Eli5: Why do things moving quickly in our peripheral vision startle us so much? Especially in a normally safe place like home
In: Biology
think about life as an ancient human. fast animals running at you can be a serious, life-ending threat. so being able to tell when an animal is running at you is very important.
if an animal is directly in front of you, it’s much easier to assess the threat level. if a lion is laying down 100 feet away and starts running at you, you instantly know you should run the other way. but it’s not really that surprising – you saw it the whole time.
however, peripheral vision isn’t good enough to tell if the thing coming at you is a lion…or a small bird.
the early humans that noticed quick things in their peripheral vision had an advantage compared to those who didn’t – if an animal might be running at you, every second counts, and if you notice it sooner you can run sooner.
overtime it got to the point that as soon as you see quick movement in your peripheral vision, your body gets alerted and ready to move. and this instinct is super useful because there’s not really a big downside to being alerted by that in terms of survival. and so this instinct got passed down through humanity (and many prey animals), because not getting eaten is very important
so today, you will get startled even in a safe environment, because being startled for a second is a much better alternative than being eaten. better safe than sorry!
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