It is claimed on Cracked.com:
There's also some evidence that our jalopy measurement system [imperial, ndr] is part of what's making U.S. students bad at math. In Malcolm Gladwell's Outliers, he suggests that Asian students may have a built-in advantage in the subject because Eastern languages are structured in a way that makes numbers intuitive. Conversely, having a language -- or a measurement system -- that makes numbers clunkier and difficult to convert would have an adverse effect on young children picking them up from the world around them. Foundation and early confidence are everything in math.
Combined, of course, with proper punishment for not learning. For this to be true, of course, U.S. students would have to be worse internationally at math than they are at other subjects ... and in fact, they are. Two recent studies show U.S. students to be right around average (12th and 15th) of 30-some industrialized nations in reading scores but among the worst (25th and 30th) in math. There are no doubt other factors involved, but a nonintuitive measurement system can't be helping.
The article links one study and one website, however none of them seem to be about Imperial units at all!
Are there any studies on the effect the choice of units has on mathematical skills? Is the Metric system advantageous, from the point of view of cognition?