Experimental Psychology: Human Perception

In pyschology and the cognitive sciences, perception is the process of acquiring, interpreting, selecting, and organizing sensory information. (At least, that’s how wikipedia defines it)

As a small experiment of perception I want show you a brief video during which you will count the number of times a basketball is passed - seems easy enough, right? Okay, follow these short steps and then we’ll discuss it..

While watching the following video, ignore the team in black - they are trying to confuse the situation. Count only the number of passes made by the team in white t-shirts.
When you are done, click the back button to return to this page with the answers and follow up discussion.
Alright, go Watch the Video by clicking here

Do not be reading below this point if you haven’t yet watched the video…

Well, how did you do? Did you concentrate?

How many times was the basketball passed among the members of the white team?
Were you also able to count the number of passes among the black team? That’s okay, you weren’t asked to.
Did you see anything else in the video, perhaps a cat, small lizard, or a gorilla?

No, really - did you se the gorilla?

Regardless of what you did or did not see, you should go post your results in the comments below. A vast majority of people (if telling the truth) probably did not observe the gorilla that showed up in the middle of the basketball frenzy, this can be attributed to perceptual blindness. Now, if you are really embarrassed about your inability to see the gorilla, you may post anonymously so that you can feel like no one knows who you are. But honestly, I’m interested to know the results. And if you’ve seen this video before - state that in your comment too. This isn’t a new concept, infact even this test has been around for a while.

Perceptual blindness — including related phenomena is known as inattentional blindness and change blindness. When people are engaged in an engrossing task, such as monitoring swimmers in a pool, they often fail to notice otherwise obvious events because they happen outside the immediate focus of attention.

This is a good example of how people who have seen a car accident or a mugging can come up with such different stories - their attention can be focused on any number of visual stimuli, where they are otherwise cognitively engaged. How about talking on the cell phone? Strikingly, those involved in these crashes usually have no idea there was an object there, and cannot explain their failure to have seen it. Scarry - but I’m sure you’ve experienced the same type of thing, even if it didn’t result in an accident. Ever forget how you got from point ‘A’ to point ‘B’ or somehow can’t recall a portion of your drive home.

Real-life case studies of this blindness include drivers running over bicyclists, train engineers plowing into cars, submarine pilots surfacing under ships and airline pilots landing on other planes. In each case, the object or obstruction should have been easily noticed but was not.

Scientists have been researching this “inattentional blindness”, and other similar phenomenon - and the theory seems to be that there is no perception without attention.

The right number is (I think) 14. But that’s not really the point.

The point is this: did you see the gorilla walk across the screen and beat its chest? According to the original research (you can read it here), there’s a fifty-fifty chance you didn’t. Which fifty are you?

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55 Responses to “Experimental Psychology: Human Perception”

on 18 Apr 2007 at 12:44 am me

i was too distracted by everything so i saw the gorilla. i lost count at one. then i juststared at the screen, then gorilla appeared.
on 18 Apr 2007 at 1:24 am daevangelist

14 passes, though there may have been one hidden pass from the guy to the girl, and i saw the gorilla.
on 18 Apr 2007 at 4:04 am Steve

14, and yes i saw the gorilla for a brief moment, i didnt recall seeing him enter or leave though, i was too engrossed.
on 18 Apr 2007 at 9:45 am Kees

I counted 15 and I did see the gorilla walk into the middle of the group.
on 18 Apr 2007 at 12:54 pm Sara

I did not see the gorilla. This is not surprising however, since I “tune out” external noises and visual stimuli pretty much whatever I want. I could study in the middle of a party and it would be just fine. I also usually don’t notice when people are talking to me while I am working. Whoops.
on 18 Apr 2007 at 10:29 pm Lisa

I counted 14. I didn’t see the gorilla…I had to go back and watch it again because I couldn’t believe that I missed a gorilla walking to the middle of the screen and pounding his chest…
on 18 Apr 2007 at 10:29 pm Tim

I counted 14 and was wondering why there was a gorilla walking across the screen at about pass 6. I guess this means I’m still allowed to talk on the phone while driving
on 20 Apr 2007 at 4:43 pm Jason

I counted 15 passes among the white team and did not see the gorilla.
on 25 Apr 2007 at 1:58 pm AV

I counted 14 and saw the gorilla, but I didn’t see it beat its chest — I remember thinking, don’t get distracted by the gorilla.
on 30 Apr 2007 at 4:39 pm Michael VanDeMar

Ok, I think I counted 13 passes the first time, but when I re-watched it I counted 14. I did not see the gorilla the first time. I re-watched it right after the gorilla comment, and I was pretty sure that I was going to see someone sneak in and start passing the ball from the black team, kind of blend in with the scenario. I had no clue it was as obvious as it was.
on 03 May 2007 at 7:20 pm Becky

14, and yes, I saw the gorilla. My thoughts, “What the- . . . is that a gorilla?? Haha. It’s a gorilla. Wait, no! Concentrate!”
on 07 Nov 2007 at 5:34 pm Anon

There were most certainly 15 passes and I did not see the gorilla.
on 18 Nov 2007 at 2:05 pm Joey Ofori

What I counted like 27 Passes…and I saw the gorilla walk by….I dont understand how someone couldnt see it
on 18 Nov 2007 at 2:09 pm Joey Ofori

Ooooooo I counted the total passes lol
on 05 Dec 2007 at 12:24 am ANDREW LANGTON

I counted 16 passes and did not see the gorilla. Don’t think there is anything deep about this, as i was focusing on the arm movements carefully. If the gorilla had of been red, it would have caught my eye, but because i wasn’t looking directly at it, it just looked like one of the other black players in my side vision. ie if i was reading a document, i would not notice a black gorilla face moving accross the bottom of my screen if there were a load of black balls also moving across the bottom of my screen. Why? Because I wasnt looking directly at it. What does this prove?
on 28 Dec 2007 at 7:05 am Nicos Leon

I counted 14 passes and I saw the gorilla. I cannot tell you at what number the passes were when I saw it.
on 23 Jan 2008 at 8:57 pm Kelly Ann

First and only viewing: I did see the gorilla, which precipitated much laughter (”There’s a gorilla!”) and caused me to lose count. I think I had only counted six or seven passes when the laughter began.
on 30 Jan 2008 at 9:17 am Barbi

I was so engrossed that I never saw the gorilla at all. I counted 14 passes by the white team and that is all I concentrated on. Lol
on 01 Feb 2008 at 5:10 am Ta

I counted 15 (well I think one of those was when the ball passed from girl to guy without being thrown in the air). I did see the gorilla, I did not however see him beat his chest.
on 01 Feb 2008 at 9:23 pm Chris Zimny

I counted 10 passes, they bounced the ball to each other a couple times, I didn’t count those as passes.

I didn’t see the gorrilla, I watched it again, I laughed hystericly.

~Chris
on 07 Feb 2008 at 12:11 pm Carolyn

I watched the white passing the ball and counted 14 passes either tossed or bouncing.

No, I did not see the gorilla. I watched it again and was amazed that I had missed. Awesome!
on 11 Feb 2008 at 4:12 pm Aoife

I counted 14 passes and saw the gorilla. Very funny to see him in the middle of it all. Thought it was a trick to make me lose count!!
on 13 Feb 2008 at 6:49 am Tony Clarke

I counted 14 passes and focused solely on the whites so as to not lose count.I’m actually happy that I didn’t see the gorilla.I had one goal and one goal only i.e. to count the passes.I went in with that mindset.Be mindful of the fact that you said that the blacks were only a distraction.
on 19 Mar 2008 at 9:24 pm YLlama

Counted 12 passes. Saw gorilla. Probably why I undercounted. Did not see him beat his chest, though.
on 20 Mar 2008 at 1:30 am Sebastian Bravo

I counted 14 passes and I saw the gorilla at the first time - I am 10 years old
on 20 Apr 2008 at 6:53 am mariana

14 passes and did not notice the gorilla at all…lol
on 09 Jun 2008 at 12:58 pm Don Rhinehart

I counted 13.

I saw this on TV a few years back. I KNEW the gorilla was coming.

The 1st time (this time) I watched it knowing that.
I watched it a 2nd time, focusing on counting.
I counted 13. I did see the gorilla, but totally missed him (or her) beating his chest.
on 20 Jun 2008 at 2:41 pm Ted Mihran

I just saw this video at a talk at the GE Research Lab. on cognitive science given by professor at RPI.
I counted fourteen white-to-white passes, and did not see the gorilla. Naturally, I saw the gorilla the second time I viewed the video, when told what to look for.

I had vaguely heard about this experiment several years ago, but had forgotten its significance. I think it broadly explains why persons belonging to one political party cannot comprehend the achievements of the other political party. They are not looking for them!

Can we use the results to improve the dynamic of the interaction between two political parties, which is sorely needed?
on 29 Jun 2008 at 9:45 pm Andrew Marks

I counted 14 and saw the gorilla beating his chest
on 01 Jul 2008 at 7:11 pm Anne

I /did/ see the gorilla and I was like what the?? and I counted fifteen passes…but one of the passes I was unsure about because I got distracted by the guy in the gorilla suit. :0)
on 01 Jul 2008 at 9:02 pm steve

1st look 14 passes no gorilla,2nd look 14 and gorilla
on 01 Jul 2008 at 9:13 pm Joe R

I counted 14 passes. There was another, but I decided it was from the black team. I did not see the gorilla at all.
on 02 Jul 2008 at 9:13 am S. Karim

I counted 13 and a posible 14th pass. I Actually thought that I saw something wierd at first but I was to focused on counting the passes. Afterwards, when I’d found out about the Gorilla walking across the screen. I realized that the wierd thing that I had seen resembled the face of a Gorilla.
on 03 Jul 2008 at 8:08 am KS

Either most people are lying or people that didn’t see the gorilla arent posting. I saw this same video shown in front of a classroom and only a handful actually saw the gorilla.
on 03 Jul 2008 at 2:28 pm davidlooney

Iam really sure ther was 15 passes,of course 1 was hidden. I never seen the gorilla not one time until I went back to look. Guess I cannot see the forest for the trees!
on 17 Jul 2008 at 2:07 am R M

What gorilla?
on 31 Jul 2008 at 8:16 pm Cars1

I tried to follow the three white-shirted players around, made it easier to focus on counting their passes only, and saw a distracting/complicating figure enter from the right and segue out to the left. Counted 12 passes, though thought there might be more, the first viewing. Saw the gorilla viewing-2, the drawn S’s and the actual cha-cha motion viewing-3,
on 03 Sep 2008 at 6:04 pm T N

14 passes I saw the gorilla hes preety hard to miss my brother saw him 2
on 06 Sep 2008 at 1:20 pm Darrell Hambley

Gee wiz Jeff, You purposefully wrote, “did you see…..a gorilla?” You have poisoned the experiment by telling people what to NOT look for before they even see the video! Viewers are certainly going to look for a gorilla now that you’ve told them.
on 07 Sep 2008 at 6:26 am Jeff Sickles

Darrell, WOW - you must have missed the bold print those pesky instructions, the BIG PICTURE LINK AND the bold text that reads “Do not be reading below this point if you haven’t yet watched the video…” Then EIGHT count them -(8) line returns below that you find the word gorilla. Me thinks you have only poisoned yourself sir. Still makes me wonder if you saw the gorilla SINCE YOU DIDN’T EVEN SEE THE INSTRUCTIONS! ha ha ha
on 09 Sep 2008 at 6:29 pm LG

I counted 14 and think maybe one was behind a couple of people that I may have missed. I saw the gorilla, but didn’t see him enter or leave.
on 10 Sep 2008 at 9:48 pm MM

I have the feeling that the difference between the people is in the ability to “stay on point” and be “focused”, rather than being able to multitask. I think it would be very interesting to show it to a group of people with ADHD and a group without it to see if there is any difference there. BTW, I saw all 14 passes but no gorilla. Not good, not bad — just “on point”.
on 10 Sep 2008 at 10:02 pm Dave Plottel

I counted 14 passes and I did notice the gorilla. When I saw it I thought “Wow, they really are trying to distract the viewer, aren’t they?”.

I think one reason so many people don’t see the gorilla is that they are trying to ignore the black-clad team, so they are primed to ignore human-shaped and human-sized things that are black (like, say, someone in a black gorilla suit).

Interesting.
on 10 Sep 2008 at 10:47 pm Bill(MN)

14
Saw the gorilla.
Saw the piece several years ago, though. Hard to forget a good gorilla.
(In a 4th year news reporting class a beating of the lecturer was staged. The range of “observed facts” in the written reports on it was amazing, and unforgettable, even ~ 35 years later.)
Cheers!
Bill
on 11 Sep 2008 at 4:55 am PS

I counted 12 passes. Saw the gorilla and it beat its chest.
on 21 Sep 2008 at 9:54 pm Bob

Jeff,
I’m intrigued by the Perception Test video. I would like to watch that entire lecture. Where might I find it. I have searched and can’t find it.
on 28 Sep 2008 at 5:31 am Pat (female)

I only counted 11, I saw the gorilla, but I didn’t see him beat his chest. I don’t use the cell when driving. I used to have a bag phone that kept a green lighted keypad. Once I actually ran a red light because I saw the green reflected in the windshield. Fortunately it was after midnight and no traffic.
on 21 Oct 2008 at 3:25 pm Paul

I saw the gorilla and counted 15 passes
on 23 Oct 2008 at 1:37 pm Diane

I counted 14 and saw the gorilla. Although I counted 14, I believe there were 15 because I know on one pass that I counted, it went to the female but the next pass went from a male, so I missed the pass from the female to a male.
on 27 Oct 2008 at 11:50 am Vicki

I saw the gorilla and couldn’t tell you when he appeared. He distracted me enough for me to multitask to think about it, but I still managed to count the “white passes”.
on 27 Oct 2008 at 3:08 pm Teri

Saw 14 passes…no gorilla…watched it the second time and was amazed that I missed it! I am an overachiever and would not miss the count!
Teri
on 28 Oct 2008 at 1:55 pm Jacqueline

Counted 14 and did not see the gorilla. I can’t believe I missed the gorilla.
on 05 Nov 2008 at 8:06 am Jacob Saaby Nielsen

I saw 15 passes. Only 14 are really visible to the eye, but the 15th pass HAS to have occured, as the ball shifted position from male to female.

So I saw 14, my reasoning says there must’ve been one extra.

No gorilla seen here. No observations on the black team.
on 13 Nov 2008 at 5:45 am ian dickson

At Uni I was in a variation of this in 1985.

A law lecture was interrupted by a guy who burst in looking for his experimental monkey.

He raced round, looked all over, climbed up the rows and basically had everyones attention for about 5 minutes before leaving.

It appeared to just be an interruption.

At the end of the lecture the teacher asked us to write down what was he wearing, and what colours. We pretty much agreed shirt and trousers, but shirt colours ranged from white to black with a lot of blues and browns. (Not many went for bright ones).

And the point was - eye witnesses are not reliable EVEN WHEN THEY ARE concentrating on something that has grabbed their attention.

All you could have concluded from interviews with us was:-

We were in a law lecture, and a medium/tall guy aged 30-60 came in looking for his monkey-cat and he was wearing office work type shirt trousers that were a sensible colour.

WHAT happened, yes. WHO DONE IT, no way.
on 18 Nov 2008 at 12:27 pm keith

I saw this at college and missed the Gorilla. I have shown this to a few friends and the % has been in favour of not seeing the Gorilla. Some think they saw an extra black t-shirt or an interuption of the passes. It is a great example of hpw the mind can be manipulated to see what a person wants it to see

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