(CNN) At his first polygraph test to enter the CIA, the future director had a secret. John Brennan on Thursday recalled being asked a standard question for a top security clearance at his early CIA lie detector test: Have you ever worked with or for a group that was dedicated to overthrowing the US? "I froze," Brennan said during a panel discussion about diversity in the intelligence community at the Congressional Black Caucus Foundation's annual conference. "This was back in 1980, and I thought back to a previous election where I voted, and I voted for the Communist Party candidate,"