A common theme throughout these images is some element that manages to catch your eye without it being entirely clear why. Just a single element out of place, like an eyeball floating around a bowl of soup, can put us on edge, before we even know what’s happening. Partially, this is just our brain reacting to danger (or what we think is danger) even if our conscious self doesn’t know what’s going on.
For example, things that are vaguely human, but off by just a bit are often said to reside in the uncanny valley. Most people have a negative reaction to the robots and CGI almost-humans people have made, even if they can’t quite understand why.
Some people weave fantastical theories about why we have such a visceral reaction to something that appears to be almost human. Many budding sci-fi novelists can no doubt put together an interesting story about this element of our evolution. But the “boring” real answer is that most likely it’s simply an evolutionary reaction to corpses.
While for modern humans, a corpse is perhaps uncomfortable, most of us will only encounter it in the context of a funeral. So it’s important to think from the perspective of our ancestors, who would probably only encounter a corpse if there was some imminent danger, a poisonous plant, or a predator.
Seeing such a thing often causes a number of physiological reactions, from an increased heart rate, adrenaline, hairs standing on end, and, of course, goosebumps. It can be a bit humbling to realize that very often, your body actually realizes or detects danger much faster than you do. This is perhaps why we are sometimes recommended to trust our instincts since they might be working with better information than our minds.
Interestingly, the hair standing on end isn’t necessarily related to fear, and many people actually misreport having this particular reaction. It’s possible that we have seen it happen in cats often enough that we just attribute it to ourselves. Alternatively, we do get goosebumps when afraid and the sensation on our skin might make it feel like our hair is also participating.
While not explicitly scary, these cursed images do in some way trigger the body's fight or flight system, mostly through the unexpected. In some cases, it’s not so much the visual at play, but the contents. Our brain begins concocting a story for why these disparate elements are all in the same image.
This is the same strategy used by many horror films and thrillers (and in rare cases, comedies, like the “Hangover” series), where just enough is left up to the imagination, that the “blank spaces” get filled in by our minds. Since we all know what scares us best, our brain does all the heavy lifting for the director.