Some people who have prosopagnosia are able to tell animal faces apart. This tells us that different areas of the brain are used for different classes of faces. A typical person has no problems with human faces, but if he does not know animals well, he may find telling animals of one group apart to be quite a challenge.
Recently, evidence has been presented that shows that some animals can tell people apart by sight as opposed to by smell. One particular animal that has been studied is the crow. http://www.npr.org/templates/story/story.php?storyId=106826971
Go to the NPR article and test yourself. Can you tell the crows apart?
Tuesday, August 25, 2009
Visualizing facial expressions
A related condition to faceblindness is the inability to discern emotions through facial expressions. We can best observe this situation when a stroke leaves a person able to visualize faces but not their expressions. This tells us that different areas of the brain are required if we are to be able to accomplish both tasks.
Of the people who have prosopagnosia, those who are severely effected from birth will not be able to tell expressions for the reason that they do not perceive the parts of the face at all. They look at a face and do not see the features. Consider that when you look at a rock, you may only see the gray mass of it and not even notice all the pits and scratches in the rock.
People with mild prosopagnosia who can learn to tell some faces apart over time may also have trouble with facial expressions. The problem is not so much visualization so much as it is a matter of not learning how to make and understand those expressions. So they may look at a person who is sad and not understand that the person looks and feels sad. A person may look angry, but the faceblind person does not recognize the angry look.
Of the people who have prosopagnosia, those who are severely effected from birth will not be able to tell expressions for the reason that they do not perceive the parts of the face at all. They look at a face and do not see the features. Consider that when you look at a rock, you may only see the gray mass of it and not even notice all the pits and scratches in the rock.
People with mild prosopagnosia who can learn to tell some faces apart over time may also have trouble with facial expressions. The problem is not so much visualization so much as it is a matter of not learning how to make and understand those expressions. So they may look at a person who is sad and not understand that the person looks and feels sad. A person may look angry, but the faceblind person does not recognize the angry look.
Visualization of faces
From the moment the infant emerges from the womb, it is trying to use its eyes. Sometimes, the eyes do not at first even work in tandem. We don't usually think of eyes as having to learn to work together. We also make assumptions such as that the eyes will be able to see. When vision is normal, we assume that we will be able to tell things apart. This ability to visualize has to be learned. For most people, learning to visualize comes naturally.
We tell things apart by shape and by color, by depth and texture. But there are some things that some people cannot tell apart well, if at all. One of those things is faces--in particular, human faces. Many people, not a rare number, have some degree of prosopagnosia, also called faceblindness. Bill Choisser coined that name (http://www.choisser.com/faceblind/).
The reason for this failure to visualize is a problem in the brain. While certain areas of the brain are involved in the visualization of faces, prosopagnosia is still not well understood. Because the condition runs in families, espcially in families where one or more members has a neurological disorder like autism spectrum disorders (ASD), pervasive developmental disorders (PDD) or obsessive compulsive disorders (OCD), a genetic component is suspected.
We tell things apart by shape and by color, by depth and texture. But there are some things that some people cannot tell apart well, if at all. One of those things is faces--in particular, human faces. Many people, not a rare number, have some degree of prosopagnosia, also called faceblindness. Bill Choisser coined that name (http://www.choisser.com/faceblind/).
The reason for this failure to visualize is a problem in the brain. While certain areas of the brain are involved in the visualization of faces, prosopagnosia is still not well understood. Because the condition runs in families, espcially in families where one or more members has a neurological disorder like autism spectrum disorders (ASD), pervasive developmental disorders (PDD) or obsessive compulsive disorders (OCD), a genetic component is suspected.
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