5.2. Hardware limitations vs. human expectations

The ultimate goal of anthropomorphism is to replicate a human being. Nevertheless our pursuit of making realistic humanoids might experience Mori's "Uncanny valley effect" at some point (Figure 6). Human expectations increase with a sophistication in design of a humanoid. This can attribute to people's rejection of anthropomorphic robots and other intelligent agents. On the other hand, recent studies like [56] suggest that shortcomings like mismatch between appearance and movement or voice can also create an uncanny or eerie feeling.

Despite great progression in the synthetic industry and mechatronics, we are still decades away from providing richer support for speech, gestures or expressions to machines. A look at the latest generation of humanoids reveals the gap between reality and fiction. The expressive behavior of robotic faces is still not life-like due to limitations of mechatronic design and control. Even for the most sophisticated generation of robots, displaying emotions reflects a certain degree of artificiality.

A robot's body is a mechanical structure composed of several rigid parts, connected to each other by joints. Currently each active joint has a restricted range of motion generated by actuators. Due to the complexity of design, manufacturing cost and mechanical dynamics, even the latest line of humanoids can imitate only basic tasks in a coordinated manner.

In contrast to conventional interactive systems, an interactive social robot must take its physical environment into consideration while communicating with users. Most real-world environments are unstructured, dynamic and noisy, making it challenging for robots. Although synthesized voice quality has improved over a period of time nevertheless communication between a human and a humanoid is still constrained by several factors like speech localization, language understanding, dialog management and non-verbal cues like gaze tracking etc.

#### 5.3. Standard models and comparability issues

An essential prerequisite to designing an intelligent system is to outline its functional requirements. Same holds true for the field of cognitive robotics. Nevertheless, the fact that cognitive science, as a discipline, is yet to establish normative models itself that can be realized in wellengineered systems, makes it difficult to give robots a capacity for cognition [57]. Research in cognitive architectures for biologically inspired agents suffers from a significant void. This has resulted in modeling and trial of such agents in a controlled environment with most demonstrated results as mere proof-of-concept. Lack of relevant HRI models is another issue limiting the interaction capacity of a socially believable robot. The field of HRI incorporates contributions from both engineering sciences (communications, computer science and engineering) and human sciences (psychology and sociology). Due to its multidisciplinary nature it is difficult to generalize a standard HRI model. This is the reason that currently most HRI models are inspired by conventional HCI models. However there is a particular need for a dedicated social human robot interaction model as human interaction with social robots differs significantly from interaction with traditional passive computer based systems or agents.

Need for a comparison criterion is equally significant as the existence of benchmark architecture in the field of social robotics. Nevertheless it is not an easy task considering the dimensions of the test environment and diversity of outcome expectations. According to Bartneck et al. [58], "quick and dirty" methods adopted by most robot developers, result in questionable success of targeted goals. Recent studies like [59], suggest introduction of "Human in the loop" approach. Application and modification of User Experience Design (UXD) evaluation techniques in addition to relevant criteria of evaluation in HCI must be considered for designing performance comparability metrics suitable for HRI. However research in this area is still in its infancy.
