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Does “free will” stem from brain noise?

June 9, 2014
Courtesy of UC Davis
and World Science staff

Our abil­ity to make choic­es—and mis­takes—might arise from ran­dom fluctua­t­ions in the brain’s back­ground elec­tri­cal “noise,” ac­cord­ing to a study from the Uni­vers­ity of Cal­i­for­nia, Da­vis.

“How do we be­have in­de­pend­ently of cause and ef­fec­t?” said Jes­se Beng­son, a post­doc­tor­al re­search­er at the uni­vers­ity’s Cen­ter for Mind and Brain and an au­thor on a re­port on the work. “This shows how ar­bi­trary states in the brain can in­flu­ence ap­par­ently vol­un­tary de­ci­sions.”

The brain has a nor­mal lev­el of “back­ground noise,” Beng­son said, as elec­tri­cal ac­ti­vity pat­terns fluc­tu­ate across the brain. In the new stu­dy, de­ci­sions could be pre­dicted based on the pat­tern of brain ac­ti­vity im­me­di­ately be­fore a de­ci­sion was made.

Beng­son sat vol­un­teers in front of a screen and told them to fix their at­ten­tion on the cen­ter, while us­ing elec­tro­en­ce­pha­lo­grapy, or EEG, to rec­ord their brains’ elec­tri­cal ac­ti­vity. The vol­un­teers were in­structed to make a de­ci­sion to look ei­ther to the left or to the right when a cue sym­bol ap­peared on screen, and then to re­port their de­ci­sion.

The cue to look left or right ap­peared at ran­dom in­ter­vals, so the vol­un­teers could not con­sciously or un­con­sciously pre­pare for it.

The brain has a nor­mal lev­el of “back­ground noise,” Beng­son said, as elec­tri­cal ac­ti­vity pat­terns fluc­tu­ate across the brain. The re­search­ers found that the pat­tern of ac­ti­vity in the sec­ond or so be­fore the cue sym­bol ap­peared—be­fore the vol­un­teers could know they were go­ing to make a de­ci­sion—could pre­dict the likely out­come of the de­ci­sion.

“The state of the brain right be­fore pre­s­enta­t­ion of the cue de­ter­mines wheth­er you will at­tend to the left or to the right,” Beng­son said.

The ex­pe­ri­ment builds on a fa­mous 1970s ex­pe­ri­ment by Ben­ja­min Li­bet, who meas­ured brain elec­tri­cal ac­ti­vity im­me­di­ately be­fore a vol­un­teer made a de­ci­sion to press a switch in re­sponse to a vis­u­al sig­nal. He found brain ac­ti­vity im­me­di­ately be­fore the vol­un­teer re­ported de­cid­ing to press the switch.

The new re­sults build on Li­bet’s find­ing, be­cause they pro­vide a mod­el for how brain ac­ti­vity could pre­cede de­ci­sion, Beng­son said. Ad­di­tion­al­ly, Li­bet had to rely on when vol­un­teers said they made their de­ci­sion. In the new ex­pe­ri­ment, the ran­dom tim­ing means that “we know peo­ple aren’t mak­ing the de­ci­sion in ad­vance,” Beng­son said.

Li­bet’s ex­pe­ri­ment raised ques­tions of free will—if our brain is pre­par­ing to act be­fore we know we are go­ing to act, how do we make a con­scious de­ci­sion to act? The new work, though, shows how “brain noise” might ac­tu­ally cre­ate the open­ing for free will, Beng­son said.

“It in­serts a ran­dom ef­fect that al­lows us to be freed from sim­ple cause and ef­fect,” he said. The work is pub­lished on­line in the Jour­nal of Cog­ni­tive Neu­ro­sci­ence.


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Our ability to make choices—and mistakes—might arise from random fluctuations in the brain’s background electrical “noise,” according to a study from the University of California, Davis. “How do we behave independently of cause and effect?” said Jesse Bengson, a postdoctoral researcher at the university’s Center for Mind and Brain and an author on a report on the work. “This shows how arbitrary states in the brain can influence apparently voluntary decisions.” The brain has a normal level of “background noise,” Bengson said, as electrical activity patterns fluctuate across the brain. In the new study, decisions could be predicted based on the pattern of brain activity immediately before a decision was made. Bengson sat volunteers in front of a screen and told them to fix their attention on the center, while using electroencephalography, or EEG, to record their brains’ electrical activity. The volunteers were instructed to make a decision to look either to the left or to the right when a cue symbol appeared on screen, and then to report their decision. The cue to look left or right appeared at random intervals, so the volunteers could not consciously or unconsciously prepare for it. The brain has a normal level of “background noise,” Bengson said, as electrical activity patterns fluctuate across the brain. The researchers found that the pattern of activity in the second or so before the cue symbol appeared — before the volunteers could know they were going to make a decision — could predict the likely outcome of the decision. “The state of the brain right before presentation of the cue determines whether you will attend to the left or to the right,” Bengson said. The experiment builds on a famous 1970s experiment by Benjamin Libet, a psychologist at UCSF who was later affiliated with the UC Davis Center for Neuroscience. Libet also measured brain electrical activity immediately before a volunteer made a decision to press a switch in response to a visual signal. He found brain activity immediately before the volunteer reported deciding to press the switch. The new results build on Libet’s finding, because they provide a model for how brain activity could precede decision, Bengson said. Additionally, Libet had to rely on when volunteers said they made their decision. In the new experiment, the random timing means that “we know people aren’t making the decision in advance,” Bengson said. Libet’s experiment raised questions of free will — if our brain is preparing to act before we know we are going to act, how do we make a conscious decision to act? The new work, though, shows how “brain noise” might actually create the opening for free will, Bengson said. “It inserts a random effect that allows us to be freed from simple cause and effect,” he said. The work is published online in the Journal of Cognitive Neuroscience.