Saturday, July 14, 2012

Height Discrimination In Football: Are Referees Biased Against The Taller Lads?

Next time you see Peter Crouch complaining about a referee’s call, you may want to consider these findings from a study by two Dutch academics. Though a couple of years old, it’s one of the more interesting pieces of academic research I have come across recently. In a study titled "How embodied cognitions affect judgments: Height-related attribution bias in football foul calls" the authors (van Quaquebeke and Giessner) examine the decisions referees make – in particular the kinds of biased decisions they can make unconsciously.

(c) Maurice Frazer

Their premise is simple (and I cite from the paper's abstract):
"Many fouls committed in football (called soccer in some countries) are ambiguous, and there is no objective way of determining who is the “true” perpetrator or the “true” victim. Consequently, fans as well as referees often rely on a variety of decision cues when judging such foul situations."
So far so good: in the heat of the match, there are many potential calls referees can make, and they have to choose in a split-second who did what even when the situation isn't completely clear-cut. So how do they judge what happened? van Quaquebeke and Giessner, the study’s authors, think that among other things referees use a player's physical characteristics as a shortcut to determine perpetrator and victim:
"Based on embodiment research, which links perceptions of height to concepts of strength, power, and aggression, we argue that height is going to be one of the decision cues used. As a result, people are more likely to attribute a foul in an ambiguous tackle situation to the taller of two players."
In other words, when in doubt, call the foul on the taller lad.

But could this really be?

To test their idea, the authors collected data on all recorded fouls for seven seasons of Bundesliga and Champions League play (an impressive 85,262 and 32,142 fouls, respectively), along with data on three World Cups (about 6,440 fouls), along with information on the height of the alleged perp and victim of the foul.

In a first analysis, they established that players who had been called for a foul were taller than players who were fouled. This was the case across all three competitions.  According to the refs, the taller players committed more fouls.

To make sure that the difference wasn’t due to important other factors not accounted for – like the fact that defenders tend to be taller than, say, midfielders, and foul more because of the tactical position they play rather than getting called more for fouls because of their height – the researchers further analyzed fouls and height by position. To make a long story short: the differences in who was called for committing the foul had nothing to do with position.

However, the actual average differences between aggressor and victim were small: in fact, only 1cm on average and too small to reasonably be detectable by referees. So as a next step, van Quaquebeke and Giessner measured the actual height difference between the two players involved in the situation with the assumption that taller players would be called more for fouls as the height differential increases. In other words, Per Mertesacker would be more likely to be called for a foul on David Silva than Kieran Gibbs.

Lo and behold, this is exactly what the data show, as the next graph makes clear.

van Quaquebeke and Giessner (2010)

When the height difference is small (1-5 cm), the odds of the taller player being called for the foul are right around 50-50. However, when we get into > 10cm territory, the odds go up significantly.

To show that these difference can be due to a judgment bias on the part of referees, participants in two experiments were shown an image of two players going for the ball – one taller and one shorter – followed by the instruction that one of the players had fallen down after the situation concluded and the question of why: (1) Foul, (2) Dive, or (3) Chance. The experiment participants were significantly more likely to say that the smaller player had been fouled than could be expected by chance.

Taken together, the study established that “people, when presented with an ambiguous foul situation, are more likely to attribute fouls to the respectively taller player.” Moreover, “people, when presented with an ambiguous foul situation, anticipate that smaller players are more likely to go to the ground than their respectively taller counterparts” and they “tend to attribute an anticipated fall by a shorter player to a foul by the taller opponent. Conversely, they are more likely to attribute an anticipated fall by a taller player to a non-foul context (dive or chance).”

The implications for referees are clear: be mindful of your own potential judgment biases. Make sure you’re sure when calling a foul on Peter Crouch or Brede Hangeland.  But it’s not clear what the lesson is for Crouch and Hangeland.  Sure – understand that referees are more likely to call a foul on you when playing against David Silva than when going for the ball against Marouane Fellaini. But surely, this can't mean holding back and not going for it in the moment? So is this really a lesson for managers, then? Understand that choosing players with different height implies variations in risking fouls, depending on who they are lining up against? Alternatively, take advantage of the biases referees find hard to control. If you are Roberto Mancini, don't play Edin Dzeko against Mertesacker - play Aguero - everything else equal, of course.

The citation is:

van Quaquebeke, N., & Giessner, S. R. (2010). How embodied cognitions affect judgments: Height-related attribution bias in football foul calls. Journal of Sport & Exercise Psychology, 32, 3-22.

A link to the paper is here: