Page 139 - Designing Sociable Robots

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120 Chapter 8

emotions are potentiated (such as anger, fear,or sorrow), which produces signs of
distressontherobot’sface.Theparticularsignofdistressprovidesthehumanwithadditional
cues as to what is “wrong” and how he/she might correct for it. For example, overwhelming
stimuli (such as a rapidly moving toy) produce signs of fear. Similarly, Infants often show
signs of anxiety when placed in a confusing environment.
Note that the same sort of interaction can have a very different “emotional” effect on the
robot depending on the motivational context. For instance, playing with the robot while all
drives are within the homeostatic regime elicits joy. This tells the human that playing with
the robot is a good interaction to be having at this time. If, however, the fatigue-drive
is deep into the under-stimulated end of the spectrum, then playing with the robot actually
prevents the robot from going to “sleep.” As a result, the fatigue-drive continues to
increase in intensity. When high enough, the fatigue-drive begins to potentiate anger
since the goal of sleep is blocked. The human may interpret this as the robot acting cranky
because it is “tired.”
In this section I present a couple of interaction experiments to illustrate how the robot’s
motivations and facial expressions can be used to regulate the nature and quality of social
exchange with a person. Several chapters in this book give other examples of this pro-
cess (chapters 7 and 12 in particular). Whereas the examples in this chapter focus on the
interaction of emotions, drives, and expression, other chapters focus on the perceptual
conditions of eliciting different emotive responses.
Each experiment involves a caregiver interacting with the robot using a colorful toy. Data
was recorded on-line in real-time during the exchange. Figures 8.5 and 8.6 plot the activation
levels of the appropriate emotions, drives, behaviors, and percepts. Emotions are always
plotted together with activation levels ranging from 0 to 2000. Percepts, behaviors, and
drives are often plotted together. Percepts and behaviors have activation levels that also
range from 0 to 2000, with higher values indicating stronger stimuli or higher potentiation
respectively. Drives have activation ranging from −2000 (the overwhelmed extreme) to
2000 (the under-stimulated extreme). The perceptual system classifies the toy as a non-
face stimuli, thus it serves to satiate the stimulation drive. The motion generated by
the object gives a rating of the stimulus intensity. The robot’s facial expressions reflect its
ongoing motivational state and provides the human with visual cues as to how to modify
the interaction to keep the robot’s drives within homeostatic ranges.
For the waving toy experiment, a lack of interaction before the start of the run (t ≤ 0)
places the robot in a sad emotional state as the stimulation-drive lies in the under-
stimulated end of the spectrum for activation A stimulation ≥ 400. This corresponds to a long-
term loss of a desired stimulus. From 5 ≤ t ≤ 25 a salient toy appears and stimulates the
robot within the acceptable intensity range (400 ≤ A nonFace ≤ 1600) on average. This corre-
sponds to waving the toy gently in front of the robot. This amount of stimulus causes the