In one of the NFL threads, we were talking about NFL home fields and OBF mentioned that the home field is considered to be worth about +3.  I thought it was worth more than that, but since home teams win 57%, then +3 is about right.  Kudos.

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NFL play is much harder to analyze mathematically than MLB play, because the players' performances can't be isolated as easily.  But that doesn't mean that football saberdweebs are any less erudite.  They may be better.

One of the great NFL sabe sites is advancednflstats.com.  On it, we caught a great article about home field advantages.

1) NFL home teams win 57% of the time.

2) For no reason that anybody can measure.  (All the fields are 55x100, right?)

Fascinating, no?  :- )   An interesting little puzzle, then.

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=== Root Cause Analysis ===

According to the author, studies have been done trying to isolate the following variables and their effect on game outcomes:

Referee bias:  whether refs tend to call more, or more critical, plays for the home team

Crowd noise:  whether inability to audible, penalties, etc amount to much

(... at this point, he had me thinking.  The sabermetrician in us immediately realizes that even if a team gets three delay-of-game penalties, that's only 15 yards, about 3-5% of the yardage on the day.)

Climate:  whether players perform significantly better-or-worse when going through weather changes

Quirks of parks:  how much turf teams suffer on grass, in AL-vs-NL studies

etc.

Seasoned saberdweebs will realize with a start, right here, that none of this stuff is going to persist across a decade's worth of games.

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=== I Know, I Know, A Dirty Word Dept. ===

But the author does suggest something that most baseball sabermetricians never would:  he suggests that players perform better at home simply because feeling more aggressive at home.

This aggression, he theorizes, isn't a mood that the player talks himself into before the game.  It is something wired into his DNA, like your dog has it wired into his DNA to retreat when challenged on your neighbor's lawn.

Sports psychologists know that peak performance is based on visualizing the positive.  Being on your home territory, from a natural-selection standpoint, means you are likely to win -- and that you therefore should fight.  (See the article for more information.)

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=== Don' Come Round Here No' Mo' ===

All this sounds obvious, but for the life of me, I'd never connected the home-field advantage that clearly.

Is it really as simple as your dog being on his own lawn, or the neighbor's?  Is it really traceable back to cavemen / nomads defending AND WINNING on their home rocks and losing when trying to invade the enemy's?

I think it probably is, yes.

Probably wayyyyyy down in his DNA, a home-field pitcher sense that he is supposed to be there and that he is supposed to fight.  A road pitcher may have a signal, deep in his wiring, telling him that he doesn't really have the right to win.

Obviously, humans are more than animals, and it's our job to use our rationality to overcome our instincts.  But home-field players don't have to fight their instincts.

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Anyway, having visited advancednflstats.com, I can enjoy and appreciate the home field advantage more than I did yesterday.  Good show, mate.

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=== Practical Implications ===

The home-field advantage is more likely to assert itself early, the author demonstrates.  ... and it's self-evident that it would assert itself early, to the extent that the crowd hostility makes the visitors feel more and more unwelcome.

That QWest environment is hard to overcome, for reasons that may be seated deep in the visitors' DNA.

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As fans, we're hoping to see it take hold in the very first drive or two.  And that makes sense, right?

The Seahawks can seem like mortal locks sometimes, when at home against a fairly equal opponent.  The crowd's opportunities often come in the first quarter, quarter-and-a-half.   If the other guys can hang on, take a lead into the 2nd half, the crowd might not be much of a factor.  But when the other guys panic in the first few drives, as the Rams did last week, they can be in for a long day. 

Seeeeaaaaa-fense.

Cheers,

Dr D