(FORTUNE Magazine) – There is a lot to like in the summer's big hit movie Forrest Gump. Tom Hanks is great in the title role. The story line, for once, asks you to sympathize with a simple young man who is quintessentially old-fashioned -- Forrest believes in God and country and loyalty to friends -- and to think of the counterculture as a bunch of creeps. Pat Buchanan wrote a cheerleading column about the movie, marveling that so many conservative ideas could be on parade in a 1994 Hollywood production. We agree that it's a marvel, yet have a bone or two to pick. / For openers, we could not help noticing that the movie is a challenge to the only book we ever wrote, a 1992 epic called A Question of Intelligence: The IQ Debate in America. A major theme of the book is that IQ is a powerful predictor of career success. A major theme of Forrest Gump is that a fellow with an IQ of 75 can be a war hero, a world-class Ping-Pong star, and a business success. Friends, it is not possible. Take Forrest's military career. Even before his gallantry in battle -- he is shown rescuing wounded comrades in Vietnam -- he is depicted as a whiz in basic training. But it is not credible that he would even be in the military, which for many years has refused to accept anybody with test scores in the lowest 10% of the intelligence distribution. At 75, Forrest would have been around the sixth percentile, classified by many psychologists as "borderline retarded." If he had somehow got into the armed forces, it would have been miraculous if he had done well in training. The central reason for excluding the bottom 10% is that recruits in that zone have endless troubles learning their training tasks. The services have worked hard at gauging the relationship between test scores -- the Armed Forces Qualification Test is in effect an IQ test -- and training performance. A 1989 Defense Department report made it clear that even those in its so-called Category IV, the lowest acceptable level (roughly equivalent to IQs of 80 to 92) were not nearly as proficient as those in the higher categories. Among other things, they couldn't shoot as straight. An odd subsidiary theme in the military section of the movie has Forrest developing quite suddenly into a Ping-Pong star and representing the armed forces in tournaments in China. This too is wildly unlikely, as Ping-Pong calls on extraordinarily fast reactions, and reaction time is powerfully correlated with IQ. Psychologist Arthur Jensen of the University of California at Berkeley, a pioneer in reaction-time testing, has generated an avalanche of data showing the correlation to be consistently negative, typically around 0.35. (Negative correlations range from 0.0 to 1.0.) In other words, smarter people react faster. Albert Einstein in his old age is a more plausible Ping- Pong champ than Gump. If you see the movie, you really ought to buy the book -- the IQ book.