Sucks how many people were taught that "horses put their ears back when they're mad" but then never taught the difference between "angry backwards ears," "mildly annoyed backwards ears," "pain backwards ears," "concentrated backwards ears," "sleepy backwards ears" and "just happens to be listening to something behind it."
"Horses put their ears back when they're mad" idk man i think it depends
These are all completely different expressions in completely different scenarios, and only two of them are decidedly negative.
Actually, I wanna talk about the third horse, the one putting its ears back in pain. Over the last 15 years veterinarians and animal scientists have worked out pain scales for most domestic animals by taking photos of the during routine procedures.
We know vaccines painful, and by comparing horses at rest with horses getting vaccinated, we've been able to determine how they express pain visually. By looking at horses with disorders like colic, broken bones, wounds, and so on, we can determine their facial expressions during more severe pain.
At zookeeper school we were drilled through the pain faces of the most common lab animals and livestock. Nowadays I believe this has become a routine lesson in all animal related fields, but the general public still doesn't know that this is a thing that exists.
Here are all the pain face/grimace scales I've been able to find. Please study them if you interact with any of these animals on a regular basis:
