Momentum vs. Confidence
Hey there, readers. We apologize for the lack of new content lately. We're busy finishing cleaning up our 2013 game charting and dealing with some other things, and the Adjusted Games Lost numbers are coming soon. In the meantime, I was cleaning out my old e-mail and came across this e-mail discussion between Football Outsiders staff members that took place right after the Colts' legendary comeback against Kansas City in the first round of this year's playoffs. It brings up some interesting points about the concept of momentum, and how it relates to player confidence, and what that might mean in a sport where there are 22 men on the field at the same time. I'm putting it out there for you to all discuss in the comment thread.
I hope that the reader whose e-mail to me is quoted below does not mind. -- Aaron Schatz
Aaron Schatz: Some of you may have followed me on Twitter Saturday arguing with people about momentum. I challenged some readers to come up with actual proof of momentum, involving a definition and then statistical analysis. I had a volunteer, but he didn't quite do that. Which is too bad, because like would be a lot easier if we could actually prove that momentum exists. It feels like it does, right? Here's his e-mail:
Paul Petrone: I’m writing this article after watching the playoff game between the Chiefs and the Colts. The game was a great one; Andrew Luck has led his team back to a win after falling behind by 28 at the beginning of the third quarter.
The game had plenty of plays and plenty of arguments for momentum and against momentum. It seemed like Luck had all the “momentum” in the second half, but he also threw a devastating third quarter pick. The Colts played well, but they also got some luck of a fumble coming right to Luck that he ran in for a touchdown. There are arguments on both sides.
That said, while I certainly believe momentum is used all-to-often in sports as a tired metaphor by announcers, I do believe it exists to some degree. The key is to clearly define it.
So What Is Momentum?
Having momentum is the same as “being in the zone,” or “feeling it,” or whatever other phrase that describes playing really well for a sustained period of time. That’s it. We’ve seen it in just about every sport: a hitter who can’t help but hit a line drive, a shooter who can’t miss a three, a quarterback who throws for 300 yards in a half.
Okay, so what really is the reason for those hot steaks? Is it the talent of the player? Is it just the randomness of doing anything, that after awhile it is fair to assume that people will both have hot and cold streaks? Yes, that’s part of the reason. But also, your emotional state plays a role.
So How Does Momentum Play into Sports?
When things start going your way, you begin to feel more confident. For example, when you have a good day at work, you generally have a good day at home. And conversely, when you have a bad day at work, you have a bad day at home.
Over a long period, our emotional state can have huge impacts on our health. Study after study shows that people who are consistently negative are more likely to get sick and have shorter lives than generally happy people. Why? Our emotions matter and have a significant affect on our bodies.
Let’s bring it back to sports. Let’s say a quarterback has a bad game, or a string of bad games. What do you begin to do? Question yourself and your confidence level will begin to fall. That will affect your play, both physically and emotionally.
On the physical standpoint, when things don’t go your way, you tend to change what you normally do. If you throw a few picks going deep, your going to have an aversion to throw deep (unless your particularly mentally tough). If the defense reads that, they can take advantage and sit on short routes. You might try to do different things, change what has worked for you in the past and play worse.
However, if you have success throwing deep on a team, your confidence will rise. You won’t question the game plan, you’ll do what you’ve been taught and continue to do it well. Physically, your game won’t change, which increases your chance for success.
Also, if you feel good emotionally, you’re going to play better. For the same reason people who are negative throughout their lives get sick more often, people who feel good about themselves will play better. The better you play, your better you’ll feel emotionally, which will only help you play better.
Is Momentum Overstated?
Yes. I don’t believe the emotions of professional players change on a play-to-play basis. But do I believe it can change if a player has a terrible half? I do. Do I think it can improve with some coaching or a great play? I do.
I also believe players are stronger mentally than others and are harder to rattle as well. And I believe that can separate players of equal talent.
So, in conclusion, do I believe your emotional state matters in doing anything in life, particularly something as emotional as sports. Is it overstated? Yes. But is it still a factor? Yes.
Here was my response to the reader:
This is not the kind of article we were looking for. It's just a subjective explanation of what you think momentum is, but not in any way a test of its existence.
What we want is the following:
- a) A definition of what momentum is: in other words, after Event X, team should play better than otherwise expected.
- b) Statistical analysis showing that this is actually true.
Cian Fahey: Whether momentum exists or not is irrelevant to me. It still affects the belief of those who do believe in it, so it's important regardless. Belief/Confidence is one of the most important aspects of playing sports. It's less an issue at the top level because most of those playing at that level have huge confidence/egos. When I played sports, at a much lower level obviously, the effects were always obvious.
Matt Hinton: "Momentum" was everywhere during the BCS title game, especially after FSU rallied from 21-3 down following the fake punt. Even Nick Saban cited it – hey, coaches have to make bold calls like that sometimes to spark some momentum. Mack Brown sent out at least a dozen tweets about momentum. Players and coaches definitely believe in it.
That's a little surprising to me because it seems like they'd be more in tune to the mechanics of what's going on, which they can understand and control, than a vague emotional state subject to lord knows what. But the emotional/effort aspect of it is a very real part of it for them, and thinking of performance in terms of probabilities and degrees of randomness isn't very productive if you're the performer, so they attempt to define it and control it to whatever extent they can.
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Peter Koski: Momentum is a psychological crutch used to validate the result of a series of random events because people are uncomfortable that we live in such a universe where events unfold the way they do "just because."
What constitutes momentum in an NFL game? When exactly does it begin? Momentum's origin is always so easily marked in hindsight, yet remains very tricky to locate in real-time. It seems that momentum's origin can never be pinpointed and instead exists as a Schrodinger's Cat that either exists or does not exist until you go back to measure it from some future point in time. In Green Bay on Sunday, the 49ers defense forced three straight 3-and-outs and held a 6-0 lead after the first quarter and were driving into Green Bay territory to start the second quarter. They had "THE MOMENTUM!" However, after riding that momentum 30 yards into GB territory, Kaepernick threw an interception and GB drove to score a touchdown and took the lead 7-6. So, was Momentum tricking us into thinking SF had the momentum, when really GB had the momentum all along because they only allowed two field goals despite being massively outgained offensively? Well, the 49ers scored five plays after GB's touchdown to grab the lead back, but did they also grab the momentum? The "Fumble Luck" touchdown was not random, it was the Momentum's righteous providence! These are but two of the enumerable examples that we see each week exposing the folly of "momentum" in the NFL. We know what momentum means within the NFL lexicon: One team's victory was possible because they achieved a series of successful outcomes that overwhelmed the opponent's ability to counter. The true alternative is frightening to many fans and leads to them to cling to "momentum;" events unfolded whose results were heavily influenced by randomness and ultimately outside direct control of either team to a certain degree.
There's a definite confusion between confidence and momentum. When negative events unfold and confidence is lost, it's possible that focus is also lost and momentum is observed as a self-fulfilling prophecy. All it takes is one play to "swing momentum," which I think in itself invalidates the definition of momentum.
Danny Tuccitto: I chimed in on Twitter at the time, but I will expand here. If we define momentum as "A player having success on Play A results in increased confidence on Play B, which leads to increased likelihood of that player having success on Play B (or vice versa)," then yes, momentum exists. The sport psychology literature is clear on it. The problem is that, in football, you have 11 vs. 11, and so these positive (or negative) feedback loops are diluted across 22 players, not to mention backups and coaches. That's why, when someone like Bill Barnwell (read here and here) or Brian Burke (read here) does an admirable job of trying to relate presumable momentum-producing situations to subsequent performance, they find no evidence of momentum in the data. With so many interactions, the overall team-wide effect seems to me to be practically imperceptible. There are situations where you have, say, most of the players on the field for Team A experiencing the positive feedback loop, while most of the the players on the field for Team B are experiencing the negative feedback loop (i.e., the optimal situation in which to find evidence of momentum), but those situations are so few and far between that they get drowned out by the "it's a wash on the field" situations.
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Scott Kacsmar: I think momentum works much better in basketball or hockey where it's a fast, back-and-forth game with fewer players on the field. When you watch a scoring run, especially from the home team, in a NBA game, momentum swings are undeniable. But measuring this in football becomes almost impossible because of the mini-breaks that take place between plays, and as Danny said, the 22 players really complicate things. It only takes one small mistake from one guy to throw off an entire play. Someone like LeBron James can practically go on a 9-0 run by himself by dominating both sides of the ball.
Danny Tuccitto: If I could offer a practical example for my point, consider something like "wide receiver A is destroying cornerback B on every play in the first quarter" or "pass rusher A is destroying offensive lineman B on every play in the first quarter." OK, so the WR/OL are in super-confidence mode and the DB/DE are in super-woe-is-me mode, and the former are probably screaming to the heavens on the sideline that they're owning their guy 1-on-1. But then what? How's the QB's confidence doing? How's the opposite WR/OL's confidence doing? How likely is the offensive coordinator to damn the torpedoes and keep feeding the ball to that WR or running behind that OL on every play until it stops working? There are just too many things that need to come together to make one guy's "momentum" translate to perceptible (data-wise, I mean) team-wide, momentum-based success.
Aaron Schatz: Actually, I think Peter's point about confidence and momentum being confused for each other combines well with Danny's points. First, that there's so much noise with 22 (actually, 90 including backups on both units) emotional feedback loops going on at once. Second -- and this ties into Cian's comments -- I would suggest it takes a lot more to shake the confidence of a professional athlete than it would to shake the confidence of a high school athlete or something. (By professional, I would also include the top college athletes.) And thus, players' lack of confidence is unlikely to heavily affect their performance, even when they are losing by three touchdowns. And, it follows, this helps explain why we have never found evidence in NFL play-by-play that big plays naturally lead to more big plays, and failure naturally leads to more failure.
35 comments, Last at 07 Apr 2014, 6:39pm
#35 by BengalFaninIN // Apr 07, 2014 - 6:39pm
Momentum is an inherently intangible concept. The idea exists because for the most part we view sports as an entertainment. So we watch and enjoy the game, then we create a narrative to explain what happened. When a game turns on a certain play, and one team has more success after that point then goes on to win. We all talk about how they got the momentum at that point. When the rally fails we simply forget and create another narrative. Maybe we decide the other team got the momentum back at that point?
#34 by Jazzaloha // Apr 05, 2014 - 7:34pm
1. If the call for a precise definition and method of statistical analysis stems from the assumption that meeting these two conditions are necessary for the phenomenon to be real or meaningful, then I strongly disagree with that. Just because an aspect of sports can't be precisely defined (for statistical purposes) or analyzed statistically, that doesn't mean the aspect isn't real or isn't important; nor does this mean we can't talk about these aspects. Our discussion and analysis of sports would be incomplete and less meaningful if we eliminated everything but stats.
2. I think momentum can involve two factors--morale/confidence and rhythm/flow. I do believe that events can occur that can be highly discouraging to a team--Schaub's penchant for pick-6s this year; Percy Harvin's TD return in the Super Bowl. Professional athletes aren't immune to discouragement. When these things happen, momentum can shift.
But momentum also involves rhythm--which usually involves the offensive side of the ball. An individual or even a team can find a groove. Even an offensive play caller can find a good rhythm as well. Can you define what being in a rhythm is? No, I don't think so. It's not something you can just see through statistics.
Finding a good rhythm isn't easily controllable, either. It's not something you can just turn on or off. Individuals and teams work to find this rhythm. Sometimes they get find it and sometimes they don't. Momentum can often involve this moving in and out of rhythm.
By the way, musicians and music fans can really understand this concept--especially if fans of jazz or funk/R&B music. These musicians and fans enjoy when the music "grooves" or "swings." When it happens you can hear and even feel it, but, again, it resists a precise definition. Musicians also can't easily control this aspect, either, although, like athletes (on offense) they're constantly trying to find "it." Now, you can't measure or statistically analyze this. Does that mean it's not real or unmeaningful? I don't think so. Same with momentum and rhythm in sports.
#33 by stanbrown // Apr 01, 2014 - 9:27pm
Sometimes there are no adjustments that work. One team is successful until the other figures it out and the first team has no answer.
The most important thing to realize is that there is no single talent level on offense vs a talent level on defense which even exists. It's not that we can't estimate it. It's that it does not exist. Those who think in those terms don't understand the game.
#31 by zenbitz // Mar 28, 2014 - 3:15pm
If you could "somehow" extract or estimate the true talent of an offense and defense on a given play context, then I think you could define momentum as the autocorrelation function of success between subsequent plays.
If you had 2 perfect 0.0 True talent DVOA teams (in all situations), then you would expect no autocorrelation between 1 play to the next. But if momentum was real, then you would observe an autocorrelation or "snowball effect"
The difficulty in real analysis is that the actual talent difference will also have an autocorrelation. So I don't know how a priori you can tell the difference between a better team (well, unit considering offense and defense independently) and one with momentum.
#32 by Jerry // Mar 28, 2014 - 5:42pm
Burke was trying to do some of that in his "run tests" article.
Of course, we come back to how we define momentum. If teams keep adjusting to each other's tactics, so that the offense has a few successful plays, them the defense adjusts and makes a few stops, then the offense makes a change..., is that momentum or just coaching?
#30 by stanbrown // Mar 26, 2014 - 8:44pm
There seems to be quite of bit of confusion about how players actually play the game. Players are NOT automatic robot-types who function at the same level all the time with differences in production being nothing more than random rolls of the dice.
Of course there is such a thing as momentum. Anyone who has seen a game where Peyton Manning eventually figures out the defense has seen momentum shift.
Momentum absolutely has an emotional element, but I would argue that the emotion usually comes initially as feedback. Players or teams often get on a roll because of strategy or tactics or individual fundamentals. And the roll can stop because the opponent figures out how to stop what was working.
A pitcher may be struggling with his arm angle, his plant foot, a blister, or a sore elbow. If he figures out what is wrong, or comes up with a way to compensate, momentum will change as he starts getting guys out. The basketball player that misses 3 FTs in a row and then realizes he is rocking to his heels rather than finishing on his toes. When he gets his fundamentals back, his shooting improves.
Players figure out how to deal with something their opponent is doing and outcomes change. The chess matches can produce runs. These runs are momentum. Emotion can take a run and make it bigger.
#21 by bubqr // Mar 24, 2014 - 4:14am
- Momentum, if it exists (which I am sure is the case), is deeply linked to human emotions, which are not only complex, but very different from person to person. -> Trying to measure "momentum"/trying to model what would be a "normal" reaction to a bad or good play is very difficult (warning, cliche alert): Player A will feel down from throwing a pick, player B will be even more "driven", and "focused", because he wants to make up for it.
- Football being a team sport, players interaction, coaching, team culture, leadership, etc. makes measuring the team's reaction to such a play/drive/quarter/game even more impossible to model/predict than the individual's one.
I think that because of those 2 things above, trying to prove the existence of momentum at a team level, is impossible. Therefore, trying to conclude anything out of studies done about football are bound not to prove not that momentum does not exist, but bound not to prove anything.
It raises the question: Is there any reliable study about momentum done for non-team sports (tennis, golf comes to mind as good ones)?
#20 by DEW // Mar 23, 2014 - 3:15am
Personally, I think the real problem is the confusion between the impact of psychological and emotional factors on the players, and the attempt to reduce the story of the game to a narrative. I think Danny captures the point well, in noting that the effect gets diluted across the team as a whole.
I'm not surprised that individual players would talk about momentum, because they'd all have experience feeling the very real psychological effects as individuals. Confirmation bias would then lead them to remember those feelings when they were answered by results on the field, and forget that they had them when the results went another way (not unlike how a mother might say "I just knew when you left the house that something bad would happen!" when her teenage son gets into an auto accident, ignoring the fact that she had the exact same anxiety the dozens of times he drove without incident).
There may be some momentum effect, that if enough data is assembled, enough tests run, and enough numbers crunched, that some discernible (though likely nominal) result is found. But football commentators go far beyond that, using "momentum" as shorthand for "two or more good things in a row just happened to Team X." In doing so, they've managed to convince themselves that they can then apply this alleged intangible predictively: "A good thing just happened to Team X, therefore good things will continue to happen."? And therein lies the problem: assigning meaning to unmeasurable factors and by doing so ignoring the impact of measurable factors--or coming to believe that random events were the product of some repeatable skill or emotional state.
#17 by cjfarls // Mar 22, 2014 - 9:39pm
I really like Noah of Arkadia's linking of momentum to "initiative", and think that is a good way to think about it. But I think the problem may be that momentum is also caught up in the very real randomness that is a huge part of every game.
A team can have momentum as defined (more likely to succeed on next play), but the effect of randomness on that play is bigger than the momentum effect. So if the momentum effect is plus-5%, there is still a huge impact of luck/randomness that could make the play fail, and thus shift initiative to the other team... a bad bounce, the D-coord lucking into the perfect play call against the DEF (leading to a pick), etc. and initiative shifts to the other team.... and then you get a run the otherway. Or on the very next play luck/randomness (or even something boring as player quality advantage) shifts the balance again and there is no run eitherway.
So it doesn't surprise me that we can't find statistically significant evidence of momentum/intiative... my guess is it actually is insignificant compared to the magnitude of luck/randomness on play outcomes, so searching for it is likely a futile endevour. It undoubtedly is over-used and hyped. But that doesn't mean it doesn't exist.
#16 by Thomas_beardown // Mar 22, 2014 - 7:03pm
We can't measure player's psychological states, nor do we know what inputs will affect them or how.
Without these things, it doesn't matter how real momentum is. You can't predict when momentum will shift. What magnitude it will have. How long it will last. So it's useless as an analytical tool.
Still fun to talk about in comments or bars though.
#18 by Jerry // Mar 22, 2014 - 9:44pm
If you can't predict when "momentum" is going to happen, or recognize its effects after the fact, then it's no different than "swagger" or "eliteness". However it exists, it doesn't have a significant effect on the game.
#19 by Thomas_beardown // Mar 22, 2014 - 11:09pm
Swagger, momentum, rhythm, confidence, these are all ways people try to label and discuss the emotional side of the game. I think emotion does exist in football and does have an impact. However, it is something outside of our means to properly understand, so it cannot be discussed with any intelligence. It can still be fun to think about.
#13 by Jason_PackerBacker // Mar 22, 2014 - 3:50pm
These concepts might have a better connection to "flow," which appears to be a relatively well-studied phenomenon in athletics. I am not familiar enough with the literature to design a statistical analysis, but the definitions are absolutely there to do so.
#11 by Led // Mar 22, 2014 - 2:01pm
Aaron above: "I would suggest it takes a lot more to shake the confidence of a professional athlete than it would to shake the confidence of a high school athlete or something. (By professional, I would also include the top college athletes.) And thus, players' lack of confidence is unlikely to heavily affect their performance. . . ."
Aaron in the Vick/Sanchez post last night: "Michael Vick signed a one-year deal with the New York Jets today for an undisclosed amount. This will of course do wonders for Geno Smith's confidence, I'm sure."
#12 by Aaron Schatz // Mar 22, 2014 - 3:48pm
Ha! You got me. I think I'm talking there about "How much does Geno Smith have to worry about the starting job in New York" as opposed to "How much does Geno Smith believe in his own ability." I'm sure he believes in his own ability. I just don't know how much he believes in his coaches' ability to not screw with his ability.
Also, there's a difference between "I just threw a pick, my confidence is shot" and "they just hired someone to replace me in my job, my confidence is shot."
#14 by Led // Mar 22, 2014 - 6:13pm
Just needling a little bit! I don't really buy that distinction, though. Anyway, I think everybody resorts to psychological explanations every once in a while. Maybe because it's an artifact of human experience or maybe we just feel compelled to tell stories to explain events, or maybe those are just two ways of saying the same thing.
#10 by MarkV // Mar 22, 2014 - 11:55am
One deeply related thing which I suspect makes momentum harder to figure out is injuries.
I have seen teams fall apart when specific injuries occur. That can give the appearance of momentum, even with there isn't anything actually happening, because the preferred competitor was replaced by one who is presumed inferior for the specific task.
I don't even think injuries would always make a team perform worse, rather causing them to perform differently. Sometimes that could cause improvements, or schematic changes. With so many variables, I think it would be hard to create a general rule. But I do think that it opposes every argument for momentum, and creates even more noise.
#9 by Noahrk // Mar 22, 2014 - 11:37am
First of all, in order to define momentum, let's move to another, competitive endeavor: chess. It might seem rather counterintuitive to look for momentum in chess, but there's actually something eerily similar there, called "initiative". Initiative means one player is dictating the action: one player acts and the other reacts. This is a great advantage and it is also temporary. You try to keep it alive as long as you can, but at a certain point, it's over. It's gone.
This is real and beyond the realm of emotion. Yet, it cannot be measured! Not even in chess! Yet to say initiative in chess doesn't exist because it cannot be measured would be beyond ridiculous. Strong players will often sacrifice material in order to gain the initiative. Its existence cannot be doubted. So I'm going to call momentum initiative since it's the only thing that makes sense.
Moving on to more physical endeavors, in war initiative exists. Of course, now there is an emotional element in it because war happens in real-time and is physical, whereas chess is turn-based and mental. Initiative in real time is related to the fact that the party that is reacting is facing new situations it can barely handle before new ones arise. He who hits first hits twice, they say.
Looking at sports, in soccer the same element of initiative is present. In fact, it's called by that same name. There will be stretches of the game when a team holds all the initiative and the opponent can only defend. This is also related to effort. Players cannot go 100% all the time. Cramps are evidence of that, if you need any. When they do, they can easily gain the initiative. In war you'll hear about "low morale", which is very similar. When a team or faction feels it has the initiative, it feels optimistic and hopeful and gives a little extra. This is sometimes called the "killer instinct".
So, does initiative exist in football? There is a lot of evidence that suggests it does. Players also cannot go 100% all the time (substitutions are evidence of this). The element of morale is reflected in home-crowds getting louder when momentum or initiative is perceived. Tactically, the no-huddle offense is further evidence. Aggressive and creative play-calling might also confuse the opponent, in both offense or defense. Same as in soccer, where the reacting team will try to cool down the game by controlling the ball, in football offenses will go back to basics, usually try to run the ball.
The measurement problem is nothing but that: a problem. It cannot be considered as evidence of initiative or momentum not existing. It's one thing to get fed up with how announcers abuse the term, but to say it doesn't exist? C'mon, son.
The man with no sig
#8 by MC2 // Mar 22, 2014 - 10:05am
For many of the reasons discussed in the article, it seems likely that the existence of momentum would be much more plausible in an individual sport, such as tennis. And indeed, if you watch a match between two great players, such as Roger Federer and Rafael Nadal, you will indeed hear the commentators constantly attributing much of the results to swings in momentum, as each player takes turns reeling off several points, or even several games, in a row.
But therein lies the problem. Why all the sudden shifts in momentum? If, as many have suggested, momentum is a manifestation of confidence, then you would expect just the opposite. It would be a vicious cycle, as each consecutive point Federer won would cause his confidence to rise and Nadal's confidence to fall, thus increasing the likelihood of Federer winning the next point, thus further increasing his confidence and reducing Nadal's confidence even further, thus increasing Federer's chances of winning the next point even more, ad infinitum. Thus, at some point, you would expect Federer to feel (and in fact be) almost invincible, while Nadal would be a broken man. At this point, Federer could be expected to cruise to an easy victory.
However, it virtually never works out like this. I have seen these two play many times, and there is virtually always at least one stretch where it seems as if one or the other of them is completely dominating the match, often winning 4 or 5 games in a row. But that person very rarely proceeds to cruise to an easy victory. Rather, their opponent almost always rebounds, often going on their own extended tear, or at the very least, returning to a competitive balance. Furthermore, these shifts are rarely gradual, but instead usually happen very quickly, just at the time "momentum" would least predict them.
So, even in a situation so apparently conducive to the influence of momentum, there appears to be very little evidence to support it.
#23 by Kevin from Philly // Mar 25, 2014 - 1:20pm
I was thinking the same thing - that the effect would be more obvious with individual sports, but using golf vice tennis. In any tournament, you can see a player meandering along hit a really good shot and just start hitting great shot after great shot. Conversely, you see players sailing along that hit a shot as bad as I might hit, and they start to fall apart. Now, how long that streak may last could be influenced by the talent or the mental toughness of the golfer - but it does happen.
#29 by Joseph // Mar 26, 2014 - 6:16pm
I would say that if you want to study this in golf, the following parameters should be used: a longer made putt (15/20+ ft), or a short miss (<10 ft), and then test the following drive. A bad drive into the sand trap or rough tends to overly influence the subsequent shot because of a bad lie, awkward angle, etc. The same could be true about most any subsequent shot--except for the one after a holed putt. The short missed putt should prob. be for par, resulting in bogey, or bogey miss leading to double-bogey. A missed birdie turned into par, or a missed eagle turning to birdie, won't have the same negative effect. The longer made putt won't matter, as it will have a positive effect regardless.
Just my $.02
#7 by Jerry // Mar 22, 2014 - 5:08am
As Danny mentioned, Brian Burke took a look at momentum. Here's a link to his last piece, which includes links to the first four:
"This series of articles examined momentum in a number of ways--using different definitions of momentum and different methods of analysis. It looked at momentum at the game level, the drive level, the series level, and the play level. Although it can't be ruled out that there is some grain of truth to the role of momentum, the effect sizes we observed are probably too small to be noticed by a fan or even by a player or coach."
#6 by Cythammer // Mar 22, 2014 - 12:05am
I think the most like explanation is that professional are so disciplined and well-trained that they aren't going to be effected to any significant degree by emotional ups and downs. Note that after almost any incredible rally or the like, the members of the team that pulled off the feat will talk about how confident they still were even in the darkest moment, how they retained belief in themselves, etc. In other words they seem to ALWAYS be confident. The attitude of athletes is generally somewhere between stoical acceptance and irrational confidence. Whatever their attitude is, they always think they can still do it… or if some part of them finds that doubtful, they're going to try as hard as they can anyway.
I'm sure motivation and something that could be called 'momentum' is important on a month to month, season to season basis. Some teams seem to have more momentum than others (Patriots), and that is probably a matter of success building on success. A great coach will be able to motivate his players to work harder and ultimately perform better over an entire season, I'm sure. We can all come up with examples of players who performed far better for certain teams than others. Think of Randy Moss' switch to the Patriots from Oakland.
But momentum actually existing in an individual game? I think it would've been found by now. Most arguments for momentum on the level of an individual game still boil down to "well, it just feels that way." Players aren't actually machines, of course, but I think they are so disciplined that they essentially function as something like a biological machine on the field. Robots competing against each other would probably operate as much by the rules of 'momentum'.
What would be interesting is to examine amateur athletic performance and see if any evidence of momentum showed up there.
#26 by Mr Shush // Mar 25, 2014 - 6:59pm
"I think the most like explanation is that professional are so disciplined and well-trained that they aren't going to be effected to any significant degree by emotional ups and downs."
There speaks a man who has not seen a lot of Mitchell Johnson...
#5 by anonymousse // Mar 21, 2014 - 9:32pm
ok, so how about this? look at a quarterback's completion percentage after completing a pass. then, his completion percentage after an incomplete pass. that's easy enough to test real quick, right? at least if it's way different, gives a reason to investigate further.
if you want to be fancy, and remove possible play-call biases (maybe coaches call more short passes after an incompletion, whatever), then break it down by length of pass and adjust for dvoa.
i suspect it'll be no real difference, but i like the general idea of breaking it down by player instead of team... instantly increases your data points by orders of magnitude.
#4 by RickD // Mar 21, 2014 - 6:56pm
I have alluded to this very vaguely in comments from time to time. The basic idea is that you could model a football team X playing a team Y with a matrix M_X,Y such that M_X,Y(ij) represented the expected yards for offensive play against defense j. This kind of model would presume that the outcome expectations were essentially constant throughout the game.
If you wanted to allow for momentum to play a role, you could postulate a second matrix M'_X,Y that was in effect when team X had momentum, which presumably had entries that expressed higher performance for X. And then what you would do is have a transition variable theta, such that on any play you had a probability of _gaining_ momentum or _losing_ momentum. So if on play k you were using M, then with a probability determined by theta, instead of using M on play k+1, you would transition to using M'.
From a standpoint of estimating parameters, this approach entails more than twice as many parameters than a simpler model. There are ways that this doubling could be reduced, say, by having all of the entries expressible as a fixed function of theta. Another thing you could do is allow for a range of matrices M_t, with t a continuous parameter.
I am just throwing ideas out here. I know there are statistical tests that are used to decide whether or not it makes sense to refine a statistical model by adding more parameters. That's what you'd be doing by incorporating "momentum" into your modeling. I'm not an actual statistician, though.
I would also say that, should you flesh all of this out and do a test for "momentum", the most you could conclude is that there's no support for such a theory, based on the data you have. You cannot really conclude "momentum doesn't exist". Our reality could always be generated by a more complicated model than the reality we actually experience.
#15 by CaffeineMan // Mar 22, 2014 - 6:14pm
"I would also say that, should you flesh all of this out and do a test for "momentum", the most you could conclude is that there's no support for such a theory, based on the data you have. You cannot really conclude "momentum doesn't exist". Our reality could always be generated by a more complicated model than the reality we actually experience."
For a number of sports analytics types, a proof that "momentum doesn't exist" seems to be the Holy Grail. I don't think that'll ever happen for the reason mentioned in the last sentence above. It may make for a fun discussion (for small values of "fun"). But pursuit of this Holy Grail doesn't really seem to advance the state of the sports analytics art. The pursuit ends up with a leap to a conclusion the data won't support. We just get statements (and re-statements) of faith by both sides of the argument.
#2 by Omroth // Mar 21, 2014 - 5:51pm
Aaron - you do realise that just because someone on the internet can't find a rigorous definition of something (such as momentum, or trap games) using available data, that doesn't imply it doesn't exist right?
Mainstream commentators say some oderous, arrogant things; but certainly nothing as bad as suggesting that.
#1 by Sporran // Mar 21, 2014 - 3:49pm
My quick off-the-top-of-my-head definition of "momentum" would be "an increased likelihood that the value of the next play will be similar to that of the previous play". This can be easily tested -- Is a good play more likely to occur (compared to random chance, adjusting for the ability of the players/teams) when the previous play was a good play? What about if there was a string of good plays in a row?
The tricky part would be adjusting for the quality of players on the field. My suspicion is that "momentum" (as defined above) is more likely after a defensive injury -- as in the defense has to play a backup cornerback that the QB can then "pick on".