Rachel E. Traxler and Kimi Nakatsukasa
Vocabulary knowledge is an essential component for communicating in any language, and sign language is no exception. In order to be efficient in communication, individuals need to have skills in both vocabulary comprehension and production. Comprehension refers to the ability of the learner to understand what is said, while production is the learner’s ability to produce utterances in the language. Without an understanding of vocabulary, learners are not able to comprehend discourse or produce their own ideas. For spoken languages, it is estimated that high achievement in good listening comprehension occurs when 95% of spoken discourse is understood (Bonk, 2000, as cited in Schmitt, 2008), which requires vocabulary knowledge. It is estimated that knowing 8,000–9,000 word families is necessary in order to comprehend a range of different texts within a spoken second language (L2) (Schmitt, 2008). Although it is not known how many vocabulary items are needed to communicate fluently in sign, spoken language studies suggest that acquiring sign vocabulary knowledge is essential to becoming a successful signer. Individuals’ language proficiency is connected to their vocabulary knowledge that enables them to produce and comprehend information rather than getting distracted by unfamiliar words (Nation, 1994).
For learners of second languages (L2), vocabulary learning typically begins with the learners connecting an already learned concept in their native, or first language (L1) with the unfamiliar item in the target, which may be a second or additional language (L2/Ln). For sign languages in particular, however, there is an additional difference. In cases where native users of a spoken language as an L1 learn vocabulary in a sign language as an L2, the modality difference between spoken and sign languages may influence how they acquire sign language vocabulary. Learners of sign language as L2/Ln must learn within and utilize the visual-gestural plane, rather than relying on the oral-aural plane, which may complicate this transfer process. When learning a sign language as a second or additional language (L2/Ln), it is expected that learner’s mental lexicon has been already developed in their L1. When learning a sign language such as American Sign Language (ASL), a learner who knows a spoken language such as English as L1 will need to make an extra effort to bridge L2/Ln sign lexicon with their L1 mental lexicon. This is exemplified when there is no one-to-one word-to-sign correspondence in lexicon. For example, a word in spoken English “right” has several meanings: (1) right as in direction, (2) right as “correct,” (3) right as in law. “Right” is one word in English but contains many meanings each of which occupies different mental lexicon. In addition, each meaning of the concept “right” has a different sign. As the learners learn ASL, they would need to learn how to map each mental lexicon to different signs because different signs are used for each meaning, unlike words in English.
Teachers are often unsure about how to best incorporate vocabulary into their teaching practices (Read, 2004) and while there are L2/Ln vocabulary acquisition studies, these studies are largely in spoken L2/Ln languages. Despite the growing number of studies in spoken languages, research on sign language as an L2/Ln remains underinvestigated regarding signed language vocabulary acquisition, applicable strategies for vocabulary instruction, and teacher development and current practices. Nonetheless, the studies provide information on the process of vocabulary acquisition and the teaching of vocabulary that can be applied to sign languages. In this chapter, theories of L2/Ln vocabulary acquisition are introduced, followed by a description of the unique features of sign languages that need to be taken into consideration when understanding L2/Ln vocabulary acquisition in sign languages. Various practices of vocabulary teaching in the L2/Ln studies and in sign languages found in the existing studies are next presented.
There has been extensive second language acquisition research about how L2 vocabularies are acquired. Vocabulary acquisition is a matter of form-meaning mapping. Research shows that for L2 learners, particularly those who are native users of spoken languages, acquiring L2 sign language vocabulary is not a simple matter of corresponding between newly learnt sign and a word in their mental lexicon. There are different processes in the acquisition of L2 sign language vocabulary by L1 spoken language and L1 sign language native users. As children begin to acquire their L1, their brain finds patterns in the L1 input that connect to specific phonemes and graphemes by being exposed to the input repeatedly (Doughty, 2003; Ellis, 2006). This connection serves as a form, which is combined, with meaning, after which it becomes vocabulary. This connection, however, becomes problematic when the L2 is phonologically or orthographically different from their L1 because learners do not process the L2 in the same way. Learners need to undergo an extensive process in establishing a new mapping for L2 vocabulary and existing mental lexicon, which may not match as shown in an earlier example of the English word “right.” In addition, learners need to construct a completely new system that connects phonemes and graphemes for the L2 by first identifying specific parameters in sign language such as handshape, palm orientation, movement, and location in L2 sign language and not in the phonemes in their L1, and then connect that with meaning. Providing vocabulary instruction may help clarify the differences between L1 spoken languages and L2 sign languages and facilitate the learners’ development of L2 mental lexicon to represent newly taught lexical signs.
L2/Ln sign language learners need to learn the sign parameters in order to be able to recognize and produce lexical signs. However, vocabulary learning goes beyond single lexical signs in isolation. Vocabulary learning also involves learning how to use the lexicon with proper definitions within the context of sentences and discourse. Depth of a vocabulary item can be facilitated by exposure to a word within different contexts, as the learner comes to understand the different ways and situations when a word can be used. This is an under-studied phenomenon since L2 vocabulary acquisition studies tended to consider individual words outside of context (Read, 2004).
Laufer and Hulstijn (2001) proposed that retention of new or unfamiliar words is dependent on how these words are processed during the learning process. They propose that three factors are essential for lexical processing, including need, search, and evaluation. Need refers to the motivation the learner has to learn a particular word. The learner has to search for the meaning of the word. The learner evaluates the new word with other words. While there is a paucity of empirical studies in the lexical processing of sign vocabulary by L2 learners, we believe that the learners attend to the same factors and undergo similar processing for lexical signs.
While we believe that the aforementioned theories of spoken languages are relevant to sign languages, it is important to note the unique aspects for sign languages that may shape how sign vocabulary is taught and acquired. Unlike spoken languages, signs are constructed differently depending on the iconicity of signs (e.g., Rosen et al., 2015; Beykirch, Holcomb & Harrington, 1990; Baus, Carreiras, & Emmorey, 2012; Lieberth & Gambel, 1991; Campbell, Martin, & White, 1992). Iconicity refers to the connection of a sign to a referent that corresponds to an item’s physical appearance or function. Spoken languages contain iconicity (e.g., the word “woof” phonetically resembles the bark of a dog), however, in sign languages, iconicity is manifested physically and visually. The physical and visual modality of sign languages allows for use of iconicity, which depicts many different concepts, including movement, object actions, individual actions, location, and shapes (Taub, 2001). For example, iconicity is present within the sign TREE in ASL as it directly resembles the shape and structure of a tree, while the sign EAT depicts the action of placing food in the mouth. This is not the case for non-iconic items. For instance, the form in the ASL sign for BLUE does not lend itself to its meaning.
It is possible that there are different processes for connecting sign lexical form containing the parameters with its meaning depending on the level of iconicity. If a sign is iconic, the production of its form reveals its meaning, and it should be easily learned. If a sign is not iconic, the production of its form does not reveal its meaning, and learning it would be more difficult than the case for iconic signs. This suggests that the process for connecting between form and meaning in L2 sign language vocabulary learning is different from L2 spoken language vocabulary learning.
However, results of studies in L2 sign vocabulary processing and acquisition are mixed. Several studies investigated the impact of learners’ individual differences such as learners’ proficiency levels and age on the processing and acquisition of iconic signs. Some studies such as Baus, Carreiras, and Emmorey (2012) found that iconicity in signs aid beginning learners to accurately recognize and translate sign vocabulary into spoken vocabulary, and it did not for advanced learners. Other studies such as Thompson, Vinson, and Vigliocco (2009) did not show that sign iconicity aid vocabulary learning and acquisition. Bosworth and Emmorey (2010) added that advanced adult signers did not recognize iconic signs better than non-iconic signs. Still, other studies such as Klima and Bellugi (1979) suggest that iconicity may not be relevant for the processing of language for all learners. While iconicity may strengthen the connection between form and meaning, the studies suggest that the benefits of iconicity are limited to lower level learners. We maintain that there may be an advantage for teachers to emphasize iconicity in sign lexicon in their teaching of sign vocabulary. Iconicity may aid some learners to make connections between sign form and meaning and remember vocabulary.
Other studies investigated the relationship between learners’ age and learnability of iconic signs. Thompson and colleagues (2012) found that learners between 11 and 20 months were able to better identify iconic items than younger learners who were between 21 and 30 months. The younger learners were unable to make the same inferences about the meanings of the signs as the older learners. Beykirch, Holcomb, and Harrington (1990) reported that adult learners retained iconic vocabulary better over non-iconic signs. This finding is supported in the studies by Lieberth and Gambel (1991) and Campbell, Martin, and White (1992), which suggest that adult learners use iconicity as a facilitative tool to remember vocabulary as long as they connect sign form with its meaning (Klima & Bellugi, 1979). The above studies suggest that the beginning level adult learners experience faster form-meaning mapping of iconic words than non-iconic words.
Effective pedagogical practices in classrooms include instructional strategies and activities that ensure learners’ access to language, foster their learning, maintain their engagement, and are challenging. Sign language instructors have shown a wide repertoire of strategies and activities that employ learners’ L1 spoken language and L2 sign language to facilitate their learning, and that includes fingerspelling for clarification or identification of vocabulary and multimedia as a medium for instruction. In the following, various teaching techniques for vocabulary teaching are explored, and strategies are proposed for instructors to apply the findings from the research studies in their own teaching.
As described in the previous section, learning sign language vocabulary as L2/Ln is not a simple process for native users of spoken languages. The most intuitive way to learn vocabulary would be through exposure, which can occur implicitly or explicitly. For example, learners can acquire vocabulary incidentally, as a result of another activity, or explicitly, with direct instruction. However, as articulated by Schmitt (2008), learners may not have a sufficient vocabulary if they focus on linguistic features or communication. In order to understand this complex learning process and maximize the learning of vocabulary, some SLA researchers investigated how vocabulary can be learned effectively.
SLA research in vocabulary has implicitly recognized that many language teachers are not clear about how to provide effective instruction. They suggest that incorporating explicit instructions may facilitate vocabulary learning. In his seminal work, Schmitt (2008) suggested the following strategies to teach vocabulary effectively:
(1)Use L1 to facilitate establishing form-meaning mapping for the beginning level learners (e.g., Laufer & Schmeli, 1997; Ramachandran & Rahim, 2004);
(2)Create an activity that allows learners to engage in vocabulary as advocated in the Involvement Load Hypothesis (e.g., target vocabulary items need to be used to complete a task, learners need to search for the meaning of the vocabulary items, and evaluate if the vocabulary is appropriately used in the context) (Hultsjin & Laufer, 2001); and
(3)Repeat the exposure to target vocabulary items consciously by recycling the taught vocabulary words.
Although Schmitt did not mention sign language in particular, these suggestions, we believe that they can apply in L2/Ln sign language classrooms. The instructors may sign, voice, and/or write while teaching vocabulary, design a task which requires learners to use target vocabulary through three steps (need, search, evaluate), and make sure that the previously taught signs are used again throughout the semester.
There are additional considerations in the teaching of sign language vocabulary to L2 learners. First and foremost, unlike spoken languages, in sign language classrooms teachers often employ voice-off instruction, that is, no spoken language is used while teaching. Second, fingerspelling, which is a manual representation of the alphabet, is often used by teachers when teaching sign vocabulary. Third, because of the visual modality of sign language, vocabulary instruction in sign language classrooms often incorporates multimedia. These three considerations are reviewed below in light of empirical studies. This is followed by suggestions for pedagogy.
A topic of debate for teachers and researchers is the language of instruction that should be used in L2/Ln language classrooms and considers whether teachers should use L2/Ln or learners’ native L1 to teach L2/Ln. Several researchers studied teacher use of the learners’ native languages within the L2/Ln spoken language classrooms and found advantages for incorporation of learners’ native L1 languages for L2/Ln learning (Nakatsukasa & Loewen, 2015; Polio & Duff, 1994; Tang, 2002). Teachers use the learners’ native language to discourage undesired behavior (Duff & Polio, 1990; Macaro, 2010), facilitate L2 comprehension (Cook, 2001; van Lier, 1995), clarify task instructions (Anton & DiCamilla, 1998; de la Campa, 2009; Ellwood, 2008; Macaro, 2001; Swain & Lapkin, 2000), promote learner-teacher relationships (Brooks-Lewis, 2009), encourage task completion (Swain & Lapkin, 2000), reduce learner anxiety (see Hall & Cook, 2012, for a review), and minimize cognitive overload (Bruen & Kelly, 2017; Scott & de la Fuente, 2008). In addition, several studies reported that using learner’s L1 facilitated the acquisition of L2/Ln vocabulary. Researchers found that while instructors may subscribe to a target language use policy, there is often a high ratio of native language use when teaching vocabulary (Tang, 2002; Nakatsukasa & Loewen, 2015; Polio & Duff, 1994). Tian and Macaro (2012) gaged the vocabulary acquisition of Chinese learners of English and found that using the target language for instruction was beneficial for them in cases when they need to use the target language.
Teachers’ instructional language has also been a topic of debate in sign language classrooms. Although studies in L2/Ln spoken language classrooms have reported benefits for using a learner’s native language as a part of instruction, the issue in the use of native language is mirrored in sign language classrooms. In sign language classrooms, the issue is the choice between the visual-gestural modality of sign language and the oral-aural modality of spoken language, the latter of which is exclusively used in L2/Ln spoken language classrooms (Hilger et al., 2015). Teachers in sign language classrooms create immersion environments by establishing “voice-off” zones where spoken language is not present, regardless of the learners being hearing or not. As a result, instruction on grammar, vocabulary, and culture is conducted through sign, gesture, pictures, and use of the dominant or majority language in writing. Teachers may incorporate props, presentations, and handouts. If spoken language is not a preferred mode of instruction in classrooms (e.g., not all the teachers and learners are hearing), teachers may choose to use the written form of the dominant language in order to aid learners in making connections between vocabulary form and meaning. Voice-off environments require learners to learn vocabulary in the visual plane and produce signs using an articulatory system that is new to the learners, particularly those who are native users of spoken languages (Hilger et al., 2015).
The debate about instructional language is further complicated in sign language classrooms by cultural considerations in pedagogy. Many teachers of sign language are Deaf themselves (Newell, 1994; Cooper, Reisman, & Watson, 2008). Using learners’ native, spoken languages would be a nonviable or unproductive option for L2/Ln instruction in sign language for most of the Deaf teachers. Even if spoken language is available to instructors, they may be hesitant to use it in any form. For sign language users, spoken language is inherently exclusionary and is privileged in the majority (hearing) society. For example, use of spoken language may be seen as oppressive or exclusionary within the voice-off context created within the classroom because it may be seen as marginalizing to members who do not engage with or have access to spoken language. The instructors may believe that use of the learners’ native spoken languages stunts the learners’ learning of sign language. In addition, voice-off communication within sign language classrooms mirrors the communication environment, that is, use of sign language, in the Deaf community. Unfortunately, there are very few studies that examine the impact of instructional language differences on the teaching and learning of sign language vocabulary. We argue that teachers and researchers should be attentive to and respectful of cultural nuances and mindful of how spoken language is often privileged in various contexts. If the studies support using spoken languages in the classroom, researchers should also offer pedagogically viable options and inclusive strategies for instructors, particularly those who are Deaf, to work with hearing, Deaf, and hard-of-hearing L2/Ln learners.
There are a few studies that examined the efficacy of voice-on and voice-off instruction on vocabulary learning in sign language classrooms. Rosen and colleagues (2014) examined the acquisition of ASL vocabulary words utilizing voice-off, voice-on, and mixed method instruction. In the first study (Boyle, 2011), 75 adolescent L2 learners of sign language were assessed on vocabulary about family signs and interpersonal relationships. Three conditions were used, including a voice-on, voice-off, and mixed methods group. Learners in the voice-on condition used spoken and written English while a strict no-talking policy was enforced within the voice-off class. Pictures, gestures, and visual explanations were used to explain vocabulary for the voice-off condition. The mixed method group utilized a balance of ASL and spoken and written English. Voice was used to present vocabulary, as well as written English, pictures, and both visual and verbal explanation. For all conditions, the instructor highlighted iconicity when present and reviewed production parameters for each target item. The results showed that production scores were highest in the voice-off group, followed by the mixed methods group and then by the voice-on condition. In the second experiment (Daley, 2011), 25 high school learners were assessed on job and career-related vocabulary, without use of a mixed methods group. This study also found advantages for vocabulary acquisition for the voice-off group. In contrast to the findings in Rosen et al. (2014), a study by Traxler and Nakatsukasa (2018) examined the effects of using voice-on and voice-off instruction with 26 adult learners in a beginning ASL class. Learners were assigned to one of two groups, where one group was received instruction via signs and fingerspelling (without voice) and the other received instruction using spoken English and signs (with voice). This study assessed knowledge of proper nouns exclusively (signs for countries). No significant differences between the conditions were found. The above studies show that the results are inconclusive about the role of sign iconicity in the learning of sign vocabulary.
To assess whether learners differ in the way they process sign vocabulary, DeLouise (2011) examined the characteristics of successful learners of voice-off instruction and found that success was dependent on learner’s auditory and visual processing abilities. DeLouise examined the retention of vocabulary for ten beginning level ASL learners diagnosed with a language disability, or difficulties with auditory or visual-language processing. Vocabulary used in this study was from a unit about the home, including topics such as rooms, transportation, furniture, directions, and other items within the home. Learners with high visual abilities and challenges with processing (or low processing abilities) learned vocabulary well with voice-off instruction, while learners with low visual abilities and high verbal abilities acquired vocabulary better with voice-on instruction. Considering these findings in combination with the two studies highlighted by Rosen et al. (2014), language modality and auditory visual capacities directly influence acquisition. These findings suggest that teachers should choose and utilize both learners’ native and target language for instruction of sign language vocabulary depending on learners’ characteristics.
The above studies have implications for teaching sign vocabulary. The studies showed that beginning level hearing learners may benefit from including spoken language as a part of instruction, and teachers should consider that learning processes for all learners are not identical. Though considerably more research is needed, teachers may choose to initially use the learners’ native spoken languages to introduce signs either through speech or, if it is a nonapplicable option for the instructor, through writing. Teachers may also choose to use voice in classrooms to explain iconic sign vocabulary and sign parameters. By describing how to sign the vocabulary (e.g., explicitly showing how iconic vocabulary are constructed, reviewing the five parameters of a sign), rather than providing learners with signs and have them practice, the teachers may facilitate the learners’ production and comprehension of sign vocabulary. Because learners’ processing abilities may vary, teachers should attend to these individual differences, differentiate their instruction, consider voice-on and voice-off instruction when appropriate, and have the learners practice producing sign vocabulary. Additionally, many L2/Ln learners are hearing individuals. These students are learning to operate in a different modality from their native spoken language, which may be cognitively taxing and tough on learner’s eyes. It may be helpful to incorporate breaks in lessons for the learners to reset their vocabulary processing in the visual-spatial plane.
Fingerspelling is a unique feature in sign languages in that it is an adaptation of alphabet systems in dominant written languages (Klima & Bellugi, 1979). For instance, ASL fingerspelling and English alphabets are related in the sense that the fingerspelled letters correspond to the letters in the English alphabet. Studies examined have found that there is a relationship between fingerspelling knowledge and reading ability. For hearing learners fluent in written and spoken English, understanding fingerspelling involves the transfer of their English reading skills to the visual/receptive context (Babbini, 1974), among other factors.1 Fingerspelling accounts for 12–35% of ASL (Padden & Gunsuals, 2003) and can be used to provide clarification for vocabulary, explain a concept, or label a word for which a sign does not exist.2 Because of the function and prevalence of fingerspelling in most sign languages, understanding full utterances often requires both fingerspelling and vocabulary knowledge.
Teachers use fingerspelling in classrooms to map meanings to forms of signs and to learners’ L1 words (Beykirch, Holcomb, & Harrington, 1990). It is pedagogically important for teachers to verify that learners are able to understand fingerspelling correctly. Without understanding fingerspelling promptly, learners may lose the opportunity to process further information in the utterance because their attention is mostly drawn to connecting the new vocabulary item with what was fingerspelled. In addition, learners should be exposed to different styles of fingerspelling by different signers and to fingerspelling from different spatial perspectives, and from inside and outside of sentential context. This may help learners attend to the similarities in the “shapes” created in fingerspelling by different individuals. For further information on fingerspelling learning and instruction, the reader is referred to Geer in Chapter 14 in this volume.
Technology is used in many language classrooms and multimedia has been a vehicle for sign language teaching since the 1980s (Teuber et al., 1980; Beykirch, Holcomb, & Harrington, 1990). Sign language teachers often incorporate technology with authentic materials created by members of the Deaf community, and use it to expose learners to different signers and signing styles, increase the amount of input and interaction with sign language, and provide learning opportunities such as independent learner practice outside of the traditional classroom. Technology is used in many forms for sign language learning. Sign language curriculum often comes with supplemental content on CD-Roms (see Smith, Lent, & Mikos, 2008; Zinza, 2006) and several programs are available online such as online sign language dictionaries, fingerspelling quizzes, and other content created by members of the Deaf community.
Several studies have found benefits of such technology use, particularly the video recordings, on vocabulary learning (Beykirch, Holcomb, & Harrington, 1990; Slike, Chiavacci, & Hobbis, 1989). Beykirch and colleagues taught vocabulary to college-aged learners using computer-assisted instruction and videotaped presentation. Learners in the computer-assisted condition were taught vocabulary by an animated figure on computer screen. Those in the videotaped condition viewed a video of their classroom instructor teaching the same vocabulary items. In both conditions, each sign was produced four times, accompanied with captions. Researchers examined learners’ comprehension and retention of target vocabulary items and found significantly higher scores for the videotaped condition in both comprehension and retention. Beykirch and colleagues were cautious regarding their findings, however, because positive gains may have been due to learners’ novelty with technology, differences in instruction speed, and instructor familiarity. Similarly, Slike, Chiavacci, & Hobbis (1989) found that the learners’ comprehension scores of vocabulary items were higher after watching a videodisc containing the target vocabulary items than after attending a traditional lecture on vocabulary. These studies provide evidence that the use of technology can supplement classroom instruction, and is an effective tool for learning vocabulary in sign language. As sign languages are typically minority languages used by communities of the Deaf and have considerably less users than spoken languages, technology can serve as a useful tool for helping learners gain exposure to the language through interactions online. Yet, as technology advances, it is crucial to examine in what way technology can be used to maximize learning and what types of sign language learners (e.g., personality, aptitude) benefit most from technology-enhanced instruction.
The above studies measured the effectiveness of instruction for learning target sign language vocabulary. There is one study that investigated learner attitude toward technology use for learning sign language. Ehrlich-Martin (2006) conducted a case study to examine learner perceptions of an online video conferencing in an ASL course. Several learners experienced technical difficulties and were frustrated with their experience learning ASL virtually. The online modality may negatively influence learner’s ability to engage in meaningful interactions. While videoconferencing or online courses are popular within institutions of higher education, the use of technology should be carefully introduced as it may inhibit the naturalistic discourse that exists within a face-to-face classroom. Educators, along with coordinators and researchers of sign language courses, may need to investigate how to prepare prospective learners for online or hybrid courses.
Multimedia and technology provide the platform for sign language teachers to store and draw the materials and videos of poems, news, and stories that are signed by Deaf individuals from which they introduce learners to different individual styles and regional variances in the production of sign vocabulary. However, some of the technologies have the potential to reduce the opportunities for learner-learner peer interactions. For instance, if classes are offered using online instruction only, teachers should consider activities that bridge online studies to face-to-face interactions such as giving assignments to learners that require one-on-one interaction with classmates, the local Deaf individuals, and/or interpreting learners online (e.g., through use of video chat room, such as Skype, Facetime, and Zoom).
The field of L2/Ln sign language research is admittedly a new field worldwide, considering that sign languages of the world were not official languages until the late twentieth century. Interest in sign languages from an educational standpoint has increased in many countries with increased number of sign language classrooms at the secondary and postsecondary levels (e.g., Rosen, 2015 for the US). At the occupational level, sign language interpreters have sought to professionalize the career and many national certifications now require prospective interpreters to obtain bachelor degrees. As a result of increased interest, desire to optimize learning and legitimize pedagogy and consideration of best instructional methods becomes increasingly important.
The studies reviewed in the above have shown differences among learners in their learning of vocabulary for comprehension and production, the influence of sign iconicity in vocabulary learning, and effectiveness of instructional languages and multimedia use in vocabulary instruction. However, compared to the studies conducted with spoken languages, there is paucity in the number of experimental and descriptive research studies on L2/Ln sign language vocabulary teaching and acquisition, and only a few studies that provide strong pedagogical implications exist (e.g., Rosen et al., 2015; Traxler & Nakatsukasa, 2018). The following are suggestions for future research studies and pedagogical applications in sign language vocabulary instruction and learning.
To date, little research has been conducted about how to employ different instructional techniques effectively in sign language classrooms. It is crucial for educators and researchers to conduct intervention and/or action studies that employ different teaching approaches. As researchers continue to investigate interventions for sign language learning, instructors can learn how to bridge the gaps between literature and pedagogy by conducting research in their classrooms, aligning with Rosen et al. (2015). The field would benefit from observational research (e.g., first-hand accounts by teachers of their current vocabulary teaching practices), and intervention research (e.g., the effect of identifying target items using fingerspelling or written English). These studies will help to identify the most effective teaching materials or teaching strategies for specific learner populations and will expand understanding of the specific linguistic features of sign language.
Most studies in sign language acquisition focused on Deaf learners and L1 sign language acquisition. There has not been extensive investigation of how hearing learners acquire vocabulary in L2 signed language. Though some work has focused on adult learners acquisition of sign language, more is needed surrounding hearing populations within the secondary and postsecondary classroom context to fully capture the processes of vocabulary acquisition. Because of the differences in the input modalities between signed and spoken languages, it is logical to assume that Deaf and hearing populations may experience different learning and acquisitional processes. As a result of the differences in modality between signed and spoken languages, Hilger et al. (2015) discussed that hearing sign language learners may go through additional processes when acquiring sign language. Including hearing learners as study participants, or conducting a contrastive study between hearing and Deaf L2 sign language learners, will further our understanding of the process in learning sign languages and to provide effective teaching methods for the different cohorts of learners.
Most of the research studies conducted in sign language vocabulary measured learners’ receptive skills such as recognition and comprehension (see, however Traxler & Nakatsukasa, 2018). The field calls for further studies that incorporate learners’ ability to produce learned vocabulary items, as comprehension and production are two distinct skills. Therefore, it is important to investigate which vocabulary items in both production and comprehension that the learners tend to make errors. Teachers can learn from learners’ errors and modify their teaching of vocabulary.
Though controversial within the Deaf community, the increasing enrollment of hearing learners in sign language classrooms necessitates further investigation of the effectiveness of voice-on and voice-off instructions for the acquisition of signed vocabulary and development of sign fluency. Researchers should be mindful of Deaf cultural considerations in their investigation regarding whether the use of learners’ native spoken languages in the classrooms can facilitate their sign vocabulary acquisition. It would be highly informative to know the learners’ attitudes toward voice-on and voice-off instructions in a sign language classroom to further understand their perspectives and expectations.
Regarding sign iconicity, the inconclusive findings in the studies reviewed earlier suggest that future research studies examine the relationships between different learning conditions (iconic and non-iconic sign vocabulary, and topics), groups of learners, and classrooms. In addition, the studies need to examine personal characteristics such as learners’ demographic characteristics and hearing status, and linguistic features such as sign complexity and frequency, as possible factors that shape the learners’ sign vocabulary learning and acquisition.
Regarding fingerspelling, although it is frequently used in the classroom, the relationship between fingerspelling instruction and the L2 learners’ acquisition of sign vocabulary is still underinvestigated. Researchers and educators should investigate how fingerspelling is used in the classroom to facilitate vocabulary learning specifically, and how fingerspelling can be used as an instructional intervention. A collection of such studies will enable the field to establish effective sign language teaching curriculum for future learners.
Teachers may help enhance learners’ learning of sign vocabulary by highlighting the iconicity ‒ as well as non-iconicity ‒ of sign vocabulary. Although there is no consensus about teaching about the iconicity of signs, research suggests that adult learners are better able to retain vocabulary when they are aware of the relationship between an iconic sign form and its connection with meaning that the teachers highlighted. Additionally, incorporating explicit teaching on sign parameters in both iconic and non-iconic lexical signs may help the learners become explicitly aware of how to sign accurately and improve their sign production ability.
It would be helpful for teachers when teaching vocabulary to make decisions regarding the language of instruction depending on the learners. Particularly for L2/Ln hearing learners, teachers may choose to provide instruction for vocabulary lists in a spoken language with follow-up instruction and use of vocabulary in the target language. They may suggest opportunities for learners to practice and expand their sign vocabulary knowledge by using sign language outside of classrooms. Learners can attend events within the Deaf community as is appropriate and find videos online to supplement their learning. Teachers can provide instruction to the learners on pragmatic ways to ask questions to Deaf signers during Deaf events. It is important that the learners be taught to self-advocate and become comfortable asking questions if they miss something, particularly as it relates to fingerspelling.
Finally, compared to spoken languages, there are fewer teaching materials for teaching sign language vocabulary. Much remains unknown about the extent to which the materials, both published and unpublished, in sign language vocabulary are utilized in sign language classrooms. Sign language researchers, SLA researchers, teachers, and teacher trainers need to collaborate and develop effective teaching materials in sign language vocabulary.
Notes
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