If you’ve ever wondered why people with phobias freak out, here’s a big part of the answer: Because their minds visually magnify their fears.

Researchers at Ohio State University studied a group of arachnophobes – that’s people who are afraid of spiders, and asked them to approach an aquarium that contained a large tarantula. The volunteers then rated their level of fear on a scale of zero to 100. And drew a line on an index card that represented the length of the spider they’d just seen. 

The result: All of the volunteers overestimated the size of the spider – most by about 50 percent. But the people with the highest level of fear thought the spider was three times its real size! And, other studies have shown that people who are afraid of heights consistently overestimate how far they are off the ground. 

No one’s sure whether these misperceptions are the result of the phobia - or the cause of it. But, it may make for more effective treatments. A lot of mental health professionals use something called exposure therapy to help people with phobias. The treatment requires patients to gradually confront what frightens them. 

So, knowing that scary things can appear super-sized will help therapists control the rate of exposure.