1. Language within our grasp: Gesture, mirror neurons, and meaning

2. Shared meaning and symbol grounding One mystery we have alluded to is ‘symbol grounding’: how communicators manage to synchronize their meanings –What keeps your ‘cat’ meaning the same as my ‘cat’? Wittgenstein’s emphasis on shared ‘forms of life’ as the ground of meaning was intended to buttress the idea that only shared action could bring different systems into synchrony of meaning

3. Biological meaning We can imagine (though Wittgenstein did not) that some early shared actions would be synchronized by biological necessity –For example, we all understand the basic biological needs, and can easily parse actions related to seeking food, water, sex, avoiding death and pain etc. –Thus, concepts related to these activities may be transparently (innately) obvious to us and therefore easy to communicate about –Most natural animal communication systems are about such things

4. The more innateness, the better For the purposes of meaning synchronization, especially in pre-linguistic history (and perhaps pre-linguistic development, and non-linguistic environments?) the more ‘semantics’ we can ascribe to innate factors, the smaller the mystery of symbol grounding –The more shared meaning we start with, the easier it is to imagine we could add more by building on what we have

5. Mirror neurons Mirror neurons were discovered in single- cell recording in area F5: ventral premotor cortex

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8. Mirror neurons Mirror neurons were discovered in single-cell recording in area F5: ventral [= lower] premotor cortex They discharge during active movements of the hand and/or mouth They are sensitive to different purposes –Some discharge during grasping; some during (specific kinds of) holding; some during reaching; some during tearing Surprisingly, they were also found to discharge during observation of related movements: hence their name ‘mirror neurons’ Later it was found they also discharge when the animal hears sounds associated with the purposes to which they are sensitive

9. Mirroring as communication These are very general ‘semantic’ encoders –They fire with presentation of the action from many perspective, near and far –They are sensitive to the apparent purpose of the action In this way, they represent the actions and (thereby) represent a common thread of understanding between an actor and an observer A shared link of understanding is what defines a communicative act, so some have claimed that mirror neurons are an innate (gestural) communicative mechanism

10. What’s it to humans? Many have claimed that the proper analogue to primate F5 is Broca’s area (BA44/45) –Cytoarchitectonically [in terms of the distribution of cell structures] this seems to be true –Broca’s area has been implicated in execution of arm movements; and during mental imagining and manipulation of hand movements –fMRI of grasp observation has found left hemisphere activity in BA45

11. What’s it to psycholinguists? These findings mesh very nicely with a ‘mind reading’ theory of language Recall that ‘mind reading’ was associated with the same region: ventral prefrontal cortex Some of the work of parsing and attaching meaning to action in social contexts can be underlain by mirror neurons

12. What’s it to psycholinguists? These findings mesh very nicely with the motor theory of speech perception, and with the McGurk effect) Recall that under these theories, speech perception just is a motor mirroring: to be able to parse phonology is to be able to parse the gestures of the articulators

13. What’s it to psycholinguists? These findings mesh very nicely with the finding that Broca’s area is implicated in language production in other modalities than speech: i.e. in sign language And with the fact that the main deficit after lesion of the arcuate fasciculus is in essence a deficit in mirroring: an inability to repeat words –This is because motor neurons constitute a pre- linguistic mapping between between perception and production

14. Syntax revisited As we have already discussed several times, syntax and the semantics of action are closely related Syntax assigns and handles roles to subjects and objects, mirroring in many ways the way the action unfolded The sentence “John hit Mary with his hand” encodes who who hit, who was hit, and what was used to carry out the hitting These are the kinds of things the mirror to which the mirror neurons may be sensitive

15. Verb arguments Moreover, to use syntax correctly we need to be able to understand what kind of arguments go with what kinds of verbs –You can ‘grasp a rock’ but you cannot ‘grasp a mountain’; you can ‘pinch some sand’ but you cannot (usually) ‘pinch some trees’ –You can also focus attention on the grasping method (‘Joe’s hand touched her leg.’) or the grasping person (‘Joe touched her leg’) –If these distinctions are (at least in early language evolution) mapped on to pre-existing semantic distinctions, it become easier to comprehend how language might be able to encode them

16. Does mimesis underlie language?