A new study found that even imperceptible changes in our state of arousal can influence the confidence we have in our visual experiences.

Image credits Nan Palmero / Flickr.

A team from University College London has found that subtle increases in arousal — even ones so slight we aren’t even consciously aware of — affect how confident participants felt about what they were seeing when asked to complete a simple task.

The team asked 29 volunteers to follow a cloud of moving dots on a screen, decide whether they were moving to the left or to the right, then rate how confident they are in their answer. Without the volunteers knowing, some of the challenges started with a disgusted face appearing on the screen — too briefly for the participants to consciously perceive it.

But their unconscious did pick up on the image, causing their heart rate to increase and their pupils to dilate. The team found that even when the dots were made noisier and harder to make out, participants in this aroused state maintained their confidence in the answers they were giving.

“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 from the 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.”

Previously, Allen explains, researchers have viewed the brain like “a scientist or statistician” who evaluates the quality of our experiences — and, based on this, it gives us our feeling of confidence. The study challenges this view by tying our confidence to physical states .

“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,” said Allen.

He added that the findings suggest our ability for conscious introspection is much more dependent on our body’s state than previously assumed. Professor Geraint Rees, Dean at the UCL Faculty of Life Sciences and co-author of the paper, believes that the findings could help understand people struggling with depression. Because anxiety and depression alter the body’s state of arousal, patients suffering these conditions might perceive a too certain or uncertain world.
The full paper “Unexpected arousal modulates the influence of sensory noise on confidence” has been published in the journal eLife.