To tackle the problem of appearance and behavior, two approaches are necessary:
one from robotics and the other from cognitive science. The approach
from robotics tries to build very humanlike robots based on knowledge
from cognitive science. The approach from cognitive science uses the
robot for verifying hypotheses for understanding humans. We call this crossinterdisciplinary
framework android science.

Previous robotics research also used knowledge of cognitive science while
research in cognitive science utilized robots. However the contribution from
robotics to cognitive science was not enough as robot-like robots were not
sufficient as tools of cognitive science, because appearance and behavior cannot
be separately handled. We expect this problem to be solved by using an
android that has an identical appearance to a human. Robotics research utilizing
hints from cognitive science also has a similar problem as it is difficult to
clearly recognize whether the hints are given for just robot behaviors isolated
from their appearance or for robots that have both the appearance and the
In the framework of android science, androids enable us to directly exchange
knowledge between the development of androids in engineering and
the understanding of humans in cognitive science. This conceptual paper discusses
the android science from both viewing points of robotics and cognitive

Very humanlike appearance

The main difference between robot-like robots and androids is appearance.
The appearance of an android is realized by making a copy of an existing
The thickness of the silicon skin is 5mm in our trial manufacture. The
mechanical parts, motors and sensors are covered with polyurethane and the
silicon skin. Figure 3 shows the silicon skin, the inside mechanisms, the head
part and the finished product of a child android made by painting colors on
the silicon skin. As shown in the figure, the details are recreated very well so
they cannot be distinguished from photographs of the real child.

Mechanisms for humanlike movements and reactions

Very humanlike movement is another important factor for developing androids.
For realizing humanlike movement, we developed an adult android
because the child android is too small. Figure 4 shows this developed android.
The android has 42 air actuators for the upper torso except fingers. We decided
the positions of the actuators by analyzing movements of a real human
using a precise 3D motion tracker. The actuators can represent unconscious
movements of the chest from breathing in addition to conscious large movements
of the head and arms. Furthermore, the android has a function for
generating facial expression that is important for interactions with humans.
Figure 5 shows several examples of facial expression. For this purpose, the
android uses 13 of the 42 actuators.
The air actuator has several merits. First, it is very silent, much like a human.
DC servomotors that require several reduction gears make un-humanlike
noise. Second, the reaction of the android as against external force becomes
very natural with the air dumper. If we use DC servomotors with reduction
gears, they need sophisticated compliance control. This is also important for
realizing safe interactions with the android.