We have been discussing the specialized skill of recognizing faces. What other specialized visual skills do people have? As it turns out, there is debate over how exactly to define the “face skill.” Some people think that the mechanisms we use to recognize faces are only used for faces. Other people think that these same mechanisms are used whenever two factors are in place. First, you are making judgements within a massively familiar category. Second, what you are judging is the identity of a specific individual within that category.

Some of the evidence for this debate is fun, although, tragically, it does involve brain damage which obviously is no joke. In particular, we’ve already talked about prosopagnosia and what it does to face recognition. But there is a well documented case of a prosopagnosic farmer who lost the ability to tell his cows apart. There is a prosopagnosic woman who lost her ability to tell cars apart and can only find her own vehicle in a parking lot by reading license plate after license plate. Try that at the mall… And finally, there is a prosopagnosic birdwatcher who lost the ability to distinguish different types of warblers.

And then there are the chicken sexers… they can tell apart, in hour-old chicks, who is female (valuable as ehh producers) and who is male (less valuable commercial commodity.) The do not use the face recognition processes; instead they know exactly where to look and for what to look. If you’d learn their simple trick, you, too, could be a chicken sexer!

http://scienceblogs.com/twominds/2008/04/14/how-to-sex-a-chick/

I, of course, am talking about all this to display some of my favorite bird watching images….