I recently took a Wonderlic Cognitive Ability Test at a job interview. It consisted of logic, mathematics and grammar. The NFL uses this exam as a part of their draft analysis. I can understand why I was asked to complete the assessment for the sales position I applied for. I'm not certain how it applies as a predictor of a football player's success. When did the NFL implement this assessment and how is it used in the analysis of NFL talent?
During the 1970s when Tom Landry, coach of the Dallas Cowboys, believed it could be used as a predictor of pro success(1).
This is used in analysis to measure aptitude. Some positions may evaluate its usefulness (eg, a quarterback's ability to read defenses on the fly) more than others (eg, a cornerback reacting to a ball thrown or a receiver's movement).
However, studies have shown that there is not a strong correlation between a player's Wonderlic score and his NFL performance(2). In fact, they present a negative correlation for some positions. Thus, it can be surmised that other factors (team quality, player development, character, coaching, etc.) may have more significance on NFL performance than the Wonderlic score.
Thats according to fox. It's used to measure cognitive intelligence, I'm not an expert in NFL but quarterbacks are essentially the same as playmakers in football (soccer), some playmakers have even been described as quarterbacks. One of the most important attributes for a playmaker is the ability to read and analyse situations and make the best decision in a matter of seconds. The wonderlic test is designed to test these types of attributes so for certain positions it does make sense for teams to test these abilities.
I don't think it is any definite measure of success though as some players do play purely from instinct, they may not be even able to describe how or why they make the right decision.
I guess for quarterbacks this test makes sense though as there are a lot of plays to understand and memorise.
There has been a 2009 study by Brian D. Lyons, Brian J. Hoffman, and John W. Michel that found that Wonderlic scores failed to positively and significantly predict future NFL performance for any position (wikipedia)