Does Random Brain Noise Enable Decision Making?


The human ability to make choices may come from random fluctuations in the brain’s background electrical noise, according to new research from University of California Davis. The study sought to discover why we appear to have free will and behave independently of cause and effect.

The brain has a normal level of background noise, according to Jesse Bengson, lead author, as electrical activity patterns rise and fall across the brain. Decisions could be predicted in the study, based on the pattern of brain activity just before a decision was made.

State of the Brain

In the study, the subjects sat in front of a screen and were instructed to fix their attention on the center. Electroencephalography, or EEG, was used to record their brains’ electrical activity.

The volunteers had to make a decision to look either to the left or to the right if a cue symbol appeared on the screen, then were to report their decision. Volunteers could not consciously or unconsciously get ready for the cue, since it appeared at random intervals.

“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.

Free Will and Brain Noise

This experiment investigates questions raised by a well-known 1970s experiment by psychologist Benjamin Libet.

Libet’s study also determined brain electrical activity, in this case directly 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.

Libet’s experiment raised questions about free will. If our brain is getting ready to act before we know we are going to act, how can we make a conscious decision to act? This new research demonstrates how “brain noise” might actually generate the opportunity for free will, says Bengson.

“It inserts a random effect that allows us to be freed from simple cause and effect,”

he said.

A given sensation is limited by the signals and noise in sensory receptors, which allow organisms to encode information based on their senses. It is frequently necessary to amplify a weak signal before it can be used.

Amplification can only help if the signal at the synapse is stronger than the noise. When a single photon of light strikes a rod photoreceptor in the retina of an eye, for example, amplification is required.

The noise that is a built-in feature of the cell can be overpowered by the small stimulus thanks to the amplification. However, as the stimulus increases, so does the noise. Due to this phenomenon, researchers are also trying to understand how sensory receptors can effectively reduce synaptic noise while boosting the signal to threshold.

  1. Jesse J. Bengson, Todd A. Kelley, Xiaoke Zhang, Jane-Ling Wang, and George R. Mangun. Spontaneous Neural Fluctuations Predict Decisions to Attend. Journal of Cognitive Neuroscience doi:10.1162/jocn_a_00650

Last Updated on February 17, 2023