"You never get a second chance to make a first impression." You know that. That's why your best friend's girlfriend hates you. That and the fact that you dumped a beer over her head the first night you met her.

The first impression that baseball fans and bettors had of Coors Field, home of the Colorado Rockies, was that watching teams play there was like watching a beer league softball game. The thin mountain air made it a hitter's haven, and games in Colorado posted the highest runs per game and OPS percentage in Major League Baseball from 1999-2004.

The psychological concept that helps explain why initial impressions stick with us so long is called the primacy effect. It states that the information the brain receives first is weighted more heavily because it is assumed to be more important. The primacy effect is what kept the general public from making a killing off Coors Field as an Under park in the first half of 2006.

That's right. I just said "Coors Field" and "Under" in the same sentence. And no I'm not drunk on Pete Coors' watered-down nectar. The Rockies are 34-47-6 against the total this season, third worst (or best, depending on how you look at it) in the league. That includes an absurd 14-29 mark in Coors Field.

Generally, such an obvious glitch in the numbers would be quickly corrected by oddsmakers. However, the books have been lagging a bit on this one. Only recently have Colorado's totals started to consistently dip below double-digits. In fact, their 8.5 closing line on July 8 was only the second time in since 1999 that a run total in Coors Field was posted at less than nine.

Why are the books seemingly slow to catch on? Most likely its that the books are still cleaning up on Over players because people still look at the Rockies in Colorado like they're the 1986 Red Sox on Nintendo's RBI Baseball. It's the primacy effect at work. The squares are so conditioned to Coors Field as an Over park that they continue to bet that way.

Granted, fans and bettors have good reason to hold onto that first impression. Looking at Colorado as anything but an Over team is kind of like looking at Star Jones as anything but a fat pig on "The View". It's unsettling. How do you forget so many 24-12, 18-15 and 19-16 slugfests?

In 2000, Colorado averaged 14.37 runs per game. In 2004 that number dipped, but was still a hearty 12.69 runs per game. This season Coors Field patrons are witnessing just 9.57 runs per game, 19th in the league.

The first reason for the significant dip is that Colorado's pitching is vastly improved. The starting staff is built around hard-throwers that use sinkers and sliders. That's significant because sinkers aren't as affected by the thin air as a curve ball or other off-speed pitches. The result is the eighth-lowest ERA in the Majors and one of the lower ground out-to-fly out ratios in the league.

Of the 250 pitchers with records against the total in 2006, the Rockies have four pitchers ranked lower than 208th. Besides ace hurler Jason Jennings, Colorado's other four starters are just 20-39 against the number and average a modest 8.7 runs in their 65 starts.

The second and perhaps more significant factor why teams are scoring less in Colorado has to do with their in-stadium humidor. The longer that balls are exposed to Colorado's thin, dry air the harder and more dried out they get. The humidor keeps the game balls at a temperature of 70 degrees and at 50 percent humidity, and by limiting the balls' exposure to the air it succeeds in taking some of the "juice" out of them.

In fact, after a three-game series in June in which they only managed three runs, some Oakland A's players and coaches were openly complaining to the media about the effects of the humidor. Naturally, all three of those games went under and the A's looked like candy-asses.

Colorado should still be considered an Under play. However, be wary of the market correcting itself, which it has started to. The flip side is that you may be able to find tremendous value if the totals start to pop up at 8.5 or 8.0. I mean, it is still Coors Field.

Think of it in terms of Coors Lights. If the total is closer to the number of beers you can drink during the game and still drive home - a six-pack or so - then go over. If that total is closer to a twelve-pack, play the under and crash on the couch.

Questions or comments for Robert? E-mail him at robert@docsports.com or check out his Insider Page here.