Professor V. G. Shebalin was a teacher at the Moscow Conservatoire, and had composed several acclaimed symphonies as well as an opera that was performed at the Bolshoi Theatre. In 1959, a stroke damaged the left hemisphere of his brain and left him severely aphasic. He struggled to find words or speak grammatically. One attempt to speak to his wife was noted down by his doctor, and roughly translates from the Russian as ‘Expressive…compressive…no…suppre…no…what for a trasom have I today…’ (i.e., uninterpretable by all concerned). And yet, miraculously, during the four years that he survived following his vascular accident, Shebalin composed ten major orchestral works. Among them was his 5th symphony, which his friend Shostakovich called ‘a brilliant creative work, filled with highest emotions, optimistic and full of life’. And it’s not just musical talent that is spared in aphasia. A more recent case concerns patient S.O., who suffered a stroke that caused a massive lesion to the left hemisphere of his brain.[*8] He became densely aphasic, and could barely speak or write at all, mustering only the occasional social word (‘bye’ or ‘hello’). However, the patient had no difficulty solving complex algebraic expressions like 2b + (3b + c) − (4c + 5b) = ? So although his language skills had been obliterated, that patient’s mathematical reasoning was spared. There are also anecdotal reports of aphasic patients who continue to play chess at expert levels, despite not being able to name any of the pieces on the board. Unlike LLMs, our ability to think clearly does not depend on our capacity to generate meaningful sentences.

Christopher Summerfield, These Strange New Minds: How AI Learned to Talk and What It Means (2024)