emotions are powerful. in fantasy, this is taken for granted more commonly than it’s justified. monsters feed on emotions, spells are fueled by emotion. why? how?

the unit of energy is the calorie; it’s in food, it’s in fuel. brains consume calories, they don’t produce it. yet in these worlds, a brain experiencing a powerful surge of emotion becomes an energy source able to do work.

does that make any sense?

here’s a possible explanation. it’s signalling. why do we blush and cry and contort our faces? to communicate. we do it involuntarily, our bodies response to our emotions. it’s not easy to hide emotional reactions, which makes it meaningful signal.

we can imagine a magical process (a passive spell, if you will) innate to the brain that produces waves of magical energy in accordance to mood. the output of the spell depends on the brainstate, such that it’s intractable to output anger‍-​waves without any genuine frustration. just as innate to the brain is a (subconscious) sensitivity to the output of other brains. humans in this setting are generally born empaths.

if humans evolve to power energy into this spell, it becomes an meaningful signal of emotional intensity‍ ‍‍—‍ you aren’t going to waste energy on a fleeting impulse. it could be a locus of sexual selection‍ ‍‍—‍ the ability to pour energy into emotion‍-​waves indicates being healthy and well‍-​fed, on top of the actual info about your personality it conveys.

i can think of three ways it would make sense for such large amounts of energy to go into adaptations like this. the first is that it isn’t actually a waste of energy. you aren’t turning the food you eat into emotional emissions. rather, humans have souls of some sort with pools of mana of some sort. mana‍-​calories aren’t easily digested into a form useful to the body, so venting them for social purposes doesn’t have much of a cost.

the second is that humans evolved in a very low trust environment where they needed stronger signals than facial expressions and body language, and even existing social rituals weren’t enough‍ ‍‍—‍ a world with changelings and shapeshifters, perhaps, fain to deceive and manipulate humans.

this circles back to our premise in an oddly iatrogenic way. if there are monsters that feed on human emotions, and thus humans grow more sensitive and loud with their emotional broadcast, that will help them rat out those who fail to properly imitate humans, selecting for better imposters who have more emotional energy to feast on. a cure that brings the disease back twice as strong.

the third possibility is that humans didn’t evolve to do this at all. rather, humans were infected with a kind of parasite of the soul. the energy stems from metabolizing that spiritual tissue, and it’s vented out as sexual signalling, but not human sexuality‍ ‍‍—‍ it’s parasite pheromones that let them find other hosts they might breed with. parasitic mind‍-​control is a classic, so you can imagine that the parasite might make its host trust other hosts and be suspicious and uncomfortable around healthy humans.

it’s not unheard for parasites to evolve to mutualism, and it’s easy to imagine how humans might get social benefits from symbiotic signalling, so you can work out how it’d evolve to look more like the situations described in the prior hypotheticals. what’s neat about this approach is that because it’s a symbiont rather than a feature of humanity, you don’t have to think quite as hard about how many things would be different if we all had innate psychic powers

finally, one interesting knock‍-​on effect of sketching out a world where emotions generate so much energy is that there can’t be enough energy vampires or changelings to slurp up everything that wafts off a human (the point of these things is that they’re rare and dangerous), but you should totally expect there to be something in the niche created by all the free food

i’m imagining tiny incorporeal creatures like spiritual plankton, perhaps faintly visible as a crown or aurora around the human head, drooping and fading while a human is calm and resting, yet becoming bright and animated when they get exciting. you might be imagining the spren from stormlight archives, but what i’m thinking is a world where emmanata are diegetic