Arachnophobia affects around 6 percent of the global population. That's 420 million people. And yet, even in Australia - the land of deadly spiders - there hasn't been a recorded death from a spider bite since 1979. What's going on here? The latest episode of It's Okay To Be Smart investigates.

I'm terrified of spiders. Terrified. And so is Joe Hansen from It's Okay To Be Smart. But unlike my fear, Joe's isn't completely irrational - he was bitten by a black widow spider when he was 17, so at least his fear has some basis. And yet, of the 500,000 or so known spider species in the world, only around two dozen of them have venom that could hurt a human, so even Joe's fear isn't particularly rational. So why are we all so afraid?

According to the American Psychiatric Association, 40 percent of phobias have to do with creepy-crawlies, including insects, spiders, snakes, and mice. One reason some of us don't like spiders is thanks to a phenomenon called conditioning - like in Joe's case, a past traumatic experience with a spider instills a more generalised fear. But studies have shown that many people don't even have to have encountered a spider before being afraid of them. It could be that arachnophobia is inheritable, in which case, genetics are at play.

In fact, even if they don't fear them, children are able to pick out spiders and snakes in images faster than images of non-threatening animals, such as fluffy bunnies, ducklings, or kittens. "We must have evolved some sort of built-in creepy-crawly detection system for strange, slithery movements or a few too many legs," says Joe in the latest episode of It's Okay To Be Smart, "a spidey sense for… spideys."

Watch It's Okay To Be Smart above to find out more, and be sure to have yourselves a safe, spooky, and spider-free Halloween.

Source: It's Okay To Be Smart