This is just anecdotal, but me, a friend, and plausibly Randall Munroe are significantly more socially risk-taking at night than during other times of day. This might be directly connected to the time of day, or just be a consequence of sleep deprivation.
I also have irrational fears during the night, sometimes, but I would guess that this is largely due to being sleepy, stupid, and alone, which causes me to be more suggestible to stray thoughts in general. I wouldn't be surprised if darkness also contributes, though.
There was a long-lasting man-made sound outside my home last night. I couldn't come up with a good explanation for what the sound was or why it was outside my house. My brain naturally promoted the hypothesis that a psychopathic murderer was outside my house making the strange noises. I noticed this was absurd, and predicted that, in the morning, I would find this explanation much less concerning. Sure enough, when I woke up, I thought the whole thing was rather goofy.
Now, supposing there had been a psychopathic murderer outside my house, it wasn't like I was at much more risk at night, since I was planning on staying indoors. This seems like a pretty clear manifestation of nychtophobia: fear of the dark magnifying our fears of being attacked or victimized.
My question is: does this apply more generally? Might we be more risk-averse at night, or otherwise biased?[1] Suppose I plan to soon leave work and walk home along a dimly lit path. Then suppose I make an unrelated decision - am I more likely to be conservative or fearful in weighing that decision, above and beyond the normal effects of having recently considered something slightly distressing?
One study indicated that night owls are actually risk-takers, but there's a lot of confounders there with respect to nychtophobia-related explanations. ↩︎