One specialist told Sheila that medics aren't keen on strokes because they are "messy". The aftermath of a stroke is like that of a fire in an office, a brutal insult to orderly arrangements of information. Yet highly detailed information can be generated from the mess. Different patients have different "deficits": some make telegraphic utterances, others speak fluent nonsense; some can't understand words that they hear, but can say them, others can understand words they cannot say or write. By comparing deficits, psychologists can piece together the machinery of language. Among the strangest deficits displayed by people after strokes is a lack of awareness that there is a deficit. John Hale made conversation, and even jokes. But it was all in the expression. Though he believed he was uttering words, about the only sound he made was "da woahs", repeated where previously he would have spoken in sentences. It took 18 months of painstaking tuition to teach him what a sentence was.