A Clue to Referee Bias?

Soccer referees have taken some hits lately, thanks to a controversial call in the England-Germany World Cup match (among many others). Economists have already gotten involved; now here come the psychologists. The BPS Research Digest reports that “[a] simple perceptual bias could influence football referees’ judgments about whether a foul occurred or not.” Alexander Kranjec, Matt Lehet, Bianca Bromberger and Anjan Chatterjee showed 268 images of player tackles to 12 soccer players for half a second each; 134 of the pictures were mirror images of the other 134. “The key finding was that more fouls (66.5 vs. 63.3 – a statistically significant difference) were judged to have occurred when assessing the images in which movement was captured in a leftward direction than when assessing the same images mirror-reversed and therefore featuring implied rightward motion,” writes the BPS Digest. “The researchers think this anomaly may have to do with our bias (at least in cultures that read from left to right) for rightward motion.”[%comments]


I don't know that anyone has ever expected referees to be flawless in their judgment... no one else ever is. What I think the focus should be, and this has obviously been discussed extensively, is to allow technology to assist in making calls. Many of the World Cup problems would have been alleviated if they'd been able to go back to the tape to ensure an accurate call.


So if England wants replay now, will they return the 1966 World Cup?


Both the economist's and the psychologist's contribution are 1) statistically neat observations 2) entirely unhelpful if you care about the game.


"66.5 vs. 63.3 - a statistically significant difference"

Really? considering the small sample size (not only the number of players judging the tackles but also the number of actual tackles shown), I would interpret these results to be pretty inconclusive at best.

Brian S

Everything is good until this point, which is where a lot of research articles go wrong - they draw conclusions that are really just speculation:

"The researchers think this anomaly may have to do with our bias (at least in cultures that read from left to right) for rightward motion. Motion from right to left is perceived as less natural and this may be responsible for influencing judgements about fouls during play in that direction. Apparently film directors exploit this same bias by having villains arrive on-screen from the right."

I'd be interested to see some explanation of this.

Richard, Uk

CRR- What makes you think we want a replay? Pretty much everyone in the country accepts that we lost to a better team and has put the world cup behind them.

The only reference I see about it is in the US press, or more accurately, this blog!!!


Being a referee, I will safely call BS on this research because 12 PLAYERS wouldn't know a foul if it bit them in the rear. How about if we show 12 REFS the photos?

How can you make a judgement on a group of people (refs) based on an observation by a different set of people (players)?

Cmon, guys, you can do better than that.


The major flaw in this study is asking a group of players to determine if a foul occurred. As a referee, I am often amazed by what some players consider to be a foul and what objections they have to fouls that are called.


apart from the small sample size. if this is a culture thing, then the same test replicated with arabic speaking players/referees should have the exact opposite result.


Assuming 66.5% fouls in one direction, 63.3 % in the other, these are not statistically significant by chi square. Numbers don't round anyway.


Its not the statistical significance thats the issue. It is the effect size.

And yes Fritz depending upon the cell sample sizes a difference between 66.5 compared to 63.3 could be significant.

Paul Thomas

Offhandedly, I'd suggest that, assuming the difference holds up, it is more likely to be an offshoot of unbalanced brain/body structure than something as venally cultural as which direction you write.

In which case, the correct question might be whether people with situs inversus call fouls in the opposite direction or not... perhaps Randy Foye could weigh in on this issue?


The difference COULD be statistically significant, depending on the sample size. But in this case, it is NOT significant.