Page 140 - Designing Sociable Robots

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The Motivation System 121

Interaction with Toy
2500
Anger
2000 Fear
Activation Level 1500 Sadness
Interest

1000
500
0
0 20 40 60 80 100 120 140
Time (seconds)

2000

1000
Activation Level 0

Stimulation drive
1000
Play behavior
Non face stimulus
2000
0 20 40 60 80 100 120 140
Time (seconds)
Figure 8.5
Experimental results for the robot interacting with a person waving a toy. The top chart shows the activation levels
of the emotions involved in this experiment as a function of time. The bottom chart shows the activation levels
of the drives, behaviors, and percepts relevant to this experiment.

stimulation-drive to diminish until it resides within the homeostatic range, and a look
of interest appears on the robot’s face. From 25 ≤ t ≤ 45 the stimulus maintains a desir-
able intensity level, the drive remains in the homeostatic regime, and the robot maintains
interest.
At 45 ≤ t ≤ 70 the toy stimulus intensifies to large, sweeping motions that threaten the
robot (A nonFace ≥ 1600). This causes the stimulation-drive to migrate toward the over-
whelmed end of the spectrum and the fear process to become active. As the drive ap-
proaches the overwhelmed extreme, the robot’s face displays an intensifying expression of
fear. Around t = 75 the expression peaks at an emotional level of A fear = 1500 and experi-
menter responds by stopping the waving stimulus before the escape response is triggered.
With the threat gone, the robot “calms” somewhat as the fear process decays. The in-
teraction then resumes at an acceptable intensity. Consequently, the stimulation-drive
returns to the homeostatic regime and the robot displays interest again. At t ≥ 105 the