An Intriguing ‘Laboratory’ of Visual Illusions

Professor Andrew Stockman

This exhibition of Visual Illusions comprises 3 videos compiled by Professor Andrew Stockman of the UCL Institute of Ophthalmology.

Andrew was part of the Bloomsbury Festival Creative Development Lab over the winter of 2019-2020.  When he showed examples of illusions to the participants – professional artists, fellow academics and local residents – we were intrigued and entertained.

How the eyes and brain fail to respond correctly to the visual input is brought to life in these three videos that feature visual illusions in Colour and Brightness, Depth and Shape, and Geometric Patterns.

Illusions are fun but they can also give us important insights into how our eyes and brain work.

We think of what we see as being a true representation of what is out there in the world, but these illusions show that this is often not the case.  Flat images of the outside world are formed by our eyes on their rear surfaces. There they are sensed by light-sensitive photoreceptors and signals encoding the images are sent to our brains. For us to survive, the representation of the world we construct in our brains from those flat images must be good enough and created quickly enough to allow us to interact with all manner of stationary and moving objects in the world. To reconstruct the outside world, the brain uses assumptions and short cuts to interpret the information that it receives. These often work well, but sometimes they fail, and so produce the visual illusions that you can see in these illusions. Enjoy and be intrigued. A brief explanation of each illusion is given.

Professor Andrew Stockman

Andrew is a leading vision scientist, who specialises in physiological optics, colour vision, rod vision, visual adaptation, temporal sensitivity, retinal processing and clinical psychophysics.

Colour and Brightness Illusions

This video looks at how the eye and brain sometimes fail to process colour and brightness correctly, so that the colour or brightness you see in a video does not correspond to its actual colour or brightness. Examples include various colour after-effects, colour and brightness contrast, the Stroop effect, and other illusions.

Depth and Shape Illusions

This video looks at how the eye and brain sometimes fail to process depth and shape information correctly. Examples include depth-from-shading illusions, pictures with ambiguous depth cues that can be seen in different ways and illusions in which shapes appear distorted.

Geometric Pattern Illusions

This video presents illusions in which lines or shapes in a two-dimensional drawing appear strangely distorted. Many of the distortions are related to the brain seeing or reconstructing the two-dimensional picture as a three-dimensional scene. Examples include the Müller-Lyer, Zöllner, , Ehrenstein, Fraser, Wundt, Hering, Poggendorf, Ponzo and Ebbinhaus illusions.