What is inattentional blindness?
The term comes from a 1998 book, the gorilla from a 1999 experiment, and the radiologists from a 2013 study. What each one showed, and what decides who notices.
Answer to the question
What is inattentional blindness?
Inattentional blindness is the failure to notice an unexpected object in plain view because attention is committed to another task. Arien Mack and Irvin Rock named it in 1998. In a 2013 study of 24 radiologists, 83 per cent did not see a gorilla image in a lung scan.
Key takeaways
- Drew and colleagues (2013) inserted a gorilla image about 48 times the size of an average nodule into a lung scan; 83 per cent of 24 radiologists did not see it, and most who missed it had looked directly at its location.
- Rock and colleagues (1992) published the method, and Mack and Rock (1998) named the phenomenon, so the term predates the gorilla video by a year.
- Simons and Chabris (1999) reported that noticing depended on how similar the unexpected object was to other objects and how demanding the main task was, and not on its distance from attended locations.
- Simons and a co-author (2009) found that task demands affected noticing even when main-task performance was equalised, and that individual differences in that performance did not predict who noticed.
- Hyman and colleagues (2010) found that people walking while on a phone were less likely to notice a unicycling clown; they suggest phone use may produce inattentional blindness during simple activities.
Inattentional blindness is the failure to notice an unexpected object in plain view while attention is committed to another task. The eyes stay open and the object is visible, yet the observer reports seeing nothing.
What Did Radiologists Miss in the Lung Scan Study?
The clearest evidence that this is more than a party trick comes from a working setting, and the structure is the same in every study of inattentional blindness covered below. Each one has three parts:
- a main task that holds the observer's attention;
- an unexpected object that appears while the task is under way;
- a report afterwards on what the observer noticed.
A team led by Trafton Drew gave 24 radiologists a task from their working lives: searching lung scans for nodules. In the final case the team inserted the image of a gorilla, about 48 times the size of an average nodule. Of the radiologists, 83 per cent did not see it. Eye tracking showed that most of those who missed the gorilla had looked directly at the place where it appeared. The study appeared in Psychological Science in 2013, under a title that borrows the gorilla from an earlier experiment.
The result separates inattentional blindness from poor eyesight, because the gaze reached the object and the object was not registered. It also separates it from inexperience, because the observers were expert searchers working in their own field.
Irvin Rock and three colleagues, among them Arien Mack, published a new method for studying perception without attention in Cognitive Psychology in 1992. Mack and Rock then gave the phenomenon its name in a 1998 book that carries the term as its title. Credit for inattentional blindness as a term belongs to them, even though the best-known demonstration came later.
That demonstration is Daniel Simons and Christopher Chabris's 1999 experiment, built on classic divided-attention research. People watched a staged video of a ball game and followed one team's passes while an unexpected figure in a gorilla suit crossed the scene. Their paper put inattentional blindness in front of a general audience, and the gorilla has stood for it ever since.
Why Some Unexpected Objects Get Noticed While Others Do Not?
Researchers file the effect under selective attention, the capacity to favour one stream of input and leave the rest unprocessed. The listening version of that capacity is the cocktail party effect, which we cover in What is the cocktail party effect? and, from the side of names, in Why You Hear Your Name in a Crowd. Inattentional blindness is the same limit met through sight.
The abstract of the 1999 paper names two things that governed noticing. One was how similar the unexpected object was to the other objects in the display. The other was how demanding the main task was. The unexpected object's distance from the places observers were attending had no effect, which the authors read as a sign that observers attend to objects and events rather than to positions in space. How much an object stands apart from its surroundings is a related question, and we take it up in Why the Odd One Out Gets Remembered.
Simons and a co-author later asked whether differences between people explain who notices. They pointed out that most earlier work rested on a single critical trial, so one person's noticing could reflect chance. In the first of two experiments, a staircase procedure equalised performance on the main task across participants, and task demands still affected noticing. In the second, individual differences in main-task performance did not predict whether people noticed the unexpected object. The authors concluded that task difficulty affects inattentional blindness and that differences in the ability to meet the demands do not.
Read beside the radiology study, these results place the explanation in the task and the display more than in the person. Training did not remove inattentional blindness among the radiologists, and skill at the main task did not sort the noticers from the rest in the Simons experiments. A reader who tries to predict who will miss an unexpected object from ability alone has little to go on in this evidence.
Where Phones, Pavements and The Distracted Mind Meet
Ira Hyman and colleagues took the question outdoors in a 2010 paper in Applied Cognitive Psychology. They compared people walking while talking on a mobile phone with people listening to an MP3 player, people walking with no electronics, and people walking in pairs. In the first study, phone users walked more slowly, changed direction more often and were less likely to acknowledge other people. In the second, phone users were less likely to notice an unusual sight along their route, a unicycling clown.
In this design the phone conversation plays the part that counting passes plays in the gorilla video, and the clown plays the part of the gorilla. The authors suggest that phone use may produce inattentional blindness even during simple activities that need few cognitive resources.
Adam Gazzaley and Larry D. Rosen's book The Distracted Mind brings the invisible gorilla into its discussion of safety and then moves to Hyman's clown. The book sets both studies inside its wider argument that modern technology competes for a limited resource, and it treats the pair as a case that a phone conversation can occupy a walker so fully that an odd sight passes unseen, which is the reading Hyman's authors offer themselves.
Common questions
What is inattentional blindness?
Inattentional blindness is the failure to notice an unexpected object in plain view while attention is on another task. Irvin Rock and Arien Mack named it in 1998. In the 2013 radiology study, 83 per cent of 24 radiologists did not see a gorilla image in a lung scan.
Who named inattentional blindness?
Arien Mack and Irvin Rock introduced the method in 1992 and gave the phenomenon its name in their 1998 book. Daniel Simons and Christopher Chabris made it widely known with the gorilla video in 1999.
Does inattentional blindness mean poor eyesight?
No. In the radiology study, most radiologists who missed the gorilla had looked directly at its location, so the object reached their gaze and was not noticed.
Sources
Gazzaley, A., & Rosen, L. D. (2016). The Distracted Mind: Ancient Brains in a High-Tech World. MIT Press. Seed book; vault hub Books/The Distracted Mind.
Mack, A., & Rock, I. (1998). Inattentional Blindness. MIT Press. doi:10.7551/mitpress/3707.001.0001.
Rock, I., Linnett, C. M., Grant, P., & Mack, A. (1992). Perception without attention: results of a new method. Cognitive Psychology, 24(4), 502-534. doi:10.1016/0010-0285(92)90017-V.
Simons, D. J., & Chabris, C. F. (1999). Gorillas in our midst: sustained inattentional blindness for dynamic events. Perception, 28(9), 1059-1074. doi:10.1068/p281059.
Simons, D. J., & Jensen, M. S. (2009). The effects of individual differences and task difficulty on inattentional blindness. Psychonomic Bulletin & Review, 16(2), 398-403. doi:10.3758/PBR.16.2.398.
Hyman, I. E., Jr., Boss, S. M., Wise, B. M., McKenzie, K. E., & Caggiano, J. M. (2010). 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.
Drew, T., Võ, M. L.-H., & Wolfe, J. M. (2013). The invisible gorilla strikes again: sustained inattentional blindness in expert observers. Psychological Science, 24(9), 1848-1853. doi:10.1177/0956797613479386.