Pupil Size Reveals Reliability of Decisions, Study

First Posted: Sep 19, 2014 06:43 AM EDT

A new study reveals that the size of the pupil helps predict the precision with which people make decisions.

According to the latest study led by Peter Murphy of the Leiden University, measuring the pupil size before presenting any information to the people, helps predict the accuracy with which the decision was made. The finding is based on the measurement of the pupil size of 26 subjects who were made to participate in a visual choice-based task that was designed to imitate the kinds of challenging perceptual decisions frequently encountered in everyday life.

Dr Murphy explains, "We are constantly required to make decisions about the world we live in. Researchers have long known that the accuracy and reliability of such everyday decision making can be tremendously variable for different people at different times, but we understand quite little about where this variability comes from. In this study, we show that how precise and reliable a person is in making a straightforward decision about motion can be predicted by simply measuring their pupil size..."

The researchers measured the pupil size at the beginning of a task. The participants' performance in deciding which direction the cloud of dots was moving in was monitored. They then combined the results with a simple mathematical model that described how people make decisions.

Pupil size is a strong indicator of how responsive a person is at a given situation. Larger pupil correlates with increased responsiveness, according to ScienceDaily.

The study shows that spontaneous, moment-to-moment fluctuation in the size of the pupil helped predicting how the selection made by the participants varied in their successful decision making. A larger pupil hinted towards poorer upcoming task performance. This was due to greater variability in the decisions made when the relevant information was given. Those with largest pupils remained least consistent in their decision making.

The findings show that a person's state of responsiveness that is measured by the size of the pupil acts as a key factor for the variability of the decisions he or she makes. Being in a hyper-responsive state shows that the decision-making is less reliable and will lead to undesirable outcome.

"This finding suggests that the reliability with which an individual will make an upcoming decision is at least partly determined by pupil-linked 'arousal' or alertness, and furthermore, can potentially be deciphered on the fly. This new information could prove valuable for future research aimed at enhancing the precision of decision making in real time," said Dr. Murphy.

The finding is documented in PLoS Computational Biology.

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