We grow up believing that as each day comes to an end, the dark night-time is scary and full of terrors - well, so our brains would have us think.
If you think you were scared of the dark as a child or maybe you still are now, it might actually be the night you are frightened of, not the lack of light.
Researchers in China believe it is more to do with our brains switching to a more vigilant, nocturnal mode.
120 young women were asked to look at neutral pictures like nature scenes, scary pictures like spiders and listen to scary sounds like screams and neutral sounds like bird song while they sat in a windowless cubicle.
Some of the women were asked to do this at different times of day and in different lighting. Some during the day in a well lit room and others with only the glow from a computer monitor.
Based on self-evaluations and measurements of heart rate and perspiration levels, results showed that the night-time groups were far jumpier, irrespective of the lighting.
There was no difference in the responses to the neutral images and sounds between the day and the night. However, the fear inducing images and sounds made the women more frightened at night than in the day.
So, the findings would suggest that we're far more sensitive to threats at night-time because it's the night, not because it's dark.
This raises the possibility that our mental and behavioural changes that respond primarily to light and darkness affect our fear sensitivity.
It could be argued, however, that cultural factors are involved, in that we've learnt to become more alert at night.