Who Needs Emotions? The Brain Meets the Robot

architectural basis of affect 219
Now suppose that there are some situations in which an overall damping
of action is adaptive: for instance, hibernation, being in the presence of a dominant
conspecific, or having a brutal parent who reacts violently on the slightest
provocation. The adaptivity of restricting actions in such situations might
result in the evolution of a damping mechanism, D, that, when activated, globally
reduces the possibilities for action, via internal controls. So, when the
system detects a situation in which such damping would be advantageous, this
produces state P (an example of a mood) where P reliably activates D, which
in turn both activates or enhances the negative affective state N and enhances
P. While those conditions in which damping is advantageous persist, P would
be a positively affective state: it can be desirable to lie low in a dangerous situation
even though it is not desirable to be in a dangerous situation and lying
low is not normally desirable (e.g., when hungry). So, there will be a conflict
between P, whose function is to reduce activity, and N, whose function is to
increase possibilities for action; but P wins in certain circumstances. In some
cases, positive feedback mechanisms could make it very difficult to break out
of P, even after the initiating conditions have been removed and continuation
of damping would no longer be advantageous.
The actual nature of depression is probably far more complex; this
explanatory sketch is offered only to show that there is no incompatibility,
in principle, between complex states like depression and our analysis
of affect.
Incidentally, this explanation sketch also shows that what we call positively
or negatively affective states need not be consciously experienced as
pleasant or unpleasant. In fact, the state itself need not be recognized, even
though some of its consequences are.
Crucial to this explanation is the fact that if two affective substates coexist,
one positive and one negative (or if there are two positive or two negative
affective states that tend to produce conflicting actions), their effects
do not in general “sum up” or “cancel out” as if they were coexisting physical
forces. It is even possible for one substate to have the specific function
of disabling the normal effects of another, for instance, when being paralyzed
by fear prevents the normal escape behavior that would reveal one’s
location, as in freezing in rats. More generally, vector summation is often
not suitable either for combining the effects of coexisting affective states or
for dealing with conflicts. Instead of summing, it is normally sensible to select
one from a set of desirable but incompatible actions since any “summing”
could produce disastrous effects, like Buridan’s proverbial ass placed halfway
between food and drink. More intelligent organisms may invent ways
of satisfying two initially incompatible desires, instead of merely selecting
one of them.