Inattentional blindness

Inattentional blindness, also known as perceptual blindness, is failure by a person to notice some stimulus that is in plain sight. This stimulus is usually unexpected but fully visible. This typically happens because 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.

Experiments demonstrating inattentional blindness

The term inattentional blindness was coined by Arien Mack and Irvin Rock in 1992. It was used as the title of Mack and Rock's book published by MIT Press in 1998. The book describes the discovery of Inattentional Blindness and the procedure used for revealing it.

Invisible gorilla test

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.

The basic Simons and Chabris study was re-used on British television as a public safety advert designed to point out the potential dangers to cyclists caused by inattentional blindness in motorists. In the advert the gorilla is replaced by a moon-walking bear.

Computer red cross experiment

Another experiment was conducted by Steven Most, along with Daniel Simons, Christopher Chabris and Brian Scholl. Instead of a basketball game, they used stimuli presented by computer displays. In this experiment objects moved randomly on a computer screen. Participants were instructed to attend to the black objects and ignore the white, or vice versa. After several trials, a red cross unexpectedly appeared and traveled across the display, remaining on the computer screen for five seconds. The results of the experiment showed that even though the cross was distinctive from the black and white objects both in color and shape, about a third of participants missed it. They had found that people may be attentionally tuned to certain perceptual dimensions, such as brightness or shape.

Clown on a unicycle experiment

One interesting experiment displayed how cell phones contributed to inattentional blindness in basic tasks such as walking. In this experiment a brightly colored clown on a unicycle traveled by. The individuals participating in this experiment were divided into four sections. They were either talking on the phone, listening to an mp3 player, walking by themselves or walking in pairs. The study showed that individuals engaged in cell phone conversations were least likely to notice the clown. This experiment was designed by Ira E. Hyman, S. Matthew Boss, Breanne M. Wise, Kira E. Mckenzie and Jenna M. Caggiano at Western Washington University.

Blindness despite fixation

Daniel Memmert conducted an experiment which suggests that an individual can look directly at an object and still not perceive it. This experiment was based on the invisible gorilla test. The participants were children with an average age of 7.7 years. Participants watched a short video of a six player basketball game (three with white shirts, three with black shirts). The participants were instructed to watch only the players wearing black shirts and to count the number of times the team passed the ball. During the video a person in a gorilla suit walks through the scene. The film was projected onto a large screen (3.2 m X 2.4 m) and the participants sat in a chair 6 meters from the screen. The eye movement and fixations of the participants were recorded during the video and afterward the participants answered a series of questions. Only 40% of the participants reported seeing the gorilla, leaving 60% who did not. There was no significant difference in accuracy of the counting between those who saw the gorilla and who did not. Analyzing the eye movement and fixation data showed no significant difference in the time spent looking at the players (black or white) between the two groups. However, the 60% of participants who did not report seeing the gorilla spent an average of 25 frames (about one second) fixated on the gorilla, despite not perceiving it.

Effects of expertise

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. 62% of the adult experts and 60% of the junior experts noticed the gorilla, suggesting that the difference between five and twelve years of experience has minimal effect on inattentional blindness. However, only 38% of the adult, 35% of the junior, and none of the children novices noticed the gorilla. Only 18% of the children with two years of practice noticed. This suggests that both age and experience can have a significant effect on inattentional blindness.

Perception and inattentional blindness

In 1995, Boston Police Officer Kenneth M. Conley 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. In this experiment, Psychology professors Christopher Chabris of Union College and Daniel Simons of the University of Illinois demonstrated 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 a fight, simply because of how you are directly concentrating on other things .

Overall, perception can be affected while you are focusing on something else, it solely depends on the person as well as the type of event that is taken place. This all concludes to “inattentional blindness”

Possible causes

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

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 crazy 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 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

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.

Expectation

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.

Capacity

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.

Exploitations

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.

See also

• Attention
• Attentional Blink
• Attribute substitution
• Blindsight
• Change blindness
• Choice blindness
• Salience (neuroscience)
• Three-card Monte
• Visual perception
• Somebody Else's Problem

Further reading

• Mack, A. & Rock I. (1998) Inattentional Blindness. MIT Press
• Chun, Marvin M.; Marois, René (2002). "The dark side of visual attention". Current Opinion in Neurobiology. 12 (2): 184–189. doi:10.1016/S0959-4388(02)00309-4. PMID 12015235.

External links

• Scholarpedia entry on inattentional blindness written by Daniel Simons
• Gorillas in our midst: sustained inattentional blindness for dynamic events
• Gorillas in our midst article and other papers on inattentional blindness from Daniel Simons
• Visual Cognition Lab University of Illinois
• Chinese, Americans Truly See Differently, Study Says
• None So Blind from Scientific American
• Why lifeguards sometimes can't see bodies at the bottom of a pool?
• Change Blindness and Inattentional Blindness
• Christopher Chabris Harvard webpage
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