We perceive the world through the processing of information given by our senses. Sometimes, this processing is faulty leading to illusions: shapes or sounds that we perceive differently from their physical reality. These illusions have delighted children and scientists alike for centuries. This lecture reveals how simple geometric illusions can be modelled mathematically, based on our understanding on how visual signals are coded and decoded by the brain, leading to a better understanding of how we process information. This lecture was recorded by Alain Goriely on the 17th of June 2025 at Barnard's Inn Hall, London. Alain is Gresham Professor of Geometry. He is currently the Director of the Oxford Centre for Industrial and Applied Mathematics and was elected as a Fellow of the Royal Society in 2022. The transcript of the lecture is available from the Gresham College website: https://www.gresham.ac.uk/watch-now/deceived-brain Gresham College has offered free public lectures for over 400 years, thanks to the generosity of our supporters. There are currently over 2,500 lectures free to access. We believe that everyone should have the opportunity to learn from some of the greatest minds. To support Gresham College's mission, please consider making a donation: https://www.gresham.ac.uk/get-involved/support-us/make-donation/donate-today Website: https://gresham.ac.uk X: https://x.com/GreshamCollege Facebook: https://facebook.com/greshamcollege Instagram: https://instagram.com/greshamcollege Bluesky: https://bsky.app/profile/greshamcollege.bsky.social TikTok: https://www.tiktok.com/@greshamcollege Support Us: https://www.gresham.ac.uk/get-involved/support-us/make-donation/donate-today Support the show
