HQ BaselineSideline screening
King-Devick Test: The 2-Minute Sideline Screening That Catches What Other Tests Miss
A deceptively simple test that captures multiple brain functions simultaneously.
The King-Devick (K-D) test is deceptively simple: the athlete reads single-digit numbers aloud from three test cards as quickly as possible without making errors. The total time and error count are recorded. That’s the entire test — three cards, under two minutes.
What it actually measures
Beneath that simplicity lies a screening tool that captures multiple brain functions simultaneously. Rapid number naming requires intact saccadic eye movements (the quick jumps your eyes make between fixation points), visual scanning of a spatial field, sustained attention, language processing, and processing speed. A concussion that impairs any of these functions will slow the athlete’s completion time — even if they can’t articulate what feels different.
The evidence base
Originally developed as an ophthalmological screening tool by Dr. Alan King and Dr. David Devick, the test was adapted for concussion assessment and has been validated across multiple contact sports. Studies published in the Journal of Neurological Sciences, Neurology, and Concussion have demonstrated that concussed athletes take significantly longer to complete the K-D test compared to their baseline performance. Validation studies span boxing, rugby, hockey, football, and MMA, with research published in the British Journal of Sports Medicine and JAMA Ophthalmology.
Practical strengths
The K-D test’s greatest clinical strength is its practicality. It can be administered by anyone — parents, coaches, teammates, referees — with no medical training required. The cards (or tablet app) and a stopwatch are the only equipment. This makes it uniquely suited for settings without athletic trainers, including club sports, recreational leagues, youth programs, and international competitions where medical staff may not speak the local language (the test uses universal Arabic numerals).
The specificity limitation
The test’s limitation is specificity — factors other than concussion (fatigue, distraction, alcohol use) can slow performance. It is best used as a screening tool that flags athletes for comprehensive evaluation, not as a standalone diagnostic.
How we use K-D at Headquarters
At Headquarters, we include King-Devick in our baseline battery and recommend it to families as a take-home sideline screening tool. If your athlete’s K-D time increases from their baseline, that’s a signal to stop play and seek professional evaluation. See also our overview of how K-D compares to other baseline tools.