Broca's area: The full story

Chapter 8 endnote 25, from How Emotions are Made: The Secret Life of the Brain by Lisa Feldman Barrett.
Some context is:

Broca’s area is actually a failure to localize a psychological function to a brain blob. Nevertheless, history was rewritten in Broca’s favor, lending strength to essentialist views of the mind.

Among the scientists who disagreed with Broca was the neurologist John Hughlings Jackson, who noted that many patients with nonfluent aphasia have a healthy Broca's Area (left frontal cortex near the third frontal convolution). Jackson argued that language depends on different arrangements of brain tissue in different people. In other words, he was arguing for what later became known as degeneracy.

Broca and Hughlings Jackson presented their evidence at the same conference in 1868, and according to reports in the medical journal The Lancet, scientists were skeptical of Broca's view because it was not well supported by his evidence. But then a strange thing happened. Scientists eventually adopted Broca’s view anyway for ideological reasons. It gave them an alternative, evolutionary explanation for the origin of language—a triumph of science over religion. Once again, an essentialist idea was magically protected by the cloak of Darwin, and the brain area was named in Broca’s honor.

Until recently, textbooks told a story that Broca and Hughlings Jackson had debated at the conference (they hadn't) and that Broca had won (he didn't). In actuality, the two men presented separately, and Broca’s claims had scant evidence and were carried along on Darwin's coattails. The incorrect story had surfaced by the 1950s, as in Kurt Goldstein's biography of Broca: "...in 1868, the enthusiastic support of his [Broca’s] view by the audience, coupled with their indifference to Jackson’s part in the discussion, was a personal triumph for Broca, and from that time his basic idea dominated research [and was] considered to be established beyond doubt" (p. 260).

Interestingly, when Broca presented his views again in 1869, he did not mention Hughlings Jackson's presentation.

Scientific details

In 1868, at the British Association for the Advancement of Science, Paul Broca and John Hughlings Jackson both presented addresses on the brain basis of the new and controversial subject of aphasia, which resulted in an animated debate among scientists of the day. Broca argued that there was cerebral localization of language, and aphasia was due to damage to the posterior portion of frontal lobe on the left (which came to be known as Broca's area). The idea of cerebral localization of language function was introduced by Broca in 1861 in a speech to the Society of Anthropology, which he helped to found.

Interestingly, Broca's argument was an example of faculty psychology and was not particular to Broca per se; A particularly iconic example of faculty psychology is Franz Gall’s “craniology” (better known by Johann Spurzheim’s term “phrenology”), where mental faculties were thought to correspond to bumps on the skull). The idea that language was localized to the frontal lobes was not novel; what Broca had was patients with lesions in a particular spot in the inferior left frontal lobe who also had aphasia.

Hughlings Jackson, by contrast, argued argued strongly against the phrenological view. He argued that aphasia was not localized to the left frontal lobe, and based his argument on two observations:

• some of of his aphasic patients had damage to the right frontal cortex instead of the left, or had damage to the striatum.
• some patients with damage to the region that came to be known as Broca's Area did not suffer from aphasia.

Without knowing it, Hughlings Jackson was arguing that language was degenerate in the brain (he believed that language is much more complicated than previously assumed and that the causes of the aphasia may vary). His characterization was more or less correct: "I think, then, that the so-called ‘faculty’ of language has no existence, and that disease near the corpus striatum produces defect of expression (by words, writing, signs, etc.), to a great extent, because this is the way out from the hemisphere to organs which the will can set in motion." He was saying, in effect, there is a general function that is necessary for but not specific to language (i.e., a problem with the control of motor output), and when it is damaged, language problems ensue. Hughlings Jackson's view was the dominating force in the British scientific community's discussions of the 1868 meeting.