A French research team collected 32 volunteers for this experiment, the volunteers are asked to form words from a number of letters on a computer screen. Meanwhile, the researchers scanned the respondents’ brains by using functional magnetic resonance imaging to observe component of the brain drive, that is, the activities in the medial prefrontal cortex. Firstly, all capital letters appeared on the computer screen, respondents who correctly spell the words could be got material incentives, the researchers found that the higher the prize money, the more active of the brain activities of the medial prefrontal cortex. Secondly, the test become more difficult, lower-case letters appeared with the capital letters at the same time, the respondents must spell a word with lower-case letters or capital letters, it is also a piece of cake, the activities in the brain still rise with the increased prize money, the scan showed that the task would be distributed to the hemispheres of the brain by the frontal, so that the two parts carried out the different tasks. Finally, the researchers added a group of letters, the accuracy of the respondents’ answers was decreased significantly. Koechlin, leader of this research project, said: "the respondents always seem to forget one of three tasks."

People has two frontal lobe in the brain, when faced with two tasks, the medial prefrontal cortex would automatically divide the task, which make one mind with two tasks become a reality, but if you try to handle three different things at the same time, things will become worse. "This study may explain why people were confused when faced with a number of options." Koechlin said. Previous studies showed people were always willing to make choices like either-or choice. "When you faced more than two choices, people would be irrational and confused, this may related to the brain can only do dual tasking.

Neuroscientist Rene Maroie who is from the Vanderbilt University in the United States said this finding was so surprising. He said this would imply that people tried to do two or more different things simultaneously. For example, writing reports as well as viewing e-mail, however, if the message needs to response, the brain can do nothing.

David Meyer, from the University of Michigan, announced his view which is that the study can’t prove that the brain can’t simultaneously deal with three tasks. " At a very critical juncture, the frontal occur abnormal reaction, which allows the implementation of multi-tasking."