Showing posts with label perception. Show all posts
Showing posts with label perception. Show all posts

Thursday, December 9, 2010

Prosopagnosia: A Podcast from Oliver Sacks

A NEUROLOGIST’S NOTEBOOK is about prosopagnosia, or the inability to recognise faces and places. The writer describes his own difficulties recognising and remembering faces. He also has the same difficulty with places and often becomes lost when he strays from familiar routes.

At the age of seventy-seven, despite a lifetime of trying to compensate, he has no less trouble with faces and places than when he was younger. He is particularly thrown when seeing a person out of context, even if he was with that person five minutes before.

The writer gives several examples of his inability to recognize familiar people out of context, including his therapist and his assistant. After learning that his brother suffered from the same problem, the writer came to believe that they both had a specific trait, a so-called prosopagnosia, probably with a distinctive genetic basis.

He mentions several other people who have the same trait, including Jane Goodall and the artist Chuck Close. Face recognition is crucially important for humans, and the vast majority of us are able to identify thousands of faces individually, or to easily pick out familiar faces in a crowd.

People with prosopagnosia need to be resourceful and /or inventive in finding strategies for circumventing their deficits: recognising people by an unusual nose or beard, or by their spectacles, or a certain type of clothing.

The Notebook describes research done on the way the brain recognises facesand tells about the work of Christopher Pallis, Charles Gross, Olivier Pascalis, Isabel Gauthier, and other scientists. Above all, the recognition of faces depends not only on the ability to parse the visual aspects of the face—its particular features and their over-all configuration—and compare them with others, but also on the ability to summon the memories, experiences, and feelings associated with that face.

The recognition of specific places or faces goes with a particular feeling, a sense of association and meaning. He also briefly discusses déjà vu and Capgras syndrome and considers the difference between acquired prosopagnosia—through trauma, stroke or Alzheimer’s —and congenital prosopagnosia.

The writer discusses the work of Ken Nakayama and Brad Duchaine, who have explored the neural basis of face and place recognition. They have also studied the psychological effects and social consequences of developmental prosopagnosia. Severe congenital prosopagnosia is estimated to affect two to two and a half per cent of the population—six to eight million people in the United States alone.

A Podcast with Oliver Sacks : The New Yorker

Monday, May 17, 2010

Optical Illusions are Fun



An animation that appears to have illusory contours was awarded second place in the contest. Created by Bart Anderson at the University of Sydney, Australia, it's made up of four circles and four dots that move back and forth over the outline of a rectangle. Contours connecting the moving dots in the middle seem to appear, creating a diamond that sometimes seems to morph into a more rounded shape as it stretches out.

Contours appear in many illusions. They can normally be explained by the way fragments of objects are arranged: a well-known shape without visible contours is inferred because our brains choose the most likely configuration based on the visual information.

But this explanation doesn't seem to apply to Anderson's illusion. The moving circles and dots are never partially obscured, so the brain shouldn't have to infer another shape. "This illusion can't be understood with any known mechanism that has been proposed to explain the formation of illusory contours," says Anderson.

Tuesday, April 7, 2009

What's behind the mask?

Is this the front or back of the mask? People with schizophrenia will know (Image: bluegum/stock.xchng)

Is this the front or the back of the mask? Are you looking out or in? New research claims that people with schizophrenia will know (Image: bluegum/stock.xchng)