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If you’ve ever taken a psychology class,
chances are you’ve learned
about the so-called “gorilla experiment”.
Maybe you’ve even done it, yourself.
In this study, participants are
asked to watch a video of two “teams”
passing a couple basketballs around,
and count the passes made by just one team.
And many people, including myself,
were so focused on that task,
that they somehow miss
the human in a gorilla suit that shows up
halfway through the video
to stroll right through the scene.
Scientists have been researching this strange kind of blindness for decades.
And much like a video
with a gorilla hiding in plain sight,
there’s still more to see.
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The gorilla experiment was first published back in 1999,
So I saw it when I was in college like a year after it came out
but it was a variation on a type of experiment
from the 1970s and 80s
that featured a woman carrying an open umbrella,
instead of a woman in a gorilla suit.
But instead of having her walk through the scene,
the video of this Umbrella Lady
was superimposed over the video
of the basketball players,
so both she and the players
were all a little transparent.
That’s not exactly a sight
we encounter in the real world.
So some follow-up research was needed
to get a better sense of why
so many people didn’t see her,
and what tweaks to the scenario
might make her more or less likely to stand out.
Enter a couple of dudes from Harvard.
In addition to having a woman with an umbrella
actually walk through the basketball players,
they added an alternative condition that was…
a little more amusing.
And there were a few other parameters to the experiment.
Like, half of the participants
were told to monitor the team wearing white shirts,
and half monitored the team wearing black.
Meanwhile, a different half
only had to count the total number of passes,
while the rest had
the more difficult task of remembering
how many passes were thrown
and how many were bounced.
And people were more likely to notice the interruption
if they were doing the easier task.
It was also easier for people to spot the black gorilla
when they had been instructed
to count passes between the black shirt team.
That suggests humans are more likely to notice unexpected things
that are more similar to the task at hand.
Maybe that’s why more people
noticed the human carrying an umbrella
than the non-human gorilla suit.
But out of the nearly 200 participants in this study,
46% of them completely missed
either the Umbrella Lady or Gorilla Lady
walking through the scene.
It was a perfect demonstration
of what scientists call
inattentional blindness,
or the failure to perceive something
simply because you’re not
paying attention to it.
And to understand how this inattentional blindness actually works,
we’ve got to understand
where it happens inside of us.
Because visual processing takes several steps.
Sure, light hits our retinas
and a signal gets sent from our eyes to the brain.
But the brain takes a few steps of its own, too.
First, it figures out the basic features of an image,
like orientation of lines, color,
and direction of motion.
Then, it starts to organize those into general shapes.
Those shapes get put together,
the bigger picture starts to emerge,
and we start to apply our previous knowledge to figure out what things are.
And finally,
it enters our conscious awareness
and we actually perceive the image.
But unfortunately, these steps aren’t entirely linear.
Information that’s processed in later steps,
like how much attention you’re paying,
is often sent back to previous steps
for another round of updated processing.
So inattentional blindness
arises at some point in this big,
loop-filled process,
but scientists are still working on finding exactly where.
One hypothesis is that when you’re focused on one thing,
like counting basketball passes,
you literally don’t even look at others,
like a wayward gorilla.
Your eyes just skip over it.
However, one study from 2006
tracked where 21 German children
were looking while they watched a gorilla experiment video.
And the kids who didn’t see the gorilla looked at it
for the same amount of time
as the children who did report seeing it.
So it’s probably happening somewhere in the brain.
It could be that feedback from a later processing step loops back
around to the start and tells your brain
to not even bother processing the gorilla,
because it isn’t important right now.
Maybe the brain processes that there’s totally a gorilla there,
but the news gets filtered out
right before you can become consciously aware of it.
Or maybe you do actually perceive the gorilla,
but your focus on basketball passes
makes you less likely to remember you did.
These are all things researchers are trying to figure out.
In a 2023 paper,
this year, a long time after the experiment,
one team considered that other attention studies demonstrate
we tend to see objects
moving really fast through our field of vision
or things that just pop up and disappear.
So they repeated the 1999 experiment, but with a few changes.
In one version,
they had the gorilla move faster,
taking 2 or 6 seconds to move across the screen
instead of the 10 seconds in the original video.
They also had a version where the gorilla leapt across the scene,
more like an actual gorilla would move.
And sure enough, people who were counting passes made
by the white shirt team
were more likely to report seeing the gorilla
the faster it was moving,
as well as when it was leaping.
For participants counting passes by the black shirt team,
a speed boost didn’t matter as much.
But that’s probably because the gorilla was already easy enough
for them to spot in the original conditions.
Because the basic features of movement
like direction and speed are handled
in some of the earliest stages of visual processing,
this new study would suggest
the blindness part comes in at a later stage,
and we’re at least unconsciously aware that the gorilla is there.
Which would make sense,
because while inattentional blindness might help us focus
and perform better on tasks,
zero processing of other things
would leave us vulnerable to external dangers.
Whether it’s a tiger trying to eat you in the wild,
or your kid about to stick a metal fork in an open socket.
So instead, this study supports
the idea of a flexible attention hierarchy.
More important things get more attention,
but since the brain can’t always know ahead of time
what things are going to be important,
it has to be able to reorder that hierarchy at a moment’s notice.
And that might be what movement does.
If the movement is slow, the attentional hierarchy carries on as is.
If it’s fast, that early visual processing step signals the brain
to reorder the hierarchy and pay attention to the speeding gorilla.
So clearly, there are a lot more details to understand about inattentional blindness.
And It’s important research,
because while a rogue gorilla at a basketball game is a bit unlikely,
inattentional blindness does have real world
and potentially deadly consequences.
But it might be getting harder to do,
because now a ton of people know about the gorilla experiment.
And people who know about it are more likely to see the gorilla.
So while this amusing experiment
has served us well for over two decades,
we might need to try something new
if we want to see the unexpected.
Inattentional blindness is a part of our everyday lives.
So to help you understand these everyday science topics,
Brilliant has a Physics of the Everyday course.
It covers topics like car collisions and traffic
that can be outcomes of inattentional blindness,
along with things like spinning and flipping in gymnastics,
which you might miss in a video created to study inattentional blindness.
And Brilliant courses are designed
to focus and keep your attention
on the subject at hand,
through interactive puzzles and real-world examples.
This online learning platform includes
thousands of interactive lessons in math,
science, and computer science,
with bonus puzzles in each of those categories.
To try them out for yourself free for 30 days,
you can visit Brilliant.org/SciShow
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