YOUR EYES do a relatively poor job delivering a visual image. It is up to the brain to fix things up and provide a high-quality picture.
So argued Prof Richard Abadi who delivered a lecture on perception at NUI Maynooth last night titled: “It ain’t what you see – it’s the way that you see it!”
Prof Abadi is a visual scientist at the University of Manchester and is on a one-year Walton fellowship at NUI Maynooth. His lecture was part of the university’s contribution to Science Week, which ends on Sunday.
“The image that falls on your retina is in two dimensions and is in drastic need of reconstruction and improvement by the brain,” he said in advance of the lecture.
“It is computed in the brain to give it three dimensions, depth and texture and it gives whatever you see some meaning.”
This vision-brain integration evolved over millions of years as a way to help us survive and yet the eye delivered relatively poor optics, Prof Abadi said. It was up to the brain to fix things up.
Doubters in the audience were given an object lesson in this when Prof Abadi introduced a sleight-of-hand expert. A good illusionist knows how to trick the eyes, leaving the brain confused and unable to explain how a coin might suddenly vanish.
The brain was also very willing to fill in any blanks in the visual panorama, Prof Abadi suggested. Closing one eye should leave a hole in the view but it doesn’t, the brain adds in the missing content. “The brain extrapolates what it expects to be there.”
He likens what the brain does to the operation of a computer algorithm. “An algorithm is essentially a programme or a line of processing that calculates the input to make something of the output.” The eye was also like a detector, giving the brain information that allows space to be topographically mapped.
“We have this sort of file in the brain. We have to make quick and accurate decisions on what we are seeing,” he said.
Speed is of the essence because the dark shape approaching at night might be your brother or might be a foe.