Inattentional blindness

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Inattentional blindness, also known as perceptual blindness, is categorized as a psychological lack of attention and is not associated with any vision defects or deficits.

Inattentional blindness defined[edit]

Inattentional blindness is the failure to notice an unexpected stimulus that is in one's field of vision when other attention-demanding tasks are being performed. It is categorized as an attentional error and is not associated with any vision deficits. This typically happens because humans are overloaded with stimuli, and it is impossible to pay attention to all stimuli in one's environment. This is due to the fact that they are unaware of the unattended stimuli. Inattentional blindness also has an effect on people’s perception. There have been multiple experiments performed that demonstrate this phenomenon.[1]

Cognitive capture[edit]

Cognitive capture or, cognitive tunneling, is an inattentional blindness phenomenon in which the observer is too focused on instrumentation, task at hand, internal thought, etc. and not on the present environment. For example, while driving, if the driver is focused on the speedometer and not on the road, they are suffering from cognitive capture.[2]

Experiments demonstrating inattentional blindness[edit]

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 a series of experiments that demonstrated inattentional blindness.

Invisible gorilla test[edit]

To test for inattentional blindness, researchers ask participants to complete a primary task while an unexpected stimulus is presented. Afterwards, researchers ask participants if they saw anything unusual during the primary task. The best-known study demonstrating inattentional blindness is the Invisible gorilla test, conducted by Daniel Simons of the University of Illinois at Urbana-Champaign and Christopher Chabris of Harvard University. This study, a revised version of earlier studies conducted by Ulric Neisser, Neisser and Becklen, 1975, asked subjects to watch a short video of 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 on attention than was previously thought.[3]

Although it was found that 50% of the test subjects demonstrated change blindness to the introduction of the gorilla or the umbrella, it is difficult to find published information on what percentage of study participants were able to accurately count the passes.[4]

Theoretical Background[edit]

The perceptual cycle framework has been used as a theoretical basis for inattentional blindness. The perceptual cycle frame work describes attention capture and awareness capture as occurring at two different stages of processing. Attention capture occurs when there is a shift in attention due to the salience of a stimuli, and awareness capture refers to the conscious acknowledgement of stimuli. Attentional sets are important because it is composed of characteristics of stimuli an individual is processing. Inattentional blindness occurs when there is an interaction between an individual's attentional set and the salience of the unexpected stimulus. Recognizing the unexpected stimulus can occur when the characteristics of the unexpected stimulus resembles the characteristics of the perceived stimuli. The attentional set theory of inattentional blindness has implications for false memories and eyewitness testimony. The perceptual cycle framework offers four major implications about inattentional blindness 1) environmental cues aid in the detection of stumuli by providing orienting cues but is not enough to produce awareness, 2) perception requires effortful sustained attention, interpretation, and reinterpretation, 3) implicit memory may precede conscious perception, and 4) visual stimuli that is not expected, explored, or interpreted may not be perceived.[5]

Other bases for attentional blindness include top down and bottom up processing.

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.[6]

Computer red cross experiment[edit]

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. Inattentional blindness is most likely to occur if the unexpected stimuli presented resembles the environment.[7]

Clown on a unicycle experiment[edit]

One interesting experiment displayed how cell phones contributed to inattentional blindness in basic tasks such as walking. The stimuli for this experiment was a brightly colored clown on a unicycle. 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.[8]

Blindness despite fixation[edit]

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 experiment. 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 report seeing the gorilla. There was no significant difference in accuracy of the counting between the two groups. 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.[9]

A more common example of the above is illustrated in the game of Three-card Monte.

Effects of expertise[edit]

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 experiment 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.[9]

Perception and inattentional blindness[edit]

In 1995, Boston Police Officer Kenneth M. Conley was put on trial for claiming he did not see a violent assault incident between people while he was chasing a suspect. His alibi was accepted due to “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. Officer Conley was in a similar situation.

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.[10]

Overall, perception can be affected while you are focusing on something else, it depends on the person as well as the type of event that takes place, and the resemblance between the unexpected stimuli and the environment .

Possible causes[edit]

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.[11]


Conspicuity refers to an object's 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 and Working Memory[edit]

Mental workload is a person's cognitive resources. The amount of a person's workload can interfere with processing of other stimuli. 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 to 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 – the task becomes automatic. Automatic processing can lessen one's mental workload, which can lead to a person to missing the unexpected stimuli. Working memory also has an effect on inattentional blindness. Those that experience inattentional blindness are more likely to have a lower working memory capacity.

Working memory also contributes to inattentional blindness. Cognitive psychologists have examined the relationship between working memory and inattention, but evidence is inconclusive. For example, some researchers state that individuals that have more space in their working memory and those with stronger working memory are less likely to be susceptible to inattentional blindness. Other researchers state that working memory does not influence inattentional blindness because working memory does not influence all attentional processes. For example, research conducted by Bredemeier and Simons, participants were given working memory tasks and a sustained-attention task. The first working memory task required participants to indicate whether a combination of letters matched a previous combination of letters that appeared earlier on a computer screen. The second working memory task required participants to determine if a target letter was in the same position as previous letters. For the sustained-attention task, participants were asked to count how many times a white square touched the edges of a computer screen. Once the tasks were completed, researchers asked participants if they noticed anything else besides the white squares during the sustained-attention task. During the sustained-attention task, a grey cross moved around the screen during some of the trails. Results indicated that 70% of participants did notice the grey cross moving on the computer screen, suggesting working memory does not have an influence on susceptibility to inattentional blindness.

On the other hand, a follow-up study to the Bredemeiser and Simons was conducted to further explore the impact of working memory using another working memory task. For this study, participants were asked to complete a math problem, and a letter was presented after each problem. After completing the math problems, participants were asked to recall the series of letters in sequential order. This task served as a working memory measure. The same sustained attention task was completed after the working memory task. Using this method, only 27% of participants noticed the grey square. Researchers concluded that working memory does influence one's experience of attentional blindness, but not an individual's ability to handle the task demands. These two studies demonstrate the inconsistencies in the relationship between working memory and inattentional blindness.[12]


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, or neurological salience, is a measure of how much attention must be focused to complete a task. 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.

Utilizations of Inattentional Blindness[edit]

Inattentional blindness is utilized by illusionists in the presentation of magic shows by focusing the audience's attention upon a distracting element, away from elements of the scene under manipulation by the performer. This is called misdirection.

See also[edit]


  1. ^ Most, Steven B. (2010). "What's "inattentional" about inattentional blindness?". Consciousness and Cognition 19 (4): 1102. doi:10.1016/j.concog.2010.01.011. 
  2. ^ Note: The term has also been applied to the "cognitive capture" of government regulatory agencies by the industries they are charged with regulating. The regulators may be seen as being so "captured" by the industry that they focus all their energy on the welfare of the industry and not on the welfare of the public. This concept may interact with "cognitive dissonance" to explain why people create local cultures that reflect some of the values in their local community, while completely ignoring others.
  3. ^ Most, SB; Simons, DJ; Scholl, BJ; Jimenez, R; Clifford, E; Chabris, CF (January 2001). "How not to be seen: the contribution of similarity and selective ignoring to sustained inattentional blindness". Psychol Sci 12 (1): 9–17. doi:10.1111/1467-9280.00303. PMID 11294235. 
  4. ^ Change Blindness Study; The Invisible Gorilla online; retrieved ?
  5. ^ Most, Steven B; Scholl, Brian J; Simons, Daniel J; Clifford, Erin R (2005). "What you see is what you get. Sustained intattentional blindness and the capture of awareness". I-Psychological Review 112 (1): 217–242. doi:10.1037/0033-295X.112.1.217. 
  6. ^ Tracy McVeigh (2008-11-16). "Invisible bear makes cyclists safer". Retrieved 2013-12-31. 
  7. ^ Carpenter, Siri (2001). "Sights Unseen". Monitor on Psychology 32 (4): 54. Retrieved 10 October 2012. 
  8. ^ Hyman, Ira E.; Boss, S. Matthew; Wise, Breanne M.; McKenzie, Kira E.; Caggiano, Jenna M. (2009). "Did you see the unicycling clown? Inattentional blindness while walking and talking on a cell phone". Applied Cognitive Psychology 24 (5): 597–607. doi:10.1002/acp.1638. 
  9. ^ a b Memmert, D (September 2006). "The effects of eye movements, age, and expertise on inattentional blindness". Conscious Cogn 15 (3): 620–7. doi:10.1016/j.concog.2006.01.001. PMID 16487725. 
  10. ^ Chabris, Christopher F; Weinberger, Adam; Fontaine, Matthew; Simons, Daniel J (2011). "You do Not Talk About Fight Club if You Do Not Notice Fight Club: Inattentional Blindness For A Stimulated Real-World Assult". I-Perception 2 (2): 150–153. doi:10.1068/i0436. 
  11. ^ Mack, Arien (2003). "Inattentional blindness: Looking without seeing" (PDF). Current Directions in Psychological Science 12 (5): 179–184. doi:10.1111/1467-8721.01256. Retrieved 10 October 2012. 
  12. ^ Bredemeiser, Keith; Simons, DJ (April 2012). "Working memory and inattentional blindness". Psychonomic Bulletin & Review 19 (2): 239–244. doi:10.3758/s13423-011-0204-8. 

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