James Angelini of the University of Delaware and colleagues recorded and tracked NBC's prime time coverage of each day's events and found NBC highlighted Americans at three to four times the rate their successes suggested.
"You see all this coverage of American athletes even when they fail and there's so little coverage of the gold, silver and bronze medal winners in certain sports," Angelini said in a statement.
For the 2008 Summer Games in Beijing, the researchers tracked U.S. and China CCTV coverage, while this year, they'll also be screening the BBC during the London Summer Olympics July 27-Aug. 12.
The study, published in the International Journal of Sport Communication, also found:
-- When American athletes succeeded, commentators were more likely to focus on their intellect, commitment and luck both good and bad.
-- When non-American athletes failed, commentators were more likely to say they failed because they lacked the strength and skill of other athletes.
-- American athletes received enhanced comments about their outgoing/extroverted nature.
-- When discussing African-American athletes, commentators focused more on physical ability and strength.
-- Asian athletes garnered a disproportionate number of comments about intelligence.
-- When discussing white athletes, commentators were more likely to mention commitment and composure.
"People build their belief systems about gender, races and ethnicities, based in part, by what they see on television," Angelini said. "Sports tend to draw large audiences, particularly among young men. The danger in these skewed representations could be in their effects on viewers' perceptions."