It’s to test how they look at colors. No, I don’t know why.

Scientists do all sorts of weird shit. Sometimes, it has a practical purpose; other times, it’s just a lot of time spent figuring out why an animal does a certain thing then, upon learning the answer, saying “huh” and publishing a paper about it. That’s how progress is made, baby!

The setups for some of these studies can be pretty elaborate. For example, in this study, they were trying to see how spiders detected color. And so, they glued a magnet to a spider’s head, then had it stare at a screen while holding a little soccer ball.

Science!