Scientists Say This Phenomenon Explains Why You Miss Things Right In Front Of You

Paying attention to something seems pretty simple: watch, listen, and take mental note of what is going on. We commonly used the phrase "pay attention" to instruct others, often children, to concentrate on what they are doing, but thanks to a phenomenon called inattentional blindness, there may be times when your brain is not paying quite as much attention as you think.

If you are familiar with the phrase "can't see the forest for the trees," inattentional blindness is the literal version of that, where you are not simply missing the picture in a metaphorical sense, but actually miss a huge tree right in front of you. With inattentional blindness, your eyes could be looking directly at an object, but your attention is focused on something else so you don't even notice it. As in the case of perceptual illusions, perception is not purely what the eyes physically see, but how the brain processes it. 

This is not a medical condition experienced by certain individuals, it is a physiological phenomenon that any one of us could, and probably already have, experienced at any time. The term inattentional blindness was coined by Arien Mack and Irvin Rock in 1998. Their work showed that when the brain is focusing hard on one stimulus, it is possible for other items and actions to go unnoticed. As far-fetched as this may seem, a study the following year proved it to be true, with the now famous invisible gorilla experiment.

In the brilliantly-titled study "Gorillas in our Midst," researchers carried out an experiment with 192 participants. They were asked to watch a video of a small group of people playing basketball, and count how many passes were made between team players. Some participants were asked to simply count the passes and others were required to differentiate between aerial and bounce passes, which required even further concentration. During the video, either a woman holding an umbrella, or a woman dressed head to toe in a gorilla suit walked straight across the screen.

Unbelievably, 47% of the participants failed to notice the "unexpected event" as they focused on counting the passes. More people in the group with the harder task failed to notice the person, suggesting that the more intense focus of counting the different types of passes increased the level of inattentional blindness. There was an interesting difference between those watching black versus white too. Those counting black passes were more likely to spot the gorilla, who was dressed in black, compared to those counting white passes. The researchers concluded that our attention is more likely to notice items that share features with whatever we are focused on, and miss things that are different.

A later study followed up on this concept in a more serious medical setting, where 24 radiology experts were asked to examine lung scans looking for nodules, with a very obvious outline of a gorilla having been placed in one scan. 83% of the radiologists failed to notice the errant gorilla, further demonstrating the inattentional blindness phenomenon when individuals are focusing hard on a specific task.

While these studies are fascinating and hard to believe, inattentional blindness has real world implications, and could put people in danger. Driving involves many levels of muti-tasking, and focusing on a certain object or event could lead to inattentional blindness when something unexpected moves into your path. While you would hopefully notice a gorilla-sized object on the road, a small animal or debris  could initially go unnoticed by your single-minded brain, leading to swerving or crashing the car. Like highway hypnosis, you may not even realize it is happening until afterward. 

Inattentional blindness seems to increase with age, as a study from 2014 showed. In a group of adults aged between 60 and 80 years, 89% missed the unexpected stimulus, whereas with younger adults aged from 18 to 25, only 5% missed it. This suggests that older adults are more likely to miss crucial objects, even when looking directly at them. Interestingly, a study measuring inattentional blindness in individuals with ADHD found that they have "little-to-no inattentional blindness," showing that their difficulty focusing on one task could be a strength when it comes to spotting things in the world around them.

While the likelihood of inattentional blindness can vary from person to person, it is a normal limit of our attention span, and the way our brain functions.  In most cases it is an advantage, allowing us to filter out unnecessary distractions. In some situations, though, it can cause us to miss even gorilla-sized events, so remember the next time you are arguing about something you are certain didn't happen — maybe it did, but your brain simply wasn't paying attention.