Who Needs Emotions? The Brain Meets the Robot

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of the eliciting stimulus or can be produced, as in depression,
sometimes in the absence of an eliciting stimulus, perhaps
owing to dysregulation in the system that normally enables
moods to be long-lasting (see Rolls, 1999a).
6. The emotion elicited can depend on whether an active or passive
behavioral response is possible (e.g., if an active behavioral
response can occur to the omission of a positive reinforcer, then
anger—a state which tends to lead to action—might be produced,
but if only passive behavior is possible, then sadness,
depression, or grief might occur).
By combining these six factors, it is possible to account for a very wide
range of emotions (for elaboration, see Rolls, 1990, 1999a). Emotions can
be produced just as much by the recall of reinforcing events as by external
reinforcing stimuli 2 ; cognitive processing (whether conscious or not) is important
in many emotions, for very complex cognitive processing may be
required to determine whether or not environmental events are reinforcing.
Indeed, emotions normally consist of cognitive processing that analyzes the
stimulus and determines its reinforcing valence, then elicits a mood change
according to whether the valence is positive or negative. In that an emotion
is produced by a stimulus, philosophers say that emotions have an “object”
in the world and that emotional states are intentional, in that they are about
something. A mood or affective state may occur in the absence of an external
stimulus, as in some types of depression; but normally the mood or affective
state is produced by an external stimulus, with the whole process of
stimulus representation, evaluation in terms of reward or punishment, and
the resulting mood or affect being referred to as “emotion.” The external
stimulus may be perceived consciously, but stimuli that are not perceived
consciously may also produce emotion. Indeed, there may be separate routes
to action for conscious and unconscious stimuli (Rolls, 1999a).
Three issues are discussed here (see Rolls, 1999a, 2000a). One is that
rewarding stimuli, such as the taste of food, are not usually described as
producing emotional states (though there are cultural differences here). It
is useful here to separate rewards related to internal homeostatic need states
associated with regulation of the internal milieu, for example, hunger and
thirst, and to note that these rewards are not generally described as producing
emotional states. In contrast, the great majority of rewards and punishment
are external stimuli not related to internal need states such as hunger
and thirst, and these stimuli do produce emotional responses. An example
is fear produced by the sight of a stimulus that is about to produce pain. A
second issue is that philosophers usually categorize fear in the example as
an emotion but not pain. The distinction they make may be that primary