No, I don't see dead people. In fact, often I don't see live people. And sometimes I can't tell the difference.
What I'm going to be talking about is the way we sense things and don't quite know why. We tend to like to put labels on things, as if that explains them. So, for instance, we label something an instinct, as if that takes care of the problem. But it doesn't, 'cause for it to really explain, we have to have a mechanism in place that connects you and the experience. Labels are just labels.
So, let's take a look at the sixth sense. Say you're driving along the highway, daydreaming a little, and suddenly, you come alert, sensing danger. Without thinking, you swap lanes and a giant, huge, 72-wheeler, double-clutching semi runaway goes roaring by in the precise place where you were a second ago.
Saved by your sixth sense, or angels, or the influence of the second star to the left of Antares.
Can you tell I don't buy this? "Well, smart ***," you say, "what did save me?"
Enter James Gibson, whose book The Senses Considered as Perceptual Systems, gives us a mechanism. Mr. Gibson will tell you more than you probably want to know about how we humans (and other animals) interact (or don't --consider a jellyfish) with gravity. It's astonishing how much we use gravity as a way of interacting with the world around us.
Back to the highway and the big truck. It turns out that we are extremely sensitive to changes in ambient light (that's the kind of surrounding light that makes it so we can see things). If I'm in my car and there is a change in the ambient light caused by a huuuuge truck coming up on my rear, then I'll react to that, without (and this is the key), actually knowing what I'm reacting to.
Now, you can believe in the sixth sense if you want to, or in angels, or in astrally projected beings from another dimension (expressed as mice (that's for you Hitchhiker's Guide fans)), but I'll stick with Gibson. I think humans are more attuned to their environment than we really know. And I don't think we need posit anything outside ourselves to account for the fact that we've survived as a species lo these many years.