Top players play worse against Tiger Woods. You can measure it, which is what Northwestern professor Jennifer Brown did. Her conclusion, related in Jonah Lehrer's Frontal Cortex blog, is that players don't believe they can win when Woods is in the field, resulting in worse performance.

Despite the individualistic nature of the sport, the presence of Woods in the tournament had a powerful effect. Interestingly, Brown found that playing against Woods resulted in significantly decreased performance. When the superstar entered a tournament, every other golfer took, on average, 0.8 more strokes. This effect was even more pronounced when Woods was playing well. Based on this data, Brown calculated that the superstar effect boosted Woods' PGA earnings by nearly five million dollars.

Brown argues that this phenomenon is caused when "competitors scale back their effort in events where they believe Woods will surely win." After all, why waste energy and angst on an impossible contest?

Lehrer, whose Frontal Cortex blog is one of the best out there, has a different take on the Woods effect. Instead of giving up, Lehrer believes pros playing against Woods have the opposite problem.

I'd argue that the superstar effect has more to do with "paralysis by analysis" than with decreased motivation. I'd bet that playing with Tiger Woods makes golfers extra self-conscious, and that such self-consciousness leads to choking and decreased performance. The problem, then, isn't that golfers aren't trying hard enough when playing against Tiger -- it's that they're trying too hard.

Another guy who thinks this? PGA Championship winner Y.E. Yang. After he outlasted Woods at Hazeltine in August, a reporter asked Yang how he was able to wrestle a major from Woods when so many others had failed. Yang's response jibes completely with Lehrer's explanation of the Woods effect: "I think that the good players, the great names that you've mentioned, when they tee off with Tiger, they try to -- their competitive juices sort of flow out and they go head to head and try and win. For me, I don't consider myself as a great golfer. I'm still more of the lower than average PGA tour players. So my goal was today to just hit at least even, not go over par. I think probably that's the different mind-set that I had."