"Syntactic disorder" can be defined as an impairment of sentence processing, in comprehension as well as production, in spoken language as well as written, despite relatively intact processing of individual words. It is a terrible disorder. Our communication is mostly about who did what to whom, and when. If we lose this ability the complexity of what we can say and understand suffers a lot. People with aphasia can have a complex mental life and above average intelligence, but can find themselves unable to share any of that.
This paper is based on my PhD project. We found that some people with syntactic disorder have difficulties even when they are processing structured not sentences, but structured sequences of nonsense blobs. This phenomenon cannot be explained by differences in intelligence or visual perception. I believe that it is related to the grammatical disorder we see in their language use.
I still find it hard to put this work into a wider perspective. If our aphasic participants cannot even see that blue blobs appear before red blobs, and if this is related to their inability to understand the difference between "The man kills the lion" and "The lion kills the man", why did we not find the same relationship between artificial grammar learning and the ability to solve mathematical equations, or play a board game, or other types of behaviour?
In any case, we see much potential for clinical practice. Sentence processing is very demanding, and loss in any of a number of capacities can break it. I can imagine refined methods being part of a more thorough diagnosis. The problem with our study is the low number of cases, so all we could do is to point at what we think is an important direction.