Designing Artificial Emotions
The design phase must decide which emotions are experienced by the animat, which sensations trigger changes in emotions, and how they are portrayed in the behavior. This prototype will be extended later in Chapter 42 with additional primary emotions, secondary emotions, and moods.
Because this chapter builds the first emotional prototype, it seems appropriate to include the most important emotions only. As such, the animats have only four of the primary emotions defined by Robert Plutchik in his psychoevolutionary theory [Plutchik80]:
As complementary emotions, only two of four may be observable at any point in time. Each of the emotions is defined as a binary value: either fully active or inactive.
Sensations and Stimuli
The sensations are patterns that cause changes in the emotions. These patterns can be present in the current state, but also over periods of time. In this prototype, the sensations are based directly on the stimuli from the environment. Sensations are identified as sequential combinations of stimuli (see Table 39.1).
The emotions need to be portrayed by the behaviors for them to have any purpose. Selecting the most obvious manifestations of emotions improves the realism, and keeping their number to a minimum keeps the system simple. In this chapter, we'll use the following parameters—applied via the interfaces to the body:
These are restrictive modifications, because they decrease the capabilities of the animats. In the best case, the animat will not be affected by its emotions. Chapter 42 extends upon these ideas by influencing the decision making with moods, too.