PUPIL SIZE SHOWS RELIABILITY OF DECISIONS
The precision with
which people make decisions can be predicted by measuring pupil size before
they are presented with any information about the decision, according to a new
study published in PLOS Computational Biology this week.
The study, conducted
by Peter Murphy and colleagues at Leiden University, 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 reveal
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.
Dr Murphy comments,
"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.
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."
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