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Inattentional blindness is the failure to perceive something in plain sight. This psychological phenomenon was most famously illustrated in an oft-repeated experiment that asked students to view a video and count the number of times a group of basketball players passed the ball. Focused on this task, most study participants completely missed the fact that a person in a gorilla suit walked onto the court, danced around, and then left midway through the activity. This has significant implications for human perception in a variety of settings, explaining why incidents like medical errors, car accidents, and other events occur even though people should have seen a threat and responded to it.
A number of explanations have been put forward to explore inattentional blindness and the way in which it works. In these situations, people fail to perceive a stimulus that is directly in front of them and fully visible. Whether in experimental or real settings, after the incident they don’t report anything unusual. Drivers, for example, may say that a cyclist “came out of nowhere” when video evidence indicates the bicycle was in plain view of the driver at all times.
One issue is the conspicuousity, as psychologists put it, of the target. Things that are brightly colored or patterned tend to attract more attention, which is one reason road workers wear bright orange vests to make sure they will be visible. In cases of inattentional blindness, it is common for the stimulus to be dully colored or patterned, which can make it harder to see. Mental workload is another factor. Someone who is focusing intently on a task may miss stimuli that don’t appear to be related to that task.
This has been demonstrated in a number of experimental settings, where participants fail to see moonwalking bears, vicious fights, and other events because they’re being asked to focus on something else. Concentrating on one kind of visual stimulus can overload the brain so it doesn’t notice others. In real world settings like a car, this could be a serious problem. The driver looking for a specific exit sign on the freeway, for example, may not notice a car ahead slamming on its brakes, or a vehicle about to change lanes.
Expectation has also been documented as a player in inattentional blindness. People tend to see what they expect to see; people watching a basketball game don’t expect someone in a gorilla suit, so they gloss over it when it happens. Researchers on inattentional blindness have also explored the role of individual capacity, which can vary widely. Some people may be more alert and capable of handling complex visual stimuli, while others are not because of fatigue, age, vision problems, or other factors.