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Blue plaque to commemorate Professor Richard Gregory.

Cafe Wall

Blue plaque unveiling

11 May 2017

A blue plaque to commemorate the life and work of a great interdisciplinary thinker, whose interest was in optical illusions and what these revealed about human perception, will be unveiled this month.  Bristol Vision Institute (BVI) at the University of Bristol organised a plaque to honour Professor Richard Gregory, CBE, DSc, FRSE, FRS (1923-2010), a  leading Bristol academic and psychologist.

The plaque will be unveiled by the Lord Mayor with family, friends and colleagues, at the Workhouse Café, at the bottom of St Michaels Hill, a central point for vision scientists. This cafe was where Richard rediscovered an illusion contained in the tiles. Professor David Bull, Director of BVI and Professor of Signal Processing in the Department of Electrical and Electronic Engineering at the University of Bristol, said: “Richard was an experimental psychologist whose work has been crucial to our understanding of sensory, and in particular visual, perception and illusion.

“The plaque commemorates Richards’s significant achievements including the rediscovery of the café wall illusion, and helps celebrate his connection to Bristol. We hope the unveiling will ignite thought and intrigue of this and other illusions and historical sites in and around Bristol. ”

What is the Café Wall Illusion?

The Café Wall Illusion is a geometrical-optical illusion, which appears on the “Workhouse Café” at the bottom of St Michael’s Hill. It has come to be a great Bristol Landmark. The illusion is made of green and cream tiles that, although perfectly straight and parallel, appear to be long wedges. 

Richard Gregory wrote several books on vision and was especially interested in explaining illusions. In order to understand this mysterious illusion, he first built a wooden chessboard where every other row could be slid across. He found that there was no illusion if there was no gap between the rows; so he had to add a metal strip, then there was a good wedge illusion which could reversed by moving the sliding tiles. More experiments were done in his lab and it became rather famous.  

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