I don't agree.  One ghost I saw in a place where I worked was the ghost of a small child dressed in rags.  A short time later another staff member saw a group of ghost children and he heard them singing a particular and old fashioned nursery rhyme.  The poor man was petrified and begged me to believe him and what he had seen and heard.  I told him that our two sightings were likely linked.  

A few years later, long after I had left my job in that place and moved to another part of UK, a medium singled me out sat right at the back of a spiritualist church and told me about some children that were 'with me'.  As I did not know any deceased children personally I said that the message was probably not meant for me.  But then he went on and told me what they were wearing, that they were from a past century and the nursery rhyme they sang.....I've never been so utterly gobsmacked.

How could he have possibly known?