The Science of Allomancy in Mistborn: Zinc and Brass

Emotional allomancy is the power described in Brandon Sanderson’s Mistborn novels which allows an allomancer to influence another’s emotions. Allomancers that posses the appropriate powers can burn zinc or brass to riot or soothe someone’s emotions, causing them to change their behavior.

The mechanism for how these emotional changes are brought about aren’t well understood. However, as I mentioned last week, I have reason to believe that emotional allomancy makes use of symbiotic parasites.


Parasites and Behavior

Most of you are probably familiar with the fungus Ophiocordyceps unilateralis, thought you might recognize it by its more popular name, “The Zombie Ant Fungus.”

While this kind of parasitic behavior might seem like the forerunner for a zombie apocalypse, it’s nothing new, nor is it unique to ants. There are many examples1 of parasites modifying host behavior to suit their needs, from nemotodes that force grasshoppers to drown themselves in order to make it easier for the parasites to mate2, to protozoa that alter the behavior of rats in order to make them more likely to be eaten by predators that can help spread the protozoan oocysts in their feces3.

How exactly the parasites enact this behavioral change isn’t completely understood, but in the case of the nematode and the grasshopper (which sounds vaguely like one of Aesop’s fables), a recent proteomics study4 has shown that the parasite causes the host  to express certain proteins in its central nervous system which alter the host’s behavior.

It’s also known that while some parasites may have a strong effect on one species, they may produce no symptoms (or even beneficial side-effects) in another3. It is therefore possible that all humans have some type of symbiotic parasites within them which are affected by allomancers burning brass and zinc. 

As I mentioned last week, since burning copper might trigger an antimicrobial effect, temporarily killing or inactivating these symbiotic bacteria within the allomancer, this would explain why an allomancer burning copper can’t be affected by emotional allomancy.


Brass and Zinc

So if parasite-induced behavioral changes are involved in emotional allomancy, how exactly does the allomantic metabolization of brass and zinc trigger these changes? With Zinc, there are many possibilities, as Zinc is known to participate in hundreds of biochemical reactions5.

Brass is a bit more of a mystery. Since brass is an alloy of copper and zinc, it also shares copper’s antibacterial properties I mentioned last week. It could be, as one commenter suggested, that when an allomancer burns brass, its copper component kills off certain microbes, leaving the zinc component to affect others. 

While brass alloys can be made from different relative amounts of zinc and copper, in the Mistborn novel, Kelsier tells Vin that allomantic alloys are made from very specific percentages of each component metal:

“If the mixture is off by a bit, you’ll still get some power out of it…However if it’s too far off, burning it will make you sick.”

Since the relative amounts or allomancer’s brass isn’t specified in the novel, it makes it difficult to work with the hypothesis of a metal’s effects resulting from the sum of its parts. Alternatively, it may be that some emergent property of the alloy itself that gives brass its allomantic effects.



While we don’t yet have enough evidence to derive a complete mechanism for emotional allomancy, parasite-induced behavior changes commonly found in nature provide a reasonable hypothesis which could be tested if we had suitable test subjects available.

Speaking of hypotheses, if you’re interested in what might happen should a behavior-altering parasite start affecting humans, you might want to check out the YA short story I wrote about that very subject in my Science Fictioned series called “Social Climber.” I promise that there are no zombies involved.


Other Installments in the Science of Allomancy



  1. Pontoppidan et al., “Graveyards on the Move.”
  2. Thomas et al., “Do Hairworms (Nematomorpha) Manipulate the Water Seeking Behaviour of Their Terrestrial Hosts?”.
  3. Webster, “Rats, Cats, People and Parasites.”
  4. Biron et al., “Behavioural Manipulation in a Grasshopper Harbouring Hairworm: A Proteomics Approach.”

Dr. Lee Falin is the host of the Everyday Einstein’s Quick and Dirty Tips podcast and the author of the “Science Fictioned” series, in which he takes scientific research articles and turns them into sci-fi and fantasy short stories. You can follow him on twitter at @qdteinstein.


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