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IS SEEING BELIEVING: WHAT IS THE VISUAL SYSTEM LOOKING FOR, AND HOW CAN IT BE TRICKED?

Dr Hugh Matthews

Reader in Sensory Physiology, Department of Physiology, Development & Neuroscience, University of Cambridge

The human visual system works over an astronomical range of illuminating intensities: a white sheet of paper would be a billion times brighter in outdoor sunlight than on a starry moonless night. We are still able to see the sheet of paper in both cases, although much less detail is visible in near-darkness. The process of light adaptation is a sort of automatic gain control which matches the performance of the rod and cone photoreceptors in the eye (the subject of my own research) and the neural circuits processing their signals in the retina to the intensity of light they are receiving at any particular moment. Consequently, the visual system is principally interested in contrast: differences in brightness, colour and movement within the visual scene.

In my talk at this year’s Science Festival I will explain how the visual system achieves this wide operating intensity range, and how and why it uses contrast to visualise objects. I will also demonstrate how this strategy allows it to be tricked to produce visual illusions.

Following my talk I will be joined by my colleagues Professor Simon Laughlin and Dr David Williams for a panel discussion about the performance and limits of vision in humans and animals.

SEE HUGH’S EVENTS:

Is seeing believing

11AM – NOON
SAT 17 MAR
PAGE 15

Vision in nature: performance and sensitivity

3.15PM – 4.15PM
SAT 17 MAR
PAGE 17