Was This in Doubt?

We weren’t made to multitask
It’s read­i­ly appar­ent that han­dling two things at once is much hard­er than han­dling one thing at a time. Spend too much time try­ing to jug­gle more than one objec­tive and you’ll end up want­i­ng to get rid of all your goals besides sleep­ing. The ques­tion is, though, what makes it so hard to process two things at once?

Two the­o­ries try to explain this phe­nom­e­non: “pas­sive queu­ing” and “active mon­i­tor­ing.” The for­mer says that infor­ma­tion has to line up for a chance at being processed at some focal point of the brain, while the lat­ter sug­gests that the brain can process two things at once – it just needs to use a com­pli­cat­ed mech­a­nism to keep the two process­es sep­a­rate. Recent research from MIT points to the for­mer as an explanation.

Yuhong Jiang, Rebec­ca Saxe and Nan­cy Kan­wish­er, in a study to be pub­lished in the June issue of Psy­cho­log­i­cal Sci­ence, a jour­nal of the Amer­i­can Psy­cho­log­i­cal Soci­ety, exam­ined the brain activ­i­ty involved in mul­ti­task­ing. They gave peo­ple two sim­ple tasks. Task one was iden­ti­fy­ing shapes, and for some sub­jects, task two was iden­ti­fy­ing let­ters, for oth­ers it was iden­ti­fy­ing col­ors. The sub­jects were forced to switch from one task to the oth­er in either one and a half sec­onds or one tenth of a sec­ond. When they had to switch faster, sub­jects would take as much as twice as long to respond than when switch­ing more slowly.

Using MRI tech­nol­o­gy, Jiang, Saxe and Kan­wish­er exam­ined sub­jects’ brain activ­i­ty while per­form­ing these tasks. They observed no increase in the sort of activ­i­ty that would be involved in keep­ing two thought process­es sep­a­rate when sub­jects had to switch faster. This sug­gests that there are no com­pli­cat­ed mech­a­nisms that allow peo­ple to per­form two tasks at once. Instead, we have to per­form the next task only after the last one is finished.