Remember the 1984 Civil War film Glory with Matthew Broderick, Morgan Freeman, and Denzel Washington? It told the true story of the Massachusetts 54th Infantry,

Yes and no, according to researchers at Washington University in St. Louis. In a small study due to be published soon in the journal Psychological Science, graduate psychology student Andrew C. Butler and his colleagues find that teaching history with popular films can be a double-edged sword.

On the one hand, the researchers found, students really do recall more factual information (50 percent more, in fact) when they read text and watch a movie than they do when they read the text alone. But when the information in the movie conflicts with the historical facts in the text, students are more likely to remember the film version, regardless of whether it's correct.

And Hollywood movies are apparently rife with such historical inaccuracies, according to the study. The movie, Glory, for example, depicts the soldiers in the 54th as recently freed slaves from the South when, in fact, they were Northern freemen. (For a heads up on other historical errors in commercial films, check out this slide show at the Wash U Website.)

It turns out that such mistaken notions, once formed, are tough to shake: Students held on to the movie misinformation even when told beforehand that the film clips they were about to see were fictional! Fewer students retained misinformation, though, when their teachers were more specific about the inaccuracies they would see, saying, for instance, that "the film presented it this way but it really happened like this..."

This study was conducted with 54 undergraduate psychology students whose factual recall was measured on tests taken a week later. It's not unreasonable to think, though, that the dynamics would be different for high school and middle school students.

So, teachers, carefully screen those popular films for misinformation before you show them in class. But you were probably doing that already, weren't you?

Though not yet published, the full study, "Using Popular Films to Enhance Classroom Learning" is already posted online and can be accessed for a fee at Psychological Science.