2.3. Cognition and perception

As we try to make machines that look and behave like people, we need to equip them with perceptual abilities similar to that of humans. As user expectations exceed, a robot's perception must go beyond basic functionalities (e.g. localization, navigation or obstacle avoidance etc.). A key mechanism to achieve this is user modeling. Comparative studies of humans and robots can lead to new approaches [21–23]. The classical approach is to deliberately abstract computational instructions from physical realization of a human's cognitive system. Such robots that can perceive, infer and learn to mimic human behaviors are called cognitive robots. Intelligence, in a cognitive robot is the ability to transform sensed information into behavior. Human beings exhibit multitude of communicative signals while interacting. For a successful social interaction, a socially interactive robot should recognize the interaction roles, verbal and nonverbal cues and situation; thus exhibit a considerable degree of "social intelligence".

Speech signals contain information about who is saying, what is being said and how it is being said. Context, tone, pitch and loudness all combine to convey information. Research regarding speech understanding in robotics include works like [24, 25], etc. In addition to vocalization, facial expressions, also give an insight into the intent of the social agent. Detection of human face and recognition of facial expressions is being incorporated in a socially believable robot. Cognitive empathy [26] is the phenomenon which models perception of emotions in robots. Gaze tracking [27] is another important aspect of perceiving the intentions of people while interaction, as it can indicate the focus of their attention. However gaze tracking involves detection of both face and eye orientation. Work is being carried out in this area but there are still numerous challenges that need to be addressed. Gestures and activity recognition [28], is also a promising area of research that can contribute to designing a socially intelligent robot.

#### 2.4. Emotions and personality

are providing a platform for innovative researches in this area. Nevertheless there is always room for further improvement especially in the out-of-routine challenging situations, multiple and diverse contacts etc. The concept of sight in robots is now possible due to various components like servo-motors, actuators, 2D or 3D cameras and embedded optical sensors. Computer vision techniques for object recognition, human gestures, gaze and speaker tracking and collision or obstacle avoidance mimics sense of sight for the humanoids [12]. Distant communication with a robot using voice in an unconstrained environment is a highly challenging task. Methods to improve the auditory and speech recognition of a robot are being given much

Figure 3. Comparison of three humanoid faces based on emotion expression capabilities [7].

Speech is the most effective and natural mode of communication and interaction. From the view point of social robots, not only the robots need to be equipped with state-of-the-art automatic speech recognition (ASR) software [14], language models for interaction [16, 17] are also required to make semantic sense of what is being communicated to the robot. While ASR

attention by the researchers [13–15].

8 Human-Robot Interaction - Theory and Application

2.2. Speech and linguistics

Emotions play a significant role in human interaction; thus it was inevitable to induce emotions in socially interactive robots. The use of artificial emotions in social robots helps enhance believability and provides feedback to the users regarding the internal state of the robot, its goals and intentions. Artificial emotions [29], can also act as a control mechanism to understand robots perception of its surroundings. Numerous architectures have been proposed for introduction of artificial emotions but the most popular ones are based on bio-inspired models that include ethology, structure and psychology [30]. As mentioned in the previous section, there are several ways in which a robot can be made to express its emotions. Robots are now equipped with LEDs, motors and actuators beneath a flexible artificial skin to mimic various primary and secondary emotions. Aside mechanical actuation, computer graphics and animation techniques can also be applied to project emotions. Aside from facial gestures, robots are being designed to display emotions by other non-verbal cues like sound tone and pitch and body movements. The main purpose of expressing emotions is to convey readable signals to human for providing feedback and giving insight about robots intended plan of action.

robot cognition-centered approaches. In robot-centered HRI model, social robots are preprogrammed to interact with humans. Sociable robots are usually designed based on such approaches. They proactively engage people in a social manner and the interaction is designed to be mutually beneficial for both participants i.e. humans can be motivated to perform a specific task (e.g. for therapeutic purposes etc.) whereas robots can use the conversation for learning purposes. On the other hand, socially evocative robots are designed to interact with humans based on human-centered perspective. Anthropomorphism plays a key role in such kind of interaction. In a way, human participant attributes social responsiveness to the robot participant. Reasoning and consequently learning capabilities of the robot are not central objective in this HRI model. Socially interactive robots have instigated another HRI approach which is centered on robot cognition. These robots aim to intelligently interact with their human counterparts. Nevertheless such type of HRI models are greatly influenced by various

Socially Believable Robots

11

http://dx.doi.org/10.5772/intechopen.71375

Significant efforts are being made to model HRI with the objective to inculcate social intelligence in robots. Some suggest modeling of human behaviors and cognition as a sequence of instructions which are pre-programmed into the robots while the other approach is to imitate human behaviors and learn from interactions. Irrespective of the approach selected for designing a social HRI model, several common factors play vital role in shaping it and thus should be

According to Beer et al. [36], HRI is greatly influenced by levels of robot autonomy (LORA). From tele-operators to humanoids, LORA influences the way in which humans and robots interact. Hence in order to model HRI, we must first identify the variables that influence and

A robot's intelligence and learning capabilities are important considerations as they influence what tasks a robots performs and how it performs them. A robots learning process may require a number of interactions with its human counterpart. Robots with high intelligence require lesser frequency of interactions than those with comparatively lesser intelligence.

Distance and orientation in social encounters between humans and robots is an important aspect [37]. A robot in close proximity may be able to hear human voice and detect facial expression clearly but might not be able to detect human gestures due to limitation in vision. On the other hand, a robot at a distance may detect full body gestures but is unable to carry out

factors and mainly require deep modeling of human cognition.

3.1.1. Factors influencing human robot social interaction

given due consideration.

3.1.1.1. Robot autonomy

3.1.1.3. Proxemics

are influenced by robot autonomy.

3.1.1.2. Robot intelligence and cognitive ability

facial expressions and speech recognition.

Psychology defines personality as distinctive traits that distinguish an individual [31]. It is mainly the observers who define a person's personality. In terms of robots, five types of personalities are usually considered, i.e. Tool like, Pet or Creature, Cartoon, Artificial being and Human-like based on its morphology and functionality. According to studies [32], personality of a robot can also be determined based on its ability to interact, express emotions and react in a given situation. Much has been done to make a believable human replica, however our biological and psychological complexities are still not fully discovered or understood, making it extremely difficult to project them into a robot.
