Fear of the unknown is universal. If you've never seen something before, you can't make a judgment about it; you don't know if it' good or bad, dangerous or safe. And your brain always wants to make that judgement; that's how the brain works. Researches have found that even nonsense syllables spark positive and negative emotions; to your brain, there's no such thing as neutral. So if you can't tell what something is, you get anxious trying to decide whether it's good or bad.