Inattentional blindness, also known as perceptual blindness, is when a person fails to notice some stimulus that is in plain sight. This stimulus is usually unexpected but fully visible. This typically happens when humans are overloaded with inputs. It is impossible to pay attention to every single input that is presented. A person’s attention cannot be focused on everything, and therefore, everyone experiences inattentional blindness. People can falsely believe that they do not experience inattentional blindness.
This is due to the fact that they are unaware that they are missing things. Inattentional blindness also has an effect on people’s perception. There have been multiple experiments performed that demonstrate this phenomenon. The term ‘inattentional blindness’ was coined by Arien Mack and Irvin Rock in 1992. It was used as the title of their book on the topic published by MIT Press in 1998.
The best-known study demonstrating inattentional blindness is the Invisible gorilla test, which was conducted by Daniel Simons of the University of Illinois at Urbana-Champaign and Christopher Chabris of Harvard University. Their study, a revised version of earlier studies conducted by Ulric Neisser, Neisser and Becklen, 1975, asked subjects to watch a short video in which two groups of people (wearing black and white t-shirts) pass a basketball around. The subjects are told to either count the number of passes made by one of the teams or to keep count of bounce passes vs. aerial passes.
In different versions of the video a woman walks through the scene carrying an umbrella, or wearing a full gorilla suit. After watching the video the subjects are asked if they saw anything out of the ordinary take place. In most groups, 50% of the subjects did not report seeing the gorilla. The failure to perceive the gorilla or the woman carrying an umbrella is attributed to the failure to attend to it while engaged in the difficult task of counting the number of passes of the ball. These results indicate that the relationship between what is in one’s visual field and perception is based much more significantly on attention than was previously thought.
Another experiment conducted by Daniel Memmert tested the effects of different levels of expertise can have on inattentional blindness. The participants in this experiment included six different groups: Adult basketball experts with an average of twelve years of experience, junior basketball experts with an average of five years, children who had practiced the game for an average of two years, and novice counterparts for each age group. In this experiment the participants watched the Invisible gorilla test video. The participants were instructed to watch only the players wearing white and to count the number of times the team passed the ball. The results of the experiment showed that experts did not count the number of passes more accurately than novices but did show that adult subjects were more accurate than the junior and children subjects. A much higher percentage of experts noticed the gorilla compared to novices and even the practiced children. This suggests that both age and experience can have a significant effect on inattentional blindness.
In 1995, Officer Conley (Boston Police Officer) was put on trial for claiming he did not see a violent assault incident between a few people while he was chasing a suspect. Scientist accepted his alibi because of ‘inattentional blindness.’ This case now leads to an experiment: psychology professors Christopher Chabris of Union College and Daniel Simons of the University of Illinois recreated the same situations of the original incident of Officer Conley, with the help of their students. During the experiment, the students were asked to go on a three minute run around the campus. They were then asked to focus on keeping a steady distance and to count the number of times he touched his head to wipe off sweat. While focusing on running and keeping a steady distance, the students then came across a staged fight ahead of their running path.
Most of the students missed the staged fight while running in the dark (in which officer Conley had his experience). During the day, 40 percent of the students still missed it. They all were so focused on running that they missed the staged fight. This is the same situation officer Conley was in. Professor Simons stated that we can’t state with confidence that Conley didn’t see the fight during the suspect chase, but the results of the study show that it is still possible to miss something as obvious as fight, simply because of how you are directly concentrating on other things.
The research that has been done on inattentional blindness suggests that there are four possible causes for this phenomenon. These include: conspicuity, mental workload, expectations, and capacity. Conspicuity refers to an objects ability to catch a person’s attention. When something is conspicuous it is easily visible. There are two factors which determine conspicuity: sensory conspicuity and cognitive conspicuity. Sensory conspicuity factors are the physical properties an object has. If an item has bright colors, flashing lights, high contrast with environment, or other attention-grabbing physical properties it can attract a person’s attention much easier. For example, people tend to notice objects that are bright colors or detailed patterns before they notice other objects. Cognitive conspicuity factors pertain to objects that are familiar to someone. People tend to notice objects faster if they have some meaning to their lives. For example, when a person hears his/her name, their attention is drawn to the person who said it.
The cocktail party effect (selective attention, the ability to make out one voice amid many such as at a cocktail party) describes the cognitive conspicuity factor as well. When an object isn’t conspicuous, it is easier to be intentionally blind to it. People tend to notice items if they capture their attention in some way. If the object isn’t visually prominent or relevant, there is a higher chance that a person will miss it.
Mental workload has to do with how much a person has on their mind. Having a heavy mental workload can cause issues. Having too little of a workload can cause issues too. When a person focuses a lot of attention on one stimulus, he/she focuses less attention on other stimuli. For example, talking on the phone while driving – the attention is mostly focused on the phone conversation, so there is less attention focused on driving. The mental workload could be anything from thinking about tasks that need to be done, or tending to a baby in the backseat. When people have most of their attention focused on one thing, they are more vulnerable to inattentional blindness. However, the opposite is true as well. When a person has a very small mental workload – he/she is doing an everyday task – that person tends to go into autopilot. In autopilot, people tend to do things without thinking about them. This can cause a person to miss crucial details and to become inattentionally blind to their surroundings.
When a person expects certain things to happen, he/she tends to block out other possibilities. This can lead to inattentional blindness. For example, person X is looking for their friend at a concert, and that person knows their friend (person Y) was wearing a yellow jacket. In order to find person Y, person X looks around for people wearing yellow. It is easier to pick a color out of the crowd than a person. However, if person Y took off the jacket, there is a chance person X could walk right past person Y and not notice because he/she was looking for the yellow jacket. Because of expectations, experts are more prone to inattentional blindness than beginners. An expert knows what to expect when certain situations arise. Therefore, that expert will know what to look for. This could cause that person to miss out on other important details that he/she may not have been looking for.
Attentional capacity is a measure of how much attention must be focused on a task to complete it. For example, an expert pianist can play a piano without thinking much, but a beginner would have to consciously think of every note they hit. This capacity can be lessened by drugs, alcohol, fatigue, and age. With a small capacity, it is more possible to miss things. Therefore, if a person is drunk, he/she will probably miss more than a sober person would. If your attentional capacity is large, you are less likely to experience inattentional blindness.
Inattentional blindness is exploited by illusionists in the presentation of ‘magic shows’ in the performance of some tricks by focusing the audience’s attention upon some distracting element, away from elements of the scene under manipulation by the performer. This is called misdirection by magicians.