Who Needs Emotions? The Brain Meets the Robot

32 brains
It is useful to begin with two important premises: first, that specific and
phylogenetically ancient motivational systems exist in the brain and have
evolved over the course of millions of years to ensure adaptation and survival
and, second, that these systems are engaged by perception of environmental
events or stimuli, that is, information, and when so engaged generate
specific affective states (positive or negative emotions) that are temporarily
powerful drivers and/or sustainers of behavior. Positive emotions generally
bring the organism in contact with potentially beneficial resources: food,
water, territory, mating, or other social opportunities. Negative emotions
protect the organism from danger: mainly ensuring fight-or-flight responses
or other appropriate defensive strategies such as submissive behavior or
withdrawal, protection of territory or kin, and avoidance of pain. Brain systems
monitor the external and internal (bodily) worlds for signals and control
the ebb and flow of these emotions (see Fig. 3.1).
Regarding the first premise, the vertebrate brain contains multiple selective
systems that are adapted for specific purposes, such as mating, social
communication, and ingestion. Corresponding systems exist in the invertebrate
brain. These were termed “special purpose” systems by Buck (1999; in
contrast to general purpose systems, see below) and, within an anatomical
framework, behavioral control columns by Swanson (2000). A typical example
is a system designed to procure water under conditions of dehydration. Sensory
information indicating a need for water (dry mouth, stimulation of
volume receptors, osmoreceptors) is conveyed via specifically designed anatomical
and neurochemical routes (e.g., neural information converging on
the periventricular nucleus of the hypothalamus and the neurohormone
angiotensin II detected in the subfornical organ). Hypothalamic output pathways
connect to the motor system, and the motivated, thirsty animal seeks
and procures water. Depending on how thirsty the animal is, the behavior is
more or less vigorous and sustained. Other complex neurochemically, anatomically,
and hormonally coded systems, discussed in detail below, exist to
optimize survival of the individual and the species, ranging from opioids
signaling distress calls in rat pups separated from their mother to sex steroids
directing sexual differentiation and reproductive behavior. Thus, hunger,
thirst, sex, aggression, the need for air and water, and the need for shelter
or territory—what Paul MacLean (1969) calls “the primary affects”—are
specific drive states that exist to goad the organism to seek the stimuli that
will address its basic survival. Among these are the needs to breathe, to have
freedom of movement, to rid the body of filth and excrement, and to rest or
sleep. Descriptive words for the primary affects associated with many of these
basic needs come readily to mind, for example, hunger, thirst, suffocation,
fatigue, pain.