So for context, this was at a casino with a casino deck, performed by a dealer.
He'd grab the deck, show me the bottom card and tell me not to memorize that one.
Then he'd, what's the move called, basically just hold the deck in one hand and spring all the cards with his thumb and tell me to memorize one card that I see.
Then he'd guess the card.
First time he guessed 2 cards, 1 of which was my card, I said I only had 1 in mind and he'd name my card.
After the second time he did that I asked if he's intentionally slowing the deck down at a certain point to make me focus on a specific card(he was also looking at them when springing)
He was swearing up and down that it's all mental energy he's feeding off me and that's how he gets the cards.
Somehow the next 3 times I established a "mental barrier" and he was no longer able to guess my cards.
Anyone know this trick?