Researchers have found that the size of opening for light in our eye (pupil) changes even if we are only thinking of bright and dark objects and/or scenes.
“Visual imagery is a private and subjective experience which is not accompanied by strongly felt or visible physiological changes,” explained psychological scientist and lead researcher Bruno Laeng of the University of Oslo. “It is a particularly difficult topic to research, as years of controversy about the nature of mental imagery testifies.”
Researchers, in the present study, used eye-tracking device to monitor pupil size in volunteers. In the study, participants were asked to look at a screen showing triangles of different levels of brightness. Then the participants were asked to imagine the triangles. Researchers found that the pupil size decreased, when the participants imagined brighter triangles while the pupil size was larger in case of imaging darker triangles.
In other experiments, researchers found that the size pupil changed when the participants thought of a sunny sky, a dark room, or a face in the sun compared with a face in the shade.
Further experiments also showed that these changes are not voluntary.
“Because humans cannot voluntarily constrict the eyes’ pupils, the presence of pupillary adjustments to imaginary light presents a strong case for mental imagery as a process based on brain states similar to those which arise during actual perception,” Researchers wrote.
Our Pupils Adjust as We Imagine Bright and Dark Scenes – APS (http://goo.gl/CGohH5)
Bruno Laeng, Unni Sulutvedt (2013). The Eye Pupil Adjusts to Imaginary Light Psychological Science DOI: 10.1177/0956797613503556