Pupil size adjusts when we imagine light or dark settings

It is common knowledge that our pupils adjust in size when exposed to light or dark enviornments. But new research published in the journal Psychological Science suggests that the size of our pupils also changes when we imagine these surroundings, even when our eyes are not directly exposed to light and dark.

Researchers from the University of Oslo in Norway say their findings may be useful in studying the mental experiences of patients who suffer from severe neurological disorders.

To reach their findings, the investigators monitored pupil diameters of study participants by using an infrared eye tracker throughout a series of experiments.

The first experiment required participants to look at a screen that showed triangles with various brightness levels. They were then asked to actively imagine the triangles.

Results of this experiment revealed that the subjects' pupils varied in size, depending on the brightness of the triangle they were imagining. When they imagined brighter triangles, their pupils were smaller but enlarged as they imagined darker triangles.