A Quick Thought On Momentum

The other day, Dave tweeted something about Mike Sweeney. Since homering and lifting his OPS to .980 on May 26th, Sweeney has batted .203, with two doubles and zero dingers.

Troy Glaus had one of the season's wildest hot streaks, going deep 12 times and posting a 1.011 OPS over 38 games between May 10th and June 19th. Since then, he's batted .174 with two dingers and had his job taken by Derrek Lee.

Delmon Young was absolutely on fire for more than a month, posting a 1.093 OPS between July 1st and August 5th. Since then, he's batted .186 while going deep just once.

On a team scale, with emotions running high, the Cardinals swept the Reds on their own home turf two weeks ago in what could've been interpreted as Cincinnati waking the St. Louis giant. The Reds then immediately embarked on a seven-game winning streak, overlapping the Cardinals' five-game skid.

Hot streaks (and cold streaks) exist, but they are not predictive. This isn't anything new. The good folks who wrote The Book already figured that one out.

What I wonder, then, is: in the face of this evidence, why does the belief in the significance of momentum exist?

I don't even mean after The Book was published. I mean ever. The study in The Book was based on historical results, and at least within the scope of their investigation, they didn't find any evidence that streaks would sustain. Yet the feeling's always been there. This team's on fire. That team's in a slump. This guy's swinging a hot bat. That guy can't buy a single. Momentum in baseball has always been lent a certain validity, even when there wasn't any good reason to believe that it mattered, or existed in the first place.

Why?

I wonder if the answer might not fall along the same lines as the reasoning for why people have been so hesitant to accept DIPS and BABIP theory and all that. With balls in play, as with hot streaks, there's an inclination to assign responsibility to the guy pitching, or the guy hitting, or the team winning. They're the ones performing, so they must be the ones behind their performance. Fans and players alike will assume that the players and teams are in control of how they do on the field.

But what turns out to be the case is that this simply isn't true. No player or team is singularly responsible for what happens on the field. There's also the huge matter of the opposition, and the equally huge - if not huger - matter of luck, or flips of the coin, or however you want to put it. When a hitter's on a hot streak, he'll usually say that he's seeing the ball really well. Is the hitter doing something differently with his body or his eyes? Or is it more likely that he's guessed right a few  times while benefiting from the opponents throwing bad pitches?

If I had to hazard a guess, I'd say the belief in momentum stems from an assumption of control that greatly exaggerates reality. It's not the only possible explanation, but it's the first one that comes to mind. Hitters and teams always assume they're the reason that what's taken place has taken place.

I wonder what would happen if players realized how much is out of their hands.