seeing sentence boundaries

Sign Language amp Linguistics 102 (2007) 177ndash200issn 1387ndash9316 e-issn 1569ndash996x copy John Benjamins Publishing Company

Seeing sentence boundaries

Jordan Fenlon Tanya Denmark Ruth Campbell and Bencie WollUniversity College London

Linguists have suggested that non-manual and manual markers are used in sign languages to indicate prosodic and syntactic boundaries However little is known about how native signers interpret non-manual and manual cues with respect to sentence boundaries Six native signers of British Sign Language (BSL) were asked to mark sentence boundaries in two narratives one presented in BSL and one in Swedish Sign Language (SSL) For comparative analysis non-signers undertook the same tasks Results indicated that both native signers and non-signers were able to use visual cues effectively in segmentation and that their decisions were not dependent on knowledge of the signed language Signed narratives contain visible cues to their prosodic structure which are available to signers and non-signers alike

Keywords segmentation sentence boundaries

1 Introduction

In this paper we show that visual cues in production are used by native signers to indicate sentence boundaries and that these visual cues can also be seen by those who do not know a signed language These findings as part of a larger study investigate the importance of visual cues in British Sign Language (BSL) in com-munication and language processing in general

11 Prosody and boundary detection in spoken and signed languages

Spoken languages use prosody to group words into phrases These phrases are marked by suprasegmental cues such as a phrase-final lengthening a rise or fall in pitch a change in intensity or pauses (Cruttenden 1995 Warren 1996) Evidence from perceptual studies involving spoken languages have illustrated that these prosodic cues have an important role in language processing and comprehension

178 Jordan Fenlon Tanya Denmark Ruth Campbell and Bencie Woll

(Cutler Dahan amp Van Donselaar 2007 Frazier Carlson amp Clifton Jr 2006 Pynte amp Prieur 1996) In particular when people listen to speech they use cues from pros-ody to organise the message into phrases so that they may be better understood Prosodic cues used to indicate boundaries not only indicate when the speaker has finished talking but can also resolve syntactic ambiguities (Pynte amp Prieur 1996) and listeners in English are also able to predict whether an utterance is complete using cues from prosody (Grosjean amp Hirt 1996) Additionally it has been shown that listeners are able to reliably indicate boundaries in a language that they do not know using prosodic cues alone (Carlson Hirschberg amp Swerts 2005) Us-ing fragmented Swedish utterances of varying length two groups of participants (speakers of American English and speakers of Swedish) were not only able to predict whether or not a boundary would occur but could also predict the strength of the upcoming boundary Since one group (the American English group) did not know Swedish prior to testing the authors concluded that it is possible to predict boundaries in the absence of lexical and grammatical cues that come from know-ing the language using prosodic cues alone Interestingly the test sentences were fragmented so as to eliminate the most obvious cue in boundary detection pauses As a result participants had to rely on intonational cues (such as pitch and length-ening) on which to base their decisions

As we turn to signed languages there are many questions to consider What does prosody look like in sign languages What are the functions of prosody in sign language Is sign language prosody different or similar to spoken language prosody There has been little formal research in this field and very little in BSL to date As a consequence the research referred to here reflects findings in other signed languages (namely American Sign Language (ASL) and Israeli Sign Lan-guage (ISL)) and although it is understood that worldrsquos signed languages are not universal they can be very similar (Aronoff Meir amp Sandler 2005 Meier 2002 Newport amp Supalla 2000) As there is little typological research looking at prosodic cues in sign language any similarity (or differences) between sign languages in how prosodic cues are used to mark boundaries would have a significant effect on the outcome of this study Whilst we expect that sign language prosody may vary from one to another sign language the findings in other sign languages will form the basis of investigation into visual cues present in BSL and SSL narratives

For sign language prosody Wilbur (1999) states that there is no modality ef-fect (aside from form) above the syllable (the syllable being a level in the prosodic hierarchy (Nespor amp Vogel 1986)) That is signed languages have a prosodic system that is comparable in function to spoken languages and a signed stream can be re-structured into prosodic constituents and marked by suprasegmental cues (Brentari amp Crossley 2002 Sandler 1999 Sandler amp Lillo-Martin 2006) These prosodic cues can occur simultaneously (prosodic layering (Wilbur 2000)) and sequentially

Seeing sentence boundaries 179

For instance Wilbur (1994 1999) states that blinking in American Sign Lan-guage (ASL) is ldquolinguistically constrainedrdquo She identifies a class of blinks which she calls periodic blinks that occur at intonational phrase (IP) boundaries and pattern in a similar way to breaths in spoken languages In another study dura-tion (lengthening) is identified as a kinematic feature that occurs in phrase final position1 (Wilbur amp Zelaznik 1997) a position that has been reported as more prominent than other phrase boundaries (Nespor amp Sandler 1999) Furthermore IP boundaries are marked by a change in head or body position and an lsquoacross the boardrsquo change in facial expression Other non-manual phenomena have been linked to sign language prosody Brow movements in sign languages are thought to be intonational lsquotunesrsquo (although named superarticulation in light of the dif-ference in modality (Sandler 1999)) which distinguish between declaratives and interrogatives (Sandler amp Lillo-Martin 2006 Nespor amp Sandler 1999) in a par-allel way to spoken language intonational tunes Additionally head tilts and eye gaze (MacLaughlin 1997) and body leans (Brentari amp Crossley 2002 Wilbur amp Patschke 1998) have been classed as domain markers Although systematic manu-al and non-manual behaviour has been observed in signed languages few studies have investigated how native signers perceive them Do they access a broad range of cues to indicate boundaries or is there a single cue that they attend to What is the most reliable (and frequent) indicator of sentence boundaries in signed lan-guages (like pauses in spoken languages)

Perceptual studies in sign languages have revealed that like spoken languages signers use visual cues to group signs into phrases in ASL (Nicodemus 2007) In her study which involved ASL native signers segmenting an interpreted lecture Nicodemus investigates what visual cues coincide with a cluster of agreement (6 or more ASL participants) and reports a number of cues occurring simultaneously and sequentially at boundary points She found cues involving larger articulators to be those most frequent at boundary points (such as hand clasps and body leans) and suggests that if these (larger) cues are more successful at indicating bound-ary points in ASL then the cues used may be driven by the perceptual need of the viewer (cues involving larger articulators are more frequent than others such as blinks and brow movement)2 In another study it was revealed that non-signers were able to use visual cues to determine the presence of a(n IP) boundary in ASL

1 Wilbur amp Zelaznik identify two further kinematic features velocity and displacement They note that velocity marks prominence while displacement is dependent on the categories of ve-locity and duration

2 Since Nicodemusrsquo study involves ASL interpreters it is possible that they may differ from ASL native signers in the occurrence and temporal organisation of prosodic cues at boundary points


performing at a level similar to a group of ASL native signers (Brentari 2007) Interestingly the groups appeared to differ in their strategies The non-signers at-tended to a broad range of cues3 whilst signers focused on a single cue Brentari suggests that familiarity allows native signers to use a specific cue to isolate bound-aries whilst non-signers must search a broader range of cues Taken together these perceptual studies support a cue-based approach to sign language segmentation However it has also been shown that whilst formal markers such as blinks change of gaze lengthening and transitions are useful in determining sentence boundar-ies in German Sign Language (DGS) they are not conclusive for sentence bound-aries and can not be determined independently from meaning in DGS (Hansen amp Heszligmann this volume)

12 Research questions

Despite advances in sign language research little is known about the production and perception of prosodic cues at sentence boundaries in BSL How do native signers decide where the ends of sentences are in a signed stream What cues may native signers recruit to decide where a boundary occurs Can boundaries be reli-ably detected using prosodic cues alone This study aims to clarify exactly what sentence segmentation involves whilst setting the groundwork for future research

In a similar line of enquiry how might a native signer of BSL segment an unknown sign language If sign languages do show limited cross-linguistic varia-tion with respect to prosodic marking we might expect that native signers have an advantage over non-signers That is they would have a lsquomodalitytypology ad-vantagersquo in that they would understand how sign languages (in general) structure and mark their constituents and be able to apply this language experience when segmenting an unknown language

To explore this question we additionally asked how well a non-signer might perform on segmentation tasks in comparison to a native signer Can prosodic cues used to mark boundaries be detected on a lsquosuperficialrsquo level The inclusion of non-signers in the present study not only allows us to explore what sign lan-guage segmentation involves but enables us to address the question of what is sign language-specific knowledge and what can be recognized by those who do not know a signed language Although hearing non-signers have no experience of using sign languages speakers do use facial expressions on a prosodic level whilst speaking (Bolinger 1986) Therefore non-signers may be able to detect boundar-ies in sign languages by using cues with which they are familiar from face-to-face spoken communication

3 Brentarirsquos study focuses on five cues pauses blinks holds lengthening and drop hands


In sum this study addresses the following research questions

1 Which potential cues are evident in a signed narrative and how do they relate to prosodic boundaries

2 Can these prosodic cues reliably indicate boundaries on their own (in the ab-sence of cues from the grammar)

3 How do non-signers and native BSL signers compare when segmenting a BSL narrative into sentences

4 How do native BSL signers and non-signers compare when both segment an unknown sign language

5 How do native BSL signers perform on their own SL compared to an unknown SL

The following study will focus on the perception of IP boundaries in relation to syntactic structure Since syntactic and prosodic structure are non-isomorphic (Nespor amp Vogel 1986) not all IP boundaries will coincide with the end of a sen-tence However we predict that native signers will be better able to identify IP boundaries that co-occur with the end of a sentence since they can access cues from the grammar (such as being able to detect the absence of a linguistic ele-ment) Since hearing non-signers are unable to define a sentence in a signed nar-rative using cues from the grammar they must look to prosodic cues in order to successfully mark the end of a sentence If prosodic cues are not reliable markers of sentence boundaries then we expect to see no pattern of differences in non-signers between the identification of IP boundaries that occur at the end of sentences and those that do not However if non-signers are able to correctly indicate IP boundaries that co-occur with sentence boundaries this would not only suggest that these boundaries are marked differently from other IP boundaries but that visual cues alone can reliably indicate sentence boundaries The inclusion of an unknown sign language will allow these suggestions to be tested further since both groups will be unable to access lexical or grammatical information and must rely on prosodic cues alone

2 Methodology

Six Deaf native BSL signers (4 females) and six hearing non-signers (4 females) were recruited for this study Four of the native signers have two signing parents the remaining two deaf participants have one signing parent The six non-signers had no previous knowledge of any sign languages


Four narratives (produced by different signers) were taken from the ECHO4 corpus (two in BSL (Woll Sutton-Spence amp Waters 2004) and two in Swedish Sign Language (SSL) (Bergman amp Mesch 2004)) Two narratives were used for the seg-mentation task and two for practice Each narrative consisted of a retelling of one of four different Aesoprsquos fables to an unseen addressee The narratives which were segmented and are analyzed here are lsquoThe Tortoise and the Harersquo presented in BSL and lsquoTwo Friends and the Bearrsquo presented in SSL Both narratives are one and a half minutes long and are told by male signers An annotated file providing a detailed transcription was available for each fable each transcribed by different coders

Narratives were presented to participants using ELAN5 software ELAN was ideal for the study since participants could use the on-line segmentation controls to mark boundaries whilst simultaneously watching the narratives Participants could not see the annotation viewer in ELAN so that their responses were not influenced by existing codings or a previous participantrsquos responses The order in which these narratives were shown varied between participants Participants had two practice runs (one for BSL and one for SSL) in order to familiarize themselves with the tasks Each practice task was immediately followed by the experimental task in the selected language Participants were asked to press a button whenever they saw a sentence boundary The test took no more than 30 minutes in total to complete Responses for each participant were recorded in the annotation tier of ELAN so that participantsrsquo responses could be compared with each other and with a detailed transcription (provided by the ECHO corpus)

Participants were asked to segment each narrative twice so that intra-partici-pant reliability could be assessed This method has advantages since increased de-mands on decision making and hesitation present a confounding variable for the study Since participants parsed the narrative in real time they had little time to think about their decisions Additionally each participant was offered an optional third attempt at the task if they felt they had not done well at the task Only one participant (a native signer) chose to do this (for the SSL narrative)

Before assessing participantsrsquo responses all IP boundaries in both the BSL and SSL narrative were identified using a cue-based approach Firstly the occurrence of a blink between signs was used to indicate possible IP boundaries and these boundaries were further verified by the presence of other cues such as pauses and

4 The ECHO corpus provides video data which can be viewed with an annotated file (using ELAN) for three sign languages Sign Language of the Netherlands (NGT) British Sign Lan-guage (BSL) and Swedish Sign Language (SSL) For each sign language five fable stories are available The corpus is located at httpwwwletrunlsign-langecho

5 The ELAN software is freely available from httpwwwlat-mpieutoolselan


head nods Since these cues have been identified as IP markers in signed languages other than those used in this study (such as ASL and ISL) we assume that they were also found in BSL and SSL In order to strengthen our analysis these deci-sions were verified by asking native signers with a background in linguistics to judge whether a boundary had occurred or not Following identification a strict 15 second window was applied to all IP boundaries in both signed narratives in which responses associated with that boundary could occur The starting point for this window was fixed at the end of the final sign in an IP specifically the last frame in which the hand-shape of the final sign was held the window was then extended to 05 seconds before that frame and 1 second afterwards In total 26 IP boundaries were identified in the SSL narrative and 21 IP boundaries in the SSL narrative The following section describes the responses logged and the cues pres-ent at these boundaries Since prosodic constituency can be determined in part by the speakerrsquos style (such as the speed of delivery) more than one sentence may be contained within an IP Additionally participants may have responded to other boundaries (such as a phonological phrase boundary or a syntactic boundary) elsewhere in the narrative These are possibilities the researchers are aware of and have not dismissed However results indicate that the majority of responses from both groups in both narratives fall at IP boundary points Findings discussed here are restricted to these responses

3 Results

31 BSL narrative

Table 1 below shows the total number of responses from both the native sign-ers and hearing non-signers whilst watching the BSL narrative The figures given here represent the number of responses during the first and second attempt at segmentation the total number of responses that were in agreement (occurring within one second of another response) and the total number of responses for each group

Responses from the native signers whilst watching the BSL narrative were slightly higher than for the hearing non-signers across all four columns No sig-nificant group differences were observed when intra-participant reliability was

Table 1 Total number of button pushes for the BSL narrative

BSL Narrative 1st attempt 2nd attempt In agreement TotalDeaf participants 81 87 106 (53 pairs) 168Hearing non-signers 73 77 98 (49 pairs) 150


assessed Both groups show a similar number of responses for their first and sec-ond attempts at segmentation Additionally for both groups the majority of re-sponses in the first run occurred within one second of a response in the second run (63 for the BSL signers and 65 for the non-signers) However these figures only reflect the total number of responses across the whole BSL narrative Table 2 represents the number of responses that occurred within the 26 IP boundaries (the 15 second window) that we identified in the BSL narrative

Of the total number of responses logged by the native signers in the first run 74 occurred at the 26 IP boundaries identified whilst 26 did not For both groups the majority of responses occurred at an IP boundary For the native sign-ers more responses in agreement are recorded at IP boundaries (88) compared to the non-signers (69) An overview of the data reveals that responses were not equally distributed at all IP boundaries but had a tendency to cluster at certain IP boundaries Across the BSL narrative we recorded 13 boundaries (out of 26) that displayed a majority response (3 or more participants) from either group These were identified as lsquostrongrsquo boundaries for the purpose of further analysis (below)

Since a relatively high number of boundaries were identified from cues across each narrative random pressing of the keys could have coincided with boundaries simply by chance In order to test whether either group responded to boundaries at a level significantly different from that predicted by random pressing simu-lated group data (lsquorandom grouprsquo) were generated and the data for this group were compared with the other groups

In order to create the random group data the experiment was recreated in Excel Firstly the number of intervals was calculated (length of narrative divided by 15 second windows) which gave us 57 intervals for the BSL narrative Secondly the average number of responses per group was calculated (14 responses per na-tive signer and 13 responses per non signer) For each group we then recreated 20 trials with six participants to a trial Using a random distribution function in Excel we distributed responses at random across 57 intervals in each trial Fol-lowing distribution 26 intervals were chosen at random to represent IP bound-aries and the number of responses that fell in these intervals was counted Since responses from the actual experiment were not distributed evenly but tended to cluster at certain boundaries a further 13 intervals were chosen at random (from the 26 already selected) to represent lsquostrongrsquo boundaries and the number of re-sponses that fell in these intervals were calculated The results from the random

Table 2 Number of button pushes that occurred at an IP boundary in the BSL narrative

BSL Narrative 1st attempt 2nd attempt In agreement TotalDeaf participants 60 (74) 59 (62) 94 (88) 119 (71)Hearing non-signers 48 (65) 52 (67) 68 (69) 100 (66)


trials are displayed below in Table 3 alongside the data from the native signers and non-signers That shows that for the random group 6 responses fell within the 26 identified boundaries with just 3 within lsquostrongrsquo boundaries

Table 3 shows the numbers of boundaries marked by each native signer and non signer in relation to the random data pattern obtained according to the ra-tionale above In order to test for significant differences between real and random groups the random data pattern was used to construct a dummy group compris-ing 6 data sets reflecting the distribution outlined above (ie 6 responses within overall boundaries of which 3 were within strong boundaries) and the data were subjected to nonparametric between-group tests (MannWhitney) applied to the following pairs random vs native signers random vs non-signers In addition native signers vs non-signers were compared For random vs native signers no significant difference was found for responses occurring for the 26 IP boundar-ies However a significant difference was found for responses occurring at the 13 lsquostrongrsquo IP boundaries (both attempts U = 000 p lt 01) That is responses oc-curring at these 13 IP boundaries are at a level significantly greater than chance This finding was replicated for random vs non-signers (both attempts U = 000 p lt 01) For native signers vs non-signers no significant difference was found

Table 3 BSL narrative button pushes at IP boundaries by participant and group

1st attempt 2nd attemptNative signers All IPs 13 IPs All IPs 13 IPsPS01 16 10 14 8PS02 12 8 12 9PS03 5 4 5 4PS04 9 9 11 10PS05 6 6 8 5PS06 12 10 9 8TOTAL 60 47 59 44Non signers All IPs 13 IPs All IPs 13 IPsPS07 8 6 11 9PS08 9 8 9 8PS09 9 8 7 7PS10 6 5 8 8PS11 9 7 12 8PS12 7 7 5 5TOTAL 48 41 52 45

(compared to random group data 63)


32 SSL narrative

Table 4 shows the total number of responses for the native signers and hearing non-signers whilst watching the SSL narrative As before the figures given here represent the total number of responses for the first and second attempt at seg-mentation and the total number in agreement with each other across the entire SSL narrative

Table 4 Total number of button presses for the SSL narrative

SSL Narrative 1st attempt 2nd attempt In agreement TotalDeaf participants 75 78 96 (48 pairs) 153Hearing non-signers 77 76 102 (51 pairs) 153

In Table 4 we can see that the total number of responses is highly similar between the two groups Again no significant group differences were observed when in-tra-participant reliability was assessed Both groups show a similar number of re-sponses for their first and second attempts at segmentation In both groups the majority of their responses in both runs occurred within one second of each other (63 for the native signers and 67 for the non-signers) Table 5 displays the total number of responses that occur at the 21 IP boundaries marked in the SSL narra-tive As before the percentages are also given

Table 5 Number of button presses that occurred at an IP boundary in the SSL narrative

SSL Narrative 1st attempt 2nd attempt In agreement TotalDeaf participants 46 (61) 52 (67) 80 (83) 98 (64)Hearing non-signers 50 (64) 51 (67) 88 (86) 101 (66)

In both groups the majority of responses are recorded at IP boundaries and the total number of responses from both groups is very similar A large majority of responses that were in agreement also occurred at IP boundaries for both groups (83 for the native signers 86 for the non-signers) Additionally at 12 IP bound-aries a majority response from one or the other group was observed In order to assess whether either group responded to boundaries at a level significantly differ-ent than that predicted by random pressing we again created random data as we did for the BSL narrative (59 intervals and 13 responses per participant for both groups) The data for each participant and group are displayed in Table 6 along with the random group data

5 IP boundaries and 3 lsquostrongrsquo IP boundaries were identified by random dis-tribution Both groups and the random dummy group were then subjected to nonparametric between-group tests (MannWhitney) We found that there was a significant difference between native signers vs random only for the second trials


(U = 000 p lt 01) for all IPs and 12 IPs That is responses for the second run oc-curred at a level greater than chance This finding was replicated for non-signers vs random (U = 000 p lt 01) No significant difference was observed between na-tive signers and non-signers

33 Discussion

Firstly our results indicate that the stimulus material and our partitioning of the stimulus display sequence may not reveal a simple relationship between possible cues and boundaries when 15 second boundary tolerances are imposed The number of 15 sec windows that represent IP boundaries is not much greater than the total number of 15 sec windows present (2653 for the BSL narrative 2159 for the SSL narrative) Unsurprisingly therefore random responding would have coincided with actual boundaries about as frequently as actual responses Thus we do not observe a significant difference from chance for either group watch-ing both narratives when the dependent variable is the lsquorawrsquo boundary response score However we do see a significant difference when we isolate IP boundar-ies which recorded a high level of agreement among respondents This group of lsquostrongrsquo IP boundaries for both the BSL and SSL narrative differ significantly from the random group data (although not for the first attempt at SSL narrative) An

Table 6 SSL narrative button pushes at IP boundaries by participant and group


(Compared to random group data 53)


important finding here is that there appears to be no significant difference between signers and non-signers when watching either narrative Both the frequency data and statistical tests reveal that the native signers and non-signers respond in a similar way Non-signers are clearly capable of indicating boundaries since the majority of their responses in both the BSL and SSL narratives not only agree with one another but occur at IP boundaries that we have identified in this study Ad-ditionally native signers of BSL also show that they are able to indicate boundar-ies in a language that they do not know Therefore it appears that manual and non-manual cues are highly informative for segmentation That these cues appear to be accessible to both non-signers and native signers suggests that there are no specific cues available exclusively to those who know the language (as is the case for the BSL task) and that signers appear to have no lsquomodality advantagersquo over non-signers when marking boundaries in an unknown sign language In the fol-lowing section we will discuss specifically where responses occur in order to shed more light on any strategies in boundary marking across groups and narratives in relation to specific boundary points and the cues that mark them

4 Linguistic analysis

In this section we discuss the nature of the visual cues found at boundaries in both narratives In the previous section it was shown that the number of responses from each group for each boundary varied in a similar way That is some bound-aries recorded a high level of responses and some boundaries received few or no responses What is it that makes these boundaries different from each other so that some boundaries can be identified correctly even by those who do not know the language Does the explanation lie in the type or number of cues used at a bound-ary In the following sections we present a general picture of cues present in each signed narrative before focusing on cues present at all IP boundaries we isolated and then specifically at those which show a high level of agreement

41 Prosodic layering

Because of the nature of responses (participants are segmenting narratives on-line) and because sign languages can articulate prosody both simultaneously and sequentially it is difficult to identify the primary cues used to mark boundar-ies based on single responses This is illustrated in Figure 3 (taken from the SSL narrative)6

6 Boundary markers are glossed using the convention lsquorsquo


bjoumlrn aldrig anfalla naringgon doumld (bear) (never) (attack) (someone) (dead)Figure 1 lsquobears wonrsquot attack you if you play deadrsquo

In Figure 1 the boundary occurs after doumld marked with a backward head tilt raised eyebrows and a hold on the final sign doumld These cues occur simultane-ously and are followed by a head nod Five native signers and four non-signers marked this boundary Interestingly for the non- signers five responses occurred before the onset of the head nod and coincide with the hold on doumld In contrast three responses (from the same group) coincide with the head nod following doumld This variation in timing of responses indicates that multiple cues are available to participants and that an analysis based solely on timing is problematic Partici-pants may use one cue to mark a boundary (as is the case with five responses from the non-signers) or more than one cue such as a hold followed by a head nod Additionally where two cues are present only one of these cues may be used in boundary marking

In both the BSL and SSL narrative the number of different cues recorded at the IP boundaries we isolated for the study varied from 2 to 8 We compared the num-ber of responses from each group to the number of cues present at each boundary to determine whether we could see a relationship In other words does multiple cue-marking make a boundary perceptually stronger A correlation analysis re-vealed no relationship between the number of cues present at an IP boundary and the number of responses for both groups watching the SSL narrative Additionally no significant relationship was observed for the hearing non-signers watching the BSL narrative However a weak correlation was recorded between the number of cues present and responses from the native signers for the second attempt (= 548 p =lt 005) and for responses that were in agreement with one another (= 567 p =lt 005) This may be evidence for different boundary marking strategies be-tween the two groups (or for the native signing group watching a signed narrative in their native language) but this will need to be tested using different measures (the number of available cues is small so correlations are unlikely to be strong since the range of scores is limited) and with a larger group of respondents


42 Overview of visual cues

In order to determine boundary locations prior to setting the segmentation task each narrative was carefully analysed for the presence of visual cues This was how the 26 boundaries in the BSL narrative and 21 boundaries in the SSL narrative were established Now we will examine which cues contributed to these boundar-ies and the extent to which the experimental respondents performing the online sentence segmentation task were sensitive to them Each IP boundary was coded for 9 different cues Although annotations in both the BSL and SSL files were avail-able from the ECHO corpus we also created our own annotations for certain cate-gories (such as hold and head rotations) Each cue was associated with a particular boundary point if it occurred in (or overlapped in part with) a one second window applied to all IP boundaries The starting point for this one second window began from the last frame in which the hand-shape of the final sign in a phrase was held and extended 05 seconds before and after this point The table below represents the total number of each cue found at IP boundaries the total number for each cue found across both narratives and the proportion of each cue found at IP boundar-ies given in percentages (when weighed against the number of occurrences across the entire narrative)

Table 7 Overview of cues in the signed narratives and at IP boundariesBSL Narrative SSL NarrativeNumber at lsquostrongrsquo IP boundaries

Number at IP boundaries

Total number present

Number at lsquostrongrsquo IP boundaries



Head Rotation 11 (25) 19 (43) 44 5 (12) 10 (24) 41Head Nod 5 (45) 6 (55) 11 4 (36) 7 (64) 11Head Movement 1 (6) 10 (63) 16 4 (40) 8 (50) 16Blinks 13 (28) 21 (45) 47 7 (16) 13 (30) 44Eye-gaze 8 (9) 15 (18) 85 8 (11) 10 (14) 72Eyebrows 9 (33) 17 (63) 27 5 (29) 12 (71) 17Hold 7 (88) 7 (88) 8 7 (44) 9 (56) 16Pauses 2 (50) 3 (75) 4 4 (57) 6 (86) 7Drop Hands 3 (100) 3 (100) 3 2 (100) 2 (100) 2

In Table 7 IP boundaries marked as lsquostrongrsquo are those that attracted the highest number of responses These boundaries were identified by four or more native signers or hearing non-signers The total number of lsquostrongrsquo IP boundaries marked were 13 for the BSL narrative (out of 26) and 12 for the SSL narrative (out of 21)


Head rotation Head nods Head movementsFor the head we assigned three separate categories The first category represents all head rotation which was defined as a single head rotation in any plane Strictly speaking this means head nods fall under this category but since they are said to have a rhythmic function and mark IP boundaries in ISL (Nespor amp Sandler 1999) they were coded as a separate category The head movement category was used for repeated head movements In both narratives head rotations were one of the most frequent cues (after eye-gaze and blinks) present across the whole narrative The high frequency of head rotations in both narratives may be related to the nature of the stories as a change in head position may be used to represent a change in role or point of view Since both signed narratives are stories that involve more than one character it is not surprising that a high number of head movements and head rotations are found These cues are discussed further in 43

BlinksBlinking was one of the most frequent cues observed across both narratives but only a small proportion of blinks were detected at boundaries with high agree-ment It is difficult to ascertain whether blinks are used as a primary cue for boundary detection by participants Blinks in ASL and ISL have been claimed to pattern in a similar way to breaths in spoken languages (Wilbur 1999 for ASL Nespor amp Sandler 1999 for ISL) In both of these languages blinks are optional but have a tendency to occur at IP boundaries so it might be assumed that they are a reliable indicator of boundaries However for online segmentation they are not highly visible and cues using larger articulators (such as the head or hands) may be favoured

Eye-gazeThe term eye-gaze is used to refer to any point of change in eye-gaze Eye-gaze rep-resents the most frequent cue in both narratives Again only a small proportion of eye-gaze changes were detected at boundaries

Brow movementThe term brow movement refers to any change in brow position Brows may be furrowed raised or in neutral position The majority of brow movements were found at IP boundaries in general for both narratives which is consistent with Nespor and Sandlerrsquos (1999) analysis of ISL in which IP boundaries are marked with an lsquoacross the boardrsquo change in facial expression Since the use of the brow in sign languages is often compared to intonation in spoken languages we might view a lsquoresettingrsquo of brow position as comparable to a resetting of pitch for a new constituent in speech


HoldsIn some cases the hand-shape of a sign was held in its final position for an ex-tended duration This was identified primarily by calculating the average length of phrase-internal signs Signs that were longer than average were then examined to see if they could be classed as holds For both narratives holds were one of the most frequent cues present at lsquostrongrsquo IP boundaries

PausesPauses are one of the least frequently occurring cues in both narratives Where they do occur they almost always found at IP boundaries

Drop HandsDrop hands were the least frequently occurring cues for both narratives but all instances occur at lsquostrongrsquo IP boundaries Although we might say that their oc-currence marks an IP boundary their occurrence is only associated with specific points in the narrative structure for both BSL and SSL after the title of the fable and at the end of the story

43 Discussion

An overview of visual cues in both signed narratives shows that the three cues most strongly associated with lsquostrongrsquo IP boundaries were pauses drop hands and holds These cues occurred relatively infrequently and when they did they occurred mainly at boundary positions In contrast blinks occurred more fre-quently throughout the narratives with a relatively lower proportion at boundary positions In signal detection terms this would mean that pauses drop hands and holds showed greater sensitivity (higher lsquohitsrsquo lower lsquofalse alarmsrsquo) compared with blinks This differential distribution of salient cues may have guided respondents Additionally pauses drop hands and holds are highly visible cues and they all involve the cessation of movement for both hands The transition between move-ment and no movement clearly marks boundaries in signing This may be the most important characteristic of actions signaling sentence boundaries for viewers re-gardless of whether they know the language or not

The cues identified at boundary points (both lsquostrongrsquo and other IP boundar-ies) not only are the same as those identified in prosodic research in other signed languages but also indicate that these prosodic cues are applicable to narratives as well as single sentences although with important differences We recorded a high number of head rotations in both narratives which we attribute to the nature of the narratives they are stories featuring multiple characters The head performs semantic and domain marking functions which distinguish between roles and


point of view and the domain in which a selected character lsquospeaksrsquo The use of this linguistic device indicates that head rotation is sensitive to boundary points and may be used by participants to segment narratives as seen below

which arrive first proof

alright well if-you-wishFigure 2 lsquohellip wersquoll see who arrives first alright Wellhellip if you wishhelliprsquo

In this example the head faces the right periphery of the signing space and then switches to the left periphery of the signing space The identification of this bound-ary by non-signers shows that they are as effective at interpreting these non-man-ual features as marking boundaries as are native signers Very similar devices (the use of the head to represent a characterrsquos point of view) can be used in spoken language face-to-face communication (McClave 2000) Therefore knowledge of how gestural cues are used in spoken language may be applied here

Similar observations can be made for the SSL narrative The SSL narrative fea-tures a conversation between two speakers As in the BSL narrative orientations of the signerrsquos head (towards the left or right periphery of the signing space) are used to mark each characterrsquos voice Although the body does not change position the role shift is accompanied by a slight backwards body lean Both signers and non-signers marked a boundary preceding NEJ7

7 In addition to head movements this boundary is marked by other non-manuals such as a lengthening of the final sign oumlra and the onset of raised eyebrows on nej These are further candidates as cues for triggering a response from participants


beraumltta naringgot hemlig till (tell) (something) (secret) (to)

dig oumlra nej (to-you) (ear) (no)Figure 3 lsquohellip he must have whispered a secret in your ear No helliprsquo

This example raises the question of the extent to which we can be certain that ei-ther group is interpreting non-manual and manual cues at a superficial level when segmenting an unknown sign language As with the BSL narrative non-signers may be using their experience of gestural cues in face-to-face communication to mark boundaries Additionally the signing group may be able to apply their un-derstanding of role shifts in BSL to SSL Brentarirsquos (2007) study revealed that sign-ers and non-signers differed in the strategies used to identify IP boundaries Her data showed that signers attended to specific cues whilst non-signers attended to a broad range of cues and that these differences were due to differences in language exposure We have not seen similar results here but our sample size is too small for any possible difference to be observed However if the high occurrence of head rotation and head movements is characteristic of narratives and are cues used by both native signers and non-signers then both groups demonstrate that they can adapt their strategies to whatever prosodic cues are available to them

5 Discussion

When asked to indicate sentence boundaries in a signed narrative native signers are able to use visual cues as a means to identify boundaries Since native signersrsquo responses agree with those of hearing non-signers when watching either the BSL or SSL narrative we can assume that not only do native signers use visual cues to determine sentence boundaries in their own language but that these visual cues can also be seen by those who do not know a signed language This is further


supported by findings in the SSL narrative No significant differences were ob-served between native signers (of BSL) and hearing non-signers when watching a language that they both do not know Again since no differences between the two groups are found we infer that language experience may play little part here These suggestions need to be subjected to a large scale study before they can be confirmed

However although no differences are observed between signers and non-signers the responses of both combined presented interesting results Not all IP boundaries were marked with a high level of agreement Only those that coincided with the end of a sentence (according to the participants) were marked with a high level of agreement The non-signers were able to indicate these boundaries in both the BSL and SSL narratives which suggest that not only is knowledge of syntax not a prerequisite to define a lsquosentencersquo in signed language but also that some IP boundaries (that do coincide with the end of a sentence) are perceptually stronger than others This must mean that not only are IP boundaries marked differently but also that they interact with the syntax in a way so that important boundaries (such as the end of a sentence) may be more marked than others Additionally this finding also suggests that non-signers are not only able to indicate the presence of a boundary in a signed narrative but they can also predict the strength of that boundary on prosodic cues alone More research is needed to discover exactly how these boundaries differ whether in duration intensity or type of cue marking

The potential cues available to participants are similar to those found in other sign languages such as ISL and ASL and the non-signers performance in both the BSL and SSL narratives indicate that these cues can reliably indicate boundaries on their own (in the absence of cues from the grammar) In this study we have shown that there are multiple cues available to participants when segmenting a signed language However because these cues can occur simultaneously and sequentially it is difficult to pinpoint which cue participants may be using to segment each nar-rative particularly in a real-time on-line segmentation test However some con-clusions can be drawn here Firstly the number of cues present at each band varies from 2 to 8 which is evidence of prosodic layering (Wilbur 2000) Secondly some cues such as pauses drop hands and holds have a tendency to occur only at lsquostrongrsquo IP boundaries although there other cues were frequently present such as head ro-tation head nods blinks and eyebrows Thirdly looking at Table 7 it is clear that similar cues are present at strong IP boundaries in both the BSL and SSL narrative which may indicate that participants are looking for the same cues in a signed nar-rative regardless of whether they know the language or not A larger sample size is needed to pinpoint differences (if any) in boundary marking strategies between groups That is whether one cue is more successful at indicating boundaries for a particular group Finally we have said that the many occurrences of head rotation


and head movements may be unique to narratives What is also clear is that sign language segmentation involves devices that are also used in spoken language seg-mentation Vaissiegraverersquos (1983) typological study indicates that unrelated languages exhibit similarities in the function and form of prosodic cues Our findings sug-gest that there is a modality-independent match between elements in spoken and signed languages For example both signed narratives use phrase-final lengthen-ing to mark phrases Therefore non-signers watching a signed narrative may rec-ognise an abstract category of lsquoholdrsquo as one possible method of lengthening and apply knowledge of how spoken language is structured prosodically (phrase-final lengthening) to the analysis of signed languages Alternatively the visual features of narratives may be the same in signed narratives and spoken narratives per-ceived audio-visually (eg the use of the head for role shifts) ie the visual prosody of spoken languages uses the same or similar devices as the visual prosody of sign language (Barkhuysen Krahmer amp Swerts 2006 Flecha-Garcia 2006 House 2007 McClave 2000 Munhall Jones Callan Kuratate amp Vatikiotis-Bateson 2004 Pyers amp Emmorey 2008) Bolinger (1986) notes that eyebrow movements correspond with pitch movement and identifies other visual features in spoken language such as movements of the mouth and hands eye contact and the degree to which the eyes are open Speakers can distinguish between questions and statements using brow movements and head position and are able to determine which item is re-ceiving focus or stress using visual cues alone (Bernstein Eberhardt amp Demorest 1998)8 These studies together with the current study suggest that non-signers are not gesturally naiumlve and are able to use experience from spoken languages when determining sentence boundaries in a signed language

Since signed and spoken languages use similar elements (such as head move-ment to represent characterrsquos voice) to mark boundaries these elements may be perceived by participants in a similar way The status of these cues is a matter of interest These elements may be gestural in both signed and face-to-face commu-nication alternatively these elements are gestural in face-to-face spoken commu-nication but have been linguisticised in sign languages (similar claims have been made for negation in Greek Sign Language (Antzakas 2007)) Even if the latter is true it may not apply equally to all visual cues in signed languages since some cues may be more linguisticised than others An in-depth comparative analysis looking at these cues in both signed and face-to-face spoken communication will shed light further on these alternatives

8 Eisenstein amp Davies (2005) report that whilst manual gestures correlate significantly with sentence boundaries in spoken language they are redundant cues in the context of language and pause features The authors argue that gestural cues can be a useful tool for segmenting speech when speech is unclear


Some cautions about the analyses should be mentioned here The BSL and SSL narratives feature two different signers telling stories in two different languages As a consequence it is difficult to ensure that the two narratives are well matched and this may account for differences found in the quantitative and qualitative analysis Cutler and Isard (1980) (cited in Warren 1996) have shown that speakers differ in the prosodic cues used to mark boundaries In their study one speaker marked boundaries by lengthening and the second speaker by changes in pitch If pro-sodic cues are not robust across signers this could present a challenge for each group when marking boundaries For instance the narratives involving a high number of role shifts could lead to an over-reliance by the non-signers on head and body movement to mark boundaries Furthermore the BSL signers may have some variable degree of access to the content of the SSL narrative We interviewed participants following each task in order to determine the extent to which they had understood the narratives The non-signers stated that both tasks (BSL and SSL) presented the same level of difficulty The BSL signers of course found the BSL condition easier than SSL but generally reported that whilst they did not fully understand the SSL narrative they had understood some of the content

Finally not all IPs are isomorphic with the sentence and therefore we need to analyse responses that occurred outside the IP boundaries we isolated in the study It is possible that a single IP could contain more than one sentence since prosodic re-structuring can be influenced by the signerrsquos style Although few responses out-side IP boundaries were recorded (for both groups and for both narratives) these responses may coincide with a lower level prosodic constituent or another syntac-tic boundary The analysis of these responses will provide further evidence to back up the findings presented here

6 Conclusion

Visual cues can be used by both native signers and non-signers to determine sen-tence boundaries Native BSL signers and non-signers perform similarly when segmenting a BSL narrative suggesting that cues from the grammar are not es-sential for segmentation tasks and that cues from prosody are reliable indicators of sentence boundaries This is supported by the findings from the SSL narrative where both groups also performed similarly However we also found that both groups do not respond to all IP boundaries and that responses have a tendency to cluster at certain boundaries over others indicating that some IP boundaries are perceptually stronger than others and can even be identified by those who do not know the language Furthermore visual cues present at IP boundaries reveal a modality-independent match between spoken and signed languages as well as mo-


dality-related cues that may serve to mark boundaries in both sign language and face-to-face spoken language narratives (head rotations) However a larger study is required to verify the findings in this paper and to analyse further the differences (if any) in boundary detection between those who are native users of a language and those who are not These questions have been left for future research

Acknowledgements

This work was supported by Deafness Research UK (Grant 357 Grant Ref 357 Proceedings visual prosody of speech and sign) and by the Economic and Social Research Council of Great Britain (Grant RES-620-2B-6001 Deafness Cognition and Language Research Centre)

References

Antzakas Klimis 2007 Negation in Greek Sign Language Unpublished doctoral dissertation City University London

Aronoff Mark Irit Meir amp Wendy Sandler 2005 The paradox of sign language morphology Language 81(2) 301ndash334

Barkhuysen Pahiera Emiel Krahmer amp Marc Swerts 2006 How auditory and visual prosody is used in end-of-utterance detection In Proceedings of the International Conference on Spo-ken Language Processing (Interspeech 2006) Pittsburgh PA USA

Bergman Brita amp Johanna Mesch 2004 ECHO data set for Swedish Sign Language (SSL) De-partment of Linguistics University of Stockholm

Bernstein Lynne E Silvio P Eberhardt amp Marilyn E Demorest 1998 Single-channel vibrot-actile supplements to visual perception of intonation and stress Journal of the Acoustical Society of America 85 397ndash405

Bolinger Dwight 1986 Intonation and its parts Stanford CA Stanford University PressBrentari Diane 2007 Perception of sign language prosody by signers and nonsigners Paper pre-

sented at Workshop on Visual Prosody in Language Communication Max Planck Institute for Psycholinguistics Nijmegen May 10ndash11 2007

Brentari Diane amp Laurinda Crossley 2002 Prosody on the hands and face Evidence from American Sign Language Sign Language amp Linguistics 5(2) 105ndash130

Carlson Rolf Julia Hirschberg amp Marc Swerts 2005 Cues to upcoming Swedish prosodic boundaries subjective judgment studies and acoustic correlates Speech Communication 46 326ndash333

Cruttenden Alan 1995 Intonation Cambridge Cambridge University PressCutler Anne Delphine Dahan amp Wilma Van Donselaar 2007 Prosody in the comprehension of

spoken language a literature review Language and Speech 40 141ndash201Flecha-Garcia Maria L 2006 Eyebrow raising in dialogue discourse structure utterance func-

tion and pitch accents Unpublished doctoral dissertation University of EdinburghFrazier Lyn Katy Carlson amp Charles Clifton Jr 2006 Prosodic phrasing is central to language

comprehension Trends in Cognitive Science 10(6) 244ndash249


Grosjean Franccedilois amp Cendrine Hirt 1996 Using prosody to predict the end of sentences in English and French normal and brain-damaged subjects Language and Cognitive Processes 11(12) 107ndash134

Hansen Martje amp Jens Heszligmann This volume Matching propositional content and formal markers Sentence boundaries in a DGS text Sign Language amp Linguistics 10(2) ADD PAGES

House David 2007 Investigating expressive auditory and visual repertories in speech Paper pre-sented at Workshop on Visual Prosody in Language Communication Max Planck Institute for Psycholinguistics Nijmegen May 10ndash11 2007

MacLaughlin Dawn 1997 The structure of determiner phrases Evidence from American Sign Language Unpublished doctoral dissertation Boston University

McClave Evelyn 2000 Linguistic functions of head movements in the context of speech Jour-nal of Pragmatics 32 855ndash878

Meier Richard P 2002 Why different why the same Explaining effects and non-effects of mo-dality upon linguistic structure in sign and speech In RP Meier K Cormier amp D Quin-to-Pozos (eds) Modality and structure in signed and spoken languages 1ndash25 Cambridge Cambridge University Press

Munhall Kevin G Jeff A Jones Daniel E Callan Takaaki Kuratate amp Eric Vatikiotis-Bateson 2004 Visual prosody and speech intelligibility Head movement improves auditory speech perception Psychological Science 15(2) 133ndash137

Nespor Marina amp Wendy Sandler 1999 Prosody in Israeli Sign Language Language and Speech 42(2ndash3) 143ndash176

Nespor Marina amp Irene Vogel 1986 Prosodic phonology Dordrecht Foris PublicationsNewport Elissa amp Ted Supalla 2000 Sign language research at the millennium In K Emmorey

amp H Lane (eds) The signs of language revisited An anthology to honor Ursula Bellugi and Edward Klima 103ndash114 Mahwah NJ Lawrence Erlbaum

Nicodemus Brenda 2007 The use of prosodic markers to indicate utterance boundaries in Ameri-can Sign Language interpretation Doctoral dissertation University of New Mexico

Pyers Jenny E amp Karen Emmorey 2008 The face of bimodal bilingualism Grammatical mark-ers in American Sign Language are produced when bilinguals speak to English monolin-guals Psychological Science 19(6) 531ndash536

Pynte Joel amp Benedicte Prieur 1996 Prosodic breaks and attachment decisions in sentence parsing Language and Cognitive Processes 11(12) 165ndash191

Sandler Wendy 1999 Prosody in two natural language modalities Language and Speech 42(2ndash3) 127ndash142

Sandler Wendy amp Diane Lillo-Martin 2006 Sign language and linguistic universals Cambridge Cambridge University Press

Vaissiegravere Jacqueline 1983 Language-independent prosodic features In A Cutler amp DR Ladd (eds) Prosody models and measurements Berlin Springer

Warren Paul 1996 Parsing and prosody An introduction In P Warren (ed) Prosody and pars-ing 1ndash16 Hove Psychology Press

Wilbur Ronnie B 1994 Eyeblinks and ASL phrase structure Sign Language Studies 84 221ndash240

Wilbur Ronnie B 1999 Stress in ASL Empirical evidence and linguistic issues Language and Speech 42(2ndash3) 229ndash250


Wilbur Ronnie B 2000 Phonological and prosodic layering of nonmanuals in American Sign Language In K Emmorey amp H Lane (eds) The signs of language revisited An anthology to honor Ursula Bellugi and Edward Klima 215ndash244 Mahwah NJ Lawrence Erlbaum

Wilbur Ronnie B amp Cynthia G Patschke 1998 Body leans and the marking of contrast in American Sign Language Journal of Pragmatics 30 275ndash303

Wilbur Ronnie B amp Howard N Zelaznik 1997 Kinematic correlates of stress and position in ASL Paper presented at the Annual Meeting of the Linguistic Society of America (LSA) Chicago Illinois

Woll Bencie Rachel Sutton-Spence amp Daffydd Waters 2004 ECHO data set for British Sign Language (BSL) Department of Language and Communication City University London

Authorsrsquo addresses

Jordan Fenlon Tanya Denmark Ruth Campbell and Bencie WollDeafness Cognition and Language Research Centre (DCAL)University College London49 Gordon SquareLondonWC1H 0PDGreat Britain

jfenlonuclacuk tdenmarkuclacukrcampbelluclacuk bwolluclacuk


(Cutler Dahan amp Van Donselaar 2007 Frazier Carlson amp Clifton Jr 2006 Pynte amp Prieur 1996) In particular when people listen to speech they use cues from pros-ody to organise the message into phrases so that they may be better understood Prosodic cues used to indicate boundaries not only indicate when the speaker has finished talking but can also resolve syntactic ambiguities (Pynte amp Prieur 1996) and listeners in English are also able to predict whether an utterance is complete using cues from prosody (Grosjean amp Hirt 1996) Additionally it has been shown that listeners are able to reliably indicate boundaries in a language that they do not know using prosodic cues alone (Carlson Hirschberg amp Swerts 2005) Us-ing fragmented Swedish utterances of varying length two groups of participants (speakers of American English and speakers of Swedish) were not only able to predict whether or not a boundary would occur but could also predict the strength of the upcoming boundary Since one group (the American English group) did not know Swedish prior to testing the authors concluded that it is possible to predict boundaries in the absence of lexical and grammatical cues that come from know-ing the language using prosodic cues alone Interestingly the test sentences were fragmented so as to eliminate the most obvious cue in boundary detection pauses As a result participants had to rely on intonational cues (such as pitch and length-ening) on which to base their decisions

As we turn to signed languages there are many questions to consider What does prosody look like in sign languages What are the functions of prosody in sign language Is sign language prosody different or similar to spoken language prosody There has been little formal research in this field and very little in BSL to date As a consequence the research referred to here reflects findings in other signed languages (namely American Sign Language (ASL) and Israeli Sign Lan-guage (ISL)) and although it is understood that worldrsquos signed languages are not universal they can be very similar (Aronoff Meir amp Sandler 2005 Meier 2002 Newport amp Supalla 2000) As there is little typological research looking at prosodic cues in sign language any similarity (or differences) between sign languages in how prosodic cues are used to mark boundaries would have a significant effect on the outcome of this study Whilst we expect that sign language prosody may vary from one to another sign language the findings in other sign languages will form the basis of investigation into visual cues present in BSL and SSL narratives

For sign language prosody Wilbur (1999) states that there is no modality ef-fect (aside from form) above the syllable (the syllable being a level in the prosodic hierarchy (Nespor amp Vogel 1986)) That is signed languages have a prosodic system that is comparable in function to spoken languages and a signed stream can be re-structured into prosodic constituents and marked by suprasegmental cues (Brentari amp Crossley 2002 Sandler 1999 Sandler amp Lillo-Martin 2006) These prosodic cues can occur simultaneously (prosodic layering (Wilbur 2000)) and sequentially





















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seeing sentence boundaries

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