Who Needs Emotions? The Brain Meets the Robot

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memories to be held in place correctly, preferably with the temporal order
of the different items coded correctly. This may be another building block
for the multiple-step “if . . . then” type of computation in order to form a
multiple-step plan. Such short-term memories are implemented in the (dorsolateral
and inferior convexity) prefrontal cortex of nonhuman primates and
humans (see Goldman-Rakic, 1996; Petrides, 1996; Rolls & Deco, 2002) and
may be part of the reason why prefrontal cortex damage impairs planning
(see Shallice & Burgess, 1996; Rolls & Deco, 2002).
Of these two routes (see Fig. 5.2), it is the second, involving syntax,
which I have suggested above is related to consciousness. The hypothesis is
that consciousness is the state that arises by virtue of having the ability to
think about one’s own thoughts, which has the adaptive value of enabling
one to correct long, multistep syntactic plans. This latter system is thus the
one in which explicit, declarative processing occurs. Processing in this system
is frequently associated with reason and rationality in that many of the
consequences of possible actions can be taken into account. The actual computation
of how rewarding a particular stimulus or situation is or will be
probably still depends on activity in the orbitofrontal cortex and amygdala
as the reward value of stimuli is computed and represented in these regions
and verbalized expressions of the reward (or punishment) value of stimuli
are dampened by damage to these systems. (For example, damage to the
orbitofrontal cortex renders painful input still identifiable as pain but without
the strong affective “unpleasant” reaction to it; see Rolls, 1999a.) This
language system that enables long-term planning may be contrasted with the
first system in which behavior is directed at obtaining the stimulus (including
the remembered stimulus) that is currently the most rewarding, as computed
by brain structures that include the orbitofrontal cortex and amygdala.
There are outputs from this system, perhaps those directed at the basal ganglia,
which do not pass through the language system; behavior produced in
this way is described as “implicit,” and verbal declarations cannot be made
directly about the reasons for the choice made. When verbal declarations
are made about decisions made in this first system, they may be confabulations,
reasonable explanations, or fabrications of reasons why the choice was
made. Reasonable explanations would be generated to be consistent with
the sense of continuity and self that is a characteristic of reasoning in the
language system.
The question then arises of how decisions are made in animals such as
humans that have both the implicit, direct, reward-based and the explicit,
rational, planning systems (see Fig. 5.2). One particular situation in which
the first, implicit, system may be especially important is when rapid reactions
to stimuli with reward or punishment value must be made, for then
the direct connections from structures such as the orbitofrontal cortex to