Keywords

1 Introduction

Greeting gestures are one of the most important aspects of social robot behavior design. Existing research has shown different greeting gesture design methods [1, 7] for social robots when they interact with humans [2]. However, although recognized as an important factor between human greetings, cultural difference [13] in robot greeting gesture design is less explored [4, 18]. For any social relationship, greeting is one of the common universal actions people follow to be close to each other [3, 6, 26]. Greeting study has been extensively explored in the social sciences in an effort to analyze the parameters that arbitrate and configure the nature of interactions between humans. Greeting is a principle component of daily intercommunication and is considered necessary for building and maintaining social relationships. It is nearly impossible for human beings to be present physically near each other and indicate that they are “conscious” and “properly engaged” without physical or emotional subsistence [26,27,28]. The dimension of greeting can be easily welcoming and assuring to others. In this way, humans use greetings as a means for making apart the other side of the interaction, and to signal approval and rejection [26].

Social interactions are a leading framework in Human-Computer Interaction [HCI], Human-Machine Interaction [HMI], Human-Robot Interaction [HRI] and Robot-Robot Interaction [RRI] research. The nature of popular greetings in a special engagement may have a wide range of influence on the management of social interaction [27]. “Social robots” are specifically designed to add a social aspect to HRI and RRI [5, 6, 39]. Figure 2 show a human-human greeting approach.

Social robots have also been developed for diverse contexts [41] including child education and development [20, 36, 37, 40], such as boosting children’s creativity through robot storytelling [29, 31,32,33], as well as physiotherapy and medical treatment [15, 35]; care-giving company for the elderly and lonely in affective state [3, 8,9,10]; learning systems for human communication and speech perfection [14, 21, 28]; education and social development [22, 33], wireless power charging robots and networking [39], virtual reality, augmented reality, mixed reality, human-robot teaming and cognition [30], smart robot homes and restaurants [2, 23, 25], intelligent robot systems [12], and so on. Robots are about to become commonplace in our personal and professional lives and in common working spaces [6], and human-robot teamwork approaches [24] for long term interaction are being developed accordingly [11, 17]. As such, it is important to design the HRI carefully [9, 19], and specifically the first “encounter” between humans and robots, i.e. greeting. The social importance of greeting provides an opportunity for social robot researchers to influence people’s interaction and engagement with the robot [23]. Findings from these studies draw an interesting picture and confirm the possibility of creating a meaningful greeting experience in a HRI [13, 16].

2 Related Work

2.1 Cross-Culture Technology

The use of mobile and computing devices, e.g., personal computers, mobile phones, smart watches, glasses, and wearable devices has become common in our daily life [39, 42]. These devices can be significant in influencing the quality of our conversations and social attention [52]. For example, when talking with partners, we may occasionally search for information on our smart devices. In these scenarios, our partners may notice such attention shifts, and react accordingly, e.g., by raising their voice, or pausing until our attention returns back, to prevent possible intercommunication breakdowns. Similar situations, whereby humans shift their attention to peripheral computing devices, could happen in HRI and RRI [2].

2.2 HRI Greetings

The idea of robot greeting gesture design comes from human-human gestures, which are an essential part of human introductions. Figure 2 shows a common human-human greeting gesture, while Fig. 3 shows greeting gestures in Japan and Thailand. Greeting has been shown to take different forms in different cultures, including verbal and nonverbal aspects of the interaction. Researchers have also argued that robots should adapt to cultural differences in order to communicate effectively. In one study, a humanoid robot performed physical gestures including bowing, raising a hand, moving it to the heart and nodding. Results showed that participants felt more comfortable when interacting with a robot that greets using language and gestures that matched the participants’ culture [4].

Human-robot greeting is important toward connecting human-robot intimacy, and could be important in contexts such as personal robot assistance. For example, a robot could act as a shopkeeper that recommends the best product selections. In this scenario, the robot greeting gesture could play a significant role in influencing the customer’s affective state [34, 44,45,46]. Performing a greeting gesture that matches that of the customer’s culture could be important in establishing trust, reliability, and affecting the customer’s decision-making [38, 48,49,50].

2.3 Robot Greeting Gesture Design

Robot greeting gesture design so far is less explored in the cross-cultural context as greeting gesture design is a challenge for robotic researchers. Related research on robot greeting gesture is mainly focused on bowing, waving, handshakes and nodding [43,44,45,46,47, 51].

Figure 4 shows the common greeting gesture between a NAO humanoid robot and a human. In the next section we will introduce four robot gesture designs. For example, Fig. 1 shows the common hand gestures in China and Thailand for representing Chinese and Thai greeting culture, respectively. We decided to design greeting gestures by NAO robot for four countries greeting culture, namely China, Bangladesh, Thailand and Japan.

Fig. 1.
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Common greeting hand gesture in China and Thailand.

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Fig. 2.
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Human-human greeting approach.

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Fig. 3.
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Greeting gesture in Japan and Thailand.

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Fig. 4.
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Common greeting gesture in HRI.

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3 Evaluation Experiments

We design four interactive greeting processes using the NAO robot platform based on our research questions.

  • Research question 1: Whether a user could perceive a robot coming from a specific country or region if the robot has a specific greeting gesture; and

  • Research question 2: If the user demonstrates higher valence when the robot has the same greeting gesture with his/her country.

3.1 Experiment Design

This section describes the four interactive greeting processes using the NAO robot. We designed four greeting interactions according to culture-based greetings in China, Bangladesh, Thailand, and Japan. Figure 5 shows our greeting design for these four countries. For China, the robot is bowing with both hands together in front of the torso, and the head faces downwards; Bangladesh, the robot is raising one hand up, and the head is facing directly forward; Thailand, the robot is holding both hands together near the chest, with the head is facing directly forward; Japan, the robot is bowing with both hands at each side of the body, and head facing downwards.

Fig. 5.
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Native robot greeting design, (1) China, (2) Bangladesh, (3) Thailand and (4) Japan.

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3.2 Experiment Protocol

Participants filled out a questionnaire surveying their basic demographics (e.g. gender, age, major, robot experience, etc.), and were given a brief tutorial regarding the basics of the NAO robot interaction before they participated in the experiment. In the first part, the robot performs a common greeting gesture once, and then a native greeting gesture once, and the participant is asked to answer the question of “where the robot is coming from?” after looking at the robot gesture. Participants from four different countries participants had the chance to participate in this experiment for two rounds. In the common greeting gesture part of the experiment, many participants answered that the robot performed a common or standard greeting gesture, whereas for the native greeting gesture part, most participants answered that the robot is coming from their native countries. This is explained in the data analysis section of this paper in Sect. 4.

For the second part of the experiment, we observed whether the user demonstrated higher valence if the robot has the same greeting gesture with his/her country. This was measured via a Likert chart. Figure 6 shows the native human-human greeting gesture (upper row) and native human-robot greeting gesture design (lower row), for (1) China, (2) Bangladesh, (3) Thailand and (4) Japan.

Fig. 6.
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Native human-human greeting (upper row) and native human-robot greeting design (lower row), (1) China, (2) Bangladesh, (3) Thailand and (4) Japan.

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3.3 Procedure and Measurement

Evaluation items are scored using self-report questionnaires. The questionnaire includes evaluation items for both common and native gesture conditions. There are two parts to the evaluation. The first is to measure participants’ ability to perceive where the robot comes from (the country) by understanding the robot gesture; the second part is for understanding likeability and valence toward the robot. Figure 7 shows the Self-Assessment Manikin used to rate the affective dimension of valence, i.e. to gauge participants’ emotional response towards the robot (Table 1).

Fig. 7.
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The Self-Assessment Manikin (SAM) used to rate the affective dimension of Valence.

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Table 1. Qualitative description list for study 1.
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3.4 Participants

Participants consisted of four nationalities including China, Bangladesh, Thailand and Japan. For Experiment 1 and 2, a total number of 20 participants (10 males, 10 females, average age: 24.7; min age: 18: max age: 32) were recruited from different universities in Beijing. The same participants were recruited for experiment 1 and 2.

3.5 Assessment

We used a 7-point scale to measure different emotional responses of participants towards the robot, after the robot greeting was performed.

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4 Data Analysis

Two experimental studies have been done during the experimental process. Study 1 findings show the calculation of the percentage ratio of participants’ preferred choice of the answered countries. Study 2 findings carry out the ANOVA analysis results.

Study 1- Findings

Four greeting gestures were demonstrated by our designed NAO robot to each participant, where the robot only performs body gesture with a counterbalancing technique to offset order bias. After the robot greeting gesture was performed, participants were asked whether the robot performed a common greeting gesture, or a greeting gesture native to his/her country. Among 20 participants from different countries, the ratio of answers identifying the robot greeting gesture was 70%, 10% and 20% for Native, Common and Others, respectively (Fig. 8). This indicates that users often correctly identified where the robot greeting gesture came from. Participants who answered “Others” mostly confused the greeting behavior of Thailand with India or other countries in south Asia, and the greeting behavior of China with Japan, while the greeting behavior of Bangladesh was sometimes regarded as a western greeting by participants.

Fig. 8.
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Ratio of calculating native, common and others in terms of evaluating where the robot coming from.

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Qualitative description list: We used some frequent descriptions written by the participants in study 1 (as answered to the open ended questions) and created a measurement list for NAO robot greeting. These included: Happy to see, look at me, good morning, good afternoon, welcome and laughing, scared of robot greeting behavior, avoiding eye contact with the robot, careless, resting, good eye contact, normal movement (See Table 1).

Study 2- Findings

We conducted a 1-way-ANOVA with the following independent variables: Greeting acceptance rate for valence (Common vs Native). A single factor ANOVA (Common vs Native) on the valence scale reveled a main effect: native feeling significantly affected valence F = 7.43, p < .05, p = .009. Participants rated native gestures as more close compared to the common gestures designed by the NAO robot greeting. Figure 9 shows the mean and SD comparison for calculating valence.

Fig. 9.
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Mean and SD comparison for calculating valence.

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We conducted a 1-way-ANOVA with the following independent variables: greeting acceptance rate for likeability (Common vs Native). A single factor ANOVA (Common vs Native) on the Likeability scale revealed a main effect: native feeling significantly affected the likeability F = 5.22, p < .05, p = .028. Participants rated native gestures as more likeable compared to the common gestures designed by the NAO robot greeting. Figure 10 shows the mean and SD comparison for calculating likeability.

Fig. 10.
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Mean and SD comparison for calculating likeability.

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5 Discussion

In this work we presented the NAO greeting design, implementation and user evaluation. In the design and implementation section we showed the NAO greeting design process for four Asian countries: China, Bangladesh, Thailand and Japan. We then reported two studies in which we used qualitative and quantitative methods to evaluate whether participants perceived the NAO robot greeting gesture as a greeting experience, and how the movement features of the gestures influence greeting expressivity.

In study 1, participants watched a common greeting gesture and native greeting gesture, then described the greeting feeling by using the Self-Assessment Manikin (SAM) and 7-point Likert scale. Qualitative analysis also showed that participants perceived the gestures as either a Positive Greeting or a Negative Greeting or a Normal Greeting using different emotional state descriptions.

In study 2, participants experience the native greeting interaction with the NAO robot. This was found to have a profound impact on participant’s perception. The native gesture was perceived as a Positive Greeting, reflecting that the user has higher valence if the robot has the same greeting gesture with his/her country.

6 Conclusion and Future Work

In this work we presented a greeting design process during HRI that performs body gesture to welcome people from different nationalities. The design evaluation method has been verified by a cross-cultural user experiment to investigate the research question. In the future we aim to develop greeting technology by designing expressive social robots with more functionality. We would also like to develop emotion-based social robots, given their importance during the human-robot greeting interaction process.