Friday, June 09, 2006

perceptions on traveling

There have been a few comments recently on traveling and calling travels. It's not a strict relationship between the amount traveled and the likelihood of being called, either, since the perception of the marker (or nearby travel-calling defender) is important.

A Swedish player named Edmund England has written a paper on the perception of novices and experts in regards to traveling. The full title is "Differences in Perception Between Novices and Experts in Judging a Complex Movement in Ultimate Frisbee." Here is the abstract:

Sport researchers have lately realised that perception is an
important ability of the sport performer. In open sports, perceiving
movement of the co-players and opponents is crucial. Biological
motion, attention and decision-making are used as theoretical
background in this thesis. It examines the differences between one
group of experienced ultimate players and a group of novices in
their qualitative judgement of a complex movement in ultimate
frisbee. In this experimental digitalvideo study a total of 162
subjects participated, 104 experts and 58 novices. Twelve pretest
throws and 40 test throws were judged by the subjects. The result is
that experts are slightly better than novices. On the whole men
excel though less among experts. The background to this can be
that expert players don’t value this ability in comparison to other
ultimate frisbee skills. The intriguing difference found between
pretest and test can have implications for this paradigm in the

Another key quote is:
"The hypothesis in this thesis is as follows:
• Experienced ultimate player’s judge travelling in ultimate frisbee better than
In the following thesis I also intend to answer these questions:
• Can humans judge this complex situation with more certainty than random?
• Which of the independent variables examined seem to influence the result?"
My email response to him bounced, so Edmund, please respond here with a link to the paper, if you would like others to read it.

I only had a chance to skim the paper, but I'm not sure that I would agree with the classification of "expert". Some expert players and travel-callers I've seen are actually not experts at discerning travels. I would instead have tried to select Observers as the experts. Unfortunately, the WFDF world does not believe in Observers.

Ooh, here's a juicy conclusion:
Differences between men and women
By analysing previous studies in a neighbouring field, time to contact field where gender differences are found by e.g. Schiff and Oldak (1990), McLeod and Ross (1983). Their findings show that women are less accurate at judging point of contact than men judge. Schiff and Oldak, (1990) mean that this can have two reasons, either it is of the women’s tendency to underestimate or that women have poorer spatiotemporal skill. This present study show that women are more defensive in their judgements (women have lower beta values than the men) which supports the former reason of gender differences.



Anonymous said...

Can we get a better translation of the last paragraph? What does "women are more defensive in their judgements" mean?

Anonymous said...


That is a good question and will try to answer it. When judging travelling there are four outcomes. You judge travelling but it isn’t that. You judge travelling and it is that. You judge it isn’t a travelling but it is. You judge it isn’t a travelling and that was correct. When I then did a gender comparison on the two different types of incorrect judgements, women had a tendency to say that it wasn’t a travel when it was. That is what I mean about that women had a more defensive strategy of judgement. I know this was a very complicated way of explaining but I hope you got it.



Anonymous said...


Yes, Mr Parinella, I could agree that mabe my choice of expert group is not perfect. In sweden we don't use observers (fortunately) so that was not an option. I don't claim that the players in the expert group are experts on judging travelling but they are experts at ultimate. I used the novice-expert paradigm which is interested in checking the differences between novices to experts and through that understand experts (and novices). I didn't have the technology at that time to also measure the time between observation and decision where I guess bigger diffrences between the groups would have been found. This study is far from perfect. But in a scientific way it shows that the human eye has a possibility that is higher than random to judge traveling. But in this test I did not make the particpants fatigue, stressed or on a wanting-to-win-the-match-bias.


myles said...

You can view the paper off his website. Found it thanks to the power of google...

Differences in Perception Between Novices and Experts in Judging a Complex Movement in Ultimate Frisbee

degs said...

"fortunately"? that same "fortune" allowed several ambiguous line calls at the World Games. but I guess it's not important to get calls right -- or even allow the possibility of such -- in front of the IOC.

Anonymous said...

I dont believe in observes because I think that the decisions should be made by the players and not by anyone else. That does not imply that the decisions would be better by the players. I like the idea of the players doing the decisions and taking the full responsibility. Ulitmate has fantastic idea that many dream that the other parts of society would work.

I did not attend World Games and don´t understand what you mean.


parinella said...

With Observers, the players still make the decisions about fouls, picks, travels, etc. (although Obsrevers have, at different times, been empowered to make active in/out or up/down calls; whether those are "decisions" or just simply right/wrong situations is up to you to decide). In most situations, the Observers are just there to help keep people honest, similar to locking your doors or not leaving your wallet lying around in public. In situations where one of the teams doesn't want to follow the rules, whether because of malice or simply ignorance, the Observers provide for a more fair playing situation for the honest players.

I believe Degs is saying that there were several calls that everyone in the stadium except for the caller knew were incorrect. Although these can also be corrected by the caller's teammates and not just the Observer, it might be considered "poor spirit" in some parts of the world to tell a teammate that his call is bad and to ask him to retract it. I wrote about this back in 1996, playing against one of the northern European teams, where a player landed well out of bounds right in front of his teammates. You knew from their expressions that they knew the player was out, but they just looked away and hid. "Unspirited" Americans would have called their teammate out, as would have an Observer.

It is true that there are many plays where only the two players involved are able to know exactly what happened, and sometimes it would really be better just to do a replay (and that option is open to Observers, although it's not used very often). Any play involving contact is going to have some interpretation involved as to when it occurred and how important/incidental it was. But a lot of plays look pretty clear-cut, and there are also a lot of plays that do not involve contact and are simply a matter of facts, and an impartial person with a good view of the play and who is trained and experienced ought to be able to deliver a more fair outcome.

It's not a matter of whether a player is trying to cheat and whether we respect our opponents' integrity. For the most part, it is only that the caller really thinks he's right but he's not.

Anonymous said...

Yes it i correct that a trained observer has potential to deliver a more correct outcome. My reasons for being negative to observers are some. But I also understand these thought of more correct judgements. If we look at the refrees job in soccer. They have one person running around and two linesmen. Do they do correct judgements? Yes they do, but in every match there are many incorrect calls. So there are different discussions in soccer how you should do to get more correct decisions. Give them possibility to look at a reply, have another on running round the field and other ideas. But I don´t think you will ever manage to get 100% correct decisions. I don´t believe that the quality of decisions with a observer will counter balance that a big part of the power o decision will move from the players to someone outside. In the long run I believe that you will se teams take advantage of observers, as in done e.g. soccer.

I have also seen matches with bad calls where you miss a correct decision. But its difficult to claim that the observer would make the correct decision. I remember the final in Wugc in heilbronn 2000 between Sweden and USA. It was the last point and us was attacking when a Swedish player made turn over which the Amercian player call a foul on. I was standing very close to this incident and my point of view was that it was a perfect turn over. I have understood later that many players in American wasnt happy with the call. In those situations you want something to be done, lika wanting a observer. But will that really help? Probably not, may be the certain situation would be solved in a more correct way. But then observers can also do incorrect judgments as professional refrees in soccer also do. bit in this thread is may be more corrcect to discuss my thesis.:)


parinella said...

I remember that final very well, too. I was standing a few yards away and I could not tell what the correct call was. What I could tell was that the outlandish antics of the Swedish defender and his refusal to even consider that he had significant contact with the receiver stole something big from us. (I've stated elsewhere that if I'm just watching a play, I watch it differently than if I'm an OBserver, in which case I take in more of the details that are necessary in order to make a qualified judgment.)

Back to the thesis: there seems to be an asymmetry in the setup. Each play was grouped into one of four sets (travel or not, borderline or obvious), but the subjects were only given a choice of two (travel or not).

And I was surprised that the percentage of correct calls wasn't much higher (they were close to (but higher than) 50/50 on the borderline cases). It would be interesting to repeat the study with feedback. Perhaps do a test of 10, replay the 10 and tell them the correct answer, then do another 10. It may be that the definition of travel is too abstract for the beginners, and for the experts the difference between "as written" and "as called" is large enough that they have trouble making the right call (and I think you suggest this in the thesis).

Anonymous said...

To clarify Mr Parinellas question on if the study had asymmetry. 20 throws where traveling (10 of these where obvious, 10 where bordeline), 20 throws where correct (100 of these where obvious, 10 where bordeline). Why i chose to categorize them in two different difficult levels was to see if was easier to see obvius corrct throws/travels in relation to bordeline correct/incorrect. I thing that myself think is a weakness is that coding the throws into obvious and bordeline was made by me and could be coding differently by someone else.

I agree the complications of the experts difference between the degree differences in when they would call travelling during a match and in the study. I really tried when giving them information on the test before they had started it. That they where suposed to call travelling when it was travelling forget what they would do in match.

After I had written this thesis I have noticed the enormous amounts of travell in games. I would guess that more than 50% of all throws are travelling in a game. Which makes the rule little bit difficult to use.


Anonymous said...

Now I remember the reason to why I did this study. Quite often did players who marking the disc call travelling. Those who made that type of call and stood max 0,5 m from me, how could they see the travelling? It puzzled me. They were often very certain and sure of their call. A travel call i sort of complex when more thought is made. You have to see both the foot movement and the when the disc i released from the oponents hand. It is similar to the offside rule in soccer. Our eyes can´t view a whoel area with precision. We use focus points and from the focus point we have peripheral vision. The periphela vision has a lower prcision than our focus point. We move our focus point often. So observing travelling on a short distance makes us must move our head also to be able to see two different places at nearly the same time. There is always a short time interval between changing focuspoint. So a motivated question is, should a player who stands close to the thrower have the right to call a travel? The problem is that they are sometimes very clear travel faults which even a person staning close can see. But my study the viewers are on a five metre distance.


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