London: A new study from UCL researchers finds that subtle, unconscious
increases in arousal – indicated by a faster heartbeat and dilated
pupils – shape our confidence for visual experiences. The study, published in eLife, investigated the
effect of unconscious arousal on how confident participants felt about
what they were seeing when completing a simple task. “Typically when we see something, we have insight not only
into what it is that we’ve seen, but also how clearly we’ve seen it,”
explains lead author Micah Allen (UCL Institute of Neurology). “If the
picture is clouded or obscured, our feeling of confidence in what we’ve
seen is lessened. This ability to accurately appraise our own
experiences is an important part of our everyday lives. To explain this
ability, research has previously suggested that the brain acts a bit
like a scientist or statistician, evaluating the quality of our
experiences to inform how confident we feel. Our study challenges this
view, instead finding that confidence is closely related to unconscious
states of physiological arousal.”
In the study, the researchers had 29 volunteers view a
cloud of moving dots on a screen, decide whether the dots moved to the
left or right, and rate their confidence in this decision. Unbeknownst
to the volunteers, on some trials a startling image of a disgusted face
appeared too briefly to be consciously perceived, causing their heart
rate and pupil dilation to increase. Although the volunteers’ confidence
was reduced when the dots were noisier and more difficult to detect,
this effect was counteracted by the increased arousal.
“Our results suggest that subtle, unconscious changes in
the physiological state of our bodies impact how we perceive
uncertainty. Interestingly, we found that not only did confidence
correlate with how fast a participant’s heart beat on each trial, but
that artificially increasing arousal actually caused participants to act
as if they were blind to the quality of their visual experiences. This
suggests that our capacity for conscious introspection is much more
embodied than previously thought,” Micah Allen added.
Co-author Professor Geraint Rees (Dean, UCL Faculty of Life
Sciences) said: “As disorders such as depression and anxiety can be
linked to altered states of arousal, our findings raise the possibility
that patients suffering from these conditions might perceive an
unrealistically certain or uncertain world.”
The research was supported by funding from Wellcome, the European Research Council and the Swiss National Science Foundation.