From Abracadabra to Zombies | View All
Inattentional blindness is an inability to perceive something that is within one's direct perceptual field because one is attending to something else. The term was coined by psychologists Arien Mack and Irvin Rock, who identified the phenomenon while studying the relationship of attention to perception. They were able to show that, under a number of different conditions, if subjects were not attending to a visual stimulus but were attending to something else in the visual field, a significant percentage of the subjects were "blind" to something that was right before their eyes.
Because this inability to perceive, this sighted blindness, seemed to be caused by the fact that subjects were not attending to the stimulus but instead were attending to something else ... we labeled this phenomenon inattentional blindness (IB).*
Mack and Rock go on to argue that, in their view, "there is no conscious perception without attention."
Others, such as U. Neisser, D. Simons, and C. Chabris, have replicated and extended the work of Mack and Rock with experiments that have subjects attending to a specific task while watching a film, such as counting how many times a basketball is passed from one team member to another, while someone walks through the scene carrying an umbrella or wearing a gorilla suit. A surprisingly large percentage of subjects do not perceive something as obvious as a person in a gorilla suit moving through the scene they are observing, if they are attending to something else in their visual field. (Several examples of these experiments can be viewed on the Simons Lab page of the University of Illinois.)
Inattentional blindness may explain, for example, how a pilot with an interest in crop circles could fly right over one without even noticing it. The pilot had flown to see a recently discovered crop circle near Stonehenge. After visiting the site, he flew back to the airport to refuel before setting off on a trip that took him back over the site he had just visited. On the return flight he noticed another crop circle near the one he had visited earlier in the day and swears that the new circle was not there just forty-five minutes earlier. The new circle is very elaborate and could not have been produced by human hoaxers in such a short time. He concludes that some mysterious force must have been at work. Perhaps, but it seems more likely that the pilot experienced inattentional blindness when he was flying to the airport. He was focused on other tasks when he flew over the site and didn’t notice what was right beneath him all the time. (See "Crop Circles - Quest for Truth.")
Research by Chabris and Simons indicates that inattentional blindness is a "necessary, if unfortunate, by-product of the normal operation of attention and perception" (2010, p. 38). They point out that even radiologists, who are highly trained experts at detecting visual signs of medical problems, "can still miss subtle problems when they 'read' medical images." This may explain why my dentist didn't see a crack in one of my teeth on an x-ray until I started to complain about the pain in a particular area. To eliminate inattentional blindness, we'd have to eliminate focused attention. That would not be a good idea. Even worse would be the condition of being able to attend to everything in our sensory field at once. It would drive us mad.
Research also shows that training people to improve their attention abilities may do nothing to help them detect unexpected objects. "If an object is truly unexpected, people are unlikely to notice it no matter how good (or bad) they are at focusing attention" (Chabris and Simons: 2010, p. 32). Remember this the next time you're at the airport watching the transportation security screener do his or her job. It should not be surprising to find that these folks miss a lot of contraband planted by their bosses to test them. You might also remember this: there is no scientific evidence to support the belief that driving while talking on a hands-free phone is safer than driving while holding a cell to your ear. Worse, both have about the same effect as driving under the influence of alcohol (Chabris and Simons: 2010, pp. 22-26).
books and articles
Simons Lab (teachers may be interested in purchasing the DVD the VCL sells)
new Why Even Radiologists Can Miss A Gorilla Hiding In Plain Sight by Alix Spiegel - 83 percent of the radiologists didn't see the gorilla in the X-ray. [/new]
Study reveals how memory load leaves us ‘blind’ to new visual information "The new results reveal that our visual field does not need to be cluttered with other objects to cause [inattentional blindness] and that focusing on remembering something we have just seen is enough to make us unaware of things that happen around us."
gorillas, working memory, and the media by Daniel Simons
The news media doesn't get it quite right about a new study from the University of Utah. Typical is this Eureka alert:
University of Utah psychologists have learned why many people experience "inattention blindness" – the phenomenon that leaves drivers on cell phones prone to traffic accidents and makes a gorilla invisible to viewers of a famous video. The answer: People who fail to see something right in front of them while they are focusing on something else have lower "working memory capacity" – a measure of "attentional control," or the ability to focus attention when and where needed, and on more than one thing at a time.
"The media is reacting to the finding that, under some conditions, differences in working memory capacity predict noticing of an unexpected gorilla. They over-generalize the finding to suggest that people who are high in working memory capacity are immune to inattentional blindness....Any scientist reading the journal article would recognize that the correlation between working memory and noticing is imperfect and would separate speculative conclusions from definitive results. Unless the press release makes those limitations explicit, the media will not either. Unless the press release explicitly identifies the limited scope and imperfect correlation and flags speculation as such, an untrained reader (or headline writer) will naturally infer that the result and the speculation are one and the same. In this case, they will infer that working memory differences explain inattentional blindness in its entirety. By not reining in the speculation, the release suggests that the working memory is the primary (if not the only) reason that some people notice and some people miss unexpected objects."
Ghost busters, parapsychology, and the first study of inattentional blindness "More than 50 years ago, Tony Cornell, a parapsychology researcher, decided to test how people would react upon seeing him dressed as a ghost. Would they experience him as a "real" ghost or as something more mundane?....Each night, Cornell or his assistants dressed in a white sheet and strolled down a path, making various hand gestures before shedding the sheet 4.5 minutes later. Other assistants observed how many people were "in a position to observe the apparition." His finding: "although it was estimated that some 70-80 persons were in a position to observe the apparition, not one was seen to give it a second glance or to react in any way." That's true even though a number of cows apparently followed the ghost around."