I think it depends who you ask! Each will give a total different opinion. The answer will depend on ones spiritual beliefs too. Their religions!

The best way to know is by your own experienes and perception of it all.

I see spirit in many forms, not just the human form. The human form is only for our benifit so we know who they are when they visit. If one needs to "See" to believe in something, like knowing a spirit is real if they see it, ythen spirit will come in there last human form for that person. Otherwise they will just come as their true natural form, which is just light, sparks, ect.

My experience only!!!!