Many post-stroke aphasia studies select participants according to two criteria: they must have a left-hemisphere stroke, and the must present with language deficits. These selection criteria create a feedback loop where all the studies focus on individuals with left hemisphere damage and language deficits, without examining patients with left hemisphere damage but without language deficits or patients with right hemisphere damage who still have language deficits.
By examing a large, unselected sample, we can get a clearer picture of how language is lateralized, free from the selection bias of traditional aphasia studies.
