Language Teaching through the Flipped Classroom: A Systematic Review

: Language teaching is in question for reasons related to methodology. For years now, the focus has been on learning and the search for active methodologies such as the ﬂipped classroom (FC). This methodology was chosen because of its emergent character and because of the advantages and limitations that have arisen after its implementation in the classroom. Hence, the aim of this paper is to determine the level of expansion of the FC approach in language teaching over the last ﬁve years. For this purpose, a systematic review was carried out according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Two international databases, Web of Science (WOS) and Scopus, were used for the search, until 1 July 2022, using both Spanish and English descriptors: “language learning*”, “ﬂipped classroom,” and “language teaching”. In this process, inclusion and exclusion criteria were established for a sample (N = 181) which resulted in a ﬁnal selection of 26 articles. It can be seen that the majority of the articles published are between 2021 and 2022, aimed at L2 teaching, speciﬁcally English, and also show that they produce motivation in students and improve results in the development of language teaching, among others.


Introduction
The European Higher Education Area (EHEA) model and the ECTS credit system brought with it the search for new methodologies to optimise the development of curricular content, and a new structural order that affected the interaction of subjects with knowledge on the following: its organisation, the way of accessing and construction of knowledge, the relationship with teachers, and the participating role of each agent involved.In other words, there is a profound change in the educational relationship, that of teaching and that of the recognition of learning, in its double meaning of value: of use and of exchange.In the words of Rué [1], the implementation of the EHEA was aimed at a transformation of the structural frameworks that were to bring about new realities and new situations in university institutions, in general, and in the classroom in particular.
De Miguel [2], in this sense, highlighted the importance of redesigning and selecting scenarios, methodologies, and working methods for teachers and students; hence the need to study in depth both the organisational methods (distributed in number of hours of dedication until the corresponding ECTS credits are reached), and the teaching/learning methods that we integrated from our teaching conception.A new learning, based on the conjugation of these verbs "to learn and to teach" was used.Moreover, one of the most original, suggestive ways would be to conjugate them together in a single verb "aprenseñar" [3], which means trying to turn every act of teaching into a learning activity not only for others, but also for oneself, and conversely, to turn every personal learning situation into an opportunity to teach others.This educational space, as anticipated by Area [4], has been acquiring a dual pedagogical function: firstly, linked to face-to-face teaching, to facilitate the integration and use of new technologies (multimedia, web tutorials, educational chats, videoconferencing, etc.); and secondly, as a scenario for virtual teaching, it allows the development of synchronous and asynchronous activities (as has been happening in the different teaching scenarios developed during the pandemic: face-toface, multimodal, and online).
To this conception it is necessary to add the idea what Adell and Castañeda [5] call emerging pedagogy.These authors conceive it as "the set of pedagogical approaches and ideas, not yet well-systematised, that emerge around the use of information and communication technology (ICT) in education and that try to take advantage of all their communicative, informational, collaborative, interactive, creative, and innovative potential within the framework of a new learning culture" [5] (p.15).Moreover, it is in this context where we place the appearance of the flipped classroom approach, a model popularised by Bergmann and Sams [6], called flipped classroom (FC).Its impact on teaching performance and the role of the student [7] involves an inversion of the traditional method [8], where students prepare content that the teacher previously provided them with the idea of turning the classroom into a space for dialectical reflection on the issues and practical application.In this sense, the FC was chosen because, as Reyes-Ruiz [9] (p.9) pointed out, it "establishes a novel framework within which students receive a personalised and appropriate education to meet their individual learning needs", in this case, language teaching.This methodology advocates an interactive teaching-learning process: the learner develops his or her skills naturally through learning contexts and the teacher acts as a mediator in the construction of knowledge, in our case, the development of language skills.
Our teaching ideology led us to select not only the contents but also the way of sharing them in the classroom for the construction of learning [10].We opted for learningcentred teaching [11] so that students must participate in the construction of language learning from the contributions of the FC Table 1 model in order to successfully face their academic, social, and personal performance in and out of school.[11] to flipped classroom (FC) and language teaching.

Student centricity
Students take responsibility for their learning through the mediation of the teacher.
The teacher becomes a mediator of knowledge.From the FC approach, learning situations are generated in which students use the language and develop the mastery and use of communicative skills with a critical and autonomous vision of the information of the knowledge society.

Student activity
The student is the active actor of his own learning, he must be autonomous in his performance.

Cognition
Learning becomes an internal process as opposed to behaviourism which focuses on the external aspect of the outcome.
By means of the FC, processes are planned in the construction of learning, such is the case of the development of expression or comprehension whose teaching should be based on processes rather than on results.

Prior learning
It builds on previous knowledge and experiences to construct new learning.
The FC makes it possible to start from the nuclei of interest and to approach the contents from a learning based on enquiry and inductive reflection.

Achievement motivation
Achievement motivation should be intrinsic but accompanying teacher factors should support this line of recognition.
Use-based teaching and taking the progress of their linguistic behaviour as a positive value and the challenge offered by FC as an aspect of learner identity and improvement from self-reflection.

Collaborative learning
Learning must be underpinned by socialisation and shared learning.
The FC turns the classroom into a space for interaction where learning and the processes of access to knowledge are shared from dialogical situations and practical concreteness.

Teacher as facilitator
As opposed to the teacher-transmitter, the teacher becomes an enabling agent through mediation in the classroom.
We are living in a liquid society [12], changing and fluid, in which "the teacher is no longer considered to be the sole possessor of a knowledge that he or she should only have to transmit.He or she now becomes fundamentally the partner of a collective knowledge that he or she must organise and help to share" [13] (p. 60).This is implemented by the idea of Garrido-Lora et al. [14] by including the relational aspects of users as "media, technologies and networks should be considered not only as technologies for information and communication, but also and mainly for relationship" (p.55), whereby ICTs integrate the idea of "sharing", delimited as relationship, information, and communication technologies [15].The situation, for example, during the health emergency and confinement situation, implied "the acquisition of new competencies, skills and strategies based on processes of reflection on practice, training or training among peers or with mentors to be able to solve problems related to education" [16] (p.37), i.e., a look at teacher professional development approaches focused on facing a challenge or situation that is unknown [17].In our case, a transition from considering ICT as a methodological option to turning them into an indispensable resource for dealing with a supervening educational situation [18].
In this new scenario, we must be aware that new approaches, such as FC, make their incursion into the educational reality.Therefore, this methodology must be investigated from the historical foundations with the contributions of new sciences and disciplines.They are destined to shape emerging scenarios of horizons that fluctuate in the heart of a liquid society [12], that flows and transforms itself to lead us to a continuous dialectic of our thinking in a scientific area.It becomes essential to investigate beyond subjectivities and "manufactured uncertainties" [19] that require reflection to understand the controversial changes in the new educational and scientific policies [20].
The general objective (GO) focuses on determining the level of expansion of the FC approach in language teaching at present from a contextual and historical view of the last five years (2018-2022).There are three specific objectives: to determine the profile of research on language teaching and the FC approach (SO1), to compare its impact on learning (SO2), and to investigate motivational aspects in the implementation of a learning-centred approach (SO3).These objectives stem from a series of questions (Q) that justify a systematic review of the literature (SLR) from the perspective of the expectations of FC linked to language teaching.Table 2 begins with questions that make us reflect on what research has been carried out in recent years (Q1) and identify which institutions (Q2) and in which educational contexts (Q3) and countries (Q4) this type of practice is being carried out.From this global vision, we consider it necessary to review the objectives (Q5) and research methodologies (Q6) in order to verify the results (Q7) and the prospect (Q10) of their implementation in real contexts for the teaching of languages (Q8) as a mother tongue or foreign language (Q9).In this way, an analysis of the state of the art of language teaching including the FC approach was carried out.Gaps and research niches [21] will serve as a reference for further didactical use or new systematic studies.What is the trend in scientific publications on FC and language teaching.

GO
From which institutions is this research planned?(Q2) Which are the institutions and countries working in language teaching.GO In which country has this research been carried out?(Q4)

GO
In which contexts is this methodology being developed?(Q3) In which educational contexts is the FC approach to language teaching implemented (primary, secondary, higher education, etc.).
What is the intention behind the development of FC research for language teaching.

SO1
What methodology has been used for this? (Q6) What is the predominant trend in research (empirical versus theoretical studies).

SO2 SO3
What are the results?(Q7) What are the achievements and what are the difficulties of the FC after implementation in language teaching.How it impacts on motivational aspects of language learning.

SO2
Which languages do you work on most?(Q8) Which languages and language learning have the greatest impact on the implementation of this approach.

SO2
Is this research used more in L1 or L2? (Q9) This approach is most commonly used for teaching languages as a mother tongue (L1) or as a foreign language (L2, L3, etc.).

GO Possible prospection? (Q10)
On what achievements, considered as good practice, and on what limitations need further research in PK and language teaching.

Materials and Methods
For the development of this research, we proposed a systematic review in accordance with the principles established by Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) 2020.This was used because there are already many studies based on it and, in addition, there are a series of verification items that ensure a good systematic review [22].

Inclusion Criteria
In order to carry out the review, inclusion and exclusion criteria were established (Table 3).If another active methodology or other element is mixed in or if language teaching is not applied, the language is not used

Source of Information
Three databases are used: two general databases such as SCOPUS and Web of Science (WOS) because they are the most widely used by the scientific community and have impact factors that ensure the quality of the articles.This search was carried out between 1 March and 1 July 2022.

Search Strategies
The different search strategies used in the two databases were:

Data Selection Process
Initially, 181 records were counted and distributed as follows in the different databases (106 SCOPUS, 75 WOS).After eliminating those that were duplicated or otherwise, the following stages were established: Stage 1.The reviewers, i.e., all the authors of the article (H.H.P; M.F.R.O; and C.R.C) analysed all the articles and focused on which languages they were written in to eliminate those that were not in English or Spanish.
Stage 2. After that the titles and abstracts were looked at to exclude those that did not correspond to the research.This was reviewed by all reviewers (H.H.P; M.F.R.O; and C.R.C).In this way, all the decisions made were agreed upon.Stage 3. The different eligibility criteria were applied, i.e., whether it corresponds to the methodology we are looking for, the participants, the scope, and the HF study itself.This was also performed by all reviewers (H.H.P; M.F.R.O; and C.R.C).
All this is reflected in the following flowchart (Figure 1):

Data extraction process
For this purpose, the SPSS program was used to carry out the different descriptive results.All the authors of the article (H.H.P; M.F.R.O; and C.R.C) also participated in this process as reviewers.
Regarding the results obtained in the different articles, we found motivations to learn relating to the objectives, as seen in Table 5.
Table 5. Relation of the dimension "motivation to learn" to the results.

Discussion
The systematic literature review process was based on quality criteria [22] and took the PRISMA 2020 criteria as a reference.The findings showed that this approach takes on the role of an emerging methodology, especially in times of health pandemics, a year in which it produced a 42.3% increase in scientific production in the databases analysed (SCOPUS and WOS).The results of these studies support the efficacy of this approach and justify its validity beyond a possible positive reporting bias that would lead to a tendency to publish on FC and language teaching for reasons of occasional fashion.Their strengths focus not only on aspects related to the development of communicative language skills (Table 6) but also on aspects related to motivation as a learning strategy (Table 5).These ideas are corroborated by the different explanations which are developed throughout this section.
After selecting the different articles and analysing them according to the different research questions, we observed, as mentioned above, that the largest number of publications on FC in the classroom for language teaching is between 2020 and 2022.This growth is related to the emergence of COVID-19, an aspect that coincides with other studies [49,50].It is true that not only language teaching has been developed with this active methodology, but also with other active methodologies such as gamification [51,52] or augmented reality [53].
These publications have been developed more in the Asian region, as can be corroborated by other studies [54,55].However, research has also been carried out in other continents such as Europe [56,57].
Although the beginning of FC was linked to secondary education studies in the USA [6], this research settled in the university environment for the creation of a student identity in the learning process through interaction with peers and teacher mediation.As Rodríguez-Vélez and Cedeño-Macías [58] stated, studies in non-university contexts are declining to the point of disappearing in Early Childhood Education, due to the fact that this methodology aims to build on students' self-determination in the management of media and information, an aspect that children in Early Childhood Education, due to their age, do not have and which would hinder the teaching-learning process both in the mother tongue or L2 and in the use of ICT.One line that emerges is that since FC has not yet been integrated into the school and home culture, it is important that both educators and school administrators work together to raise parents' awareness of the benefits of FC [43].
On the results obtained, it can be seen that, in terms of the dimension "motivation in learning", the research improves the interactions with teachers and the role of students is active.This is not only seen in our articles, but also in other studies [59].In addition, in terms of the other dimension under study, "impact on learning", there are key aspects that stand out such as the creation of a more synchronous/collaborative online learning environment that can enhance the out-of-class component and thus help improve learning [36], focusing on the development of communication skills independently and not from an integrative skills approach.This trend is along two lines: foreign language teaching and the development of grammatical competence.
Assessment remains a point of reference in language learning.In this sense, the involvement of teachers and students in the teaching-learning processes [32,35,47] means that this methodology provides an ideal context for working not only on the end product but also on the process, i.e., critical, formative, and reflective evaluation [33], which aims to verify the improvement of linguistic behaviour and to provide a voice to the agents involved.
In addition, it was observed that the FC is used for teaching foreign languages [26,[38][39][40]46,47], with a predominance of English, although other languages such as Greek are also used [60].The aim is to make use of the standards and the educational model in the field of language learning [24].Although there is a tendency to develop communicative skills, we also found research that was limited to the teaching and learning of grammar [23,26,29,35,37,41], an aspect that limits language teaching, as it should focus on the use of FC in relation to other linguistic skills and explore its advantages from the point of view of language use [44].
Another aspect that stands out in the prospective studies focuses on teacher training for the implementation of CF in the classroom.We must be aware of the difficulty [47] in applying it effectively.Therefore, several studies [23,24,26,34,39,40,47] conclude that there is a need to provide technical support to teachers in institutions and universities (training courses and specific support materials, such as tutorials).Furthermore, [44] advocates training for the creation of personalised material by teachers [44].Although there are applications of multimedia programs in performance and motivation in learning [24][25][26], teaching videos should be developed with the teachers' videos or not taken from the Internet, but created by the teachers so that the students can feel the FC approach.In this sense, it would be a prospective line of research to investigate to what extent the characteristics of the instructors would affect the type of practice carried out in the classroom [40].
Regarding the objectives set out in the research, we observed that some are aimed at improving academic results, not only in L1 or L2, and others are aimed at promoting motivation [61,62] not only in the students, but also in the teachers, although this aspect was not analysed in our article [63].Both pre-service and in-service teachers should use flipped classroom models outside the writing class in order to have an efficient writing class that meets the needs of their students [30].
A key aspect is the research methodology.On the one hand, although quantitative studies are established as experimental studies with a control experimental group and a pretest-posttest to see if what is intended to be researched worked or not and thus be able to replicate it in other contexts, there are also other types of research on this topic such as systematic reviews [64].On the other hand, there are qualitative case studies, where the only technique or instrument used is a questionnaire, which may require the researcher to contrast the results with other techniques and instruments for corroboration, such as a focus group [65].However, no multiple case studies or longitudinal studies have been found.
From the analysis of the research methodologies, there is a need to broaden the specific contexts beyond the reality analysed and extrapolate the results to other areas or other levels, although similar results can be found.There is a strong need for replication studies to generalise and strengthen the results beyond the context of this study [27,35].It would be advisable to extend this study to other universities in different geographical areas, thus increasing the diversity and size of the sample [28,29,31,32,36,42,46].Furthermore, from a qualitative perspective it is essential to further investigate students' attitudes and expectations towards the purpose and value of QF in order to explore their attitudinal commitment [41] and to investigate individual differences through the analysis of their statements and diagnoses in order to understand how they can be helped to work with this methodology [46].
In this sense, we found the voices of authors proposing longitudinal studies, covering three or four semesters, beyond the implementation of a didactic experience or an experiment in the application of the method [29,31,40]; research on the perspectives of students regarding the use of this strategy in their classes, in addition to their opinions on the performance of students once this strategy is applied [34,36]; not to mention the challenge of analysing in depth the flipped classroom teaching model and the development of students' critical thinking in reading sub-skills [33] and how a cognitive model of language processing can be incorporated into all levels of language teaching and assessment [40].
Although the research questions were answered and the objectives were met, we are aware of the limitations of this work.Two aspects should be distinguished: the systematic review itself and the study itself.As for the systematic review, the main limitation is the exclusion of other databases of publications.The decision to exclude other databases was based on disciplinary reasons in the area of language teaching and, therefore, those most closely linked to Language and Literature Didactics were selected.Furthermore, the range of publications is limited to the years 2018-2022 in order to analyse the survival of a methodology in the present day, with special interest in the years of the COVID-19 health pandemic.However, the period chosen can be extended in a new research project and the results can be compared at their origins.In relation to the research itself, the option of carrying out an analysis of metadata was discarded as it would go beyond the scope of this research and would become the object of study in future research.
 WOS: The TOPIC filter was used with the following equation in both English and Spanish: ((Language learning* and flipped classroom*) OR (Language teaching* and flipped classroom*)), Quick filters ("Open Access"), Publication years (2018, 2019, 2020, 2021, and 2022), document types (Article) and open Access ("All Open Access");  SCOPUS: Article title, abstract, keywords with the following equation in both English and Spanish ((Language learning* and flipped classroom*) OR (Language teaching* and flipped classroom*)) was used as a filter.The following filters were also used in this database: open access (All open access), year (2018, 2019, 2020, 2021, and 2022) and document type (Article).

Figure 2 .
Figure 2. Number of publications by year.

Figure 3 .
Figure 3. Article production by country.

Table 1 .
Learning-centred teaching model.Adaptation of Campos' model

Table 2 .
SLR objectives and issues.

Table 3 .
Inclusion and exclusion criteria for article selection.

Table 4 .
List of selected titles and their respective authors.