That Damn Gorilla

Last week I happened to log on to twitter just as some test folks were marveling over the the massive parallels between the video with the gorilla and the basketball players and software testing. I made some cracks about the absurdity of the hype, and more than a few testers freaked out.

Somewhere in the tweet insanity, I promised to blog about my opinions on the concept, so here goes.

First off – this isn’t a new gripe of mine. Here’s a tweet from August, 2011 (edited to fix my typo). To be clear, I think all three of the items below are valuable – imageyet all also seem to be frequently hyped beyond their value. The gorilla especially comes up among testers – many of whom overreact to the value of the video to software testing.

The video shows that it’s possible to miss something right in front of your eyes. The point of the video is to show that it’s possible to miss something that’s right in front of your eyes.

IB makes you confront the illusion of attention.

That’s it.

Knowing about inattentional blindness doesn’t make you better at noticing things, and there’s zero correlation between the observational skills of those who see the gorilla vs. those who don’t. While I agree that it’s critical for testers to know that inattentional blindness exists, it’s a small nugget of information in a pretty big pool of stuff that actually helps testers. Any knowledge work requires knowledge of IB – furthermore, I’d argue that there are plenty of professions where IB is much more critical to know about than in software testing.

For example:

  • Lifeguards
  • Judges
  • TSA Agents
  • Script Supervisor (those are the people in charge of ensuring continuity in movies / tv)
  • NASCAR drivers

And I’m hard pressed to think of a profession where knowledge of IB isn’t at least equal to that of testing. My garbage man (sanitation engineer) needs to make sure he doesn’t miss any cans, and ensure I’m not throwing away anything illegal. Given that garbage collection is much more repetitive than anything I do from day to day, I’d expect viewing the gorilla video to be standard training material for the guys in the big stinky truck (and for all I know, it is). The gorilla is fascinating – for everyone. There’s no special appeal to testing that I can see.

Of course, beyond the video (which helped the people behind it earn many awards), Christopher Chabris and Daniel Simons also wrote a book called, The Invisible Gorilla which discussed the vides and a ton of other really cool stuff (stuff I find much more interesting than the gorilla video – especially when considered as a whole). I’ve read the book twice, skimmed it several other times, and met the authors briefly after attending a talk they gave a year or so ago.

Some other cool topics covered include:

  • The illusion of memory (what you think you remember clearly may not be accurate. At all).
  • The illusion of confidence (most people overate their abilities – includes a great story about chess players and chess rankings)
  • The illusion of knowledge (you probably don’t know as much as you think you do)

It’s good stuff.

The Gorilla Stunt is good.

It’s just completely over-hyped in much of  the testing community.image




So stop hyping the damn gorilla video.


  1. Hi Alan,

    Great post. This resonates a lot with my thinking about this subject. Instead of focusing to minimize the inattentional blindness, I’ve focused on ways to capture the lost information (e.g. screen recording tools, notes, colleagues) as a tester.

    Any comment on, what actions you take to cope with the presence of inattentional blindness? Especially as a tester.


    Aleksis Tulonen

    • The main thing is to remind (or force) yourself to look at code / applications from a different perspective and angle. Personas help with this, as do exploratory testing “tours” as described by James Whittaker in his ET book and blog posts.

      But the key (again) is knowing that you need to change angles to be an effective tester.

  2. I use the gorilla video often in efforts to explain the nature of testing. It’s true that knowing about inattentional blindness does not remove it, but knowing about it makes two things in testing acceptable: repeating what appears to be the same path of actions (with your head geared for different information) and not relying on steps in test cases if such exist.

    I’ve shown the gorilla video as two exercise setups – either letting people watch and observe as the video is set up, counting or narrowing their focus further with an expected result and a pass/fail conclusion. I find the latter relevant for testing. It’s not that I should consider if my test passed or failed, but to consider if there were problems to note. And if I should try looking at it once or ten times more to really make up my mind.

    • IMO, the gorilla doesn’t explain the nature of testing at all. It explains one class of mistake testers may make. It’s important to be aware of IB, but it isn’t testing.

  3. I ask my test engineers to present at least two options for a solution, test procedures or design even if the answer seems trivial, and then list the ups and downs of each one.
    This forces them to look again and again at the original idea, and sometimes helps finding the gorilla.


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