Who Needs Emotions? The Brain Meets the Robot

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tization of goals. The fear response accomplishes this by effectively “hijacking”
the behavior and motor systems to rapidly respond to the situation. For
instance, the fear response may evoke Kismet’s escape behavior, causing the
robot to close its eyes and turn its head away from the offending stimulus.
Affective Drive Influences
In addition, affective signals arising from the drives bias which behaviors
become active to satiate a particular motive. These affective influences contribute
to activating behaviors that are the most relevant to the robot’s
“health”-related needs. When the drives are reasonably well satiated, the
perceptual contributions play the dominant role in determining which goals
to pursue. Hence, the presence of a person will tend to elicit social behaviors
and the presence of a toy will tend to elicit toy-directed behaviors. As a
result, Kismet’s behavior appears strongly opportunistic, taking advantage
of whatever stimulus presents itself.
However, if a particular drive is not satiated for a while, its influence on
behavior selection will grow in intensity. When this occurs, the robot becomes
less opportunistic and grows more persistent about pursing those goals
that are relevant to that particular drive. For instance, the robot’s behavior
becomes more “finicky” as it grows more prone to give a disgust response to
stimuli that do not satiate that specific drive. The robot will also start to
exhibit a stronger-looking preference to stimuli that satiate that drive over
those that do not. These aspects of persistent behavior continue until the
drive is reasonably satiated again.
Affective Behavior Influences
Another class of affective responses influences arbitration between competing
behavioral strategies to achieve the same goal. Delayed progress of a
particular behavior results in a state of growing frustration, reflected by a
stern expression on the robot’s face. As Kismet grows more frustrated, it
lowers the activation level of the active behavior within the behavior group.
This makes it more likely to switch to another behavior within the same
group, which could have a greater chance of achieving the current goal.
For instance, if Kismet’s goal is to socialize with a person, it will try to
get a person to interact with it in a suitable manner (e.g., arousing but not
too aggressive). If the perceptual system detects the presence of a person
but the person is ignoring Kismet, the robot will engage in behaviors to attract
the person’s attention. For instance, the robot’s initial strategy might