Why Are Ventriloquist Dolls So Creepy?

For my final project in Dr. Mintler's Doppelgangers and Doubles Expository Writing course, I decided to focus on something that I have always found really creepy: ventriloquist dolls. Apparently, I'm not the only one disturbed by these dummies, because there is pretty much an entire genre of horror dedicated to them.

So why are we so afraid of these things? They're just dolls after all...
Well, there are many things about the appearance of these dolls that are simply offputting. Their overly expressive eyebrows, large, unblinking eyes, and hinged jaws all make for a very uncanny experience. The combination of both lifelike and nonlifelike features into a single doll is highly disturbing, and create uncanny feelings as familiar humanlike features are applied to an unfamiliar medium. And, as if they aren't scary enough on their own, another dimension of uncanniness is added when the dolls are manipulated by the ventriloquist during a performance to appear as though they are speaking and interacting with the ventriloquist by their own free will. If the performance is convincing enough, we even start to believe that there are two people on stage rather than one performer. This is a very eerie experience as the lines between the living and the nonliving are blurred.