The Invisible Gorilla

Christopher Chabris and Daniel Simons “The Invisible Gorilla: and other ways our intuitions deceive us”   Crown, 2010, 246 pp.

Another very worthwhile book for those interested in how human brains really work; the authors focus on attention, perception, memory, and reasoning and the problems intuition causes as well as how much of the real world we actually do not perceive.  The title is prompted by a famous psychological study where subjects are shown a video, about a minute long, of two teams, one in white shirts, the other in black shirts, moving around and passing basketballs to one another. They are asked to count the number of aerial and bounce passes made by the team wearing white, a seemingly simple task. Halfway through the video, a woman wearing a full-body gorilla suit walks slowly to the middle of the screen, pounds her chest, and then walks out of the frame. If you are just watching the video, it’s the most obvious thing in the world. But when asked to count the passes, about half the people miss seeing the gorilla.  The books purpose is to alert the reader to notice the invisible gorillas in their lives. (This same phenomena happens to drivers when talking on cell phones, speaker phone or not, when an unexpected event occurs: a child walking in to the street for instance). 

One of the messages of the book is to be wary of your intuitions, especially intuitions about how your own mind works.  Our mental systems excel at rapidly solving the problems they evolved to solve, but our cultures, societies, and technologies today are much more complex than those of our ancestors.  In solving problems of the modern world, think twice before you decide to trust intuition over rational analysis.

My Notes:

Pg. X:  The Invisible Gorilla is a book about six everyday illusions that profoundly influence our lives: the illusions of attention, memory, confidence, knowledge, cause, and potential.  These are distorted beliefs we hold about our minds that are not just wrong, but wrong in dangerous ways.  The book explores when and why these illusions affect us, the consequences they have for human affairs, and how we can overcome or minimize their impact.

Pg. 5:  A study of visual attention and awareness (“Gorillas in Our Midst” published in 1999) was designed by the authors.  Using their student as actors, they made a film of two teams of people moving around and passing basketballs.  One team wore white shirts and the other wore black.  The film was then shown to volunteers who were asked to count the number of passes made by the players wearing white while ignoring any passes by the players wearing black.  The video lasted less than a minute.  The pass-counting task was intended to keep people engaged in doing something that demanded attention to the action on the screen. Halfway through the video, a female student wearing a full-body gorilla suit walked into the scene, stopped in the middle of the players, faced the camera, thumped her chest, and then walked off, spending about nine seconds onscreen. Half the volunteers did not see the gorilla. Over the years the study has been replicated using varying sections of the populace and always about half do not see the gorilla.

Pg. 7:  When people devote their attention to a particular area or aspect of their visual world, they tend not to notice unexpected objects, even when those unexpected objects are salient, potentially important, and appear right where they are looking.

Pg. 26:  It may come as a surprise to learn that talking to a passenger in a car is not nearly as disruptive to your driving ability as talking on a cell phone.  This may be because the person you’re talking to is right next to you so you don’t need as much effort to keep up with the conversation.  Also, the person next to you provides another set of eyes—a passenger might notice something unexpected on the road and alert you, a service your cell-phone conversation partner can’t provide.  The most interesting reason for this difference has to do with the social demands of conversations.  When you converse with the other people in your car, they are aware of the environment you are in.  Consequently, if you enter a challenging driving situation and stop speaking, your passengers will quickly deduce the reason for your silence.  When talking on a cell phone, though, you feel a strong social demand to continue the conversation despite difficult driving conditions.

Pg. 49:  What is stored in memory is not an exact replica of reality, but a re-creation of it.  We cannot play back our memories like a DVD—each time we recall a memory, we integrate whatever details we do remember with our expectations for what we should remember.

Pg. 61:  When you interact briefly with a stranger, there are only few pieces of general information you can be certain of retaining: sex, race, and social group.

Pg. 79:  Emotional memories, like the ones we have for 9/11, are more likely to induce strong, vivid recall—regardless of whether they are accurate.  Beware of memories accompanied by strong emotions and vivid details—they are just as likely to be wrong as mundane memories, but you’re far less likely to realize it.  Unfortunately, people regularly use vividness and emotionality as an indicator of accuracy; thy use these cues to assess how confident they are in a memory.  Critically, people also judge the accuracy of another person’s memory based on how much confidence that person expresses in the memory (think juries).

Pg. 86:  Charles Darwin observed that ‘ignorance more frequently begets confidence than does knowledge.’  In fact, those who are the least skilled are the most likely to think better of themselves than they should. 

Pg. 151:  Mandatory MMR vaccination of children before they enter the public school system largely eliminated measles from the U.S. by the year 2000.  Vaccination levels of 90 percent of the population are needed to effectively prevent epidemics.  Yet, during May and June of 2005 34 people contracted measles in Cincinnati.  Only two of the thirty-four patients had been vaccinated and one of those two had only received one dose of the vaccine.  Although vaccination is mandatory for all children attending public schools in the U.S., in many states parents can file a ‘personal belief exemption’ that allows them to forgo vaccination for their children for religious or other reasons.  (29 percent of people in a U.S. national survey believe that vaccines given to children are partly responsible for causing autism, despite the now overwhelming evidence that vaccinations are not at all associated with autism) p. 183

Pg. 163:  A standard principle taught in introductory psychology classes is that correlation does not imply causation.  This principle needs to be taught because it runs counter to the illusion of cause.  A simple trick will help you spot the illusion in action: When you hear or read about an association between two factors, think about whether people could have been assigned randomly to conditions for one of them.  If it would have been impossible, too expensive, or ethically dubious to randomly assign people to those groups, then the study could not have been an experiment and the causal inference is not supported. 

Example:  ‘Bullying Harms Kids’ Mental Health’.  Could a researcher randomly assign some kids to be bullied and others not to be bullied?  No—not ethically, anyway.  So the study must have measured an association between being bullied and suffering mental health problems.  The causal relationship could well be reversed-children who have mental health issues might be more likely to get bullied.  

Others:  “Does Your Neighborhood Cause Schizophrenia?”  Could researchers have randomly assigned people to live in different neighborhoods?

“Housework Cuts Breast Cancer Risk”—It is doubtful that experimenters would have much luck randomly assigning some women to a ‘more housework’ condition and others to a ‘less housework’ condition.

Pg. 183:  The book explores three ways the illusion of cause can affect us.  First, we perceive patterns in randomness, and we interpret these repeating patterns as predictions of future events.  Second, we look at events that happen together as having a causal relationship.  Finally, we tend to interpret events that happened earlier as the causes of events that happened or appeared to happen later.  The illusion of cause has deep roots.  We humans are distinct from other primates in our ability to perform ‘causal inference.’  Even young children realize that when one object hits another, it can make the other object move.  They can reason about hypothetical causes as well: If an object moved, something must have caused it to move.  Our primate relatives generally do not make these inferences, and consequently, they have trouble learning about causes that they can’t see.  On the timeline of evolution, therefore, the ability to infer the existence of hidden causes is quite recent, and new mechanisms often need refinement.  We have no trouble inferring causes—the real trouble is that we are sometimes too good at inferring causes for our own good.

Pg. 198:  Sixty-one percent of respondents to a national telephone survey agreed that ‘hypnosis is useful in helping witnesses accurately recall details of crimes.’  The idea that hypnosis can put the brain into a special state, in which the powers of memory are dramatically greater than normal, reflects a belief in a form of easily unlocked potential.  But it is false.  People under hypnosis do generate more ‘memories’ than they do in a normal state, but these recollections are as likely to be false as rue.  Hypnosis leads them to come up with more information, but not necessarily more accurate information. 

Seventy-two percent of people agreed that ‘most people use only 10 percent of their brain capacity.’  This statement ought to be declared ‘void for vagueness.’  First, there is no known way to measure a person’s ‘brain capacity’ or to determine how much of that capacity he or she uses.  Second, when brain tissue produces no activity whatsoever for an extended time, that means it is dead.  So, if we only used 10 percent of our brain, there would be no possibility of increasing that percentage.  Finally, there is no reason to suspect that evolution would give us an organ that is 90 percent inefficient.  If we used only a fraction of our brain, natural selection would have shrunk it long ago.

Pg. 201:  Famous report of a 1950’s experiment in which subliminal messages were shown during movies to drive up sales of soda and popcorn.  The results of this ‘experiment’ were fabricated by an advertising expert named James Vicary, a fabrication he has publically confessed to.  Yet, despite the lack of evidence for subliminal persuasion, people persist in their belief that such mind control is possible.  The makers of self-help recordings that purport to reprogram your mind and eliminate unwanted behaviors like smoking and overeating via subliminal messages are not deterred by the double-blind, controlled studies that find zero actual benefit from them.

Pg. 209:  Unfortunately, people who do more crosswords decline mentally at the same rate as those who do fewer crosswords.  Practice improves specific skills, not general abilities.

Pg. 223:  It might seem counterintuitive, but the best thing you can do to preserve and maintain your mental abilities is exercise your body that maintains your aerobic fitness.  Just walking at a reasonable clip for thirty minutes or more a few times a week leads to better executive functioning and a healthier brain. 

Pg. 230:  In recent years, psychologists have proposed that most of our thought processes can be divided into two types: those that are fast and automatic and those that are slow and reflective.  Both contribute to everyday illusions.  Much of our automatic responses are based on what we call ‘common sense’, another name is ‘intuition’.  What we intuitively accept and believe is derived from what we collectively assume and understand, and intuition influences our decisions automatically and without reflection.  Intuition tells us that we pay attention to more than we do, that our memories are more detailed and robust than they are, that confident people are competent people, that we know more than we really do, that coincidences and correlations demonstrate causation, and that our brains have vast reserves of power that are easy to unlock.  But in all these cases, our intuitions are wrong.

That’s not a message that has been popular lately.  It has become fashionable to argue that intuitive methods of thinking and making decisions are superior to analytical methods.  This idea flies in the face of society’s long-standing celebration of rationality and logic as the purest and most objective forms of thought.