The eyes are often referred to as the "windows to the soul." In fact, there is a grain of neurobiological truth to this. An international research team from the Universities of Göttingen and Tübingen, Germany, and Baylor College of Medicine in Houston, are now able to provide answers as to why pupil size is influenced by not only sensory stimuli like light, but also by our internal state such as fear, excitement or attention.

The findings, appearing in the current edition of Nature, help to explain whether these rapid, state-dependent changes in pupil size found not only in humans but also in other vertebrates, affect the way we perceive our surroundings.

Artificial intelligence for data analysis

Researchers started their work by investigating how state-dependent changes in pupil size affected the vision of mice.

"While the eyes convert light to neural activity, it is the brain which is crucial for the interpretation of visual scenes," said Dr. Katrin Franke, research group leader at the Institute for Ophthalmology Research at the University of Tübingen and first author of the study.

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