Harvard and Wharton MBAs fail test of S&P index funds

In an interesting study that aimed to analyze how well "smart" people could discern between similar index funds, Wharton undergrads and MBAs as well as Harvard MBAs failed. The test was simple: would people choose the index fund with the lowest fees associated with it, given that each would produce the same "pre-fee" return (tied to the S&P 500)?