Who Needs Emotions? The Brain Meets the Robot

an evolutionary theory of emotion 123
(unlearned) reinforcers do not produce emotions, whereas secondary reinforcers
(stimuli associated by stimulus–reinforcement learning with primary
reinforcers) do. They describe the pain as a sensation, but neutral stimuli
(e.g., a table) can produce sensations when touched. It accordingly seems to
be much more useful to categorize stimuli according to whether they are
reinforcing (in which case they produce emotions) or not (in which case they
do not produce emotions). Clearly, there is a difference between primary
reinforcers and learned reinforcers; and operationally, it is whether a stimulus
is reinforcing that determines whether it is related to emotion. A third
issue is that, as we are about to see, emotional states (i.e., those elicited by
reinforcers) have many functions, and the implementations of only some of
these functions by the brain are associated with emotional feelings, that is,
with conscious emotional states (Rolls, 1999a). Indeed, there is evidence for
interesting dissociations in some patients with brain damage between actions
performed to reinforcing stimuli and what is subjectively reported. In this
sense, it is biologically and psychologically useful to consider that emotional
states include more than those states associated with conscious feelings of
emotion (Rolls, 1999a).
THE FUNCTIONS OF EMOTION
The functions of emotion also provide insight into the nature of emotion.
These functions, described more fully elsewhere (Rolls, 1990, 1999a), can
be summarized as follows:
1. Elicitation of autonomic responses (e.g., a change in heart rate)
and endocrine responses (e.g., the release of adrenaline). While
this is an important function of emotion, it is the next function
that is crucial in my evolutionary theory of why emotion is so
important.
2. Flexibility of behavioral responses to reinforcing stimuli. Emotional
(and motivational) states allow a simple interface between sensory
inputs and action systems. The essence of this idea is that
goals for behavior are specified by reward and punishment
evaluation and that innate goals are specified by genes. When
an environmental stimulus has been decoded as a primary reward
or punishment or (after previous stimulus–reinforcer association
learning) a secondary one it becomes a goal for action.
The animal can then perform any action (instrumental response)
to obtain the reward or avoid the punishment. The instrumental
action, or operant, is arbitrary and could consist of a left turn