People tend to judge their confidence while making choices several times a day. Researchers have uncovered the biological mechanisms behind the belief that a choice is likely to be correct.
Many studies have shown that choice certainty is closely associated with reaction time, and with decision accuracy.
The new study tested the possibility that the same brain cell mechanism that underlies decision-making might also underlie judgments about certainty.
"Choice certainty allows us to translate our convictions into suitable actions," said Dr. Roozbeh Kiani at the University of Washington (UW).
In the study, rhesus monkeys played a video game in which they watched a dynamic, random dot display, while they had to determine the direction of motion.
The difficulty of the task was varied by both the percentage of moving dots and the viewing time. After a short delay, the fixation point faded, which cued the monkey to indicate its choice of direction by moving its eyes toward one of two targets.
The monkey would receive a reward for each correct choice, and no reward for an incorrect choice.
On a random half of the trials, the monkey could pick a third, fixed-position target that guaranteed a small reward, instead of making a choice.
While watching the moving dots, the monkeys didn't know whether the third option would be offered. The sure bet was shown during the short delay.
"The monkeys opted for the sure target when the chance of making a correct decision about the motion direction was small," noted the researchers.
They suggested that the monkeys chose the sure bet because of uncertainty, not because that round of the game was too hard.
The researchers recorded activity from 70 brain cells while the monkeys made their decisions, and the cells were located in the lateral intraparietal cortex of the brain, which plays a role in spatial sensations.
In rhesus monkeys, the lateral area of the parietal lobe is attuned to movement.
After analysing detailed data from the study results, the researchers showed that the mechanism underlying certainty in these brain cells is linked with the same evidence accumulation that underlies choice and decision time.
"Some research has suggested that brain cells in an area associated with reward expectation or conflict are associated with decision uncertainty. However, these brain cells presumably receive this information from neurons involved in decision making," noted Kiani.
The results of this study advance the understanding of brain cell mechanisms that underlie decision making by coupling for the first time the mechanisms that lead to decision formation and the establishment of a degree of confidence in that decision.
The results of the study have been published in the latest edition of Science.