Who Needs Emotions? The Brain Meets the Robot

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tex of recent (episodic) memories (Rolls & Treves, 1998; Rolls
& Stringer, 2001). This is one way in which the recall of memories
can be biased by mood states.
REWARD, PUNISHMENT, AND EMOTION IN BRAIN
DESIGN: AN EVOLUTIONARY APPROACH
The theory of the functions of emotion is further developed in Chapter 10
of The Brain and Emotion (Rolls, 1999a). Some of the points made help to
elaborate greatly on the second function in the list above. In that chapter,
the fundamental question of why we and other animals are built to use rewards
and punishments to guide or determine our behavior is considered.
Why are we built to have emotions as well as motivational states? Is there
any reasonable alternative around which evolution could have built complex
animals? In this section, I outline several types of brain design, with
differing degrees of complexity, and suggest that evolution can operate to
influence action with only some of these types of design.
Taxes
A simple design principle is to incorporate mechanisms for taxes into the
design of organisms. Taxes consist at their simplest of orientation toward
stimuli in the environment, for example, phototaxis can take the form of the
bending of a plant toward light, which results in maximum light collection
by its photosynthetic surfaces. (When just turning rather than locomotion
is possible, such responses are called tropisms.) With locomotion possible,
as in animals, taxes include movements toward sources of nutrient and away
from hazards, such as very high temperatures. The design principle here is
that animals have, through natural selection, built receptors for certain
dimensions of the wide range of stimuli in the environment and have linked
these receptors to mechanisms for particular responses in such a way that
the stimuli are approached or avoided.
Reward and Punishment
As soon as we have “approach toward stimuli” at one end of a dimension
(e.g., a source of nutrient) and “move away from stimuli” at the other end
(in this case, lack of nutrient), we can start to wonder when it is appropriate
to introduce the terms reward and punishers for the different stimuli. By