Piero Scaruffi(Copyright © 2013 Piero Scaruffi | Legal restrictions )
These are excerpts and elaborations from my book "The Nature of Consciousness"
Evidence from brain lesions led the Indian neurologist Vilayanur Ramachandran to think that not only the brain has specialized circuits for language, but that there are probably three different specialized areas for three different tasks: lexicon, syntax and semantics. A patient with Broca's aphasia wants to convey meaning but has difficulty composing sentences. On the other hand, a patient with Wernicke's aphasia utters sentences that are well-formed, grammatically correct, but meaningless (they are also in a simplified syntax that shuns recursion). Therefore it appears that Broca's area is specialized for syntax, and Wernicke's area is specialized for semantics.
Like Stephen Jay Gould, Ramachandran too thinks that language evolved as a by-product of other features, but not quite of thinking. He suspects that language emerged out of interference inside the brain between signals that are similar. The sound that refers to an object is similar (in some physical manner) to the image of that object that is being processed by the brain. He calls this "the synesthetic theory". The brain might "translate" an image into a sound (into a protoword) simply because the maps that represent the two are adjacent and interfere with each other in quite a natural fashion. This cross-activation would be the primal cause of our linguistic competence. Next, Broca's area indirectly relates syntax and the movements that we use to produce speech. Hence one part of the brain puts in contact image and sound, and then another part of the brain causes those sounds to be spoken. Each of these correlations can be view as an "abstraction", which in physical terms simply means that different brain regions activate each other based on similarity of signals. A third case of cross-activation exists. Darwin himself noted that sometimes an utterance is accompanying with a gesture. Ramachandran speculates that it could be another case of cross-activation, except this one would be due to the interaction between two motor maps. This would explain how a primordial language of gestures would evolve into a spoken language. A brain that exhibits the kind of wiring that the human brain has would naturally end up translating gestures into (spoken) words. "Abstraction" is what cross-activation looks like: those brain regions activate each other because the signals within their circuitry have a similar mathematical shape, independently of whether those signals represent an image, a sound or a movement. At the neural level they are, ultimately, just electrical waves.
This whole business of cross-activation is reminiscent of how mirror neurons link concepts across brain maps.
Ramachandran suspects that the inferior parietal lobe evolved originally for cross-modal abstraction, since it has to mediate signals coming from the touch, vision and hearing regions of the brain; and then later this feature became an independent skill, the ability to think abstract thoughts. The inferior parietal lobe (IPL) in the right hemisphere became skilled at bodily metaphors and the IPL in the left hemisphere become good at linguistic metaphors. The original abstraction was probably the mapping of vision into gesture, and to this day half of the IPL, the supramarginal gyrus, is responsible for coordinating vision and gesture (a fundamental feature of the human brain, that allows us to build and use tools to an extent unknown in other species). The other half of the IPL, the angular gyrus, found by accident (by exaptation) that this same process is useful to find similarities among different domains, e.g. for metaphorical thinking.
Initially, the human brain may have been more interested in making and using tools, and therefore evolved the skills to relate vision and gesture. By exaptation, this brain function ended up also being "translated" into the domain of communication. Is this is indeed the case, then the whole process of building tools out of parts could be the precursor of and the indirect cause for the tree structure of linguistic syntax: sentences too are constructed out of parts. The original language may have been the language of building tools, not the language of speaking words.
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