Download issue (PDF) - Nieman Foundation - Harvard University

Brain PowerWatching the Human Brain Process Information‘We measure the amount of brain activity while somebody’s doing something.You can’t generate more activity beyond a certain point. There’s an upper limit.’Marcel Just is the director of theCenter for Cognitive Brain Imaging atCarnegie Mellon University, where heand his team use functional MagneticResonance Imaging ( fMRI) scans toexamine brain activation as peopleperform various high-level tasks suchas spatial thinking, problem solving,multitasking, and real-time, dynamicdecision making. In a conversationwith Nieman Reports editor MelissaLudtke, Just describes what imaginghas revealed—and what it one daymight reveal—about how the humanbrain processes information. Justbegins by talking about how the brain“codes” concepts. Edited excerpts follow:Melissa Ludtke: When you talk abouttrying to unravel or study the code ofthe mind, what do you mean by “code”?Marcel Just: Most people have seenthe illustrations in magazines andnewspapers of hot spots in the brainwhen a person is thinking. Thoseaccurately depict where the activityis and tells which brain areas are inplay. For the first time we’ve been ableto identify what concept a person isthinking about from their brain activity.We use machine-learning algorithmsto put together what is being codedin various places in the brain so thatwe can determine what concept theperson is thinking about. In effect,we can read their mind.The second finding is that the patternof brain activity for one of theserelatively concrete concepts is commonacross people. If we train the computerprogram to recognize the patterns for60 words (concepts such as apple,shoe, tomato) on one group of peopleand then a new person comes in whohas never been encountered before,the computer can tell what the newperson is thinking fairly well.It’s the first time we’ve been able toanswer the question that philosophershave been asking: Is your concept ofsomething the same as my concept ofit? For these concrete nouns it is. Andif you train the computer to recognizethose concepts in one language, it canthen identify what the bilingual personis thinking about when he or sheencounters those concepts in anotherlanguage. So the brain representationsare not only common across people,but they’re common across languagesfor translation equivalents.Ludtke: I’m wondering how you seethe notion of multitasking in termsof brain function and how the braincopes with distraction.Just: In many of our studies we areinterested in finding out the upperlimits of our thinking capability.We often put the brain on a mentaltreadmill and just see how high wecan put it. With multitasking we askpeople to do two relatively high-leveltasks simultaneously. We’ve aimed ata real-world issue: using a cell phonewhile driving and we have measuredthe brain activity with people whoare using a driving simulator whilealso listening to someone talk at thesame time.We find there’s an upper limit tohow much information a person canprocess per unit time. If you’re workingon two tasks simultaneously, you cando that, but there will be less activityallocated to each task. For example,when we compare how much brainresource allocation there is to justdriving while listening to someonespeak, we find that while listening tosomeone speak the amount of brainresources allocated to the driving goesdown by 37 percent. It’s an enormousdifference, and it shows up in the drivingsimulator in how well you maintainyour lane, whether or not you hit theside of the road. It’s possible to drivewhile listening to someone talk. Weall do it and sometimes using a cellphone. However, there’s absolutely noquestion that it takes away from thequality of the driving.You ask about distractions. Particularlywith respect to automaticity,which we study, that’s a very interestingquestion. There are driverswho say, “Oh, well, when the drivinggets tough, I’ll start ignoring my cellphone partner or my passenger ormy talk radio and I’ll just focus onthe driving.” We ran a study in whichwe told experienced drivers that theyare going to hear someone speak butto just ignore them and do the mainspatial task. But we found that theycouldn’t ignore the speaking becausethe processing of spoken languageis so automatic that you can’t turnit off. You can’t will yourself not tounderstand a speaker’s next sentence.It just gets in.In watching the brain’s activity, wecan see this. When the next sentencestarts, even though our subjects arepoised to ignore it, the activationstarts up in the language areas andthe activation in the other areas of thebrain—for the other task—goes down.There is no blocking out someone talkingto you. It goes in and it consumesbrain resources.Ludtke: I’ve been reading about howpeople aren’t processing things as effectivelyas they think they are whenthey’re multitasking.Just: There are dozens of cases wherewe overestimate our thinking ability.And it never goes in the other direction.It’s always “Oh, yes, of course Ican do this.” However, in perceptualNieman Reports | Summer 2010 13