Human likeness refers to the degree to which a robot looks and behaves like a human. Human likeness includes two categories: human-like appearance and human-like behavior. Appearance describes the static aspects of the robot (look, sound, sense of touch, etc.), while behavior describes the dynamic aspects of the robot (actions, expressions, emotions, etc.). In the process of human–robot interaction, humans would perceive social distance from the robot. Social distance can be understood as the closeness between two individuals’ relationships.
1. Introduction
Robots can be used to perform a series of complex actions
[1]. A service robot performs service tasks for humans or devices
[2]. It is an autonomous robot capable of interacting with people and completing specific service tasks
[1]. The development of artificial-intelligence technology has popularized service robots, such as educational robots, therapeutic robots, and entertainment robots
[3]. However, human acceptance of service robots is the main obstacle to popularizing service robots
[4]. Since service robots have certain social attributes
[5] and human-like characteristics that can encourage humans to treat service robots as social participants, human-like characteristics can influence the service effectiveness of robots
[5][6]. The human-like characteristics of robots can effectively influence human attitudes toward robots
[6]. Human acceptance of the human-like characteristics of robots promotes human acceptance of service robots
[7], whereas human non-acceptance of the human-like characteristics of robots inhibits human acceptance of service robots
[6].
However, scholars have different views on human acceptance of human-like robots. Some scholars believe that humans have positive emotions toward human-like robots and are more willing to deal with a robot that has more human-like features
[7][8][9], while some other scholars believe that more human-like robots can cause fear and anxiety in people, decreasing their willingness to interact with the robot
[6][10]. This entry focused on how the human likeness of a service robot affects human acceptance of it.
Human likeness refers to the degree to which a robot looks and behaves like a human
[11]. Human likeness includes two categories: human-like appearance and human-like behavior
[12][13]. Appearance describes the static aspects of the robot (look, sound, sense of touch, etc.)
[14][15][16], while behavior describes the dynamic aspects of the robot (actions, expressions, emotions, etc.)
[11][12]. To enhance the human likeness of the service robot, the designer would endow the service robot with more human characteristics. For example, the designer would make a robot’s face look like a human’s or add more human characteristics to its actions
[13]. A few previous empirical studies have explored the human-like behavior of service robots (HLBR)
[8]. However, this factor also has an important effect on human–robot interaction
[8]. Therefore, this entry focused on the effects of HLBR on human acceptance of a service robot.
In previous studies, scholars used two types of constructs to measure human acceptance of a service robot: (i) psychological constructs, such as trust
[16][17][18], likes
[11], use intention
[19], and satisfaction
[20]; and (ii) sociological constructs, such as social distance
[21]. Most studies have employed psychological constructs, while few have employed sociological constructs. However, it is important to examine the human acceptance of a service robot from a sociological perspective. The previous literature has shown that the social rules in people-to-people interactions apply to human–robot interaction
[22], and robots can be viewed as social actors with specific behavioral patterns
[23]. This entry focused on the sociological aspect of human beings’ acceptance of service robots (i.e., social distance). Social distance refers to the closeness of the relationship between the two individuals in people-to-people interactions
[24]. The social distance between humans and service robots (SDHR) can measure the closeness of the relationship between humans and service robots
[25]. Thus, SDHR can indicate human acceptance of a robot
[21].
In addition, previous studies have shown that cultural background can affect human responses to robots
[26][27][28]. In the US and China, robots are widely used in various fields, including the service industry
[29], such as Sony’s entertainment robot AIBO and Takara’s home-care robot TERA
[26]. However, the two countries differ in their views on robots. Americans regard robots as assistants, while Chinese tend to regard robots as friends
[30]. It is generally believed that the US is an individualist country, and China is a collectivist country
[31][32]. Compared to individualism, interpersonal relationships are more intimate in the context of collectivism
[33]. Social rules in interpersonal communication can also apply to human–robot interaction
[22]. A cross-cultural study of human–robot interaction found that Chinese people have a higher sense of intimacy with robots than Americans
[26].
2. Human Likeness and Social Distance
In the process of human–robot interaction, humans would perceive social distance from the robot
[25]. Social distance can be understood as the closeness between two individuals’ relationships
[34]. SDHR is the result of the dynamic interaction between human attributes (gender, age, and the experience dealing with the robot) and robot attributes (appearance and interaction cues)
[25]. Previous studies have found that humans naturally attribute human characteristics to non-human objects
[14]. Consumers would spontaneously give human attributes to, for example, cars
[35] or brands
[36]. Human-like service robots have some characteristics of humans
[4]. The higher the human likeness of the robot, the richer the human characteristics of the robot, and the stronger the human perception of the similarity between robot and human
[37]. Perceived similarity can affect an individual’s perceived social distance; the higher the similarity, the smaller the social distance
[38][39]. As an aspect of the robot’s human likeness, a higher HLBR can also lead to a smaller SDHR.
3. Human Likeness as well as Competence and Warmth
Anthropomorphism is the tendency to attribute human-like qualities to non-human objects
[40][41]. The robot’s human-like appearance can promote the robot’s anthropomorphism
[8]. Anthropomorphism can enhance human emotional attachment to non-human objects in service scenarios
[42]. When humans interact with anthropomorphized robots, they may feel an affinity with the robots
[43]. Warmth and competence are basic dimensions used to characterize others
[44]. Human perception of the robot’s competence is related to the capabilities, intelligence, skills, and other characteristics of the service robot, while the human perception of the warmth of the robot is related to the caring, friendliness, sociability, and other characteristics of the service robot
[8][44]. Anthropomorphism affects these two basic judgment dimensions
[6][45][46]. Studies have found that if the robot is anthropomorphized by the HLBR, human perception of the robot’s competence may increase
[6], and human perception of the warmth of the robot may become more positive
[8][45]. Therefore, researchers can speculate that HLBR may affect human perceptions of the competence and warmth of the service robot. A service robot with a high human-like behavior should be considered more competent and warmer by humans.
4. Competence, Warmth, and Social Distance
Social distance reflects the consciousness of kind in human sociological attributes
[25][47]. The social-identity theory holds that humans would categorize individuals based on social-categorization cues
[44]. Human perceptions of the competence and warmth of robots would serve as social-categorization cues
[48][49] and affect the results of categorizing the social groups of robots by humans
[42]. The subjective categorization of inter-and intra-social groups affects social distance
[38]. When humans regard other individuals as members of the same group, social distance tends to be smaller
[39]. Therefore, researchers can speculate that the stronger the human perception of the competence and warmth of the robot, the smaller the SDHR would be.
5. Mediating Effects of Perceived Competence and Perceived Warmth
Studies suggest that humans tend to be attracted to human-like objects because of their conformity with humans
[35][50]. Competence and warmth are the two universal dimensions of human-impression formation
[44][48], accounting for almost 80% of human impressions of others
[48]. The robot’s human likeness can significantly affect these two basic judgment dimensions
[46]. Van Doorn et al. found that perceived competence and perceived warmth mediate the relationship between a robot’s human likeness and the service performance of the robot (such as customer satisfaction and loyalty)
[51]. Kim et al. found that the human likeness of the service robot affects consumer attitudes toward the service robot indirectly through competence and warmth
[8]. Social distance is a construct close to satisfaction and attitude
[25]. Therefore, researchers speculated that perceived competence and perceived warmth might mediate the relationship between HLBR and SDHR.