How Researchers Hid a Gorilla in Plain Sight: 3 Perception-Bending Psychology Studies

Do you believe the evidence of your own eyes? Well, psychologists have found a few problems with that approach over the years. Take a look at...

• The Invisible Gorilla: Inattentional Blindness
• Car Crash Testimony: Making False Memories
• Dodgy Dual-Processing: Sound Affects Sight

The Invisible Gorilla: Inattentional Blindness

In 1999, psychologists Chabris and Simons found a way to turn a gorilla invisible.

Ok, that might be a bit of an exaggeration... but they did expose a human tendency to miss things you'd think were really, really obvious. The study they performed was pretty simple - participants would watch a short video (linked below as the Selective Attention Test) of people in black or white outfits passing basketballs. All the participants had to do was count the number of times the people in white passed the ball - simple, right?

What they didn't get told was that an interloper would pass through the middle of the players - either a tall woman with an umbrella, or someone in a full-body gorilla suit. After watching the video, participants were asked if they'd noticed something unusual in the video.

Now you'd think a gorilla would really stand out (it even paused in the center of the shot and beat its chest) but around half of the participants actually missed the furry interloper. Weirdly, more people spotted the umbrella-toting woman than the gorilla. It seemed that dedicating attention to a task could blind you to other things - as a result, the phenomenon was dubbed inattentional blindness.

Inattentional blindness can show up even in expert observers. Another study presented 24 radiologists with a standard lung nodule detection task (the kind of thing that these professionals do for a living) with a gorilla edited into the final image. Despite the furry addition being 48 times the size of the average nodule, 20 of the radiologists missed it!

Car Crash Testimony: Making False Memories

Eye-witness testimony is the gold standard in court cases... but psychologists have known for a long time that the human memory is extremely unreliable.... and that even the slightest suggestion can change details.

In 1974 psychologists Loftus and Palmer performed a simple experiment. They showed participants a short film of a car driving before getting involved in an accident. One week later, the participants were asked a few questions about the film... including whether they'd seen any broken glass.

The researchers found that simply varying the verbs used in their questions had a significant effect on the recollections of the participants. When the questions used verbs like "smashed" participants were much more likely to say they'd seen broken glass than when "hit" was used instead... despite the fact that there had been no broken glass in the film.

This experiment (and others like it) show that even the choice of words used by a questioner can change the recollection of a witness... and yet, courts and juries give huge weight to eyewitness testimony. That's a real concern, considering that those memories could be from several years in the past and have been through several police interrogations!

Dodgy Dual-Processing: Sound Affects Sight

Did you know that the human brain is similar to a computer in some ways? It only has so much processing power to use at any given time... and as a result, we've evolved a whole bunch of little tricks to save our minds time and effort. Unfortunately these shortcuts do lead to some glitches from time to time - for example, it seems that sounds can affect our sight.

This strange finding comes from a 2022 study that showed participants an image partially morphed between a bird and a plane. While the image was on display the researchers played audio cues - the roar of a jet engine, the song of a bird or something unrelated like a hammer hitting a nail. Participants were then shown a full process of the morph between bird and plane... and asked to pick how far along their image had been.

Not only did participants take less time to decide when audio cues were related to the image, they tended to adjust their interpretation of the images to match (i.e. claiming that the image they'd been shown was more morphed towards a bird after hearing birdsong.)

This "shift" towards whatever audio cue was playing didn't seem to exist when the cue was played before viewing the image, or when attempting to match it to the morphs afterwards. This suggests that the cues were directly affecting how participants saw the image, rather being a trick of the memory!

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Sources and Further Info:

• Selective Attention Test (Youtube video)
• Gorillas in Our Midst: Sustained Inattentional Blindness for Dynamic Events
• The invisible gorilla strikes again: Sustained inattentional blindness in expert observers
• Reconstruction of automobile destruction: An example of the interaction between language and memory
• Loftus and Palmer (1974): Car Crash Experiment
• Hearing is Believing: Sounds Can Alter Our Visual Perception
• What You See Is What You Hear: Sounds Alter the Contents of Visual Perception