A few weeks ago I stumbled upon a video on the internet that asked the question posed in the title. I actually never thought about this subject since it seemed to be clear. For nearly everybody it should be obvious that you get afraid when something threatens your life, e.g. a dangerous animal attacking you or standing close to a chasm you might eventually fall off from. But – as the speaker in the video asks – why do you feel uneasy in some occasions when there is no clear danger?
Japanese engineers are pioneers in working on androids that might someday help us with our daily household work for example. As long as these machines clearly look like mechanical objects you feel no fear whatsoever. In 2009 an android was developed that is able to teach students. It has a lot of motors underneath its face skin so that it can express emotions such as happiness and anger. But if you ask me, this face gives me the creeps with every intended emotion. Why is that? No clear threat comes out of this machine.
There seems to be some kind of “uncanny valley”, i.e. a region where non-human objects reach a similarity to living things in which they are just a little bit off from the real thing. So the androids look human, just not human enough. This uncertainty about the “thing” in front of us, about its feeling and intentions is supposed to be the reason for fear in these situations.
Scientists are still investigating this effect, since a lot of triggers of fear are unknown and future androids are not supposed to creep out their owners. A lot of interesting facts about the human brain might come out of these experiments.