Page 67 - Designing Sociable Robots

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48 Chapter 4

must be a common currency, shared by perceptual, motivational, and behavioral subsystems.
In this scheme, the perceptual subsystem generates values based on environmental stimuli,
and the motivational subsystem generates values based on internal factors. Both sets of
values are passed to the behavioral subsystem, where competing behaviors compute their
relevance, based on the perceptual and motivations subsystem values. The two subsystems
then compete for expression based on this newly computed value (the common currency).
Within different subsystems, each can operate on their own currencies. This is the case
of Kismet’s emotion system (chapter 8) and behavior system (chapter 9). The currency that
is passed between different systems must be shared, however.
Value-based system Based upon the use of common currency, the robot’s SNS is imple-
mented as a value-based system. This simply means that each process computes numeric
values (in a common currency) from its inputs. These values are passed as messages (or
activation energy) throughout the network, either within a subsystem or between subsys-
tems. Conceptually, the magnitude of the value represents the strength of the contribu-
tion in influencing other processes. Using a value-based approach has the nice effect of
allowing influences to be graded in intensity, instead of simply being on or off. Other pro-
cesses compute their relevance based on the incoming activation energies or messages,
and use their computed activation level to compete with others for exerting influence upon
the SNS.

4.5 Criteria for Evaluation

Thus far in this chapter, I have presented the key design issues for Kismet. To address them,
I have outlined the framework for the synthetic nervous system. I now turn to the question
of evaluation criteria.
Kismet is neither designed to be a tool nor an interface. One does not use Kismet to
perform a task. Kismet is designed to be a robotic creature that can interact socially with
humans and ultimately learn from them. As a result, it is difficult or inappropriate to apply
standard HCI evaluation criteria to Kismet. Many of these relate to the ability for the system
to use natural language, which Kismet is not designed to handle. Some evaluation criteria
for embodied conversation agents are somewhat related, such as the use of embodied social
cues to regulate turn-taking during dialogues, yet many of these are also closely related
to conversational discourse (Sanders & Scholtz, 2000). Currently, Kismet only babbles; it
does not speak any natural language.
Instead, Kismet’s interactions with humans are fundamentally physical, affective, and so-
cial. The robot is designed to elicit interactions with the caregiver that afford rich learning