Teaching language components to deaf / hard-of-hearing and cochlear implant users : a literature review

Cochlear implants are one of the possible ways for Deaf or Hard-of-Hearing (DHH) individuals to detect sounds and as a mean of insertion in the social, academic and work environments. Nevertheless, in many cases, the cochlear implant alone is not sufficient, demanding hearing and expressive language skills rehabilitation to optimize the device used. This study aimed at reviewing scientific articles that described empirical research with interventions and/or teaching methods of various language repertoires to deaf and hard-of-hearing cochlear implant users. The review was carried out in five scientific databases considering all periods. On the first phase, 156 articles were identified and from these, 24 publications were selected. After being read, these articles were categorized and analyzed as to the participants, teaching targets and procedures adopted. On the last stage of the research, 10 experimental studies were selected and analyzed regarding procedures and results, indicating important factors in teaching this population. The results point to the necessity of an increase of scientific production in the construction and evaluation of effective verbal repertoires teaching programs for cochlear implant users.


INTRODUCTION
The population with severe hearing loss that does not benefit from common sound amplification devices may find in the cochlear implant (CI) an alternative way to detect sounds, sometimes for the first time.That is usually the case of pre-lingual (when hearing loss occurs before the establishment of oral language) deaf children.Nonetheless, even with the CI, educational interventions and a rehabilitation process is necessary in order to both auditory and oral production skills be developed by CI users 1 .
The cochlear implant enables its user to detect sounds when present, but it is the auditory rehabilitation that aims to teach more complex repertoires: on one hand, discrimination between identical and different sounds, sound stimuli recognition, location of the sound source, auditory comprehension and memory 1 ; and, on the other hand, oral production.
The process of learning auditory skills is important so those individuals can learn how to handle auditory stimuli as well as being able to express themselves through oral communication and interact with others around them.Pre-lingual deaf children show significant progress regarding auditory repertoires after one year experiencing cochlear implants, even though speaking skills does not follow the same improvement levels 2 .In longitudinal studies, which followed CI users for 10 years, less than half (40%) of Uziel et al. 3 study population and 33% of the children assessed by Beadle et al. 4 had intelligible speech for a regular listener (i.e., a listener without previous experience with CI users on their daily basis).
In this regard, specialized literature point to difficulties for deaf and hard-of-hearing (DHH) population during literacy, with CI users presenting educational achievement levels lower than their hearing peers.As a result, from those initial difficulties, the difference between deaf students and hearing students in reading and writing repertoires persists even after many years of CI experience 5 .
Based on the level of expected achievements, it may be considered that this population would benefit from the teaching of auditory stimuli recognition and discrimination, especially those related to oral sounds and its extensions to oral production, focusing on more complexes repertoires like reading and writing.Therefore, on the account of auditory deprivation and other variables that can influence the learning process 6 , many CI users present difficulties regarding the learning of those verbal repertoires (i.e., receptive and expressive repertoires).Considering this variables and needs, it is necessary to adopt teaching and intervention programs previously tested and structured based on empirical evidence of its effects.Therefore, the term "teaching" is understood here as any manipulation and/or arrangement of environment, materials and/or instructional elements aiming to change a behavior or response patterns with explicit criteria related to the intervention goal 7 .This process may be presented in different formats (incidental or direct/systematic), in different environments (e.g., school, clinic) and performed by different agents (e.g., teachers, caretakers, specialists).
Despite this necessity, literature reviews about CI users point to a great number of skills assessment studies and few reporting teaching procedures.One of these literature review studies was conducted by Almeida-Verdu, da Silva e Golfeto 8 in the Web of Science database with the terms: cochlear implant, speech, perception, recognition and language.This study found 86 articles published between 1998 and 2008.As a result from the analysis, they concluded that in that past decade the main target of the studies was to assess the effects of the implant on the users' receptive and expressive skills (42% of the studies); however, little was found about the effects of particular instructional interventions on these skills.As stated by the authors, literature confirms the positive effects of the technology for deaf individuals; however, the lack of articles describing systematic instructional procedures teaching auditory and expressive skills with this population justify the interest in the subject.
Another literature review was published by Neves 9 in 2015.The author aimed to survey and analyze publications about cochlear implant recipients using terms specifically related to expressive and receptive verbal repertoires.The review selected studies from 2003 to 2013 in Brazilian and international databases adopting the terms cochlear implants, auditory recognition, recognition, speech, speech production and language.As a result, the author also found 86 articles, in which 29% was about receptive and expressive skills assessment ad 34% were theoretical studies, reviews about this population or longitudinal studies.The remaining studies aimed to characterize different groups among CI users (e.g., comparing pre-lingual and postlingual groups).Among the studies selected by the author, none of them brought reports on verbal skills teaching procedures for users of cochlear implant.
Given the fact that there are few studies describing the construction of educational programs (as much as curriculums and methods) 8,9 , the present study aimed to review the scientific literature regarding programs and/or methods of teaching receptive and expressive skills related to oral language and writing and reading to the deaf and cochlear implant users population.After the initial search, mentioned above, the objectives were to verify their incidence per year, participant's characteristics, target behaviors, adopted teaching procedures and main results achieved.

METHODS
The literature review was conducted in four phases divided as: search, selection, literature description and results analysis, described hereafter and illustrated in Figure 1: 1 st Phase: Search for studies in Brazilian and international databases using keywords selected through DECS (Descritores em Ciências da Saúde -BIREME; Terms in Health Sciences) in both Portuguese and English.In PubMed, Web of Science and IBECs databases, the following keywords and Boolean operators were adopted: [cochlear implants] and In a first search, both terms described above and more specific terms related to this study targeted behaviors (i.e., "reading", "writing", "listening", "speech", "speech production", "speech recognition" and "speech intelligibility").In that search, however, few publications were found.For this reason, a wider search was adopted during the first phase and a more laborious analysis was conducted during the subsequent phase.
2 nd Phase: Selection of studies reporting procedures, curriculums and interventions to teach repertoires related to listening, speaking, reading and/or writing skills.
Through the abstract reading from the articles found during the first phase, the ones that described researches about teaching verbal repertoires directly or indirectly related to listening, speaking, reading and/or writing skills were selected.Publications that reported direct effects of well-known educational approaches to compare methods (e.g., auditory-oral, total communication, bilingual) were also selected in this phase.
In this phase, any publication that did not fulfill the inclusion criteria was excluded.Editorials, theoretical reviews, letters to editors and reports on skills assessment that were not contingent to the explicitly described teaching methods (that is, studies that only evaluated the CI user independently of any teaching program) were also excluded.This last kind of report usually aims to identify the general status of the population in a wide environment; however, without specifying interventions that could explain these performances.
From the pool of articles selected during the first phase, 30% were chosen randomly to be analyzed by a second judge, in order to obtain the concordance index between observers.The index was characterized by the formula: number of concordances / number of concordances + number of disagreements x 100 10 .The result obtained was 94%.
3 rd Phase: Reading and analyzing full articles.In this phase, the selected publications were read and analyzed aiming to describe the following topics: a) Year of publication; b) Participants -diagnostics, hearing loss type and age; c) Goal -what specifically repertoires (dependent variables) were subjected to teaching procedures (independent variables); d) Design -if experimental (between groups or single subject) or if it was a case study; e) Method -About teaching procedures and stimuli adopted.

th Phase:
In this review's last phase, studies that presented detailed reports of experimental research's procedures and results were selected.These studies enabled a better analysis of dependent and independent variables with CI users as target of direct teaching procedures.Therefore, studies with I) hearing participants, II) studies that reported retroactively data gathering from wider educational approaches and not specific interventions, III) and case studies with little or no experimental control were excluded.After this final selection, a classification and description of the adopted procedures and results were conducted.
(already selected in other databases) were excluded, being this the only exclusion condition.
Data from the first phase is presented in Figure 1.
Phase 2 -In the second phase, articles that reported teaching or teaching methods of the targeted verbal repertoires were selected.These studies could have had different target behaviors, as reading, writing, speaking, listening, as well as other related behaviors

LITERATURE REVIEW
Phase 1 -During this initial phase 156 articles were found.Most of them were found in the PubMed database: 90 publications.In the database Web of Science, 49 publications were selected.Thus, only 7, 7 and 3 articles were selected from the databases, respectively, LILACS, SciELO and IBECS.During this phase, 12 studies found in more than one database Regarding the publication year, the studies began to appear in the year 2000 with three publications [12][13][14] .Between 2002 and 2005 no publication of this kind was found.After this period, an increase in the number of published articles until the end of 2016 (search limit) can be seen.Figure 2 presents the simple (bars) and cumulative (line) frequency of the number of studies found per year.
Figure 2 shows the increase rate of publications aiming to evaluate teaching programs for the cochlear implanted population in the early 2000's, especially in 2004.This increase may be explained by the implementation of public policies aiming to adopt cochlear implants as the main rehabilitation approach to deaf children, thus the therapeutic approach that prioritizes spoken language and inclusion of these children with the hearing population, was also adopted 15 .As an example of influent policies, laws created in the United States during the 2000's that aimed to prioritize evidence-based educational practices to teach reading in public schools.Such policies have made studies validating such practices indispensable.As stated by Tucci et al. 11 , as a product of these laws the need for evidence-based practices in reading teaching has also been extended to special education, which includes the deaf children population and CI recipients.
(e.g., auditory recognition of melodies, vocalization of phonemes, reading of stories) and also conducted directly or indirectly with CI users (e.g., intervention with peers and assessment of CI users).From the 156 articles found during the first phase, 24 studies were selected.One of the publications previously selected was excluded after further analysis since cochlear implant users was not direct or indirect targets of the teaching intervention.
From the number of articles that were not selected, there were 59 evaluation studies, aiming as much as specific behaviors (e.g., auditory discrimination, speech production) as other repertories (e.g., social skills, influence of parental skills in the CI user rehabilitation).Another 29 publications were theoretical studies.Among these publications, there were articles describing the work of care services to the population, theoretical studies on the evolution of the device itself and rehabilitation services, publications dealing with the education of deaf and hard-of-hearing children and others.
Still on the publications that were not selected, 10 studies were literature reviews on different related subjects.For example, the study conducted by Tucci, Trussell and Easterbrooks 11 aimed to investigate strategies to teach phoneme-grapheme correspondence to children who are deaf and hard-of-hearing.Although the authors report teaching methods, the article was excluded because it is a literature review.Another 21 publications were excluded because they were: I) written in other languages (i.e., three studies in German, two in Russian, one in Polish and one in French); II) were editorials, letters to editors, or even experimental studies on different subjects (e.g., surgical procedures, CI device technological improvements).
In general, it can be stated that most of publications (41%) aimed to evaluate the population repertoires, despite 17% of studies aiming to empirically test teaching procedures of this repertoires.These results replicate data found by the literature reviews conducted by Almeida-Verdu, da Silva and Golfeto 8 and Neves 9 , having a majority of evaluation studies.Although, in this review, a higher number of studies reporting teaching interventions were found.This difference may be explained by the adopted terms and more important, the time limit in both previous studies (2008 and 2014, Regarding the participants characterization, 19 studies were conducted with children under 11 years and only in three studies participated adolescents between 12 and 18 years.In six publications, the target population was adults (over 19 years of age), and among these, only one 26 were deaf or hard-of-hearing.
Table 1 shows the description of the participants, as well as the difficulties to identify the participant's diagnostics.Most of the studies (13 publications) among those that provided directly or indirectly information about when the hearing loss occurred (some studies provide only the child's age at the time of diagnosis or at the time of implantation) -if pre-lingual or post-lingual -had pre-lingual deaf children as participants 13,14,[16][17][18][19][20][21]24,26,30,35,36 . Only one studyexplicitly reported the participation of post-lingual deaf individuals 26 .Hearing individuals participated in interventions reported by seven studies [27][28][29][31][32][33]36 .Some of these studies, such as the publications from Suskind et al. 33 and Clare Allen et al. 31 aimed to establish teaching repertoires or increase the number of words and the quality of statements emitted in the context of the deaf and CI user child -thus, creating conditions for the occurrence of incidental learning of these repertoires.Despite the importance of parents and teachers skills training and the enrichment of environments in which the child can present a high number of responses, enabling procedures of modeling and shaping, many studies in point to the need for direct, individual and programmed interventions in order to teach verbal repertoires to the population 23 . Ths, incidental exposure is necessary, but not sufficient.Regarding these possible procedures, while modeling is characterized by presenting the response and asking the child to imitate, shaping is the procedure of reinforcing each response until the child emits the desired final response 37 .
Despite the importance of designs that enable a higher generalization and statistical analysis, case studies and single subject designs -usually with a low number of participants -also have an important role identifying and describing individual processes and potentially relevant variables.Single subject experimental designs are extremely versatile regarding evidences in research developed in educational  contexts (especially on teaching new skills).This type of research is characterized by an experimental design, more than only correlational or descriptive, about the relation between dependent and independent variables.Thus, making it easier to manipulate variables actively and appropriately to investigate the effects of teaching interventions.Byiers, Reichle and Symons 38 propose that the single subject design represents an important tool in the development and implementation of evidence-based practice in communication disorders and sciences.However, an intrinsic need of this design is the systematic replication of studies, which would guarantee both the internal and external validity of the procedure 38 .An evidence found here and pointed out by other reviews 11 is that such replications are often not developed and, at most, follow-up studies may be found (that is, replications with modifications, either in the method or in the population), thus, not enabling replication of results in a systematic way.
Regarding the type of intervention, nine studies reported teaching procedures in groups and 18 (the majority) reported individual procedures; it is important to point that some studies make use of both types of procedures.Many of the selected publications did not report the duration and number of sessions of the described interventions with high variability between studies and participants in the same study.Nevertheless, three interventions lasted for less than three weeks; eight studies lasted for six to 11 weeks; and five studies lasted for 11 to 15 weeks.Among the remaining publications, four reported interventions that took about six months and only two studies had Note: The shaded numbers identify values for mean age (e.g., Connor et al. (13) ) or undeclared data for the period in which hearing loss occurred (diagnosis, whether pre or post-lingual) in 9 studies.
a duration of one year.Two studies were conducted retrospectively, using data from participants exposed to interventions for more than two years 13,34 .
The analysis and categorization of the objectives is important in order to describe the dependent variables of the selected studies and possible effects when they are under the influence of independent variables.In the context of this type of studies these variables are the target behaviors and teaching procedures.The objectives of each study were quite varied within the range of receptive and expressive language skills.As an auditory skill target behavior, studies that aimed to teach sound discrimination under different stimulatory conditions (such as letters, words and/or sentences sounds) were selected, even when there were secondary learning of other skills (e.g., strengthening of reading repertoires during tasks of word discrimination after listening to the word sound).Likewise, studies that aimed to teach speech production were those in which teaching procedures focused primarily on oral language, as well as a type of response (under different stimulatory conditions, such as pictures to name, words to repeat or speech of another person to interact) and in the frequency of emitted responses.As reading and writing teaching studies were classified publications in which the focus was on the population literacy, regardless of secondary gains.
Most of the articles (15) reported goals related to speech production (oral expressive).Another 13 studies had as objective auditory discrimination skills (of dictated phonemes, syllables and receptive vocabulary) while only five articles reported reading skills teaching 17,20,21,32,35 .As shown in Figure 3, although few studies aimed reading skills teaching -that may be considered a type of speech production but differ by the nature of the stimulus presented -15 interventions used textual stimuli as printed words, letters and syllables.All the selected studies utilized auditory stimuli (e.g., dictated words, music, story reading) during teaching and testing procedures and 15 publications reported the use of non-textual visual stimuli (i.e., pictures, drawings).
The training procedures on auditory skills of three studies were based on music teaching 14,24,30 .These studies adopted group interventions focusing on musical stimuli detection and discrimination.Besides, among other materials used there were book reading, described in three publications 16,19,25 , in which different repertoires were targeted.In these studies, the books had the function to contextualize the words dictated by the teacher/researcher, without a specific teaching purpose.
Among the studies that reported expressive skills training, the one conducted by Smith and Wang 35 focused on phonological awareness and reading through the Visual Phonics program and a phonological awareness curriculum using textual, auditory and visual stimuli.This and other studies 20,21 discuss the relation between speech production and reading.Other publications aiming for speech production reported different approaches, such as the Cued Speech, adopted by Torres, Moreno-Torres e Santana 36 .Similar to the study conducted by Smith and Wang 35 , this publication is also a case study in which prompts were used during training (prompts usually are described as instructions or clues before the participant's response, such as gestural clues during recognition and discrimination of auditory stimuli and textual in speech production training).
In total, nine studies adopted receptive and expressive teaching procedures through computerized programs.Among these publications, six 20,21,25,[27][28][29]32 presented tasks known as Matching to Sample (MTS) for hearing participants, however, emulating the sound stimuli produced by the cochlear implant to deaf individuals. Thefore, these studies aimed to improve teaching methods to the population of CI users through conditional relations training between dictated words, sentences and phonemes and their respective textual stimuli.
In the Matching to Sample procedure, one stimulus is presented as sample and the task is to select the right comparison stimulus presented simultaneously among others.This procedure is very flexible and enables training of stimuli relations of different natures.An example of a MTS task is a training of auditoryvisual discrimination in which the auditory stimulus is dictated to the participant and the comparison stimuli are pictures, objects or printed textual stimuli.
Although the literature highlights the difficulties of the population during literacy and regarding the aforementioned studies that use these repertoires during auditory trainings, few articles among the selected ones aimed to teach reading repertoires.According to the study conducted by Tucci et al. 11 on teaching methods of reading repertoires to DHH individuals, the research field is still scarce, with few studies and fewer replications.The authors describes the following methods as the most prominent: I) Cued Speech -In which the relationship between graphemes and phonemes is taught through speech with specific gestural cues; II) Visual Phonics -a sign language, but different from ASL (North American Sign Language); III) Speechreading -A combination of visual cues through lip reading; IV) Fingerspelling -Teaching of graphemephoneme relations through a digital alphabet, varying between digital alphabet and more complex signs; V) Iconic / Semantic Representation -Teaching through relationships between figures, letters and words; and 6) Morpheme -Teaching word formation and its effects on reading and its generalization.
From the selected publications, four reported interventions to teach reading 17,20,21,35 .Smith e Wang 35 adopted the Visual Phonics and a phonological awareness curriculum.In the study published by Lund e Schuele 17 , five preschoolers and CI users participated in reading trainings aiming to develop vocabulary through relations between pictures and words.The only two studies conducted in Brazil 20,21 focused on teaching or strengthening reading repertoires to increase levels of speech production with greater accuracy in other types of tasks using programmed and computerized teaching with implanted children.In these studies, considering that written word provides graphical clues for a more accurate speech production during reading tasks, a more precise speech during picture naming tasks can be obtained after training or strengthening of reading repertoires (and the relations between dictated words, printed words and pictures) 39 .These data confirm and amplify Tucci et al. 11 findings on the teaching of reading repertoires to the DHH population with a focus on the relationships between graphemes, phonemes and other types of visual cues (e.g., signs and figures).
4 th Phase -In the last analysis phase of the review, 10 studies were selected from the 24 previously described.General data on procedures and results are described in Table 2.Among the 10 selected articles only two studies adopted group comparison designs, in contrast to eight studies that adopted single subject designs.Most of the publications reported interventions aiming to teach expressive vocabulary, in which the main dependent variable was oral responses while naming objects, pictures or answering questions of the researcher regarding these stimuli (e.g., to describe or define an object).In these studies, teaching procedures varied widely between tasks of vocal imitation 17,18,23 , receiving instruction on the definition of stimuli 17,23,25 , attempts at auditory-visual MTS 20,21 .The results were mostly positive, but with great variability among participants when the research presented individual data.
Three studies used MTS tasks aiming to teach auditory discriminations between stimuli dictated by the researcher and pictures and printed letters, syllables and words as comparison stimuli.These types of intervention point to the importance of the adoption of discrete trials with carefully programmed tasks beginning with instruction (prompt), followed by the participant's response and feedback.The only study that did not report high performance results from the participants was conducted by Stacey et al. 26 , in which the adopted teaching program was self-administered by adult CI users (ages between 23 and 71 years old).Only eight out of 11 participants in this intervention complete the entire teaching program (15 hours) and out of this eight, only two reported a better auditory discrimination performance when completing a satisfaction questionnaire.There are many differences between this intervention and others described here.The differences found between this intervention and others are many.In addition to the adoption of a very heterogeneous group of adults, there is a lack of difficulty progression (starting with easier stimuli towards more difficult stimuli) and criteria of performance -to repeat training steps in the presence of wrong answers -, variables found in other studies of the same type.
Finally, the only study that had as main objective the teaching of reading repertoires was developed by Nakeva von Mentzer 32 , aiming to compare the learning Lund and Douglas (23) Expressive Vocabulary Word contextualizing (describing things), imitation, auditory-visual MTS, naming.
Nine. Between 4 and 5 years old.Six using CI.
Experimental group learned a mean of 5 words per week.In contrast, 0.5 words were learned by incidental teaching per week.
Richels et al. (18) Expressive Vocabulary Response shaping and modeling technics through hearing peers that described actions.
Three.Between 3 and 4 years old.One CI user.
P1 and P3 achieved criteria after six sessions, while P2 needed 20 sessions (and did not show maintenance of performance after a few weeks) Messier and Wood (25) Expressive Vocabulary Digital book reading with parents.Programmed activities (context and phonetic focused).Control: just reading.
18 children between 4 and 9 years old.All CI users.
Experimental group showed better word definition, expressive and receptive vocabulary than control group.
Six. Between 11 and 14 years old.All CI users.
All children learned the taught relations.Four participants showed improved naming performance.
3 presented generalization to new pictures.
Lucchesi et al. (21) Expressive Vocabulary Auditory-visual MTS programmed trials using pictures, words and syllables.
Two. Between 7 and 8 years old.Both CI users.
Both children presented improvements during picture naming tasks.
Nakeva von Mentzer et al. (32) Reading Auditory-visual MTS programmed trials with letters, syllables and words.Difficulty progression.
Both groups improved.DHH had lower baseline performances.Hearing group was better at sentence comprehension and word decoding.
Three.Between 2 and 3 years old.One CI user.
All showed improvements at least in two points (0-10) accordingly to their tests.Only one participant showed improvement by standardized tests.
Lund and Schuele (17) Expressive Vocabulary Vocal imitation and picture contextualization tasks.
Five. Between 3 and 5 years old.All CI users.
Regarding auditory discrimination, participants showed improvements.However little improvement in expressive vocabulary was observed.
Stacey et al. (26) Auditory Discrimination Discrimination tasks of isolated words and words within sentences (computerized and selfadministered) 11. Between 23 and 71 years old.CI users.
8 participants completed the entire program.Improvements in consonants discrimination, but not with vowels and sentences.
Schopmeyer et al. (12) Auditory Discrimination Fast ForWord program.Many programmed tasks.In general, auditory discrimination tasks with difficulty progression.
11. Mean age of seven years old.All CI users.
All children showed improvements on 5 standardized tests of receptive and expressive language.
processes of reading between a group of children with CI and a control group of hearing children.This study also used computerized programmed teaching characterized by discrete trials of auditory-visual MTS.It is worth mentioning that the studies of Anastácio-Pessan et al. 20 and Lucchesi et al. 21, targeting oral production responses, also adopted reading training through computerized programs as a route for the development of accurate speech production (expressive vocabulary).
Some conclusions can be drawn in the analysis of the articles selected in the last phase of this review study, regarding the effectiveness of verbal repertoire teaching methods for the deaf population and users of CI: I) The importance of individualized teaching (computerized or not), based on discrete trials, with explicit learning criteria and repeating/correction opportunities in case of wrong answers 17,18,[20][21][22][23]32 ; II) The importance of interventions centered on the participant's responses, in opposition to other teaching methods based on incidental learning 23,25 ; and III) The possibility of learning repertoires not taught directly through careful teaching programming (such as training auditory discrimination of diverse stimuli and gains in speech production) [20][21][22] . Ths last point is controversial and needs further investigation, since the intervention adopted in the study of Lund and Schuele 17 did not demonstrate this capacity of generalization by all participants; however, the number of opportunities for speech production responses during the training phases seems to be a distinction between these studies.
It is important to mention that some publications known beforehand by the authors were not selected by the method and terms adopted, even if they were aligned with the targeted literature (publications reporting teaching of verbal repertoires to the CI recipients population).Although these studies were associated with the used databases, they did not use terms related to "teaching" or "cochlear implant", often adopting nonstandard keywords, which may better describe the study, however restricting their access in review studies.The choice of standardized terms in opposition to other keywords is important considering the large number of publications, in order to promote visibility between researchers and professionals 40 .This consideration does not eliminate possible limitations of this review study (that used a small number of terms in the initial survey and did not seek studies from other sources), therefore, it is necessary that future review studies take into account other terms and search methods and analysis of the publications in this field.

CONCLUSION
According to the results, although the number of studies that reported teaching interventions are small, a greater number of these publications were found in relation to previous studies 8, 9 and increased in the last three years.However, the number of studies reporting interventions is still small compared to evaluation studies.The targeted population of teaching interventions are mostly children under 11 years old, with pre-lingual hearing loss and cochlear implanted.Regarding the targeted repertoires, training of auditory discrimination and expansion of oral vocabulary have been the main teaching objectives of these studies.Finally, regarding the results of these studies, there are evidences that point to the importance of individualized procedures and direct teaching, in opposition to group interventions through incidental learning.These data suggest, therefore, the increase in the investment in teaching programs of different verbal abilities, especially related to reading and writing.It also makes clear the importance of studies conducted with greater experimental control and, mainly, based on systematic replications to increase the generality of the obtained data.

Figure 1 . 3 -
Figure 1.Diagram: Study phases and number of publications found or selected by phase

Figure 2 .
Figure 2. Simple (bars) and cumulative (line) frequency of selected publications on verbal repertoires teaching per year

Figure 3 .
Figure 3. Target behaviors and adopted stimuli in the selected publications by number of articles

Table 1 .
Distribution of participants by study and their characterization regarding age, diagnosis and rehabilitation device