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The Tracker: The invisible gorilla

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26th December, 2020

Analysis of the 2019-20 season showed that a whopping third of all goals were scored because defenders ball watch and fail to track strikers.

What could be happening inside the heads of individual defenders? The season concluded with Sydney FC 1 versus Melbourne City nil.

Was a defender ball watching when Rhyan Grant scored? Was he looking but did he not see Grant?

Psychologists Christopher Chabris and Daniel Simons conducted a study that has become one of the best known experiments in psychology. A one-minute video was made of two teams passing basketballs. Before watching the video, viewers were asked to count the number of passes made by the white team.

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However, during that time, a nine-second cameo was made by somebody wearing a full-body gorilla suit. The creature faced the camera and thumped its chest right in the middle of the game. Observers were accurate about counting the passes, but nearly half of them did not notice the gorilla.

Failing to see the gorilla is a massive mistake in perception. Scientists call it inattentional blindness. The basketball players in the video were obviously in on the experiment.

But what if they had not been told about the gorilla and just been advised to concentrate on their passing? My bet is that some of them would not have seen the gorilla either.

Chabris and Simons also write about the illusion of attention. People think they are paying attention when they aren’t.

Rhyan Grant’s goal is already likely to be a distant memory for most.

Rhyan Grant

Rhyan Grant netted the winner for Sydney in the A-League grand final. (Photo by Matt King/Getty Images)

However, rest assured right now other gorillas are happily scoring goals in football matches all over the world.

Defenders concentrating hard can fail to see what is right in front of their eyes. Judging defenders by saying “they were asleep at the back” is doing them an injustice. Inattentional blindness is the evidence that the opposite is true.


Take Eren Sami Dinkci’s goal for instance. In Germany on 20 December, Dinkci scored for Werder Bremen against Mainz.

Seconds earlier Mainz defender Jeremiah St Juste had directed his gaze at Dinkci – but St Juste surely can’t have seen him. Otherwise, why would he not have tracked Dinkci and allowed him to head into goal unopposed?

When the ball had nestled in the back of the net, fellow Mainz defender Jean-Paul Boetius – who had completed his man-marking task admirably – looked accusingly at St Juste as if to say “how did you let that happen?”

My thought is that St Juste had no idea. If we subscribe to the theory of inattentional blindness, then in St Juste’s mind he was not expecting Dinkci’s run. But surely strikers are making runs all the time. Why wouldn’t you expect them?

Chabris and Simons answer this question by offering a small shred of hope for A-League coaches in the coming season. When they warned the viewers of the basketball video to watch for something unexpected, people consistently saw the gorilla.


Now there’s an idea. We can see the physical preparation in stadiums before every A-League match. Maybe in the period when the teams go back into the dressing rooms and before coming out for the match, each player looks at his phone and watches a one-minute video of a defender noticing the perhaps unexpected run of striker and tracking him.