Who Needs Emotions? The Brain Meets the Robot

eware the passionate robot 357
fear is to offer an account of those biases which may be linked to drive states.
To link this to our own experience, we may eat because we are hungry or
simply because food is placed in front of us. Hunger is what puts us “on alert”
to get food, not the behavior of eating the food, though food itself has an
incentive value which can increase the likelihood of eating. It is not the reaction
to a stimulus but the bias on the way in which we will react to stimuli,
as well as the bias on the stimuli we will seek out, paying attention to cues
on how to locate food that might otherwise have been ignored.
Before going further, recall our observation that prey capture in the frog
includes special-purpose motor pattern generators, those for snapping and
ingestion, while predator avoidance uses only general-purpose motor pattern
generators for turning and locomotion. Our bodies have complex systems
for chewing, digestion, and excretion specialized for feeding, whereas
grasping and manipulation are par excellence general-purpose, playing vital
roles in feeding, fighting, and expressions of tenderness, to name just a few.
We must thus note an increasing dissociation between motivation and the
choice of a specific motor system. This is quite orthogonal to my view of
emotion as an evolutionary emergence but serves simply to stress that there
is no easy correlation between a motivation system and the class of effectors
used for the associated motivated behaviors. In any case, a crucial aspect of
primate evolution that may be as intimately linked to distinguishing motivation
from emotion is the ability to plan behaviors on the basis of future
possibilities rather than only in terms of present contingencies. The frog lives
in the present, with very little predictive ability and, therefore, only a shortterm
action–perception cycle. The long-term (from knowing when to refuel
to the day–night cycle to the mating season) is handled for the most part by
bodily systems and specialized neural systems closely coupled to them. As
we compare frog to rat to cat to monkey, the ability to link current decisions
to past experiences and future possibilities becomes more explicit and
more diverse as the role of the cortex expands.
The Driven Rat
Arbib and Lieblich (1977; see also Lieblich & Arbib, 1982) posited a set
{d 1,d 2, . . . d k} of discrete drives which control the animal’s behavior. Typical
drives include appetitive drives, like thirst, hunger, and sex, and aversive
drives, like fear. At time t, each drive d has a value d(t), 0 ≤ d(t) ≤ d max. 4
They say a drive increases if it changes toward d max and is reduced if it changes
toward 0. Their approach seems consistent with the scheme describing the
temporal organization of motivated behavior elaborated by Swanson and
Mogenson (1981) and recently reviewed by Watts (2003) but with an