The Invisible Gorilla: And Other Ways Our Intuitions Deceive Us

by Christopher Chabris

  29. S. B. Most and R. S. Astur, “Feature-Based Attentional Set as a Cause of Traffic Accidents,” Visual Cognition 15 (2007): 125–132.

  30. Fuoco, “Multiple Injuries, Few Answers for Roethlisberger.”

  31. E. Fischer, R. F. Haines, and T. A. Price, “Cognitive Issues in Head-Up Displays,” NASA Technical Paper 1711, 1980. See also R. F. Haines, “A Breakdown in Simultaneous Information Processing,” in Presbyopia Research, ed. G. Obrecht and L. W. Stark (New York: Plenum Press, 1991).

  32. Statistics and some of the analyses in this section are drawn from “Runway Safety Report: Trends and Initiatives at Towered Airports in the United States, FY 2004 through FY 2007,” Federal Aviation Administration, June 2008. You could encounter a runway incursion much sooner or much later than our estimate of three thousand years of daily round-trip flying, but in any case it is highly unlikely that you will in your lifetime. Details of the Tenerife crash are taken from “… What’s He Doing? He’s Going to Kill Us All!” Time, April 11, 1977 (www.time.com/time/magazine/article/0,9171,918815,00.html) and from the Wikipedia entry on the Tenerife disaster, en.wikipedia.org/wiki/Tenerife_disaster (accessed January 19, 2009).

  33. Fischer et al., “Cognitive Issues in Head-Up Displays,” 15.

  34. I. Larish and C. D. Wickens, Divided Attention with Superimposed and Separated Imagery: Implications for Head-up Displays, Aviation Research Laboratory Technical Report ARL-91-04/NASA-HUD-91-1, 1991.

  35. Evidence for driving impairment while talking on a cell phone comes from D. A. Redelmeier and R. J. Tibshirani, “Association Between Cellular-Telephone Calls and Motor Vehicle Collisions,” New England Journal of Medicine 336 (1997): 453–458; and D. L. Strayer, F. A. Drews, and D. J. Crouch, “Comparing the Cell-Phone Driver and the Drunk Driver,” Human Factors 48 (2006): 381–391. Evidence linking alcohol consumption to increased inattentional blindness comes from S. L. Clifasefi, M. K. T. Takarangi, and J. S. Bergman, “Blind Drunk: The Effects of Alcohol on Inattentional Blindness,” Applied Cognitive Psychology 20 (2005): 697–704. In this study, subjects were less likely to notice the unexpected gorilla after having had an alcoholic beverage. Alcohol could have its effect by directly altering the ability to detect unexpected objects or by making the primary counting task more difficult.

  36. E. Goodman, “We Love, Hate Our Cell Phones,” The Boston Globe, July 6, 2001. Consistent with Goodman’s claim, a survey found that cell phone users agreed more strongly with the statement “I can use a cellular phone safely when driving” than with “People, in general, can use a cellular phone safely when driving.” M. S. Wogalter and C. B. Mayhorn, “Perceptions of Driver Distraction by Cellular Phone Users and Nonusers,” Human Factors 47 (2005): 455–467.

  The New York legislation that took effect on December 1, 2001, involved adding Section 1225-c to the New York vehicle and traffic law. Part of the law stated, “The court shall waive any fine for which a person who violates the provisions of section 1225-c of the vehicle and traffic law … supplies the court with proof that, between the date on which he or she is charged with having violated such section and the appearance date for such violation, he or she possesses a hands-free mobile telephone.” This “get out of jail” provision was in effect until March 2002. The effect of this law essentially meant that rather than paying a fine, people caught using a handheld phone could pay a cell-phone vendor for a hands-free headset. Consequently, it’s not surprising that the major telecommunication companies supported the legislation.

  Nokia’s recommendation to use hands-free phones was titled “Safety Is the Most Important Call You Will Ever Make: A Guide to Safe and Responsible Wireless Phone Use” and its top safety tip was to “Get to know your wireless phone and its features such as speed dial and redial.” AT&T’s flier was headed “A special offer just for you” and provided a coupon for a free hands-free earpiece. The statistic that 77 percent of people believe that talking on a hands-free phone is safer comes from the SurveyUSA representative national poll we commissioned, conducted June 1–8, 2009.

  37. W. J. Horrey and C. D. Wickens, “Examining the Impact of Cell Phone Conversations on Driving Using Meta-Analytic Techniques,” Human Factors 48 (2006): 196–205.

  38. In most variants of the “gorilla” experiment, the gorilla did not stop to thump its chest. Instead, it just walked through the scene, remaining visible for five seconds. We created the “chest thump” version that we described earlier for a separate test to explore how dramatic we could make the event and still provoke inattentional blindness.

  39. B. J. Scholl, N. S. Noles, V. Pasheva, and R. Sussman, “Talking on a Cellular Telephone Dramatically Increases ‘sustained inattentional blindness’” [Abstract], Journal of Vision 3 (2003): 156 (journalofvision.org/3/9/156/). More recent observational studies show that people are often oblivious to their surroundings when talking on a phone. For example, people walking across a college campus while talking on a phone were less likely than undistracted pedestrians to notice a unicycling clown nearby: I. E. Hyman Jr., S. M. Boss, B. M. Wise, K. E. McKenzie, and J. M. Caggiano, “Did You See the Unicycling Clown? Inattentional Blindness While Walking and Talking on a Cell Phone,” Applied Cognitive Psychology.

  40. This finding and the explanations in the next paragraph are based on F. A. Drews, M. Pasupathi, and D. L. Strayer, “Passenger and Cell Phone Conversations in Simulated Driving,” Journal of Experimental Psychology: Applied 14 (2008): 392–400.

  41. The phenomenon of inattentional deafness can be traced to studies from the 1950s and 1960s on the ability to attend selectively to information presented to one ear while ignoring sounds in the other ear. Under those conditions, people often fail to notice unexpected messages in the ignored ear. The term “inattentional deafness” was first used by Mack and Rock in their 1998 book Inattentional Blindness. For examples of early work on selective listening, see E. C. Cherry, “Some Experiments upon the Recognition of Speech, with One and with Two Ears,” Journal of the Acoustical Society of America 25 (1953): 975–979; and A. Treisman, “Monitoring and Storage of Irrelevant Messages in Selective Attention,” Journal of Verbal Learning and Verbal Behavior 3 (1964): 449–459.

  42. G. Weingarten, “Pearls Before Breakfast,” The Washington Post, April 8, 2007, p. W10 (www.washingtonpost.com/wp-dyn/content/article/2007/04/04/AR2007040401721.html). Biographical information about Bell comes from Weingarten’s article and the Wikipedia entry on Joshua Bell (en.wikipedia.org/wiki/Joshua_Bell). The biographical quote about Bell is from his official biography, www.joshuabell.com/biography (accessed January 16, 2009).

  43. Later, Joshua Bell had a different memory of his feelings. In the revised edition of Predictably Irrational (New York: HarperCollins, 2009), Dan Ariely writes of meeting Bell and asking about his day as a busker: “I wanted to know how he felt about being overlooked and ignored by so many people. He responded that he was really not all that surprised, and admitted that expectation is an important part of the way we experience music” (p. 272).

  44. Nokia Corporation, “Survey Results Confirm It: Women Are Better Multitaskers Than Men,” press release, November 22, 2007, www.nokia.com/press/press-releases/showpressrelease?newsid=1170280 (accessed January 28, 2009). Despite the title of this press release, it reports no actual test of multitasking abilities, just a nonrepresentative survey of popular beliefs about multitasking abilities. A typical study of the inefficiency of multitasking is J. S. Rubinstein, D. E. Meyer, and J. E. Evans, “Executive Control of Cognitive Processes in Task Switching,” Journal of Experimental Psychology: Human Perception and Performance 27 (2001): 763–797. There is frequent discussion of differences in brain anatomy between men and women that could explain a difference in multitasking ability, but we have been unable to find experiments that offer unequivocal evidence for a general superiority of women in dividing attention between multiple tasks or goals.

  45. These findings are reported in D. Memmert, “The Effects of Eye Movements, Age, and Expertise on Inattenti
onal Blindness,” Consciousness and Cognition 15 (2006): 620–627; and D. Memmert, D. J. Simons, and T. Grimme, “The Relationship Between Visual Attention and Expertise in Sports,” Psychology of Sport and Exercise 10 (2009): 146–151.

  46. T. E. Lum, R. J. Fairbanks, E. C. Pennington, and F. L. Zwemer, “Profiles in Patient Safety: Misplaced Femoral Line Guidewire and Multiple Failures to Detect the Foreign Body on Chest Radiography,” Academic Emergency Medicine 12 (2005): 658–662.

  47. Omitting a final step in a process (e.g., removing a guidewire) once the main objective of the process has been achieved (e.g., placing the central line correctly) is a common sort of mistake known as a post-completion error. This is the type of error you are making when you walk away with your stack of copies while the original document is still sitting on the glass, or when you type out an e-mail saying “as shown in the document I have attached” but hit “send” before you attach the document.

  48. D. B. Spring and D. J. Tennenhouse, “Radiology Malpractice Lawsuits: California Jury Verdicts,” Radiology 159 (1986): 811–814.

  49. W. James, The Principles of Psychology (New York: Henry Holt, 1890). For a discussion of how people search for rare items, see J. M. Wolfe, T. S. Horowitz, and N. M. Kenner, “Rare Items Often Missed in Visual Searches,” Nature 435 (2005): 439–440.

  50. The examples of uses of the gorilla video are from several sources. The first is from an e-mail sent to Dan’s company, Viscog Productions, Inc., on August 5, 2004, about the usefulness of its DVD that includes the gorilla video. Mahzarin Banaji, a Harvard psychology professor, used inattentional blindness in an analysis of discrimination; see the story entitled “Tenure and Gender” in Harvard Magazine, January 2005 (harvardmagazine.com/2005/01/tenure-and-gender.html). The parallels between inattentional blindness and the failure to detect terrorists was discussed in “Background Briefing,” ABC Radio National (Australia) with Gerald Tooth, December 8, 2002. Links to diet were discussed in “Awareness, Fat Loss, & Moonwalking Bears,” December 31, 2008, www.bellyfatreport.com/?s=bear (accessed June 9, 2009). Dean Radin’s views are presented in D. Radin, Entangled Minds: Extrasensory Experiences in a Quantum Reality (New York: Paraview Pocket Books, 2006). (Later in this book we discuss one of the main reasons why people come to believe in psychic phenomena despite the absence of scientific evidence to support their existence.) Discussion of bullying was from an e-mail received by Viscog Productions on September 1, 2008. The link to religion is from a March 2008 sermon by Reverend Daniel Conklin of the Epiphany Parish in Seattle, www.epiphanyseattle.org/sermons/Lent4-2008.html (accessed June 28, 2009).

  51. Wolfe et al., “Rare Items Often Missed.”

  52. For a brief discussion, see T. Griffiths and C. Moore, “A Matter of Perception,” Aquatics International, November/December 2004 (www.aquaticsintl.com/2004/nov/0411_rm.html).

  53. Examples of GPS-induced accidents come from the following sources: “Driver Follows GPS into Sand,” Reuters, October 10, 2006 (www.news.com.au/story/0,23599,20555319-13762,00.html,); “Train Hits Car, and a G.P.S. Is Blamed,” Associated Press, October 1, 2008 (www.nytimes.com/2008/10/01/nyregion/01gps.html); T. Carey, “SatNav Danger Revealed: Navigation Device Blamed for Causing 300,000 Crashes,” July 21, 2008 (www.mirror.co.uk/news/top-stories/2008/07/21/satnavdanger-revealed-navigation-device-blamed-for-causing-300-000-crashes-89520-20656554/); “Lorry Driver Had to Sleep in Cab for Three Nights After Sat-Nav Blunder Left Him Wedged in Country Lane,” Daily Mail, November 1, 2007 (www.dailymail.co.uk/news/article-491073/Lorry-driver-sleep-cab-nights-sat-navblunder-left-wedged-country-lane.html); “Sat-Nav Dunks Dozy Drivers in Deep Water,” The Times (London) Online, April 20, 2006 (www.timesonline.co.uk/tol/news/article707216.ece). The ford in this last example is normally about two feet deep.

  Chapter 2: The Coach Who Choked

  1. Many of the details and quotes for the Bobby Knight/Neil Reed story are taken from an article entitled “A Dark Side of Knight,” first published on the CNN/Sports Illustrated website on March 18, 2000, updated September 10, 2000. The article was intended to expose some of the vulgar and abusive antics Knight exhibited during practices, with the implication that his behavior had caused the players to leave. However, the story acknowledged that Knight’s program had no more departures than other top college basketball programs. Some students who left the program, like Richard Mandeville, regretted not doing so sooner. Other players, like Alan Henderson—who stayed in the program, graduated, and became a top shooting guard in the NBA—spoke more fondly of Knight’s motivational techniques. Henderson admitted that Knight had been a tough coach who “got on me sometimes like he got on everybody,” but praised him for his desire to improve his players and his generosity and willingness to help. Other quotes were taken from the following CNN/Sports Illustrated articles: “Defending ‘The General,’” April 12, 2000; and “The Knight Tape,” September 9, 2000. Biographical details on Bobby Knight are drawn from the National Basketball Association Hoopedia blog, hoopedia.nba.com/index.php?title=Bob_Knight, and from Wikipedia, en.wikipedia.org/wiki/Bob_Knight (both accessed June 29, 2009). Many of the incidents from Knight’s career are documented in “Bob Knight’s Outburst Timeline,” USA Today, November 14, 2006.

  2. As we mentioned in a note to Chapter 1, our items were designed to present beliefs that the scientific consensus regards as false, so an ideal rate of agreement would be 0 percent. We also found that 83 percent of people believe that amnesia, or sudden memory loss, results in the inability to recall one’s name and identity. This belief may reflect the way amnesia is usually portrayed in movies, television, and literature. For example, when we meet Matt Damon’s character in the movie The Bourne Identity, we learn that he has no memory for who he is, why he has the skills he does, or where he is from. He spends much of the movie trying to answer these questions. But the inability to remember your name and identity is exceedingly rare in reality. Amnesia most often results from a brain injury that leaves the victim unable to form new memories, but with most memories of the past intact. (Some movies do accurately portray this more common syndrome, known as “anterograde” amnesia; our favorite is Memento.)

  3. This pattern of recall is known as the serial position curve. This “U-shaped” curve (better recall of items from the beginning and end of a list than from the middle of the list, hence the U-shaped function) is one of the best-established findings in the literature on memory function; see H. Ebbinghaus, Memory: A Contribution to Experimental Psychology, trans. H. A. Ruger and C. E. Bussenius (New York: Columbia University, 1885/1913). For evidence of a serial position curve with this particular type and length of list, see H. L. Roediger III and K. B. McDermott, “Creating False Memories: Remembering Words Not Presented in Lists,” Journal of Experimental Psychology: Learning, Memory, and Cognition 21 (1995): 803–814.

  4. Evidence for a seven-item limit on short-term memory comes from G. A. Miller, “The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information,” Psychological Review 63 (1956): 81–97. Evidence that children lack adult memorization skills comes from J. H. Flavell, A. G. Friedrichs, and J. D. Hoyt, “Developmental Changes in Memorization Processes,” Cognitive Psychology 1 (1970): 324–340. This study shows that preschool children also think they will remember more than they actually do. Primary school students also overestimate their memory abilities, but not nearly as much as preschoolers.

  5. J. Deese, “On the Prediction of Occurrence of Particular Verbal Intrusions in Immediate Recall,” Journal of Experimental Psychology 58 (1959): 17–22; Roediger and Mc-Dermott, “Creating False Memories.”

  6. The study was described in the following article: W. F. Brewer and J. C. Treyens, “Role of Schemata in Memory for Places,” Cognitive Psychology 13 (1981): 207–230. Some of the earliest demonstrations that memory encodes meaning in the form of associations with what we already know come from this classic: F. C. Bartlett, Remembering: A Study in Experimental and Social Psychology (Cambridg
e: Cambridge University Press, 1932).

  7. “The Knight Tape,” CNN/Sports Illustrated, September 9, 2000.

  8. This quote is also from CNN/Sports Illustrated’s report “The Knight Tape.”

  9. Increased wait times have become more common with increased use of cell phones and decreased numbers of operators. For example, in Las Vegas in 2002, only 65 percent of calls were answered within the national standard of ten seconds (A. Packer, “Metro 911 Calls Often Put on Hold,” Las Vegas Sun, October 23, 2004). At the two largest call centers in Los Angeles and San Francisco, average wait times are more than fifty seconds, and in some extreme cases, callers had to wait more than ten minutes for an operator (R. Lopez and R. Connell, “Cell Phones Swamping 911 System,” The Los Angeles Times, August 26, 2007).

  10. Chris learned of the incident in a conversation with the witnesses on May 30, 2008. He asked them not to talk about it further before he could interview each of them separately. The interview with Leslie Meltzer took place by telephone on August 5, 2008; the interview with Tyce Palmaffy took place by telephone on December 30, 2008.

  11. Different people have different roles on a movie set, and each may notice elements related to his or her area of focus. Costumers might notice changes to clothing, cinematographers focus on lighting changes, etc. The script supervisor is the one person responsible for trying to make sure all the important details match across shots. See A. Rowlands, The Continuity Supervisor, 4th ed. (Boston: Focal Press, 2000); P. P. Miller, Script Supervising and Film Continuity, 3rd ed. (Boston: Focal Press, 1999).

  12. At the time of this writing, a Google search for “film flubs” turns up more than thirty-five hundred hits.

  13. “Film Flubs: Mistakes Made and Left in Popular Movies,” Dateline NBC, March 22, 1999. Saving Private Ryan won the Academy Award for editing in 1998 and Shakespeare in Love was nominated that same year (see awardsdatabase.oscars.org). Mankiewicz also assumed that the filmmakers were unaware of the errors. Script supervisor Trudy Ramirez told Dan in an interview on June 6, 2009, “The amount of handling and viewing and the numbers of people that are involved in the post-production process and in the editing is so extensive, that for something to literally get through with every one of those people being unaware is highly unlikely. I don’t know how many times it’s happened, if ever. A number of people would have discussed the merits of utilizing the shot with an error prior to it ending up in the film.” In other words, they might have needed a shot of soldiers walking across a field, but they didn’t have one with seven soldiers, so they decided to use the one with eight soldiers despite the error. The facts about The Godfather and Spartacus come from the Internet Movie Database, www.imdb.com/title/tt0068646/goofs; www.imdb.com/title/tt0054331/goofs (both accessed November 14, 2009).