Not so private: saccadic movements give clues about decisions

New research led by scientists at the University of Colorado Boulder suggests that the eyes may actually be the window to the soul or, at least, the way humans move their eyes can reveal valuable information about how they make decisions.

The vigor of saccadic movements reflects the increase in decision variables during deliberation

Highlights

During deliberation, while calmly considering our options, the neural activities representing the decision variables that reflect the goodness of each choice increase in various regions of the cerebral cortex.

If the options are represented visually, we do saccadic movements, focusing our gaze on each option.Does the kinematics of these saccadic movements reflect the state of the decision variables? To test this idea, we engaged human participants in a decision-making task in which they considered two difficult choices that required walking across various distances and inclines. As they deliberated, they made saccadic movements between symbolic representations of their choices. These saccadic movements of the deliberation period did not influence the effort they would make later, but the velocities of the saccadic movements increased gradually and differentially: the rate of increase was faster for saccadic movements toward the option they then indicated as their choice. In fact, the rate of increase codified the difference in the subjective value of the two options. Importantly, the participants did not reveal their choice at the end of the deliberation, but waited for a period of delay and finally expressed their choice by making another saccadic move.Surprisingly, the vigor of this saccadic movement was reduced to baseline and no longer codified subjective value. Thus, saccadic vigor seemed to provide a real-time window into the hidden process of evaluating options during deliberation.

Comments

The new findings offer researchers a rare opportunity in neuroscience: the opportunity to observe the inner workings of the human brain from the outside. Doctors could also use the results to, one day, test their patients for diseases such as depression or Parkinson’s disease.

«Eye movements are incredibly interesting to study,» said Colin Korbisch, a doctoral student in the Paul M. Rady Department of Mechanical Engineering at CU Boulder and lead author of the study.»Unlike your arms or legs, the speed of eye movements is almost entirely involuntary. It’s a much more direct measure of these unconscious processes happening in your brain.»

He and his colleagues, including researchers at Johns Hopkins University in Baltimore, published their findings in the journal Current Biology.

In the study, the team asked 22 human subjects to walk on a treadmill and then choose between different settings displayed on a computer screen: a short hike down a steep slope or a longer hike on flat terrain.

The researchers found that the subjects’ eyes gave them away: Even before making their decisions, treadmill users tended to move their eyes faster when looking toward the options they ultimately chose.The more vigorously they moved their eyes, the more they seemed to prefer their choice.

Source — https://www.intramed.net/102809