Dr. Munro Cullum -- a professor of psychiatry, neurology and neurotherapeutics at the University of Texas Southwestern Medical Center in Dallas -- wrote in an online post that some athletes choose to "sandbag," to do poorly on their tests, establishing a low-performing baseline that is easier to emulate after they're taken out of a game with a suspected concussion.
"Post-concussion test results are compared with the baseline to help determine whether someone's cognitive function is back to normal. These athletes want to play no matter the cost -- even if it means returning to action with a brain injury," Cullum wrote. "Sandbagging isn't the only way to invalidate a cognitive test. At the high-school level, my colleagues and I often see invalid baseline results from computerized testing, as high as 20 percent in some samples. Among teenagers, invalid results can have a variety of sources: sandbagging, disinterest, being distracted during the test, or not understanding how important it is."
State legislatures and high-school athletic associations increasingly have become active in establishing concussion monitoring programs.
Many high school teams, especially football teams, now typically require their players to take 30-minute computerized tests to establish cognitive baselines.
"My son plays soccer, another sport that sees its share of head injuries," Cullum wrote. "Here's what I told him about the concussion testing:
-- Take it seriously in a quiet environment, away from your cellphone, family, friends and other distractions.
-- Make sure you give it your best effort. Treat these exams just as if you are seeing a doctor for a medical test.
-- Be as honest in your testing as you are with your physician.
-- There is still so much we don't know about the brain and the damage caused by concussions. We don't know what the risks of contact sports are. We know that multiple concussions aren't good for the brain, but we don't know how many is too many. We don't know why some children who get their bell rung are totally fine the next minute and others aren't OK for weeks.
-- Some kids are more vulnerable than others. Is it shape of the skull? Thickness of the skull? Nature of the hit to the head? Genetic risk factors? We simply don't know."
Celebrity Families of 2014 [PHOTOS]