It'll be 3 rounds.
First round, they'll just throw the ball to the basket without any explanation. Each participant has 5 attempts
Second round, give them 15 seconds for visualising their score. Then let them throw the ball to the basket again in the same turns
When everyone is finished, ask them what they visualised. Did you visualise the number of scores, so did you limit yourself ? Did you visualise how to throw the ball? Then, explain to them how to visualise. They should only visualise the technique for the score. They shouldn't limit themselves.
Then, start the third round and on their last turn, let them throw the ball.
When they finish, compare the results to see who got better or worse.