IL­LU­SION MA­CHINE: THE BRAIN The 5 Er­rors of Our Per­cep­tion

iD magazine - - Body & Mind -

Our brain is an im­pres­sive con­struc­tion: Weigh­ing only around 3 pounds, it pos­sesses roughly 100 bil­lion nerve cells and the to­tal length of its neu­ral path­ways mea­sures about 100,000 miles. What hap­pens here is re­al­ity— and that arises dif­fer­ently in each brain. Un­like a stan­dard­ized mea­sur­ing tool, each of us uses our own in­di­vid­ual fil­ters to ex­e­cute per­cep­tion. Our vis­ual ap­pa­ra­tus alone is con­sid­ered to be par­tic­u­larly prone to er­ror— even though 80% of our in­for­ma­tion comes through our eyes. All we can do is in­stantly in­ter­pret ev­ery­thing we see: The brain’s im­me­di­ate anal­y­sis leaves no time for rea­son­ing.

Shortly af­ter midnight on July 19, 2015, en­gine noises and a loud crash have shat­tered the si­lence in the Ger­man city of Bre­men. The sounds orig­i­nate from a fa­tal traf­fic ac­ci­dent that is about to make na­tional head­lines. Two ve­hi­cles had been rac­ing down the road side by side at 60 miles per hour, thereby block­ing both lanes of traf­fic. The driver of an ap­proach­ing Mercedes only had time to flash his high beams, and at the last mo­ment the car had swerved to the right and knocked down a tree as well as a street­light—at least that’s the way sev­eral eye­wit­nesses unan­i­mously de­scribed it to the po­lice. The 52-year-old driver of the Mercedes had been killed in­stantly, the vic­tim of an il­le­gal car race.

The prob­lem: No part of the se­quence of events hap­pened in the way that the wit­nesses de­scribed. Video record­ings re­veal that there had not been any risky lane block­ing. In fact, the Mercedes driver was found to have a blood al­co­hol level al­most two times the le­gal limit, mak­ing him com­pletely un­fit to drive. How­ever by that time the re­port had al­ready reached the news ser­vices. On the Web, an un­prece­dented hunt be­gan for the es­caped “mur­der­ers,” for lax laws and idle politi­cians, and for peo­ple con­nected to the stree­trac­ing scene, whose names cir­cu­late in on­line fo­rums. A vir­tual war ig­nited by false mem­o­ries rages on for days. But how could a fic­tion turn into the truth in the minds of the wit­nesses?


Three fac­tors led to a tragic ac­ci­dent be­ing trans­formed into a street race with fa­tal con­se­quences that night. Fac­tor 1: The ac­ci­dent took place on a warm sum­mer night, which means many res­i­dents were sit­ting out­side. The screech­ing of an en­gine would be clearly au­di­ble from where they were sit­ting, and it sug­gests rac­ers. “The louder a ve­hi­cle is, the higher we es­ti­mate its speed to be,” says so­cial psy­chol­o­gist Jörg HupfeldHeine­mann. Fac­tor 2: The im­me­di­ate fo­cus of the wit­nesses at the scene of the ac­ci­dent was only di­rected at the wreck­age. Any de­tails out­side of that ( like cars rac­ing side by side) are blurry. Fac­tor 3: Il­le­gal car rac­ing was get­ting a lot of me­dia cov­er­age around the time of the in­ci­dent, so it lent it­self to an ob­vi­ous ex­pla­na­tion. Fi­nally, res­i­dents of­ten com­plained to the po­lice about races oc­cur­ring on the ex­tremely straight road­way. “From the in­for­ma­tion avail­able we con­struct the best pos­si­ble story, and if it makes sense, we be­lieve it. Para­dox­i­cally, the act of fab­ri­ca­tion is ac­tu­ally eas­ier when you have less in­for­ma­tion,” ex­plains psy­chol­o­gist and No­bel Memo­rial Prize win­ner Daniel Kah­ne­man. And that’s how, in a mat­ter of hours, the “mem­ory” of a race that never hap­pened is born…

How­ever that’s only the tip of the ice­berg, be­cause in this case video ev­i­dence quickly ex­posed the truth. But what if there’s no video footage? Ac­cord­ing to in­de­pen­dent stud­ies, more than half of all mis­car­riages of jus­tice in court tran­spire as a re­sult of in­cor­rect eye­wit­ness ac­counts.

“We cre­ate our mem­o­ries our­selves. They do not nec­es­sar­ily cor­re­spond with what has hap­pened be­fore in the out­side world.” HANS MARKOWITSCH, mem­ory re­searcher

Th­ese come from peo­ple who were there and are sim­ply re­peat­ing what they saw—sup­pos­edly. “Wit­nesses do not lie,” says Jen­nifer Dysart, an as­so­ciate psy­chol­ogy pro­fes­sor at John Jay Col­lege of Crim­i­nal Jus­tice. “Rather, they are sub­ject to an er­ror in their re­pro­duc­tion of re­al­ity.”

Stud­ies show that just 30 min­utes af­ter an event we al­ready start to mix up the de­tails—much like a dream, the de­tails are still clearly present in our con­scious­ness shortly af­ter we wake up but they be­come more and more hazy as the morn­ing wears on.

The brain fills the re­sult­ing “blank spots” with data that fit the story— just as we im­me­di­ately com­plete the se­quence “1,2, 3, x, 5” by adding a 4. It is sim­ply “log­i­cal,” and al­ter­na­tive ex­pla­na­tions aren’t read­ily avail­able. Darkness + the sound of an ac­ci­dent + lim­ited sight + ha­tred of rac­ers = rac­ing. “Our per­cep­tion is driven by sub­con­scious hopes and goals. We usu­ally see only what con­firms our in­ten­tions,” says New York Uni­ver­sity so­cial psy­chol­o­gist Emily Bal­cetis. By the time the wit­nesses had been ques­tioned by the po­lice, the “fit­ting” truth had taken root in their minds…

For crim­i­nol­o­gists such “in­vented” re­al­i­ties do not come as a sur­prise. They are hap­pen­ing even while you read this, al­beit on a smaller scale: Ap­prox­i­mately ev­ery three sec­onds you are blind for 150 mil­lisec­onds— when­ever you blink to keep the tear film of your eyes in­tact. Only if you re­ally fo­cus on it will you no­tice the brief in­ter­rup­tion. Nor­mally the vis­ual film is not “jerky” be­cause the brain re­places the in­stant of darkness with a suit­able se­quence from mem­ory.

The re­al­ity in the brain doesn’t arise as a re­flec­tion of re­al­ity, but rather as a glimpse of it through a key­hole. Il­lu­sion­ists like David Blaine turn the spec­ta­tor’s brain into an ac­com­plice: They po­si­tion the key­hole so skill­fully that view­ers ex­pe­ri­ence the trick as re­al­ity. “Ev­ery­thing we per­ceive is a ma­nip­u­la­tor of our con­scious­ness,” says psy­chol­o­gist Daniel Kah­ne­man.


Each hu­man eye pos­sesses more than 126 mil­lion color and con­trast re­cep­tors, and th­ese trans­mit data more than 11 mil­lion times a sec­ond. But the brain can re­ally only pro­cess 40 of th­ese im­pres­sions, so all the rest end up in the vir­tual trash bin. It’s like judg­ing a novel af­ter read­ing just four words. But for our brain this “slop­pi­ness” is not a prob­lem, since it con­cen­trates on the or­der—rather than on the un­der­stand­ing: Its daily life is a sin­gle and rarely in­ter­rupted sense of achieve­ment: “I know this, I un­der­stand that, th­ese fit into that com­part­ment.” The brain checks off 99.9% of all im­pres­sions this way— re­gard­less of whether they are true or not. “This scan is only dis­turbed by im­pres­sions that are un­ex­pected, fright­en­ing, or par­tic­u­larly de­sir­able,” ex­plains Bal­cetis.

Like sleep­walk­ers, we are steered through life by our brains: “It takes only a tenth of a sec­ond to ren­der all sorts of judg­ments about a face that you’ve never seen be­fore,” ex­plains Alexan­der Todorov, a psy­chol­o­gist at Prince­ton Uni­ver­sity. In the pro­cess,

it’s not only gen­der, age, and mood that are taken into ac­count, but also how help­ful, ner­vous, or in­tel­li­gent the per­son seems to be. De­pend­ing on the cir­cum­stances, this tenth of a sec­ond can de­ter­mine whether we ap­proach a per­son or steer clear— or if we make the per­son a sus­pect in a crime. “I of­ten ask my­self, ‘Who is the boss here? Who’s in con­trol?’” says neu­ro­sci­en­tist Al­lan Sny­der, di­rec­tor of the Cen­tre for the Mind at Aus­tralia’s Uni­ver­sity of Syd­ney. “And the only an­swer al­ways is, our sub­con­scious. It down­right dic­tates our de­ci­sions. And the con­scious mind is merely the brain’s PR stunt so that we think we have some say.”

The ar­ti­fi­cial re­al­ity in our heads is well pro­tected against facts. Once ob­tained, “find­ings” are not checked—the brain hasn’t any time: Be­cause the sen­sory cen­ters are al­ready fo­cused on the next piece of in­for­ma­tion, and in­com­ing data are stream­ing in and re­quire in­ter­pre­ta­tion so they can be made to fit into a pat­tern. The re­sult: “We live con­tin­u­ously in our il­lu­sions. There is never or only very, very rarely a 100 per­cent cor­re­la­tion be­tween re­al­ity and our per­cep­tion,” ex­plains Su­sana Martinez- Conde, head of the Lab­o­ra­tory of In­te­gra­tive Neu­ro­science in Brook­lyn, New York. The lazi­ness of the brain makes the de­cep­tion within our heads per­fect: “Hu­mans are cog­ni­tive mi­sers,” says psy­chol­o­gist and au­thor Lars- Eric Petersen. “The brain at­tempts to get through life do­ing the least amount of heavy think­ing pos­si­ble.” And so, para­dox­i­cally, this means in­fants are su­pe­rior to us with re­gard to thought pat­terns be­cause their brains are still like a blank sheet of pa­per. They take in their en­vi­ron­ment im­par­tially and much more ac­cu­rately—sim­ply be­cause there is less stored ma­te­rial against which to com­pare new data.

But in cer­tain cir­cum­stances, this men­tal mode can be life-threat­en­ing. While a young child might stay still and marvel at an on­com­ing car, an adult would take coun­ter­mea­sures: We “see” the im­mi­nent peril—even if the driver may long since have been ready to brake. Uni­ver­sity of Bris­tol neu­ropsy­chol­o­gist Richard Gre­gory has con­firmed: “Yes, the brain plays tricks on us all the time—but with­out th­ese il­lu­sions, we couldn’t sur­vive.”



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