A baby rabbit, even one that has never encountered a bird before, will still cower at the sight of a hawk's shadow. Some fears are universal. The dark, heights, blood, enclosed spaces, snakes, spiders, psychopaths, pain, death, monsters, humiliation, loneliness; these fears have been with us always. They are the dangers our early ancestors faced, and their shadows still haunt our nightmares. Most people are a little nervous about such things - not many people could walk on a glass bridge over the Grand Canyon without any railings, and not feel a little anxious - and full-blown phobias are easily enough induced.