Look into the mirror before you make an important decision, as the reliability of your decisions can be predicted by the size of your pupils, according to a new study.
The precision with which people make decisions can be predicted by measuring pupil size before they are presented with any information about the decision, researchers said.
The study, conducted by Peter Murphy and colleagues at Leiden University in the Netherlands, showed that spontaneous, moment-to-moment fluctuations in pupil size predicted how a selection of participants varied in their successful decision making.
A larger pupil size indicated poorer upcoming task performance, due to more variability in the decisions made once the relevant information was presented.
The authors also found that certain individuals who had the largest pupils overall also tended to be the least consistent in their decisions.
The results were obtained by measuring pupil size before each segment of the task began and monitoring each participant's subsequent performance in deciding which direction a cloud of dots was moving in.
These results were then combined with a simple mathematical model that described how people make decisions.
These findings show that a person's state of responsiveness, as measured by pupil size, is a key determinant of the variability of the decisions they make about the world around them.
When hyper-responsive, our decision making appears to be less reliable and will more likely lead to undesirable outcomes.
Critically, the findings also open up areas for future research aimed at improving the precision with which we make decisions, to help us achieve better outcomes from the choices that we make.
The results were obtained by measuring the pupil size of 26 volunteers as they performed a visual choice-based task designed to mimic the kinds of challenging perceptual decisions that are frequently encountered in everyday life.
Pupil size gives a good indication of how responsive a person is at any given moment, with larger pupils correlating with increased responsiveness, though little was previously understood about how pupil size might relate to our ability to make reliable perceptual judgements.
"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 Murphy.
The study was published in the journal PLOS Computational Biology.