Magician and escape artist Harry Houdini was a little obsessed with the "paranormal."
As a magician, he knew that every one of the people who professed to be in contact with the dead were nothing but magicians themselves, but an evil variety — they preyed on the emotions of the grieving, in order to make a profit. It worked, and it still does to this day.
At the request of Scientific American and also to satisfy his own curiosity, Houdini put a fair amount of his time into proving that these people were charlatans. Ever the showman, he and Bess, his wife, made a pact that if he could contact her from the dead, he would. They even agreed on what that would look like, including a secret code that only they would know.
It never happened.
Someone who took up that mantle of disproving the intent of charlatans and carried it on into our time is another magician, James "The Amazing" Randi.
He picked up where Houdini left off, and has proven time and again that “communicating with” and “channeling” the dead — as well as psychic "readings" — are simply parlor tricks.
(The "JREF" referred to in the question slides of the below video is the James F. Randi Educational Foundation, which — until 2015 — offered a cool $1 million to anybody who could prove that their ability to conduct “paranormal” happenings were actually verifiable. Much like a similar reward offered by Houdini in 1925, nobody ever claimed that prize.)
Here’s his take: