2.1.1. Android: The Robot Having Human-Like Appearance

An android robot is a humanoid robot that has a very human-like appearance. For the conversation system, we employed a female android called Geminoid F (Figure 2a) and a male android called Geminoid HI4 (Figure 2b). Both androids were developed in a collaborative project between Osaka University and Advanced Telecommunications Research Institute International (ATR). These androids have skin made of silicon rubber, and the shape of their skin was molded from an actual human. Because the tactile sensation and texture of the surfaces are very close to that of a human, they can convey a human-like presence. In addition, these androids have many degrees of freedom (DOFs) in their faces (Geminoid F: 7 DOFs, Geminoid HI4: 8 DOFs), with enough DOFs on their face allowing them to convey a natural human-like presence. Since the androids are driven by air compression actuators, they can move softly and show their behavior without producing loud noises. Due to these factors, we concluded that Geminoid F and Gemenoid HI4 were suitable for showing human-like communication with people. On the other hand, neither F nor HI4 have any sensor to get environmental information inside their body, and therefore, additional external sensors were needed to obtain the voices and positions of people. Each robot had a speaker inside its body; however, a sound played from the speaker was not clear. Thus, we designed external speakers for each android.

**Figure 2.** Appearance of Geminoids: (**a**) Geminoid F: female android; (**b**) Geminoid HI4: male android.
