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Seeing the world in double vision

May 23rd, 2008

Renowned visual neuroscientist Melvyn Goodale says that two different visual systems guide our lives, one of which is largely unconscious.

Ever remarked at your ability to find your way through your house in the dark? Or noticed how you instinctively know where to find your coffee cup when typing away at your desk?

These automatic actions make life much easier, but they belong to a different visual system to that which simply takes in and registers images of our surroundings.

"We need vision to give us detailed knowledge of the world beyond ourselves, knowledge that allows us to recognize things from minute to minute and day to day. And we also need vision to guide our actions in that world at the very moment they occur. These are two quite different job descriptions," says Professor Melvyn Goodale, who holds the Canada Research Chair in Visual Neuroscience at the University of Western Ontaria in Canada, and who will visit Monash on 17 June for a guest lecture.

Famous for his pioneering research into the way that vision integrates with motor skills (also known as 'visuomotor skills'), Professor Goodale recalls how his theory of this second 'vision-for-action-system' initially met with scepticism from peers.

"The idea of two visual systems in a single brain might initially seem counterintuitive or even absurd… For most of us, it seems obvious that the visual image that allows us to recognize a coffee cup is the same one that guides our hand when we pick it up. But this belief is an illusion. Over the last decade or so, our research has made it clear that the visual system that gives us our visual experience of the world is not the same system that guides our movements in the world," he says.
After the first 'vision-for-perception' system registers a particular object and its purpose, the second visual system then takes control, "computing just how far away the cup is from our hand and how our fingers should be postured to pick up the cup successfully."

People with damage to this system may still have perfect eyesight, but will struggle to grasp their mug.

The strengths of the two systems are not necessarily equal in each brain.

"Individuals with particularly well-developed 'vision-for-perception' systems could perhaps more easily become expert bird watchers, art dealers, pathologists, or fashion designers. By the same token, it would not surprise me if natural athletes had some advantages in the 'vision-for-action' department," Professor Goodale says.

His research has already uncovered some interesting quirks in this new field. For example, Professor Goodale says that while the 'vision-for-perception' system may deteriorate with age-related changes in eyesight, the same effect will not necessarily occur in the control of physical activity.

And neuroscientists don't really know how training might improve this system.

"But recent studies show that young people who play a lot of video games exhibit improved performance in visual search tasks and other visually demanding problems - suggesting that visual systems in the brain can change in fundamental ways with practise."

Professor Melvyn Goodale will deliver the Monash Neuroscience and Mental Health Public Lecture on Tuesday 17 June from 6pm (drinks from 5:30pm) at South 1 Lecture Theatre, Building 64, Clayton Campus. For further information, contact Dr James Bourne on 9905 8020, or email  Event free.

Click here for the extended interview with Professor Goodale.

Professor Melvyn Goodale

Professor Melvyn Goodale