They are very effective teaching tools, a new study found, including for teaching aggression. "Students who played multiple violent video games actually learned through those games to produce greater hostile actions and aggressive behaviors over a span of six months," reports Science Daily, citing a study of almost 2,500 young people - "Violent Video Games as Exemplary Teachers: A Conceptual Analysis" - to be published soon in the Journal of Youth and Adolescence. It worked with 430 kids in grades 3-5, 607 in grades 8 and 9, and 1,441 students with an average age of 19, assessing "aggressive thoughts and self-reported fights, and their media habits - including violent video game exposure. Teachers and peers were also asked to rate the participants' aggressive behavior." With the grade-school students, "playing multiple violent videogames increased their risk of being highly aggressive … by 73%, when compared to those who played a mix of violent and non-violent games, and by 263% compared to those who played only non-violent games." The study's authors are father and son J. Ronald Gentile, distinguished teaching professor emeritus of educational psychology at the University of Buffalo, State University of New York, and Douglas Gentile, assistant professor of psychology at Iowa State University. At the University of Victoria in Canada, researchers Kathy Sanford and Leanna Madill have some comments on the kinds of literacy videogames can teach.