SARAH MCCAMMON, HOST:

If there was ever a season for arachnophobia, a fear of spiders, we might be in it.

AILSA CHANG, HOST:

That's right, because they are creepy, and some are dangerous. I mean, there's a reason they're a common Halloween decoration. And now, there is new evidence suggesting that some spiders are scared of themselves.

MCCAMMON: Researcher Daniela Roessler (ph) studied something called jumping spiders at Harvard University in 2020.

DANIELA ROESSLER: Jumping spiders are absolutely amazing because they have this incredible eyesight. And they can see almost as good as we do, so they pay attention to detail.

CHANG: One day, Roessler and her team put a 3D-printed model spider in front of the itsy, bitsy real ones.

ROESSLER: That's how we observed this extremely robust behavior that they would just immediately look at it and back off and run away. It was just fascinating, and we really wanted to find out more.

MCCAMMON: So the team conducted a series of tests to determine what the jumping spiders are truly afraid of, and the result - they were most scared of spiders that look like themselves and other predator spiders, even if they've never encountered spiders like that before. Roessler says it's possible they're analyzing their situation and their opponent.

ROESSLER: There's a lot of assessment of the risk in this moment, so they assess, how big is that thing? How quick could it get to me? And then also knowing that motion really triggers what jumping spiders perceive, like, moving away in this choppy fashion and really slowly maybe is also a strategy of not getting the attention from the predator.

CHANG: Roessler says jumping spiders are mostly afraid of non-web-forming spiders, typically the kind that don't have really noticeable round eyes. So that means your creepy spider decorations are still more likely to frighten humans - for now. Transcript provided by NPR, Copyright NPR.