Saturday, March 26, 2011

The swimming psychology paper

In the previous post, I wrote about a paper (gated) that showed an anomaly in team swimming relays. It turned out that the first swimmer's times were roughly equivalent to his times in individual events -- but the second through fourth swimmers had relay times are significantly faster than their individual times.

The paper concluded that this happens because people put more effort into group tasks than individual tasks. They do this because other people are depending on their contributions. However, the leadoff swimmer's time is seen to be less important to the team's finish than the other three swimmers' times, and that explains why swimmers 2-4 are more motivated to do better in the team context.

My point was not really to criticize that individual paper, but to make a broader point -- that just because the results are *consistent* with your hypothesis, doesn't necessarily mean that's what's causing them. In this case, I agreed with an anonymous e-mailer, who speculated that it might have to do with reaction times. The first swimmer starts by a gun, while the other swimmers start by watching the preceding swimmer touch the wall. I said that I didn't know whether the authors of the paper considered this or other possibilities.

Commenter David Barry kindly sent me a copy of the study, and it turns out the authors *did* consider that:


"We corrected both performance times for the swimmer's respective reaction time by subtracting the time the athlete spent on the starting block after the starting signal (also retrieved from [swimrankings.net]). ... Please note, however, that previous research did not find any differences between the individual and relay competition after a swimming distance of 10m. Thus, faster swimming times for relay swimmers are unlikely to be merely due to differences in the starting procedure."


Fair enough. But ... well, the effect is so strong that I'm still skeptical. Could it really be that swimmers, who have trained their entire lives for this one Olympic individual moment, are still sufficiently unmotivated that they can give so much more to their relay efforts?

Here are the results for the four relay positions. (Times are an average of 100m and 200m):

#1: individual 78.19, team 78.38. Diff: -0.19
#2: individual 87.30, team 86.92. Diff: +0.38
#3: individual 87.73, team 87.39. Diff: +0.34
#4: individual 87.40, team 86.66. Diff: +0.74

It seems to me that the 2-4 differences are *huge*. Are the #4 individual swimmers so blase about the Olympics that they swim almost three-quarters of a second slower than they could if they were just more motivated? My gut says: no way.

One thing I wonder, following Damon Rutherford's comment in the previous post: could it be that correcting for the swimmer's reaction time to the starting gun isn't enough? Mr. Rutherford implies that the first swimmer's reaction time is for him to *start moving*. But he implies that subsequent swimmers are already well into their diving motions when the previous swimmers touch the wall. That could explain the large discrepancies, if the reaction time correction only compensates for part of the difference.

Is there anyone who knows swimming and is able to comment?

Oh, and there's one more issue with the differences, and that's a selective sampling issue. The authors write,

"We focused our analysis on the data from the semi-finals to obtain a reasonable sample size. If a swimmer did not advance to the semi-finals in the individual competition, we included his/her performance time from the first heats."


That means the individual times are going to be skewed slow: if the swimmer did poorly in the heats, his unsuccessful time is included in the sample. But if the swimmer did *well* in the heats, his successful result is thrown away in favor of his semi-final time.

That would certainly account for some of the differences observed.


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8 Comments:

At Sunday, March 27, 2011 11:18:00 PM, Anonymous Guy said...

Like Phil, I am not convinced (yet) that the adjustment for reaction time fully accounts for the relative starting advantage of the 2nd, 3rd, and 4th swimmers. And I suspect the 4th swimmers -- many on trailing teams -- employ a higher-risk timing of their dives that improves times only if you ignore those who leave too early.

1) While the 2000 study the authors reference does not find a statistically significant reaction-adjusted advantage to using a "step start," the sample is small and the study clearly suggests there may be advantages. And that study doesn't even compare relay to non-relay performances. It certainly does not justify assuming there is no advantage.

2) The data the authors use has split times (every 50 meters) for every race. So it would be easy to see if this difference appears in the non-start laps of each race (swimmers' final 50m in the 4x100, final 150m of 4x200). That would almost entirely remove the effect of any starting advantage enjoyed by later swimmers. My guess is that the relay swimmers don't do any better in their final 50m/150m than when swimming individually (or it's a tiny difference). Perhaps the authors didn't examine these splits, but their failure to report a superior performance in "the stretch" by later swimmers (who are allegedly more motivated) is curious.

3) Many of the #4 swimmers have an incentive to take a high-risk start -- coming very close to leaving early in order to try to catch up -- because the team is losing. If they commit a foul, well, they weren't likely to win anyway. That could explain the fact that #4 swimmers post the greatest gain over their individual times. By my count, 4 of the 12 relay races had a team disqualified, and in every case it was the 4th swimmer. The higher rate of disqualification strongly suggests a more aggressive effort by #4 swimmers to get off the blocks early. So any measure of 4th swimmers' time has to include a penalty for this higher disqualification rate, and I see no evidence that the study did this.

 
At Monday, March 28, 2011 10:55:00 PM, Blogger King Yao said...

The time difference for the first swimmer makes the conclusion of the study sound very fishy.

"However, the leadoff swimmer's time is seen to be less important to the team's finish than the other three swimmers' times, and that explains why swimmers 2-4 are more motivated to do better in the team context."

I call BS on that.

 
At Wednesday, April 06, 2011 1:08:00 PM, Blogger Micah said...

The link below discusses leaders and followers and maximal/submaximal effort during races. Not the exact scenario you discuss, but these sentences gave me pause and reminded me of your question and whether this idea relates to relay splits:

And here’s my favorite: swimming races are unique because there is a brief moment when the leader gets to see the competition: at the turn. This would mean that there would be a systematic difference in effort spent on the return lap compared to the first lap, and this would vary depending on whether the swimmer is leading or trailing and with the size of the lead.

http://cheeptalk.wordpress.com/2011/04/04/effort-and-performance/

 
At Friday, April 08, 2011 12:31:00 AM, Blogger NPHard said...

I do not think these the researchers understand the sport of swimming. Reaction time adjustment is not going to compensate for the differences in time. A relay start is a totally different than a standard start and the difference carries a speed difference well past 10 meters and probably down the entire first lap. I just time this with junior swimmers last week and the difference of a relay start to a standard one varied by swimmer in the range of .5-1.0sec to the 12.5yd. I think the only impact on the second lap would be difference in how tired the swimmer is compared to a regular race all real speed advantages will be lost in the turn. So second splits would be interesting, but not definitive because of other issues like disruption of the surface.

How relay are done versus individual race is so different that trying to relate them is not insightful or useful.

 
At Tuesday, April 12, 2011 8:31:00 PM, Anonymous fang2415 said...

I just now stumbled on this and as both a social scientist and a former swimmer (with a pretty darn good relay start, if I do say so myself), I had to comment.

Relay starts make a huge different in times, and it's not just the reaction time. I used to start at the back of the block, step up with both feet and swing my arms before the start to maximize momentum off the block. (Like this guy: http://www.youtube.com/watch?v=a-lFOwJFmBs) That changes your initial speed, your angle of entry, your path through the air, you name it, it's a totally different start.

Not to mention that a really good relay start borders on illegality every time -- when the previous swimmer touches the wall, nothing but your toes should be touching the block. That's compared to a flat-footed flat start.

This is well-enough-known in the swimming world that standard practice is to just add about a second to any relay split to convert it to a flat-start time.

Although I haven't read the paper, I'd be very surprised if there's a way to control for the mechanical difference in relay starts accurately enough to make a claim about any significant psychological impact. Maybe if they only looked at times after the first length or something... (Although there still may be issues with the different ways that swimmers might pace their relays.)

Mind you, I wouldn't be too surprised if there were a psychological effect -- I always thought silent swimming starts were tough to mentally "wake up" from -- but I'd be very skeptical about any results that don't eliminate the start altogether.

 
At Tuesday, April 12, 2011 8:39:00 PM, Anonymous fang2415 said...

"Please note, however, that previous research did not find any differences between the individual and relay competition after a swimming distance of 10m. Thus, faster swimming times for relay swimmers are unlikely to be merely due to differences in the starting procedure."

Also, uh... maybe I'm misreading this, but doesn't the first sentence support the opposite of the second? As I understand it, the first sentence means: "After the first ten meters, indy swims are just as fast as relay swims." Doesn't that mean that faster relay times are exclusively due to differences in things affect the first 10M, especially starting procedure?

Oh well, old thread. But either I'm missing something or this study sounds quite confused to me.

 
At Wednesday, April 13, 2011 9:27:00 AM, Blogger Phil Birnbaum said...

Fang2415: Good catch! I interpreted the "10m" part the other way.

Maybe what the authors mean to say is: "the ONLY difference between individual and relay times, in general, is the first 10m. We corrected for the starting times, which should fix the 10m difference. Therefore, there should be no differences left except group effects."

Still doesn't really make 100% sense ...

 
At Thursday, April 14, 2011 12:17:00 AM, Blogger NPHard said...

The time difference the authors talk about is explained solely by reaction time which is captured in all high level meets. Notice the lead off swimmer was .37sec to .71 sec slower off the blocks which is consistent to the improvement found in the study vs their individual races. Adding the improvement in reaction time back to the swimmers relay time also put the swims on par with these swimmers individual times which wouldn't be the case is the author really controlled for the differential.

http://voices.washingtonpost.com/olympics/2008/08/mens_4x100_freestyle_relay_som.html

www.technion.ac.il/~olegbm/paper_18.pdf

 

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