The Attention Wager, Part 6: The Fork
Two stacks, drawn symmetrically, for a task with an input and an output. The field cut the figure in half twice. The oldest diagram of language in the brain came apart the same way.
This is The Attention Wager, a close reading of Attention Is All You Need, one section and one bet at a time.
For about a hundred years, the standard picture of language in the brain was two boxes and a wire.
Broca found it first, in 1861: damage to a region of the left frontal lobe left patients able to understand speech and unable to produce it. Wernicke found the complement in 1874, in the posterior temporal lobe, where damage produced the reverse, fluent speech that meant nothing and comprehension that had gone. Lichtheim drew the diagram in 1885, and drawing it was the contribution. Broca and Wernicke had each found a region and a deficit. Lichtheim put them on one page with a line between them and added the connections that a complete account would require, which let a clinician look at a pattern of symptoms and point at where the damage must be. A centre for hearing words, a centre for producing them, and a pathway joining the two.
The version most people have seen is Norman Geschwind’s, redrawn for Scientific American in 1979 and reproduced in virtually every relevant textbook of neuroscience, linguistics, and psychology since. Two labelled regions, one arrow between them. Comprehension here, production there, and a wire.
It is a good diagram. It explains the aphasias, it is teachable in five minutes, and it dominated the field for longer than most theories in biology survive.
In 2012, writing in the Journal of Neuroscience, David Poeppel and colleagues reproduced Geschwind’s figure with a caption calling it ubiquitous and no longer viable. Four years later a review in Brain and Language put the position in its title: Broca and Wernicke are dead.
Hold that. It comes back at the end.
