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Robotic Mechanisms 193

with elevated activity in the amygdala. This also supports the concept that if high-resolution
identity cues fall outside expected patterns, the brain will signal alarm. While these studies support
the hypothesis of a social emergency alarm that is more sensitive to high-verisimilitude cues, future
experiments are required.
Intuitively, it seems probable that humans’ visual expertise to human faces helps us to receive
the full bandwidth of paralinguistic semantics. If this is true, then realistic faces in robots will
simply be more communicative.
There are other reasons to consider making robots more realistically humanlike. Clearly, realistic
human depictions have been highly successful in arts, film, video games, and toys; so the question
naturally arises: why wouldn’t the appeal of realism extend to robots too, if the robots look good
enough? Shades of realism would certainly be critical for many applications, for example: training
models that enact face-to-face exchange, such as medical, police, or psychology simulation. More-
over, accurately modeling the human face allows scientific investigation of human communication.
Several groups use computer-simulations of realistic faces for their robots and autonomous
agents, for instance: Cassell’s Rea at MIT and Vikea of CMU’s Sociable Robots Group. Perhaps
this is because video games have made humanlike simulations more acceptable. Two exceptions
that pursue realistic faced robot identities include: Fumio Hara’s lab at the Science University of
Tokyo (Hara, 1998) and the work of the author of this paper at the University of Texas at Dallas
(Hanson, 2003; Ferber, 2003) (see Figure 6.12).
Historically, the most successful mechanically emulated faces have been entertainment anima-
tronics, but these robots actually reinforce the bias against realism by being inadequate in their
expressivity, consuming a great deal of power, and being bulky, weighty, and costly. Each of these
faults prohibits widespread deployment beyond high-end niche markets of theme parks and film.
Yet, these drawbacks all spring from one cause: the great force required by animatronics’ solid-
elastomer skins to deform into facial expressions.
The solid elastomer materials that are currently in use to emulate facial soft tissues require
relatively large amounts of force to move, which leads to high costs, high power requirements, and
aesthetic movement unlike human facial tissue. In spite of the pliable, elastic qualities of solid
elastomers, the molecules of such elastomer tangle with their near neighbors, fundamentally
constraining the material when deformed. The molecules of facial flesh are not so constrained,
being in effect an array of liquid-filled tissue-sacs, which allows molecules of liquid to flow into any

Figure 6.12 High-verisimilitude anthropomorphic robots, left: the Science University of Tokyo; right: the Univer-
sity of Texas at Dallas.