Your Pupils May Expand When You Daydream

But researchers aren’t totally sure why or how the two are connected

Eye Pupil
Ali T/Flickr CC BY-NC 2.0

The human brain is prone to daydreaming. You might be doing boring chore or focused on a serious task at hand, for example, writing a blog post, and then suddenly your mind starts to drift away.

Daydreaming has its neurological benefits, and neuroscientists hope that studying how the mind wanders could help answer some basic questions about the brain. But how do you tell when someone is daydreaming, really? Where is the line between attention and la la land? One team suspects that pupils may hold clues to when the mind shifts from the outside world to exploring inner thoughts, memories and imaginary constructs of the mind, Moheb Costandi reports for BrainDecoder.

While most work in this area has focused on scanning specific parts of the brain for signs of mind wandering activity, previous studies hinted that pupil dilation might be a good indicator of daydreaming. So Mahiko Konishi, a neuroscience grad student at the University of York, decided to investigate. Konishi and his colleagues set up three experiments, Costandi explains, in which study participants performed tasks while the scientists scanned their brains and/or measured their pupil dilation before and during the tasks.

When confronted with easier versus harder versions of the same task, more peoples’ minds strayed during the easy version, Costandi writes. In another experiment, people who had larger dilated pupils reacted more slowly as they tackled the task at hand. Those same people said they daydreamed more than others.

Clearly, there’s some kind of connection — direct or indirect — between pupil size and daydreaming, but the researchers aren’t sure of the ins and outs of the relationship. Konishi presented the results at an annual meeting of the Association for the Scientific Study of Consciousness in Paris a couple weeks ago.

On the research front, pupil diameter could provide an easy way to study daydreaming. After all, measuring pupil size is a lot easier than scanning the brain. But in the future, the researchers hope their work could have some more practical applications, writes Costandi. For example, detecting mind wandering could prove useful in preventing car accidents.

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