Children are very aware of the
other side.
When I was younger, no lie, I saw ghosts but I'd feel them more often than I saw them. My grandparents were always quick to say nothing was in the house or in any of the houses we lived in, but I know something was in all of them but one.
To this day, I can still feel when ghosts around.
Most adults brush children's claims off as imagination the same way they'll brush off a dog's growl or barking, when that growl and/or bark could be a warning.
EDIT:
My brothers never mentioned anything about ghosts when we were younger. I think I was the only one who saw them.
