Various studies suggest that the pupil dilates when a person is making decisions. It is also closely associated with the release of neurotransmitters in the brain. But it remains unknown for scientists what specific decisions trigger the pupils to dilate. Studies show that even before a person decide, their pupil dilates and it could differ based on what choices they make.
A study published in the Proceedings of the National Academy of Sciences by University of Pennsylvania neuroscientist Michael Platt and colleagues noted that it is also important to know the direction where they gaze which could reveal the decision they will make.
Both biomarkers, pupil dilation, and gaze give clues into the underlying biological processes that happen during the decision-making phase, according to Medical Xpress.
"Understanding this can help explain why people make the decisions that they do, why one individual might make a different decision than another, even why people who seem to make the same decision might do so for different reasons, in terms of the biology," Platt said.
Pupil size is related to the person's attitude
Many studies show that pupil size increase during effortful decision making. These changes are mediated by central neuromodulatory systems that affect the brain's internal state that is responsible for decision making.
On the other hand, some studies suggest that the termination of decision processes activated these neuromodulatory systems that consequently affect the postdecisional brain state. But a study by Jan Willem de Gee, Tomas Knapen, and Tobias H. Donner in 2014 contradicted this proposal and suggested an intradecisional role.
The researchers measure the pupil size of the participants while making protracted or lengthened decisions of the presence (yes) or absence (no) of the visual contrast signal in dynamic noise. They found that dilation of the pupil was significantly driven by sustained input during the decision-making process.
In short, the pupils of the participants were larger before "yes" choices than the "no" choices. The pupils reflected the individual criterion in which it is strongest during conservating subjects leading them to choose yes against their bias.
Therefore, the researchers concluded that the neuromodulatory systems that control the size of the pupils are affected during the decision-making process which reveals that the choice that a person will make is related to the attitude of the decision-maker.
Gaze and pupil dilation reveals decision
Meanwhile, a study by Penn neuroscientist Michael Platt and colleagues relates gaze and pupil dilation on loss-averse decisions in which they found is prevalent. Loss-averse decisions are the event wherein one avoids losing at the expense of gaining.
The researchers used a computational process model in tracking gaze and pupil dilation to create a framework based on physiological processes during decision making that leads to accepting or rejecting gambles that have equal odds of winning and losing.
They found that in loss-averse decisions, participants have shown preference on gaze toward losses and pupil dilation when accepting gambles. In other words, where people look presents their biases, and people can be predicted when they will accept a gamble based on the size of their pupil.
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