What is it about?

We presented a simple moving square and asked people to report the locations of tests flashed before and after the square moved. Surprisingly, the tests were seen far from where they were actually presented. They were instead seen in their positions relative to the square, as if it hadn't moved at all. The size of the illusory displacements were as large as the distance the frame travelled.

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Why is it important?

Our eyes move three times per second and each time they do, the world in front of us flies across the retina at the back of our eyes; yet as far as we can tell, nothing appears to move. The brain has its own type of frame-based steadycam so that we don't see a shaky image like we do in handheld movies taken with a smartphone. We believe our simple moving square triggers the same process that stabilizes our world during eye movements. The motion is discounted and locations are seen relative to the frame, a small square in our case, but the whole visual scene in the case of our eye movements. This simple model of visual stabilization will allow us to track down where and how this process occurs in the brain.


It was a challenge to complete this work during the COVID-19 pandemic. We combined in person experiments at Dartmouth College in the US with online experiments at York University in Canada.

Patrick Cavanagh
York University

Read the Original

This page is a summary of: Paradoxical stabilization of relative position in moving frames, Proceedings of the National Academy of Sciences, June 2021, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2102167118.
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