Here is a quote from an article on Wikipedia on Asperger's Syndrome:
People with Asperger syndrome often display restricted or specialized interests, such as this boy's interest in stacking cans.
As far as I know, the word "restricted" has two meanings in English: the first one is "forbidden" and the second one is "limited to a certain area or field".
Obviously, here it's not the first meaning.
But then I am not sure I understand how the second meaning works here. I mean an interest is by definition something limited to a certain field, isn't it?
For example, if I am interested in pop-music, than it is just natural that I don't have a similar degree of interest toward other fields like, say, culinary and photography.
In fact, if my interest were not limited to those fields that I am curious about and were equally distributed among all fields instead, then it would look more like I had not particular interest toward anything at all!
So, is the term "restricted interest" not redundant?