussion

ASL contains linguistic markers expressed by the face.We hypothesized that signers' extensive experience at-tending to and processing linguistic facial expressionmight lead to a general enhancement of face discrimi-nation ability. Five experiments, in three differentstates, investigated signers' and nonsigners' ability todiscriminate human faces photographed under differ-ent conditions of orientation and lighting, as measuredby the Benton Faces Test. The results showed thatadult deaf native signers were significantly more accu-rate than hearing adults who had no sign language ex-

DD

DH

- —O—- HH

AgeFigure 3 Performance on the inverted version of the Benton Faces Test by deaf children ex-posed to ASL from birth by deaf parents (DD), deaf children with hearing parents exposed toASL later in childhood (DH), and hearing children who have no signing experience (HH).


perience. For all experiments (except those with in-verted faces), the difference between signing andnonsigning groups was most evident for trials in whichfacial features were obscured by shadows. For these tri-als, an effective strategy is to match individual featuresof the target face with the visible features of the choicefaces. Such a strategy may not be necessary for thefront and profile conditions, in which each type of fa-cial feature is visible. Recently, McCullough and Em-morey (1997) have found evidence that ASL signersmay be particularly adept at discriminating individualfacial features. If the shadow condition draws more onmechanisms involved in featural processing (ratherthan gestalt processes), this might explain why signerswere particularly accurate in this condition. Anotherpossibility is that level of difficulty is driving this pat-tern of results. The shadow condition was most diffi-cult for all subjects (see Tables 1-6). Enhanced dis-crimination ability may only emerge when a certainlevel of difficulty is attained. Evidence for this possibil-ity can be found in the data from the children. Childrenperformed worse than adults, indicating that the taskwas more difficult for them (compare Table 5 with Ta-bles 1-3). In contrast to the adults, native signing chil-dren were significantly more accurate than hearingnonsigning children on both the profile and shadowconditions. For the children, the level of difficulty mayhave been high enough for significant differences inface discrimination skill to emerge.

The results of experiment 2 revealed that hearingnative signers performed significantly better than hear-ing nonsigners. Furthermore, Parasnis, Samar, Sathe,and Bettger (1996) found that "oral" deaf children whohad no exposure to sign language performed similarlyto hearing nonsigning children on the Benton FacesTest. Together these results strongly suggest that en-hanced face discrimination skill is due to knowledgeand use of sign language, rather than to auditory depri-vation per se. Further evidence that ASL signers are"experts" at face discrimination was found in experi-ment 3, in which subjects were presented with invertedfaces. Like Diamond and Carey (1986), we found evi-dence for an "expertise effect" in which experts aremore sensitive to inversion than novices. ASL signersperformed more poorly than nonsigners when faceswere inverted. This finding again supports the hypoth-

esis that environmental experience is driving the en-hancement effect we observe with canonically orientedfaces. Furthermore, Farah et al. (1995) present neuro-psychological data to argue that brain mechanisms spe-cific to faces do not operate when faces are inverted.Thus, we argue that since ASL signers (both childrenand adults) did not outperform hearing nonsigners forinverted faces, the enhancement that we observed forcanonical upright faces is not a general enhancement ofvisual discrimination skill, but is specific to face pro-cessing.

The results with deaf children indicated that theeffects of sign language experience can be observed asearly as 6 years of age—but only when children havebeen exposed to ASL from birth. Deaf children withdelayed exposure to ASL did not show the same per-formance enhancement as did native signing children.However, exposure to ASL during childhood does notappear to be critical since deaf adults who acquiredASL in adulthood exhibited enhanced face discrimina-tion abilities. Similarly, other researchers are dis-covering that signers who acquire ASL later in child-hood (or even in early adulthood) exhibit enhancedcognitive processing skills similar to those of nativesigners, although usually the effect is not quite asstrong for the nonnative (late-exposed) signers (seeEmmorey [in press] for a review of studies examiningthe impact of sign language use on visual-spatial cogni-tion). For example, Emmorey, Kosslyn, and Bellugi(1993) found that both native and nonnative signerswere faster in a mental rotation task than hearing non-signers, but the native signers were more accurate thanboth groups. Talbot and Haude (1993) found that hear-ing adults who had six years of experience with ASLoutperformed hearing nonsigners on a similar mentalrotation task. Bettger (1992) found that deaf native,deaf nonnative, and hearing native signers were allmore accurate than hearing nonsigners on a differentmental rotation task and on a movement perceptiontask. Thus, at least for some cognitive tasks, we mayfind that it is the consistency and the duration of expo-sure to sign language that lead to changes in cognitiveabilities, rather than the timing of that exposure dur-ing development.

Overall, the data point to a direct connection be-tween language and a nonlinguistic domain of cogni-


tion: discriminating unfamiliar faces. One might askwhether the results are evidence of a "Whorfian" effect.Do the findings support the hypothesis that the lan-guage one uses (ASL or English) has a differentialeffect on how one thinks? Thus far, the data do not in-dicate that ASL signers are actually processing facesdifferently than nonsigners or that they mentally rep-resent faces differently. Rather, the data are consistentwith the hypothesis that experience with ASL facialexpressions can fine-tune certain face-processing skills.Nonetheless, these results do support the hypothesisthat knowledge and use of a particular language (ASL)can influence nonlinguistic cognitive processes. Suchan effect has implications for modular theories of mind(e.g., Fodor, 1983). Fodor has argued that linguisticprocesses are "encapsulated," insulated from othertypes of processes. Our results suggest that central as-pects of ASL processing (perhaps mechanisms in-volved in recognizing and processing grammatical fa-cial expressions) are not domain-specific (applyingonly to language) and are not insulated from othertypes of visual processing. Furthermore, Nachson(1995) and Farah (1996) (among others) have suggestedthat face processing itself is a modular system, similarto language. Again, our results provide some limits onthe nature of this modularity. Since human face pro-cessing ability can be manipulated by certain types ofexperience, it suggests that these mechanisms aresomewhat plastic (even in adulthood) and may be re-cruited for other processes, such as interpreting lin-guistic information expressed by the face.

References

Amheim, R. (1954). Art and visual perception: A psychology of theeye. Berkeley: University of California Press.

Baker-Shenk, C. (1983). A microanalysts of the non-manual compo-nents of questions in American Sign Language. UnpublishedPh.D. dissertation, University of California, Berkeley.

Benton, A. L., Hamsher, K., Varney, N. R., & Spreen, O. (1983).Facial recognition, form SL: Stimulus and multiple choice pic-lures. Iowa City: Dept. of Neurology, University of IowaHospitals.

Bettger, J. (1992). The effects of experience on spatial cognition:Deafness and knowledge of ASL. Unpublished dissertation,University of Illinois at Urbana-Champaign.

Bettger, J., KJima, E., Ewan, B., & Smith, C L. (1995). Acquisi-tion of spatial devices in American Sign Language as evi-denced by sentence repetition. In E. V. Clark (Ed.), The pro-

ceedings of the 27th annual Stanford child language researchforum (pp. 81-90). Stanford, CA: CSLI.

Diamond, R., & Carey, S. (1986). Why faces are and are not spe-cial: An effect of expertise. Journal of Experimental Psychol-ogy: General, US, 107-117.

Emmorey, K. (in press). The impact of sign language use on vis-ual-spatial cognition. In M. Marschark & D. Clark (Eds.),Psychological perspectives on deafness. Hillsdale, NJ: Law-rence Erlbaum.

Emmorey, K., Kosslyn, S., & Bellugi, U. (1993). Visual imageryand visual-spatial language: Enhanced imagery abilities indeaf and hearing ASL signers. Cognition, 46, 139-181.

Engberg-Pedersen, E. (1993). Space in Danish Sign Language:The semantics and morphosyntax of the use of space in a visuallanguage. International Studies on Sign Language Researchand Communication of the Deaf, vol. 19, Hamburg, Ger-many: Signum-Verlag.

Farah, M. J. (1996). Is face recognition "special"? Evidence fromneuropsychology. Behavioural Brain Research, 76(1-2),181-189.

Farah, M., Wilson, K., Drain, H., Tanaka, J. (1995). The in-verted face inversion effect in prosopagnosia: Evidence formandatory, face-specific perceptual mechanisms. Vision Re-search, 35(H), 2089-2093.

Fodor, J. A. (1983). The modularity of mind. Cambridge, MA:MIT Press.

Galvan, D. (1989). A sensitive period for the acquisition of com-plex morphology: Evidence from American Sign Language.In E. Clark (Ed.), Proceedings from the Stanford Child Lan-guage Research Forum. Stanford, CA: CSLI.

Liddell, S (1980). American sign language syntax. The Hague:Mouton Publishers.

McCullough, S., & Emmorey, K. (1997). Face processing by deafASL signers: Evidence for expertise in distinguishing localfeatures. Journal of Deaf Studies and Deaf Education, 2,212-222.

Nachson, I. (1995). On the modularity of face recognition: Theriddle of domain specificity. Journal ofClinical ££ Experimen-tal Neuropsychology, 17, 256-275.

Parasnis, I., Samar, V, Bettger, J., & Sathe, K. (1996) Does deaf-ness lead to enhancement of visual spatial cognition in chil-dren? Negative evidence from deaf nonsigners. Journal ofDeaf Studies and Deaf Education, 1(2), 145-152.

Reilly, J., Mclntire, M., & Bellugi, U. (1990a). Faces: The rela-tionship between language and affect. In V. Volterra & C.Erting (Eds.), From gesture to language in hearing and deafchildren (pp. 128-141). New York: Springer-Verlag.

Reilly, J. S., Mclntire, M., & Bellugi, U. (1990b). The acquisitionof conditionals in American Sign Language: Grammaticizedfacial expressions. Applied Psycholinguistics, 11, 369-392.

Talbot, K. F., & Haude, R. H. (1993). The relationship betweensign language skill and spatial visualization ability1: Mentalrotation of three-dimensional objects. Perceptual and MotorSkills, 77, 1387-1391.

Yin, R. K. (1969). Looking at upside-down faces. Journal of Ex-perimental Psychology, 81, 141-145.

Yin, R. K. (1970). Face recognition: A special process} Unpub-lished doctoral dissertation, Massachusetts Institute ofTechnology, Cambridge.

Documents

The Journal of Deaf Studies and Deaf Educationlcn.salk.edu/publications/1997/Bettger - Facial discrimination ASL... · The Journal of Deaf Studies and Deaf Education J. Deaf Stud