# Exploring the Relationship between Interactions and Learning Performance in Robot-Assisted Language Learning

Authors: Yutong Ao; Zhonggen Yu
Journal: Education Research International
 (2022)

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## Abstract

Robot-assisted language learning is a pattern that uses a social robot in a class to enhance learning performance through human-robot interaction. While this pattern receives increasing attention, few review articles generalize whether each interactive behavior improves learning performance. This study delves into the answers to three research questions. The results show that the synthesized and prerecorded human voices are appropriate for different teaching activities. Verbal communication except for egocentric small talk and L1 translation between the robot and learners are indispensable to improve students’ confidence and learning gains. Moderate employment of nonverbal interactions helps students increase concentration, motivation, and retention of vocabulary, while undue interactions give rise to counterproductive effects. Based on the findings, future research on robot-assisted language learning is suggested to pay attention to the effectiveness of an independent interaction. Another valuable focus is the proper combination of interactive behaviors that suit different teaching tasks. A suitable level of robotic sociability is also worthy of exploration. Educators teaching with a robot should make full use of verbal and nonverbal interactive behaviors to boost students’ confidence, motivation, engagement, and learning gains. Meanwhile, they need to be cautious about the excessive employment of interactions.


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## Body

## 1. Introduction

Technology-assisted language learning (TALL) makes up numerous affordances that face-to-face environments cannot achieve, such as interactive feedback and tailored instruction. As a branch of TALL, robot-assisted language learning (RALL) is regarded as a prospective subfield [1]. Robots, qualifying properties of inference, learning, object seeking, problem-solving, and adaptiveness, have undertaken tasks in education.RALL is defined as the employment of a robot or robots to enhance language skills, from vocabulary recognition to text comprehension [1]. Scholars acknowledge the efficacy of robots in foreign language learning [2], as evidenced by past studies that learners remembered words faster [3], used grammar more accurately [2], and communicated more fluently [4].Previous scholars adopted the term “social robot” to discriminate robots in language learning from those used in engineering or surgery. A social robot features the behavioral norms of human beings and provides interactions with the audience [5]. Unlike virtual images of robots online, social robots are physical entities and thus allow learners to touch them. Although some are animal-shaped robots, most are anthropomorphized versions with movable heads, arms, legs, and even waists.Social robots are regarded as distinctive assistants from other technologies (e.g., gamification and virtual reality) because of their interactive behaviors. The two levels of interaction are verbal and nonverbal interactions. On the one hand, robots being available to perform oral communications, students can get direct knowledge. On the other hand, robots use eye-gazes or other signals to transfer information that verbal interactions cannot.The impetus of this review is to explore the efficacy of each interactive behavior robots perform, both verbally and nonverbally. Based on those findings, the study then provides suggestions for future RALL researchers and educators. Because social robots transmit knowledge through interactions, the efficacy of each interaction is crucial to research.


## 2. Literature Review

To disperse the mass gathering of people in one location, universities gradually shift from the in-person pattern of education to distant learning [6]. In the wake of COVID-19, TALL has become the trend in pedagogical activities. It is beneficial not only on the lifestyles but also on language learning activities [7, 8]. Tech-based education can be effectively adopted in smart classrooms as a supplement of the traditional approach in order to advance the learning procedure [7, 9]. As TALL is increasingly used in popularity, instructors and researchers develop many technology-supported tools as educational auxiliaries.The widely adopted technologies can be classified into three patterns: online recorded courses, APPs, and web conferences. Taking the advent of Language Massive Open Online Courses (LMOOCs) as an example, it is a practical approach to offer lifelong learning opportunities. LMOOCs enable people to learn in formal and informal settings, such as studying at home and work [10, 11]. Besides, it attracts students on the ground that it offers freedom and enables students to study at their own pace [6, 12, 13].A majority of studies in LMOOCs are carried out from the learner’s perspective. Researchers examined five elements that affect learners’ motivation: relatedness, utility value, pressure, effort, and intrinsic value [14]. In another study, researchers identified the percentage of highly self-determined learners among all LMOOC participants and found a surprisingly low proportion, accounting for 4.31% [15]. Zeng et al. [16] explored how LMOOC learners allocated their attention. The results showed that high-performing learners paid most attention, not to the start of a new course or specific course units but the maintenance and circulation of knowledge to other learning units. Besides, high-performing learners always followed the predesigned course outline. Chong and Reinders [17] analyzed 100 LMOOC courses and generalized their three limitations: the scarcity of interactions, the neglection of a student-centered approach, and the ignoring of individual differences. In terms of future trends of LMOOC studies, researchers pointed out four respects, comprising of the distinctive nature of LMOOCs, the intrinsic motivation and experience of participants, the reflection of teachers’ roles in LMOOCs, and the combination of sociability in LMOOCs [18].With regard to APPs, social networking sets comprising of Facebook and WeChat have been witnessed a wide use in education because they positively impact language learning [19–23]. The applications facilitate information literacy learning [24], incidental vocabulary acquisition, L2 pragmatic awareness [25–27], and instructor-student communications [28]. Barrot [19] scrutinized 396 documents and concluded three reasons why social media applications have an increasing status among language learners. They are flexible in communication, have a wide range of geographical distributions, and contain a considerable number of active users. Other merits are attributed to their enhancement of intercultural and sociopragmatic awareness, the facilitation of language user identities, and improving literacies, as Reinhardt [29] discussed.Web-based computer conference, for instance, ZOOM and Tencent Classroom, provides authentic and direct interactions between teachers and students [30, 31]. Researchers have found out the affirmative effects of online learning platforms in advancing learner’s self-awareness, self-regulation, and affective skills [32]. Almusharraf and Bailey [33] investigated 329 students using computer conferences and concluded that the collaborative language learning orientation, mediated by agent engagement, significantly predicts academic learning expectations. Furthermore, active students probably have more positive class expectations than those inactive. Another study conducted a four-month experiment and made a comparative analysis between traditional and online conferencing classes. It has been found that the latter approach elicited numerous nonverbal responses and could expand verbal results. An emerging issue was also pointed out that reticent students had difficulties fitting into the class [34].Apart from educational technologies above, RALL, the first of which appeared in 2004, is a new tech-based language learning approach. In its initial study, researchers intended to test whether children learned from robots as they learned from peers [35]. Robots in RALL have the attribute of socialness. They can identify, speak to, and respond to the audience through implicit and explicit expressions. Although the definitions of social robots vary in detail, all highlight four points: they (1) have physical entities, (2) resemble creatures, (3) adapt themselves to a social community, and (4) interact with humans in an effective manner.The four features of robots in RALL separate them from other electronic approaches, especially the simulation of an authentic interactive environment. Effective interaction should be considered when designing the robots. Arkin et al. [36] proposed three demands of interaction for social robots: high-level dialogue communication, perception and presentation of emotions, and the ability to use natural cues. Former studies discussed the efficacy of interactions in terms of subjects and learners’ age [35, 37–39]. Studies also generalized RALL as a whole [5] but failed to focus on interactive skills specifically. It leads to the first and the second question of this study: what verbal interactions in RALL could improve learning performance, and what nonverbal interactions in RALL could improve learning performance?Overall, previous studies lacked an in-depth analysis of the interactions between the robot and learners. It is possible that researchers and educators neglect several useful functions when setting robotic interactive behaviors. Therefore, this study proposed the third question: what are the suggestions for RALL researchers and educators?


## 3. Methodology

The literature review followed the documentary analysis method proposed by Spolaôr and Benitti [40]. Starting from searching for keywords, this study depicted the strategy of identifying exclusion criteria, quality criteria, and operations, as well as ways of retrieving and synthesizing information.


### 3.1. Keyword Searching Strategy

This review collected empirical studies through the Web of Science database. The author first identified keywords relevant to robot-assisted language learning. The article followed the opinion of van den Berghe et al. [5]. It did not restrict the quality of journals in case of missing information, in that RsALL is a new area, and there is the possibility that the number of articles with high quality is not adequate to review. The searching string was “(robot∗) AND (“language learning” OR “English learning”). To be more accurate, the author set the search scope in “Topic.” The author then constrained “Subject” in education to narrow the number of articles.


### 3.2. Identification of Exclusion Criteria

This section set the exclusion criteria (EC), which were partly drawn from the previous two papers [1, 5]. Studies colliding with one or more exclusion criteria were not considered. Twelve EC are shown in Table 1.Table 1
Excluded criteria.
EC1The robot did not play a/an (assisted-)teaching role (focusing on the robot programming or having no implications to RALL)EC7Articles that highly coincides with the previous one (similar title, abstract, and same author)åEC2The language of the article was not EnglishEC8People learned the language by programming the robotEC3The robot functioned outside a classroomEC9The robot was for sign language and special educationEC4The robot was not physical but virtual (a game in which the character is a robot)EC10ChatbotsEC5No empirical data was includedEC11Only part of the article was availableEC6The robot was for first language learning or STEM (science, technology, engineering, and mathematics) educations instead of second language learning onlyEC12The score of quality criteria is 0


### 3.3. Establishment of Quality Criteria and Strategy

The study framed quality criteria (QC) to measure if each remaining publications are of high quality (Table2). Answers to QC were yes or no. By answering QCs, 1 or 0 was recorded, respectively, providing quantitative evidence of the publications’ quality. Final scores were the sum of all criteria scores [40–42].Table 2
Quality criteria.
QC1Does the experiment have a comparative group simultaneously?QC2Is the experiment compared to previous results?QC3Is the experiment designed based on learning theories?QC4Does the experiment yield reliability and validity analysis?QC5Does the experiment yield not only statistics but also outcome exploration?


### 3.4. Information Retrieval

In light of a previous publication reviewing robotics in education, there were 26 Items (IE), highlighting the essential information of each study and horizontally comparing information under the same items. The items were packeted into four groups, as presented in Table3. Seven out of 26 items were extracted to collect helpful information for this article (Table 4).Table 3
Quality criteria (Table3 is reproduced from Spolaor et al. 2017 [31]).
Group 1. Publication identificationIE1. Publication titleIE2. Publication IDIE3. Year of publicationIE4. Authors’ nameIE5. Students’ educational institutionIE6. Publication objectiveIE7. Publication sourceIE8. NotesGroup 2. Activities reported in the publicationIE9. Comparison with previously published studiesIE10. Duration of the educational robotics activitiesIE11. Motivation to use educational roboticsIE12. Robot usedIE13. Robot priceIE14. Knowledge areas/subjects taught through roboticsIE15. Skills taught through roboticsGroup 3. Educational basis of the publicationIE16. Learning theory usedIE17. Justification for using the learning theoryGroup 4. Evaluation described in the publicationIE18. Feature(s) evaluated by the quantitative analysisIE19. Major findings (proved results)IE20. Major findings (nonproven results)IE21. Reliability or validity analysis considered during the quantitative analysisIE22. Responsible for carrying out the experimentsIE23. Sample sizeIE24. Short description of the quantitative study (information about activities carried out with robots, environment, and experimental settings)IE25. Statistical test usedIE26. Study type (nonexperimental, quasiexperimental, or experimental)Table 4
Generalization of the empirical studies.
IE10. Duration of activitiesIE11. Motivation to use educational roboticsIE12. Robot usedIE15. Skills taught through roboticsIE16. Learning theory usedIE19. Major findingsIE23. Sample sizeAdded: participantvan den Berghe et al., [5]7 sessions over 2 weeksTo explore children’s perception towards the robotic anthropomorphism and the effects on language learningNAOEnglish vocabulary/Children’s perceptions did not change significantly, and their perceptions had little impact on language learning gains.1045 years oldIio et al., [4]7 days, 30 min each dayTo explore the efficacy of RALL on adults’ English speakingComm UEnglish speaking/RALL improved speaking skills (fluency, accuracy, and pronunciation).918-22 years oldVan den Berghe, Oudgenoeg-Paz, et al., 202121-28 daysTo explore effects of individual differences on RALLNAOEnglish vocabulary/RALL positively impacted students who had worse L1 skills; RALL distracted those who had better L1 skills.1935 years oldBanaeian and Gilanlioglu, 20214 sessions within 2 weeksTo explore the effects of RALL on vocabulary learning and attitudes towards RALLNAOEnglish vocabulary/Some students had positive responds, while others were distracted by the robot.3319-24 years oldIE10. Duration of the activitiesIE11. Motivation to use educational roboticsIE12. Robot usedIE15. Skills taught through roboticsIE16. Learning theory usedIE19. Major findingsIE23. Sample sizeAdded: participantEngwall and Lopes, [49]2 days, 40-50 min each dayTo explore effects of the robotic interactive behaviors on learnersFurhatSwedish conversationCollaborative language learning theoryOne-on-one interaction between the robot and the learner was preferred, and the robotic encouragement promoted engagements.3332.4 years old on averageDemir-Lira et al., 20201 sessionTo explore effects of the robotic different gestures and differences between effects of the robotic gestures and the tablet’s visual imagesNAOEnglish vocabulary/Effects of RALL were the same as human tutoring, and RALL by on-screen led to better learning performance than by gestures.385-6 years oldKhalifa et al., 20192 sessions, 20 min each session; 4 weeks, 1 session each weekTo explore the efficacy of implicit learning and the “joining-in-type model” on learning gainsNAOEnglish grammar and conversational skillsImplicit learning/joining-in-type-humanoid RALL systemImplicit language learning promoted students’ instant construction of grammar but did not function effectively in a long-term. Repetition was important for implicit learning. The difficulty of grammar impacted the construction of conversational skills.57; 2318-24 years oldMuneeb et al., [66]4 sessions over 2 weeksTo explore effects of different emotional feedbacks on language learningNAOROILA vocabulary (an artificial language)Formation and retrieval of emotional memoriesPositive and neutral feedback enhanced language learning, while the negative feedback might not enhance language learning.2410-12 years oldIE10. Duration of the activitiesIE11. Motivation to use educational roboticsIE12. Robot usedIE15. Skills taught through roboticsIE16. Learning theory usedIE19. Major findingsIE23. Sample sizeAdded: participantVogt et al., [3, 61, 63, 67]7 sessionsTo explore the efficacy of RALL on childrenNAOEnglish vocabulary/RALL assisting by a tablet had a good impact on language learning, and the efficacy of RALL was similar to tablet-assisted language learning.1945-6 years oldLeeuwestein et al., [3]40 minTo explore effects of bilingual and monolingual robots in RALLNAODutch vocabularyCross-linguistic transferThe monolingual robot had better impacts on language learning than the bilingual robot.674-6 years oldWu et al., [43]4 sessions, 50 min each sessionTo provide a design guidelines that enhance English acquisition and reduce learning pressure and teaching load for RALL educators and researchers to followPET (powerful English tutor)English vocabulary and English speakingCommunicative language teaching (CLT), TPR (total physical response), and storytellingRALL enhanced learners’ motivation and learning outcomes.643rd gradeMeiirbekov et al., [44]5-6 minTo explore whether children would learn more if they were winning or losing the game to the robotNAOEnglish vocabulary/RALL improved learning gains, however which depended on the robotic adapting strategy. Children reacted positively and perceived the robot as a friend.228-9 years oldIE10. Duration of the activitiesIE11. Motivation to use educational roboticsIE12. Robot usedIE15. Skills taught through roboticsIE16. Learning theory usedIE19. Major findingsIE23. Sample sizeAdded: participantHong et al., 20161 sessionTo develop an instructional framework of RALLBioloidEnglish vocabulary and English speaking/RALL improved motivation, listening and reading performance.525th gradede Wit et al., 201820 minTo explore the efficacy of RALL in children’s EFL studiesNAOEnglish vocabulary/RALL helped remember and retain new words. RALL improved engagement. The robotic gestures had a positive effect on long-term memorization.614-6 years oldKennedy et al., 201611 minTo explore how social aspects of the robot influence children’s perception of the robot and LLNAOFrench vocabulary/Children had learning gains from the robot. Sociability of the robotic behavior did not influence learning performance.677-9 years oldShin & Shin, 201545 minTo explore the efficacy of RALL compared to CALLNAOEnglish vocabulary/RALL improved higher motivation, engagement, and satisfaction than CALL.6614 years oldChang et al., [45, 47]5 weeksTo explore the necessity and potential of RALLSapienEnglish vocabulary and English speaking/RALL enhanced motivation, interaction, and engagement.1003rd gradeIE10. Duration of the activitiesIE11. Motivation to use educational roboticsIE12. Robot usedIE15. Skills taught through roboticsIE16. Learning theory usedIE19. Major findingsIE23. Sample sizeAdded: participantde Haas et al., 201710-15 minTo explore how the robotic feedback influence learningNAOEnglish vocabulary/Students receiving different feedback had no significant difference towards learning performance.653-4 years oldKanda et al., [37]32 days over 2 monthsTo explore the possibility for the robot to sustain a long-term relationship with learnersRobovieEnglish texts/The robot sustained long-term interactions and established friendly relationships with students successfully.3710-11 years oldZhen-Jia You et al., [47]2 sessions over 2 weeks, 40 min each sessionTo explore how to familiarize students the robot and the effects of RALLRobosapienEnglish vocabulary/RALL boosted engagement, and students had positive attitudes to the robot.1006-12 years old


### 3.5. Information Synthesis

The following discussions were centered on empirical studies and review articles that met the demands of this review. The article answered three research questions by integrating information from the newly collected studies. Figure1 is the filtering process of prior studies.Figure 1
The flow of literature inclusion.


## 3.1. Keyword Searching Strategy

This review collected empirical studies through the Web of Science database. The author first identified keywords relevant to robot-assisted language learning. The article followed the opinion of van den Berghe et al. [5]. It did not restrict the quality of journals in case of missing information, in that RsALL is a new area, and there is the possibility that the number of articles with high quality is not adequate to review. The searching string was “(robot∗) AND (“language learning” OR “English learning”). To be more accurate, the author set the search scope in “Topic.” The author then constrained “Subject” in education to narrow the number of articles.


## 3.2. Identification of Exclusion Criteria

This section set the exclusion criteria (EC), which were partly drawn from the previous two papers [1, 5]. Studies colliding with one or more exclusion criteria were not considered. Twelve EC are shown in Table 1.Table 1
Excluded criteria.
EC1The robot did not play a/an (assisted-)teaching role (focusing on the robot programming or having no implications to RALL)EC7Articles that highly coincides with the previous one (similar title, abstract, and same author)åEC2The language of the article was not EnglishEC8People learned the language by programming the robotEC3The robot functioned outside a classroomEC9The robot was for sign language and special educationEC4The robot was not physical but virtual (a game in which the character is a robot)EC10ChatbotsEC5No empirical data was includedEC11Only part of the article was availableEC6The robot was for first language learning or STEM (science, technology, engineering, and mathematics) educations instead of second language learning onlyEC12The score of quality criteria is 0


## 3.3. Establishment of Quality Criteria and Strategy

The study framed quality criteria (QC) to measure if each remaining publications are of high quality (Table2). Answers to QC were yes or no. By answering QCs, 1 or 0 was recorded, respectively, providing quantitative evidence of the publications’ quality. Final scores were the sum of all criteria scores [40–42].Table 2
Quality criteria.
QC1Does the experiment have a comparative group simultaneously?QC2Is the experiment compared to previous results?QC3Is the experiment designed based on learning theories?QC4Does the experiment yield reliability and validity analysis?QC5Does the experiment yield not only statistics but also outcome exploration?


## 3.4. Information Retrieval

In light of a previous publication reviewing robotics in education, there were 26 Items (IE), highlighting the essential information of each study and horizontally comparing information under the same items. The items were packeted into four groups, as presented in Table3. Seven out of 26 items were extracted to collect helpful information for this article (Table 4).Table 3
Quality criteria (Table3 is reproduced from Spolaor et al. 2017 [31]).
Group 1. Publication identificationIE1. Publication titleIE2. Publication IDIE3. Year of publicationIE4. Authors’ nameIE5. Students’ educational institutionIE6. Publication objectiveIE7. Publication sourceIE8. NotesGroup 2. Activities reported in the publicationIE9. Comparison with previously published studiesIE10. Duration of the educational robotics activitiesIE11. Motivation to use educational roboticsIE12. Robot usedIE13. Robot priceIE14. Knowledge areas/subjects taught through roboticsIE15. Skills taught through roboticsGroup 3. Educational basis of the publicationIE16. Learning theory usedIE17. Justification for using the learning theoryGroup 4. Evaluation described in the publicationIE18. Feature(s) evaluated by the quantitative analysisIE19. Major findings (proved results)IE20. Major findings (nonproven results)IE21. Reliability or validity analysis considered during the quantitative analysisIE22. Responsible for carrying out the experimentsIE23. Sample sizeIE24. Short description of the quantitative study (information about activities carried out with robots, environment, and experimental settings)IE25. Statistical test usedIE26. Study type (nonexperimental, quasiexperimental, or experimental)Table 4
Generalization of the empirical studies.
IE10. Duration of activitiesIE11. Motivation to use educational roboticsIE12. Robot usedIE15. Skills taught through roboticsIE16. Learning theory usedIE19. Major findingsIE23. Sample sizeAdded: participantvan den Berghe et al., [5]7 sessions over 2 weeksTo explore children’s perception towards the robotic anthropomorphism and the effects on language learningNAOEnglish vocabulary/Children’s perceptions did not change significantly, and their perceptions had little impact on language learning gains.1045 years oldIio et al., [4]7 days, 30 min each dayTo explore the efficacy of RALL on adults’ English speakingComm UEnglish speaking/RALL improved speaking skills (fluency, accuracy, and pronunciation).918-22 years oldVan den Berghe, Oudgenoeg-Paz, et al., 202121-28 daysTo explore effects of individual differences on RALLNAOEnglish vocabulary/RALL positively impacted students who had worse L1 skills; RALL distracted those who had better L1 skills.1935 years oldBanaeian and Gilanlioglu, 20214 sessions within 2 weeksTo explore the effects of RALL on vocabulary learning and attitudes towards RALLNAOEnglish vocabulary/Some students had positive responds, while others were distracted by the robot.3319-24 years oldIE10. Duration of the activitiesIE11. Motivation to use educational roboticsIE12. Robot usedIE15. Skills taught through roboticsIE16. Learning theory usedIE19. Major findingsIE23. Sample sizeAdded: participantEngwall and Lopes, [49]2 days, 40-50 min each dayTo explore effects of the robotic interactive behaviors on learnersFurhatSwedish conversationCollaborative language learning theoryOne-on-one interaction between the robot and the learner was preferred, and the robotic encouragement promoted engagements.3332.4 years old on averageDemir-Lira et al., 20201 sessionTo explore effects of the robotic different gestures and differences between effects of the robotic gestures and the tablet’s visual imagesNAOEnglish vocabulary/Effects of RALL were the same as human tutoring, and RALL by on-screen led to better learning performance than by gestures.385-6 years oldKhalifa et al., 20192 sessions, 20 min each session; 4 weeks, 1 session each weekTo explore the efficacy of implicit learning and the “joining-in-type model” on learning gainsNAOEnglish grammar and conversational skillsImplicit learning/joining-in-type-humanoid RALL systemImplicit language learning promoted students’ instant construction of grammar but did not function effectively in a long-term. Repetition was important for implicit learning. The difficulty of grammar impacted the construction of conversational skills.57; 2318-24 years oldMuneeb et al., [66]4 sessions over 2 weeksTo explore effects of different emotional feedbacks on language learningNAOROILA vocabulary (an artificial language)Formation and retrieval of emotional memoriesPositive and neutral feedback enhanced language learning, while the negative feedback might not enhance language learning.2410-12 years oldIE10. Duration of the activitiesIE11. Motivation to use educational roboticsIE12. Robot usedIE15. Skills taught through roboticsIE16. Learning theory usedIE19. Major findingsIE23. Sample sizeAdded: participantVogt et al., [3, 61, 63, 67]7 sessionsTo explore the efficacy of RALL on childrenNAOEnglish vocabulary/RALL assisting by a tablet had a good impact on language learning, and the efficacy of RALL was similar to tablet-assisted language learning.1945-6 years oldLeeuwestein et al., [3]40 minTo explore effects of bilingual and monolingual robots in RALLNAODutch vocabularyCross-linguistic transferThe monolingual robot had better impacts on language learning than the bilingual robot.674-6 years oldWu et al., [43]4 sessions, 50 min each sessionTo provide a design guidelines that enhance English acquisition and reduce learning pressure and teaching load for RALL educators and researchers to followPET (powerful English tutor)English vocabulary and English speakingCommunicative language teaching (CLT), TPR (total physical response), and storytellingRALL enhanced learners’ motivation and learning outcomes.643rd gradeMeiirbekov et al., [44]5-6 minTo explore whether children would learn more if they were winning or losing the game to the robotNAOEnglish vocabulary/RALL improved learning gains, however which depended on the robotic adapting strategy. Children reacted positively and perceived the robot as a friend.228-9 years oldIE10. Duration of the activitiesIE11. Motivation to use educational roboticsIE12. Robot usedIE15. Skills taught through roboticsIE16. Learning theory usedIE19. Major findingsIE23. Sample sizeAdded: participantHong et al., 20161 sessionTo develop an instructional framework of RALLBioloidEnglish vocabulary and English speaking/RALL improved motivation, listening and reading performance.525th gradede Wit et al., 201820 minTo explore the efficacy of RALL in children’s EFL studiesNAOEnglish vocabulary/RALL helped remember and retain new words. RALL improved engagement. The robotic gestures had a positive effect on long-term memorization.614-6 years oldKennedy et al., 201611 minTo explore how social aspects of the robot influence children’s perception of the robot and LLNAOFrench vocabulary/Children had learning gains from the robot. Sociability of the robotic behavior did not influence learning performance.677-9 years oldShin & Shin, 201545 minTo explore the efficacy of RALL compared to CALLNAOEnglish vocabulary/RALL improved higher motivation, engagement, and satisfaction than CALL.6614 years oldChang et al., [45, 47]5 weeksTo explore the necessity and potential of RALLSapienEnglish vocabulary and English speaking/RALL enhanced motivation, interaction, and engagement.1003rd gradeIE10. Duration of the activitiesIE11. Motivation to use educational roboticsIE12. Robot usedIE15. Skills taught through roboticsIE16. Learning theory usedIE19. Major findingsIE23. Sample sizeAdded: participantde Haas et al., 201710-15 minTo explore how the robotic feedback influence learningNAOEnglish vocabulary/Students receiving different feedback had no significant difference towards learning performance.653-4 years oldKanda et al., [37]32 days over 2 monthsTo explore the possibility for the robot to sustain a long-term relationship with learnersRobovieEnglish texts/The robot sustained long-term interactions and established friendly relationships with students successfully.3710-11 years oldZhen-Jia You et al., [47]2 sessions over 2 weeks, 40 min each sessionTo explore how to familiarize students the robot and the effects of RALLRobosapienEnglish vocabulary/RALL boosted engagement, and students had positive attitudes to the robot.1006-12 years old


## 3.5. Information Synthesis

The following discussions were centered on empirical studies and review articles that met the demands of this review. The article answered three research questions by integrating information from the newly collected studies. Figure1 is the filtering process of prior studies.Figure 1
The flow of literature inclusion.


## 4. Results and Discussion

Due to the newness of robot-assisted language learning, studies on this subject are sparse. Twenty empirical studies were included after passing the filter criteria. This section answered three research questions. Robots possessing both verbal and nonverbal functions interact with learners in multiple ways. For example, robots speak and perform to learners, who respond to them in turn. The following paragraphs explored interactions from verbal and nonverbal perspective separately.


### 4.1. RQ1: What Verbal Interactions in RALL Could Improve Learning Performance?

Social robots perform verbal interactions through communication, in which the type of voice is set beforehand.


#### 4.1.1. Voice

Designers program the robotic voice to be mechanically synthetic or prerecorded by humans. The mechanical voice, although not natural, is human-like and can qualify features of human beings’ voice. A large proportion of empirical articles this paper reviewed did not mention the voice type; others either reported it explicitly or were inferred between the lines.Firstly, the synthesized voice is of use due to its flexibility to present different characteristics such as age and gender [43]. In an experiment, researchers designed English storytelling practices for 22 young children assisted by a robot with a synthesized and varied voice. The results showed that children in this group were more interactive and concentrated than the control group without a robot [44]. Researchers inferred that the male child-like voice narrowed the psychological distance and made the robot more acceptable to children. Another study set the robot to perform a story with either a male or female voice. After five weeks of learning, teachers in the class positively evaluated the voice variation as it could make the class more vivid and engaging [45].Although it is welcomed by children and teachers, the mechanical voice has a distinctive flaw. In the study described above, teachers also pointed out the robotic difficulty expressing emotions indispensable to language learning [45]. In a study, 33 first-year students of the English teaching program learned English vocabulary assisted by the NAO robot with a mechanical voice, while 32 students learned through human teachers. The results showed no significant difference between both groups in terms of learning gains. Some students commented that the voice was emotionless and robotic while they listened [46]. Another experiment doing field trails confirmed had the same results [47], but currently, no experiment supported its adverse effects on children’s engagement and performance.The prerecorded voice can perfectly express emotion as an alternative to the synthesized voice [48], but it created fewer identities in the storytelling practice than the synthesized voice. In two experiments, researchers changed the pitch of prerecorded adult voice to make it sound child-like [37]. Researchers in a Japanese experiment used a recorded voice of a native English speaker to communicate with students. After the interactions, they found that the utterances were too fast for the young Japanese students to comprehend [37], but this negative impact could be moderated by the adjusted rate of the recorded utterances.


#### 4.1.2. Type of Verbal Communication

Verbal communication is essential for social robots to interact with the audience. Researchers adopted different communication frames to adapt to language abilities, namely, two-way communication (dialogue and quiz) and one-way communication (egocentric small talk, feedback, and L1 translation).The two-way communication directly imbues learners with knowledge and fosters comprehensibility. It is a conversation that consists of questions, answers, and comments. Not only does it provide higher exposure, but it also drives learners to focus. At the first stage of RALL, the robotic talk assists learners to have a vague impression of the new knowledge. Next, robots tell stories [39] and ask questions with specific answers [4] or open questions [49] to either grab attention or facilitate understandings [1]. Another form of two-way communication is a dialogue that guides students to form discussions themselves. A study found that students’ communicative competence increased, and the new knowledge was internalized through two-way communication [40]. Researchers also input multiple expressions inside the robot. For example, the robot could say, “Can you show me the word X?” or “I don’t know the word X, can you show it to me” to increase the reliability of the robot [50].Some forms of one-way communication benefit learners, while others are controversial. One-way communication is an essential component of robotic verbal ability, including small egocentric talk, robot-to-learner feedback, and L1 translation support. They are discussed in the following paragraphs.Egocentric small talk can be either positive or negative owing to students’ individuality. In the experiment, researchers adopted the Furhat robot [49] and programmed it to dominate a discussion, only asking trivial questions and telling learners facts it wanted to tell [49]. As some learners were intrigued by the story, others performed passively, causing a decline in motivation. This difference happened presumably due to students’ differences (e.g., character).As for the feedback, robots providing positive feedback may result in higher learning performance than other feedback, but students receiving explicit feedback require less assistance from human teachers while learning. In a study testing three types of feedbacks, namely, explicitly negative, explicitly positive and implicitly negative, and no feedback, researchers found no difference in children’s engagement, but those receiving explicitly negative feedback showed a more independent performance [51]. Nevertheless, in both groups containing feedback, the robotic roles were not unified, which were peer (explicitly negative feedback) and adult (explicitly positive and implicitly negative), making it hard to decide to what extent roles influenced the research outcomes. Another study found that positive feedback from the robot resulted in a significant improvement in concentration and learning gains. Neutral and negative comments also benefited learners, although learning gains were moderate [52]. Some other articles also implemented the robotic feedback when designing the experiment but did not discuss its impact.Only one experiment explored the effect of robotic translation, according to which the bilingual robot attracted children’s attention, but the one speaking the second language stimulated more favorable learning performance [3]. In this study, [28] Turkish kindergartners learned Dutch vocabularies, half taught by the bilingual robot with Turkish translation, half by a monolingual Dutch robot. Contrary to the hypothesis, researchers found the children remembered fewer vocabularies from the bilingual robot than the Dutch-only ones.


### 4.2. RQ2: What Nonverbal Interactions in RALL Could Improve Learning Performance?

Many studies have provided evidence for the efficacy of nonverbal behaviors in enhancing learners’ understanding of the language knowledge [53]. Nonverbal behaviors function better when the robot is programmed in a personalized condition [54]. There are two typical nonverbal interactions throughout the gathered information: facial expressions and gestures [1].


#### 4.2.1. Facial Expression

It is observed that facial expressions improve learners’ concentration and motivation. Among all robots researchers got access to, only those countenances in the form of screen accomplished various emotions, including shyness, laughs, frustration, yawning, thinking, and eye-gazing [50, 55]. The most widely utilized NAO robot can only animate countenance through gaze and facial light as the robot Comm U [4].


#### 4.2.2. Gaze

Gazes gather learners’ attention, but undue gazes increase students’ learning anxiety. When the robot and the learner have eye contact, the latter is prone to focus on the learning activity [56]. A study supported the usefulness of eye-gazing. In this experiment, the robotic eyes moved casually to the children’s direction to impress them of being relaxed, accompanied by other nonverbal behaviors [39]. However, in this study, the effectiveness of gaze lacked empirical proof.In contrast, a study using an antisocial robot (a robot that avoided eye contacts) in the class resulted in better learning performance of the students than those learned from a normal robot [38]. Since this was an experiment assisted by a tablet, students having eye contact with the sociable robot looked less at the knowledge presented on the tablet. Another empirical study provided evidence for this conclusion [57]. Some students were watched by the robot while doing independent tasks. In this situation, the nature of eye contacts changes from attention-grabbing to watchfulness, causing anxiety.


#### 4.2.3. Facial Lights

Researchers adopt facial light as auxiliaries to strengthen the expressiveness of the robot. In two experiments [4, 55], facial lights were embedded in the cheeks of the robot with the aim of enhancing expressiveness. In a study teaching English to young children, the robot assistant switched its facial lamps to provide positive or negative responses [58]. In another study aiming to enhance 9 Japanese adults’ oral speaking, researchers added red LEDs to the two cheeks for strengthening the robotic expressiveness [4].


#### 4.2.4. Gestures

Gestures can improve engagement and motivation more or less. In this part, gestures are discussed in the narrow sense: limbs and body movements. Gestures are generally classified into three types: body orientation, deictic gestures, and iconic gestures. Two encouraging gestures, thumbs-up and applauding, are also involved. Iconic gestures move with limbs and the torso (e.g., bend the arms to make a circle to indicate the noun circle), and deictic gestures are index pointing gestures that implicate an entity or a place [59].Body orientation is crucial for the clarity of interactive behaviors. By changing the body direction, the robot and learners directly see each other. There are three studies that employed one-on-one interactions, where researchers placed the robot in front of the learners beforehand, so there was no need to move [51, 60, 61]. However, institutions cannot adopt the robot for each student because of the cost. In this case, most are three or above students simultaneously learned from the robot, and thus, students failed to face the robot straightforward, which might affect language learning. In another study, researchers placed the robot at a 90-degree angle to the children so that the robot and the children had a similar frame of reference, but it might reduce the clarity of gestures and hinder comprehensibility [62].Iconic gestures have instant benefits towards learning performance. A study found that a robot conducting iconic gestures was conducive to children [63]. In this study, Dutch children from two groups learned six animal words from the robot, who introduced them verbally and performed iconic behaviors in one group but did not in another. Although research results showed no difference in the immediate posttest, children who saw iconic gestures retained more words than other children in a delayed posttest a week later.Another two studies provided evidence for the distractive effect of iconic gestures. Researchers in the first study generalized three reasons. Above all, the robot faced the children in a 90-angle position, which might affect the clarity of gestures. Another reason was that the same iconic gestures were conducted many times when a new word appeared, causing distraction. The degree of children enacting the robotic gestures was also affected [62].Researchers in the second study believed that some iconic gestures are similar to deictic gestures. In this study, children answered a questionnaire to test their perception of anthropomorphism towards the robot [61]. Both groups, one seeing deictic gestures only and the other perceiving iconic and deictic gestures, had the same perception of anthropomorphism. Because the robot showed iconic gestures repetitively when introducing the same vocabulary, and because the robot failed to perform exactly iconic when teaching abstract words, such as “more,” its human-likeness did not differ from the deictic gesture-only robot, as the researchers concluded.Robots with deictic motions are more human-like than those without in the eyes of children, and a human-like robot provides a sense of confidence and cosiness [54]. They are designed to point out a particular object the new word refers to. Empirical studies in the scope of RALL all used deictic gestures except the one with robot Furhat (it only has a head), but no study explored in detail. Therefore, the efficacy of deictic gestures to learning performance is still awaiting exploration.Other body gestures can absorb learners’ attention and thus increase learning engagement and motivation. Researchers add them as an auxiliary to amplify the effect of intended interactions. During learning activities, the robot introduced itself accompanied by dancing to create closeness [63]. Stooping [4], nodding [56], applauding [58], and thumbs-up [47] were also designed to adapt the learning scenario and to give a positive response. A benefit for the robot to pose while teaching is instructing children to use appropriate gestures while speaking under a specific social context [45].


### 4.3. RQ3: What Are the Suggestions for RALL Researchers and Educators?

#### 4.3.1. Suggestions for RALL Researchers

Future studies could attach importance to the effectiveness of independent interactions, rather than the pooled impact of a series of interactive behaviors. Specifically, researchers should delve into differences of two types of voice, the mechanical and prerecorded human voice, while remaining other settings the same. Some scholars recommended robots speak in the most natural voice [64], but present studies did not have inadequate proof to support the superiority of one voice type to another in terms of learning performance. Future studies are expected to conduct more experiments of two types of voice to determine what are their suitable learning activities. Other potential functions to research are diverse communicative methods (dialogue, quiz, egocentric small talk, feedback, and translation), facial expressions (gaze and facial light), and different gestures (body orientation, iconic gestures, dancing, and thumbing-up). Since some interactions like iconic gestures may decline learning performance, researchers should explore the proper combination of interactions. Robots in language learning do not function solely based on a single interactive behavior but a series of behaviors to achieve learning gains.While some studies have been committed to the added benefits of social interactions, few have discussed a suitable level of sociability for those behaviors. Proper interactions could enhance learning motivation, engagement, and gains, but inadequate or undue behaviors could not function the most effectively, sometimes even leading to counterproductive effects. For instance, excessive gazes caused distraction and learning anxiety [56]. Researchers were expected to find the linear relation between different interactions and learning performance [65].


#### 4.3.2. Suggestions for RALL Educators

Educators should make use of interactions to optimize learning performance. If storytelling practices are necessary to foreign language learning, then the synthesized voice may be the priority, as it creates more characters and makes the story more attractive. In other learning activities, a robot equipped with a human voice is easier to familiarize students with the robot. Teachers should first clarify their class activities and then set certain interactions of the educational robot.Educators can combine robotic feedback with learning activities. Positive feedback boosts students’ confidence, concentration, and learning gains [52], while explicitly negative feedback presumably lessens students’ interest and confidence in learning, although it makes students more independent. Positive and implicitly negative feedback can be used when students are demotivated by factors, such as previous mistakes [51]. When teachers set the verbal output of robots, they should input commands for the robot to either praise students or point out where students can improve themselves.Excessive gazes from the robot negatively affect students’ performance [56]. Therefore, teachers need to employ the gaze interaction properly, although there is no approved standard to maximize the performance. Iconic gestures are effective for educators to adopt. The robot performing iconic gestures helps students retain new vocabularies longer. But teachers also need to be careful of the distractive effect of iconic gestures [47]. How to improve the expressiveness of an iconic gesture is also worthy of consideration. Abstract vocabularies like “less” are hard to be presented by image. Gestures like dance, thumbing-up, or applauding could enhance learning motivation and shorten the distance to the robot [58]. Researchers could consider excluding iconic gestures when designing the robot-learner interaction if the words taught are abstract.


## 4.1. RQ1: What Verbal Interactions in RALL Could Improve Learning Performance?

Social robots perform verbal interactions through communication, in which the type of voice is set beforehand.


### 4.1.1. Voice

Designers program the robotic voice to be mechanically synthetic or prerecorded by humans. The mechanical voice, although not natural, is human-like and can qualify features of human beings’ voice. A large proportion of empirical articles this paper reviewed did not mention the voice type; others either reported it explicitly or were inferred between the lines.Firstly, the synthesized voice is of use due to its flexibility to present different characteristics such as age and gender [43]. In an experiment, researchers designed English storytelling practices for 22 young children assisted by a robot with a synthesized and varied voice. The results showed that children in this group were more interactive and concentrated than the control group without a robot [44]. Researchers inferred that the male child-like voice narrowed the psychological distance and made the robot more acceptable to children. Another study set the robot to perform a story with either a male or female voice. After five weeks of learning, teachers in the class positively evaluated the voice variation as it could make the class more vivid and engaging [45].Although it is welcomed by children and teachers, the mechanical voice has a distinctive flaw. In the study described above, teachers also pointed out the robotic difficulty expressing emotions indispensable to language learning [45]. In a study, 33 first-year students of the English teaching program learned English vocabulary assisted by the NAO robot with a mechanical voice, while 32 students learned through human teachers. The results showed no significant difference between both groups in terms of learning gains. Some students commented that the voice was emotionless and robotic while they listened [46]. Another experiment doing field trails confirmed had the same results [47], but currently, no experiment supported its adverse effects on children’s engagement and performance.The prerecorded voice can perfectly express emotion as an alternative to the synthesized voice [48], but it created fewer identities in the storytelling practice than the synthesized voice. In two experiments, researchers changed the pitch of prerecorded adult voice to make it sound child-like [37]. Researchers in a Japanese experiment used a recorded voice of a native English speaker to communicate with students. After the interactions, they found that the utterances were too fast for the young Japanese students to comprehend [37], but this negative impact could be moderated by the adjusted rate of the recorded utterances.


### 4.1.2. Type of Verbal Communication

Verbal communication is essential for social robots to interact with the audience. Researchers adopted different communication frames to adapt to language abilities, namely, two-way communication (dialogue and quiz) and one-way communication (egocentric small talk, feedback, and L1 translation).The two-way communication directly imbues learners with knowledge and fosters comprehensibility. It is a conversation that consists of questions, answers, and comments. Not only does it provide higher exposure, but it also drives learners to focus. At the first stage of RALL, the robotic talk assists learners to have a vague impression of the new knowledge. Next, robots tell stories [39] and ask questions with specific answers [4] or open questions [49] to either grab attention or facilitate understandings [1]. Another form of two-way communication is a dialogue that guides students to form discussions themselves. A study found that students’ communicative competence increased, and the new knowledge was internalized through two-way communication [40]. Researchers also input multiple expressions inside the robot. For example, the robot could say, “Can you show me the word X?” or “I don’t know the word X, can you show it to me” to increase the reliability of the robot [50].Some forms of one-way communication benefit learners, while others are controversial. One-way communication is an essential component of robotic verbal ability, including small egocentric talk, robot-to-learner feedback, and L1 translation support. They are discussed in the following paragraphs.Egocentric small talk can be either positive or negative owing to students’ individuality. In the experiment, researchers adopted the Furhat robot [49] and programmed it to dominate a discussion, only asking trivial questions and telling learners facts it wanted to tell [49]. As some learners were intrigued by the story, others performed passively, causing a decline in motivation. This difference happened presumably due to students’ differences (e.g., character).As for the feedback, robots providing positive feedback may result in higher learning performance than other feedback, but students receiving explicit feedback require less assistance from human teachers while learning. In a study testing three types of feedbacks, namely, explicitly negative, explicitly positive and implicitly negative, and no feedback, researchers found no difference in children’s engagement, but those receiving explicitly negative feedback showed a more independent performance [51]. Nevertheless, in both groups containing feedback, the robotic roles were not unified, which were peer (explicitly negative feedback) and adult (explicitly positive and implicitly negative), making it hard to decide to what extent roles influenced the research outcomes. Another study found that positive feedback from the robot resulted in a significant improvement in concentration and learning gains. Neutral and negative comments also benefited learners, although learning gains were moderate [52]. Some other articles also implemented the robotic feedback when designing the experiment but did not discuss its impact.Only one experiment explored the effect of robotic translation, according to which the bilingual robot attracted children’s attention, but the one speaking the second language stimulated more favorable learning performance [3]. In this study, [28] Turkish kindergartners learned Dutch vocabularies, half taught by the bilingual robot with Turkish translation, half by a monolingual Dutch robot. Contrary to the hypothesis, researchers found the children remembered fewer vocabularies from the bilingual robot than the Dutch-only ones.


## 4.1.1. Voice

Designers program the robotic voice to be mechanically synthetic or prerecorded by humans. The mechanical voice, although not natural, is human-like and can qualify features of human beings’ voice. A large proportion of empirical articles this paper reviewed did not mention the voice type; others either reported it explicitly or were inferred between the lines.Firstly, the synthesized voice is of use due to its flexibility to present different characteristics such as age and gender [43]. In an experiment, researchers designed English storytelling practices for 22 young children assisted by a robot with a synthesized and varied voice. The results showed that children in this group were more interactive and concentrated than the control group without a robot [44]. Researchers inferred that the male child-like voice narrowed the psychological distance and made the robot more acceptable to children. Another study set the robot to perform a story with either a male or female voice. After five weeks of learning, teachers in the class positively evaluated the voice variation as it could make the class more vivid and engaging [45].Although it is welcomed by children and teachers, the mechanical voice has a distinctive flaw. In the study described above, teachers also pointed out the robotic difficulty expressing emotions indispensable to language learning [45]. In a study, 33 first-year students of the English teaching program learned English vocabulary assisted by the NAO robot with a mechanical voice, while 32 students learned through human teachers. The results showed no significant difference between both groups in terms of learning gains. Some students commented that the voice was emotionless and robotic while they listened [46]. Another experiment doing field trails confirmed had the same results [47], but currently, no experiment supported its adverse effects on children’s engagement and performance.The prerecorded voice can perfectly express emotion as an alternative to the synthesized voice [48], but it created fewer identities in the storytelling practice than the synthesized voice. In two experiments, researchers changed the pitch of prerecorded adult voice to make it sound child-like [37]. Researchers in a Japanese experiment used a recorded voice of a native English speaker to communicate with students. After the interactions, they found that the utterances were too fast for the young Japanese students to comprehend [37], but this negative impact could be moderated by the adjusted rate of the recorded utterances.


## 4.1.2. Type of Verbal Communication

Verbal communication is essential for social robots to interact with the audience. Researchers adopted different communication frames to adapt to language abilities, namely, two-way communication (dialogue and quiz) and one-way communication (egocentric small talk, feedback, and L1 translation).The two-way communication directly imbues learners with knowledge and fosters comprehensibility. It is a conversation that consists of questions, answers, and comments. Not only does it provide higher exposure, but it also drives learners to focus. At the first stage of RALL, the robotic talk assists learners to have a vague impression of the new knowledge. Next, robots tell stories [39] and ask questions with specific answers [4] or open questions [49] to either grab attention or facilitate understandings [1]. Another form of two-way communication is a dialogue that guides students to form discussions themselves. A study found that students’ communicative competence increased, and the new knowledge was internalized through two-way communication [40]. Researchers also input multiple expressions inside the robot. For example, the robot could say, “Can you show me the word X?” or “I don’t know the word X, can you show it to me” to increase the reliability of the robot [50].Some forms of one-way communication benefit learners, while others are controversial. One-way communication is an essential component of robotic verbal ability, including small egocentric talk, robot-to-learner feedback, and L1 translation support. They are discussed in the following paragraphs.Egocentric small talk can be either positive or negative owing to students’ individuality. In the experiment, researchers adopted the Furhat robot [49] and programmed it to dominate a discussion, only asking trivial questions and telling learners facts it wanted to tell [49]. As some learners were intrigued by the story, others performed passively, causing a decline in motivation. This difference happened presumably due to students’ differences (e.g., character).As for the feedback, robots providing positive feedback may result in higher learning performance than other feedback, but students receiving explicit feedback require less assistance from human teachers while learning. In a study testing three types of feedbacks, namely, explicitly negative, explicitly positive and implicitly negative, and no feedback, researchers found no difference in children’s engagement, but those receiving explicitly negative feedback showed a more independent performance [51]. Nevertheless, in both groups containing feedback, the robotic roles were not unified, which were peer (explicitly negative feedback) and adult (explicitly positive and implicitly negative), making it hard to decide to what extent roles influenced the research outcomes. Another study found that positive feedback from the robot resulted in a significant improvement in concentration and learning gains. Neutral and negative comments also benefited learners, although learning gains were moderate [52]. Some other articles also implemented the robotic feedback when designing the experiment but did not discuss its impact.Only one experiment explored the effect of robotic translation, according to which the bilingual robot attracted children’s attention, but the one speaking the second language stimulated more favorable learning performance [3]. In this study, [28] Turkish kindergartners learned Dutch vocabularies, half taught by the bilingual robot with Turkish translation, half by a monolingual Dutch robot. Contrary to the hypothesis, researchers found the children remembered fewer vocabularies from the bilingual robot than the Dutch-only ones.


## 4.2. RQ2: What Nonverbal Interactions in RALL Could Improve Learning Performance?

Many studies have provided evidence for the efficacy of nonverbal behaviors in enhancing learners’ understanding of the language knowledge [53]. Nonverbal behaviors function better when the robot is programmed in a personalized condition [54]. There are two typical nonverbal interactions throughout the gathered information: facial expressions and gestures [1].


### 4.2.1. Facial Expression

It is observed that facial expressions improve learners’ concentration and motivation. Among all robots researchers got access to, only those countenances in the form of screen accomplished various emotions, including shyness, laughs, frustration, yawning, thinking, and eye-gazing [50, 55]. The most widely utilized NAO robot can only animate countenance through gaze and facial light as the robot Comm U [4].


### 4.2.2. Gaze

Gazes gather learners’ attention, but undue gazes increase students’ learning anxiety. When the robot and the learner have eye contact, the latter is prone to focus on the learning activity [56]. A study supported the usefulness of eye-gazing. In this experiment, the robotic eyes moved casually to the children’s direction to impress them of being relaxed, accompanied by other nonverbal behaviors [39]. However, in this study, the effectiveness of gaze lacked empirical proof.In contrast, a study using an antisocial robot (a robot that avoided eye contacts) in the class resulted in better learning performance of the students than those learned from a normal robot [38]. Since this was an experiment assisted by a tablet, students having eye contact with the sociable robot looked less at the knowledge presented on the tablet. Another empirical study provided evidence for this conclusion [57]. Some students were watched by the robot while doing independent tasks. In this situation, the nature of eye contacts changes from attention-grabbing to watchfulness, causing anxiety.


### 4.2.3. Facial Lights

Researchers adopt facial light as auxiliaries to strengthen the expressiveness of the robot. In two experiments [4, 55], facial lights were embedded in the cheeks of the robot with the aim of enhancing expressiveness. In a study teaching English to young children, the robot assistant switched its facial lamps to provide positive or negative responses [58]. In another study aiming to enhance 9 Japanese adults’ oral speaking, researchers added red LEDs to the two cheeks for strengthening the robotic expressiveness [4].


### 4.2.4. Gestures

Gestures can improve engagement and motivation more or less. In this part, gestures are discussed in the narrow sense: limbs and body movements. Gestures are generally classified into three types: body orientation, deictic gestures, and iconic gestures. Two encouraging gestures, thumbs-up and applauding, are also involved. Iconic gestures move with limbs and the torso (e.g., bend the arms to make a circle to indicate the noun circle), and deictic gestures are index pointing gestures that implicate an entity or a place [59].Body orientation is crucial for the clarity of interactive behaviors. By changing the body direction, the robot and learners directly see each other. There are three studies that employed one-on-one interactions, where researchers placed the robot in front of the learners beforehand, so there was no need to move [51, 60, 61]. However, institutions cannot adopt the robot for each student because of the cost. In this case, most are three or above students simultaneously learned from the robot, and thus, students failed to face the robot straightforward, which might affect language learning. In another study, researchers placed the robot at a 90-degree angle to the children so that the robot and the children had a similar frame of reference, but it might reduce the clarity of gestures and hinder comprehensibility [62].Iconic gestures have instant benefits towards learning performance. A study found that a robot conducting iconic gestures was conducive to children [63]. In this study, Dutch children from two groups learned six animal words from the robot, who introduced them verbally and performed iconic behaviors in one group but did not in another. Although research results showed no difference in the immediate posttest, children who saw iconic gestures retained more words than other children in a delayed posttest a week later.Another two studies provided evidence for the distractive effect of iconic gestures. Researchers in the first study generalized three reasons. Above all, the robot faced the children in a 90-angle position, which might affect the clarity of gestures. Another reason was that the same iconic gestures were conducted many times when a new word appeared, causing distraction. The degree of children enacting the robotic gestures was also affected [62].Researchers in the second study believed that some iconic gestures are similar to deictic gestures. In this study, children answered a questionnaire to test their perception of anthropomorphism towards the robot [61]. Both groups, one seeing deictic gestures only and the other perceiving iconic and deictic gestures, had the same perception of anthropomorphism. Because the robot showed iconic gestures repetitively when introducing the same vocabulary, and because the robot failed to perform exactly iconic when teaching abstract words, such as “more,” its human-likeness did not differ from the deictic gesture-only robot, as the researchers concluded.Robots with deictic motions are more human-like than those without in the eyes of children, and a human-like robot provides a sense of confidence and cosiness [54]. They are designed to point out a particular object the new word refers to. Empirical studies in the scope of RALL all used deictic gestures except the one with robot Furhat (it only has a head), but no study explored in detail. Therefore, the efficacy of deictic gestures to learning performance is still awaiting exploration.Other body gestures can absorb learners’ attention and thus increase learning engagement and motivation. Researchers add them as an auxiliary to amplify the effect of intended interactions. During learning activities, the robot introduced itself accompanied by dancing to create closeness [63]. Stooping [4], nodding [56], applauding [58], and thumbs-up [47] were also designed to adapt the learning scenario and to give a positive response. A benefit for the robot to pose while teaching is instructing children to use appropriate gestures while speaking under a specific social context [45].


## 4.2.1. Facial Expression

It is observed that facial expressions improve learners’ concentration and motivation. Among all robots researchers got access to, only those countenances in the form of screen accomplished various emotions, including shyness, laughs, frustration, yawning, thinking, and eye-gazing [50, 55]. The most widely utilized NAO robot can only animate countenance through gaze and facial light as the robot Comm U [4].


## 4.2.2. Gaze

Gazes gather learners’ attention, but undue gazes increase students’ learning anxiety. When the robot and the learner have eye contact, the latter is prone to focus on the learning activity [56]. A study supported the usefulness of eye-gazing. In this experiment, the robotic eyes moved casually to the children’s direction to impress them of being relaxed, accompanied by other nonverbal behaviors [39]. However, in this study, the effectiveness of gaze lacked empirical proof.In contrast, a study using an antisocial robot (a robot that avoided eye contacts) in the class resulted in better learning performance of the students than those learned from a normal robot [38]. Since this was an experiment assisted by a tablet, students having eye contact with the sociable robot looked less at the knowledge presented on the tablet. Another empirical study provided evidence for this conclusion [57]. Some students were watched by the robot while doing independent tasks. In this situation, the nature of eye contacts changes from attention-grabbing to watchfulness, causing anxiety.


## 4.2.3. Facial Lights

Researchers adopt facial light as auxiliaries to strengthen the expressiveness of the robot. In two experiments [4, 55], facial lights were embedded in the cheeks of the robot with the aim of enhancing expressiveness. In a study teaching English to young children, the robot assistant switched its facial lamps to provide positive or negative responses [58]. In another study aiming to enhance 9 Japanese adults’ oral speaking, researchers added red LEDs to the two cheeks for strengthening the robotic expressiveness [4].


## 4.2.4. Gestures

Gestures can improve engagement and motivation more or less. In this part, gestures are discussed in the narrow sense: limbs and body movements. Gestures are generally classified into three types: body orientation, deictic gestures, and iconic gestures. Two encouraging gestures, thumbs-up and applauding, are also involved. Iconic gestures move with limbs and the torso (e.g., bend the arms to make a circle to indicate the noun circle), and deictic gestures are index pointing gestures that implicate an entity or a place [59].Body orientation is crucial for the clarity of interactive behaviors. By changing the body direction, the robot and learners directly see each other. There are three studies that employed one-on-one interactions, where researchers placed the robot in front of the learners beforehand, so there was no need to move [51, 60, 61]. However, institutions cannot adopt the robot for each student because of the cost. In this case, most are three or above students simultaneously learned from the robot, and thus, students failed to face the robot straightforward, which might affect language learning. In another study, researchers placed the robot at a 90-degree angle to the children so that the robot and the children had a similar frame of reference, but it might reduce the clarity of gestures and hinder comprehensibility [62].Iconic gestures have instant benefits towards learning performance. A study found that a robot conducting iconic gestures was conducive to children [63]. In this study, Dutch children from two groups learned six animal words from the robot, who introduced them verbally and performed iconic behaviors in one group but did not in another. Although research results showed no difference in the immediate posttest, children who saw iconic gestures retained more words than other children in a delayed posttest a week later.Another two studies provided evidence for the distractive effect of iconic gestures. Researchers in the first study generalized three reasons. Above all, the robot faced the children in a 90-angle position, which might affect the clarity of gestures. Another reason was that the same iconic gestures were conducted many times when a new word appeared, causing distraction. The degree of children enacting the robotic gestures was also affected [62].Researchers in the second study believed that some iconic gestures are similar to deictic gestures. In this study, children answered a questionnaire to test their perception of anthropomorphism towards the robot [61]. Both groups, one seeing deictic gestures only and the other perceiving iconic and deictic gestures, had the same perception of anthropomorphism. Because the robot showed iconic gestures repetitively when introducing the same vocabulary, and because the robot failed to perform exactly iconic when teaching abstract words, such as “more,” its human-likeness did not differ from the deictic gesture-only robot, as the researchers concluded.Robots with deictic motions are more human-like than those without in the eyes of children, and a human-like robot provides a sense of confidence and cosiness [54]. They are designed to point out a particular object the new word refers to. Empirical studies in the scope of RALL all used deictic gestures except the one with robot Furhat (it only has a head), but no study explored in detail. Therefore, the efficacy of deictic gestures to learning performance is still awaiting exploration.Other body gestures can absorb learners’ attention and thus increase learning engagement and motivation. Researchers add them as an auxiliary to amplify the effect of intended interactions. During learning activities, the robot introduced itself accompanied by dancing to create closeness [63]. Stooping [4], nodding [56], applauding [58], and thumbs-up [47] were also designed to adapt the learning scenario and to give a positive response. A benefit for the robot to pose while teaching is instructing children to use appropriate gestures while speaking under a specific social context [45].


## 4.3. RQ3: What Are the Suggestions for RALL Researchers and Educators?

### 4.3.1. Suggestions for RALL Researchers

Future studies could attach importance to the effectiveness of independent interactions, rather than the pooled impact of a series of interactive behaviors. Specifically, researchers should delve into differences of two types of voice, the mechanical and prerecorded human voice, while remaining other settings the same. Some scholars recommended robots speak in the most natural voice [64], but present studies did not have inadequate proof to support the superiority of one voice type to another in terms of learning performance. Future studies are expected to conduct more experiments of two types of voice to determine what are their suitable learning activities. Other potential functions to research are diverse communicative methods (dialogue, quiz, egocentric small talk, feedback, and translation), facial expressions (gaze and facial light), and different gestures (body orientation, iconic gestures, dancing, and thumbing-up). Since some interactions like iconic gestures may decline learning performance, researchers should explore the proper combination of interactions. Robots in language learning do not function solely based on a single interactive behavior but a series of behaviors to achieve learning gains.While some studies have been committed to the added benefits of social interactions, few have discussed a suitable level of sociability for those behaviors. Proper interactions could enhance learning motivation, engagement, and gains, but inadequate or undue behaviors could not function the most effectively, sometimes even leading to counterproductive effects. For instance, excessive gazes caused distraction and learning anxiety [56]. Researchers were expected to find the linear relation between different interactions and learning performance [65].


### 4.3.2. Suggestions for RALL Educators

Educators should make use of interactions to optimize learning performance. If storytelling practices are necessary to foreign language learning, then the synthesized voice may be the priority, as it creates more characters and makes the story more attractive. In other learning activities, a robot equipped with a human voice is easier to familiarize students with the robot. Teachers should first clarify their class activities and then set certain interactions of the educational robot.Educators can combine robotic feedback with learning activities. Positive feedback boosts students’ confidence, concentration, and learning gains [52], while explicitly negative feedback presumably lessens students’ interest and confidence in learning, although it makes students more independent. Positive and implicitly negative feedback can be used when students are demotivated by factors, such as previous mistakes [51]. When teachers set the verbal output of robots, they should input commands for the robot to either praise students or point out where students can improve themselves.Excessive gazes from the robot negatively affect students’ performance [56]. Therefore, teachers need to employ the gaze interaction properly, although there is no approved standard to maximize the performance. Iconic gestures are effective for educators to adopt. The robot performing iconic gestures helps students retain new vocabularies longer. But teachers also need to be careful of the distractive effect of iconic gestures [47]. How to improve the expressiveness of an iconic gesture is also worthy of consideration. Abstract vocabularies like “less” are hard to be presented by image. Gestures like dance, thumbing-up, or applauding could enhance learning motivation and shorten the distance to the robot [58]. Researchers could consider excluding iconic gestures when designing the robot-learner interaction if the words taught are abstract.


## 4.3.1. Suggestions for RALL Researchers

Future studies could attach importance to the effectiveness of independent interactions, rather than the pooled impact of a series of interactive behaviors. Specifically, researchers should delve into differences of two types of voice, the mechanical and prerecorded human voice, while remaining other settings the same. Some scholars recommended robots speak in the most natural voice [64], but present studies did not have inadequate proof to support the superiority of one voice type to another in terms of learning performance. Future studies are expected to conduct more experiments of two types of voice to determine what are their suitable learning activities. Other potential functions to research are diverse communicative methods (dialogue, quiz, egocentric small talk, feedback, and translation), facial expressions (gaze and facial light), and different gestures (body orientation, iconic gestures, dancing, and thumbing-up). Since some interactions like iconic gestures may decline learning performance, researchers should explore the proper combination of interactions. Robots in language learning do not function solely based on a single interactive behavior but a series of behaviors to achieve learning gains.While some studies have been committed to the added benefits of social interactions, few have discussed a suitable level of sociability for those behaviors. Proper interactions could enhance learning motivation, engagement, and gains, but inadequate or undue behaviors could not function the most effectively, sometimes even leading to counterproductive effects. For instance, excessive gazes caused distraction and learning anxiety [56]. Researchers were expected to find the linear relation between different interactions and learning performance [65].


## 4.3.2. Suggestions for RALL Educators

Educators should make use of interactions to optimize learning performance. If storytelling practices are necessary to foreign language learning, then the synthesized voice may be the priority, as it creates more characters and makes the story more attractive. In other learning activities, a robot equipped with a human voice is easier to familiarize students with the robot. Teachers should first clarify their class activities and then set certain interactions of the educational robot.Educators can combine robotic feedback with learning activities. Positive feedback boosts students’ confidence, concentration, and learning gains [52], while explicitly negative feedback presumably lessens students’ interest and confidence in learning, although it makes students more independent. Positive and implicitly negative feedback can be used when students are demotivated by factors, such as previous mistakes [51]. When teachers set the verbal output of robots, they should input commands for the robot to either praise students or point out where students can improve themselves.Excessive gazes from the robot negatively affect students’ performance [56]. Therefore, teachers need to employ the gaze interaction properly, although there is no approved standard to maximize the performance. Iconic gestures are effective for educators to adopt. The robot performing iconic gestures helps students retain new vocabularies longer. But teachers also need to be careful of the distractive effect of iconic gestures [47]. How to improve the expressiveness of an iconic gesture is also worthy of consideration. Abstract vocabularies like “less” are hard to be presented by image. Gestures like dance, thumbing-up, or applauding could enhance learning motivation and shorten the distance to the robot [58]. Researchers could consider excluding iconic gestures when designing the robot-learner interaction if the words taught are abstract.


## 5. Conclusion

This study presented a literature review on the relationship between interactions and learning performance in robot-assisted language learning.


### 5.1. Major Findings

RQ1 discussed verbal interactions in RALL that could improve learning performance. The synthesized voice is widely used. It shows various identities to make the storytelling process more engaging and concentrated, but some teachers and students regard it as cold and emotionless, reducing the effectiveness of language learning. The prerecorded human voice is natural and can express emotions powerfully, but not flexible to change the present multiple identities. Quiz and dialogues are indispensable in verbal interactions to transmit knowledge and foster comprehensibility. Feedbacks also function in RALL. However, egocentric small talk declines motivation, and students having a bilingual robot perform worse than those with a monolingual robot.RQ2 discussed nonverbal interactions in RALL that could improve learning performance. Facial expressions of a robot increase concentration and motivation. To mention one point, gaze from the robot should be moderate in case of distraction and learning anxiety. The position of the robot and learners influences the clarity of gestures. Iconic gestures help learners retain vocabulary. Many other gestures, including thumbing up, applauding, and dancing, enhance language motivation and confidence. Still, these behaviors may distract learners’ attention and reduce their performance.RQ3 proposed four suggestions for future RALL research and educators. As for the researchers, they are expected to determine the degree of effectiveness of each independent interactive behavior. How to combine different behaviors to adapt to different learning activities and how to maximize learning performance are also waiting to explore. Another suggested direction is to determine a suitable level of sociability for the robot in order to avoid excessive interactions. It is suggested that in the future, scholars conduct empirical studies, in which they set a solely interactive behavior each time to compare their effectiveness. Through the permutation and combination of each interaction, researchers can test some more practical groups of interactions than others. In terms of the proper behavior to particular teaching activity, researchers should select potential behaviors and compare their effectiveness by empirical studies.Suggestions for educators are specific. Educators should choose a suitable type of voice to accord to teaching activities. If the activities require a variation of characteristics, the synthesized voice probably functions better than the recorded human voice. Positive feedback and implicitly negative feedback are functional, as they boost confidence and stimulate learners. Gazes and gestures are indispensable to interactions, but to what extent the robot performs needs careful design beforehand. The match of iconic gestures to the new knowledge is another concern to enhance comprehension.


### 5.2. Limitations of This Study

The main limitation is that discussions on effects of the aspects except interactions are out of the scope of this study. These factors are different robots, different roles a robot plays, different participants, different degrees of human teacher interference, different skills being taught, and different learning environments.Another limitation lies in the limited studies this literature explored. It is inevitable to miss some studies because of the limited number of pathways or the loss of some relevant keywords while searching. Additionally, some studies are inaccessible to acquire full texts and thus are excluded in this study.It would be grateful if scholars or other readers put forward precious suggestions for the improvement of this study. Future researchers are expected to determine whether each interactive behavior contributes to learning performance and the degree of its effectiveness when interrupted by other factors.


## 5.1. Major Findings

RQ1 discussed verbal interactions in RALL that could improve learning performance. The synthesized voice is widely used. It shows various identities to make the storytelling process more engaging and concentrated, but some teachers and students regard it as cold and emotionless, reducing the effectiveness of language learning. The prerecorded human voice is natural and can express emotions powerfully, but not flexible to change the present multiple identities. Quiz and dialogues are indispensable in verbal interactions to transmit knowledge and foster comprehensibility. Feedbacks also function in RALL. However, egocentric small talk declines motivation, and students having a bilingual robot perform worse than those with a monolingual robot.RQ2 discussed nonverbal interactions in RALL that could improve learning performance. Facial expressions of a robot increase concentration and motivation. To mention one point, gaze from the robot should be moderate in case of distraction and learning anxiety. The position of the robot and learners influences the clarity of gestures. Iconic gestures help learners retain vocabulary. Many other gestures, including thumbing up, applauding, and dancing, enhance language motivation and confidence. Still, these behaviors may distract learners’ attention and reduce their performance.RQ3 proposed four suggestions for future RALL research and educators. As for the researchers, they are expected to determine the degree of effectiveness of each independent interactive behavior. How to combine different behaviors to adapt to different learning activities and how to maximize learning performance are also waiting to explore. Another suggested direction is to determine a suitable level of sociability for the robot in order to avoid excessive interactions. It is suggested that in the future, scholars conduct empirical studies, in which they set a solely interactive behavior each time to compare their effectiveness. Through the permutation and combination of each interaction, researchers can test some more practical groups of interactions than others. In terms of the proper behavior to particular teaching activity, researchers should select potential behaviors and compare their effectiveness by empirical studies.Suggestions for educators are specific. Educators should choose a suitable type of voice to accord to teaching activities. If the activities require a variation of characteristics, the synthesized voice probably functions better than the recorded human voice. Positive feedback and implicitly negative feedback are functional, as they boost confidence and stimulate learners. Gazes and gestures are indispensable to interactions, but to what extent the robot performs needs careful design beforehand. The match of iconic gestures to the new knowledge is another concern to enhance comprehension.


## 5.2. Limitations of This Study

The main limitation is that discussions on effects of the aspects except interactions are out of the scope of this study. These factors are different robots, different roles a robot plays, different participants, different degrees of human teacher interference, different skills being taught, and different learning environments.Another limitation lies in the limited studies this literature explored. It is inevitable to miss some studies because of the limited number of pathways or the loss of some relevant keywords while searching. Additionally, some studies are inaccessible to acquire full texts and thus are excluded in this study.It would be grateful if scholars or other readers put forward precious suggestions for the improvement of this study. Future researchers are expected to determine whether each interactive behavior contributes to learning performance and the degree of its effectiveness when interrupted by other factors.



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*Source: 1958317-2022-04-20.xml*