The Purpose of Emotions

Emotions are behavioral instincts, triggered in a specific context, which impell a specific behavior. Generally, successfully executing the impelled behavior alleviates the contextual trigger, which then brings about "catharsis" (the resolution of the emotion).^alleviation Given this structure of emotions, we can say an emotion has an implicit "purpose", which is to alleviate the triggering condition, and an implicit "strategy", which is to engage in the impelled behavior until the trigger is alleviated.

There is strong neuroscientific evidence for this structure of emotions, but even without any of that evidence, defining emotions as motivational states with triggers and impelled behaviors is sufficient to embark on an evolutionary analysis of the purpose of emotions.^ledoux-fn From the ubiquitous presence of emotions throughout the animal kingdom, we can infer that emotions have been tremendously useful for the propagation of species.

 Emotions for Homeostasis

One frame for linking emotions to purpose focuses on the curious, multifaceted nature of survival. In the modern world, most of our tasks can be framed as a single-dimensional optimization problem. At work, we want to maximize the money we can take home as salary or bonus. To do that, we are told perhaps to maximize sales, or perhaps to maximize the production of some goods. In these situations, there is a clear, singular metric which we can use to measure "goodness".

Biological life, fundamentally, does not have a single metric. Life is a multidimensional satisficing problem.

Biological living beings require a delicate homeostasis, a dynamic equilibrium where all of our processes can function in harmony. To maintaining this homeostasis, we must satisfy a host of biological needs. We must have enough water to drink, enough air to breath, enough food to eat, so that we do not die from lacking any of these. We must find a way to regulate our body temperature, which for humans generally means clothes and shelter. We must find a way to avoid threats to our bodily integrity, which may require shelter, and may also mean staying on good terms with fellow humans. Failing on any of these will lead to death, even if all the other constraints are satisfied. Excess resources for any of these is also generally not useful -- if we have twice as much water as we need, that is not any better than having just enough.

To stay alive, we must balance the goals of satisfying all of these needs. If a deer is thirsty, and also being pursued by wolves, escaping from the wolves should likely take priority. Our emotions provide us with prioritized strategies for maintaining our body's homeostasis, to avoid deadly circumstances long enough for us to propagate our genes to the next generation.

Note that, in the homeostasis model, emotions are inherently pre-emptive -- they must trigger before the homeostatic constraint has been failed, because failing a constraint causes death, and the impelled corrective behavior would be too late. Thus, emotions are inherently involved in predicting the future (what situations might kill you) and in causal reasoning (what can you do to not die).

 Emotional Triggers as Fundamental Life Tasks

Another similar model which links emotions to purposes focuses on common problems organisms face. Throughout the course of an animal's life, from birth up to reproduction, there are a host of archetypical problems which the animal will encounter.^ledoux-flt For example, an animal may need to forage, or to hunt, or to escape another animal hunting it. Emotions can be analyzed as coupled with particular strategies (the impelled behavior) for solving the fundamental life task (associated with the trigger).

While triggers (the fundamental life tasks) are generally common across mammals, different species may have highly variation in behavioral strategies for approaching the life tasks.^{panksepp-diff} The psychological evolution of a species, then, is intimiately involved with developing their emotional strategiies so that their behavioral adaptations harmonize with their physical adaptations in their ecological niche.

 Emotional Homology

Emotional triggers and reactions are largely shared across mammalian species. From neurological investigation, we can confirm that this is not a shallow similarity. It is not the case that mammals independently converged to the same emotions in the course of their evolution. Rather, the shared emotions use largely the same neuromodulators (signaling chemicals) and the same brain architecture in emotional processes. If you look at a dog and it looks sad, that is not a perceptual error caused by anthropomorphizing your perception, but rather it is actually participating in the same neurological processes as humans. That is, shared emotions across species are homogolous (they are the same), they are not simply analagous.^{panksepp-homo}

The homology of emotion should give us a great deal of comfort that when we feel empathy for another being, we are in a very deep sense sharing in that experience. We use the same chemicals and the same brain structures, so that we do, in fact, know what they are going through. The supposed siloing of emotional experience is a myth.

In the course of evolution, oftentimes new functions arise from the modification of previous functions rather than being evolved from scratch. Evolution is frugal in her adaptations, and will more often repurpose old tools than create new ones. This repurposing is called "exaptation".^{panksepp-exaptation}