ideomotor effect that is the fuel of ouija and other "paranormal" phenomena.
Someone always beat me to it.
Talking boards are a parlor trick that exploits the tendency of people to think alike and move a thingy without knowing. Same reason the 14 year old new age girl can tie a crystal to a string.
It is useful bullshit. It's the most likely answer as assumed by all participants. When done alone it's what you really
think. The power of supernatural wiring lets one believe a wise spirit is misspelling names and entertaining slumber parties everywhere.
At most it can help you realize what you really think.
When I was 12 I was at one of my sister's softball games. Myself, and the othing siblings dragged to the ballpark, were doing "light as a feather..." 5 kids lifting 110 pounds. Index fingers are surprisingly strong. I wasn't convinced. I thought if this is real we should be able to do this to a car in the parking lot. So I got them to try it. We lifted the suspension a half inch. I made unbelievers out of all of them...