My girlfriend have been casually collecting data on this over the past 2 years. We occasionally end up in social situations with people who are flaky enough to take this stuff seriously. They'll usually -- after about 15 minutes of conversation -- make note of our 'auras' or personalities, and then guess a sign for each of us. We encourage them to try. Of the eight guesses we've had about our signs so far, none have been correct within 2 tries. I hope a few more years of this (and maybe some more data from less flaky friends) will offer enough data points to see if there's any bias, or if the odds of a good initial guess are uniform.