"They have these new (brain) tests we have to take," he said. "Before the season, you have to look at 20 pictures and turn the paper over and then try to draw those 20 pictures. And they do it with words, too. Twenty words, you flip it over, and try to write those 20 words.
"Then, after a concussion, you take the same test and if you do worse than you did on the first test, you can't play. So I just try to do badly on the first test."
The four-time league MVP made the revelation in an ESPN.com article when he was asked for his opinion about recent research into the long-term effects of concussions during a joint interview with his father, Archie, and brother, Eli.
As an aside in the ESPN.com article, Archie Manning slapped his forehead in disapproval.
Last week, former NFL safety Matt Bowen also admitted to hiding concussions, responding to a FOXSports.com piece by writing: "Every offseason I would miss questions on the concussion test. Bad move looking back."
The NFL has standardized sideline concussion examinations for all 32 teams. Dr. Richard Ellenbogen, co-chairman of the league's head, neck and spine committee, said in a conference call earlier this month that a decision to let Philadelphia Eagles linebacker Stewart Bradley back into the 2010 opener against the Green Bay Packers led to significant improvement in the detection and treatment of concussions during the rest of the season. Bradley sustained a concussion as the team was evaluating quarterback Kevin Kolb, who also suffered a concussion and whose injury paved the way for the re-emergence of Michael Vick.
"We rely on the players quite a bit on concussions," Ronnie Barnes, the New York Giants' vice president of medical services, said on the same conference call. "We are constantly assessing players and often we are told by other players: 'Watch this guy. He might have a concussion.' "
Hall of Fame quarterback Terry Bradshaw recently revealed he's feeling the effects of numerous concussions that he sustained during his Hall-of-Fame career and now struggles with short-term memory loss, depression and anxiety.
"I thought it would be good for a lot of players for this to get out, for me to tell my story because I was a quarterback," he wrote in a FOXSports.com column. "I know how much my late center Mike Webster suffered. I can only imagine what a lot of defensive players from my era are going through. "I also think other players should speak up and say what they've been experiencing. It's good for the soul and your brain."
The Associated Press contributed to this report.