Skilled musicians are not subject to the McGurk effect
At this regard it can be hypothesized that the lesser susceptibility of musicians to the McGurk illusion is related to a different pattern of functional specialization of auditory, and speech processing brain areas. Specifically, with regard to basic audiovisual integration, differences between musicians and non-musicians have been demonstrated.
a greater contribution of the right temporal cortex for multisensory integration and the left inferior frontal cortex for identifying abstract audiovisual incongruences.... enhanced connectivity relating to pitch identification in the right superior temporal gyrus (STG) of musicians.
musicians seemed to rely more on acoustic (than phonetic) inputs
Corballis:
Vocalization, in contrast, does not involve direct interaction
with the spatial environment. Rather, it is programmed
internally and results in output that is patterned in time, not
space, and there is no apparent disadvantage to having that
programming accomplished asymmetrically in the brain.
Indeed, there may be advantages to asymmetrical organization
in the absence of strong environmental pressures toward
symmetry. Asymmetrical organization can make for
more efficient packaging, which might explain why the internal
organs of the body tend to be asymmetrically structured
and located, and it is probably more efficient to have
brain mechanisms programmed within a cerebral hemisphere
than to have them spread between the hemispheres.
This may also explain why vocalization was lateralized very
early in our evolutionary history.
So as I posted recently Corballis argues that the ancient left brain dominance of vocalization as communication (found even in frogs) going back 170 million years ago is the basis for right handed dominance in humans.
But musicians rely on right brain Pitch or Frequency perception just as much as left brain language perception. So the difference in musicians is based on a physiological difference of 170 million years ago!!
As a commentary on Corballis notes:
patterns of movement informed by neural connections associated
with signs. Therefore, the dual facts that the left hemisphere is, in
most higher animals, the side of the brain that is primed to serve
as the substrate for rapid acoustic processing and that the left side
of the brain controls the right hand, makes it plausible that the left
side of the brain would be used to create the neuronal assemblies
which allow the extension of gesture into speech as an adaptive
tool. This would also imply that language is an intensely practical
or world-involving activity and that the hand controlled by the left
hemisphere would become the one entrusted with acting in concert
with the discourse that has such a formative effect on much
of our human activity.
Professor Chris Knight's comment on Corballis is awesome:
The Zahavis add that a human being who is in control of a situation
likewise tends to issue threats in an ordered, rhythmic sequence,
as if celebrating the fact that external reality can be ignored.
To disconnect from reality is to lose touch with the right brain.
Less dominant figures cannot afford to do this, which may explain
why they tend to rely more heavily on the right hemisphere while
speaking (Armstrong & Katz 1983; Ten Houten 1976). Phonological
processing is certainly less lateralised in human females than
in males (Shaywitz et al. 1995).
Where trust is sufficiently
high, resistance on the part of listeners disappears, allowing
the subtlest of signals to produce effects. Comprehension now
involves inserting oneself imaginatively in the signaller’s mind
(Tomasello 1999). Speech signals do not need to generate their
own trust – at the most basic processing level, an assumption of
automatic trust is already built in. In fact, on this level it is legitimate
to assume a conflict-free – in Chomsky’s (1965, p. 3) terms,
“completely homogenous” – speech community. So great is the
trust, that language works almost as if one component of the brain
– or one component of a computing machine – were simply transmitting
digital instructions to another (Chomsky 1995; 2002).
Quite regardless of whether signs are manual or vocal, it is this
bizarre situation which liberates the potential of one hemisphere
to arrange complexity independently of the other. We are left with
a puzzling intellectual challenge: to elucidate how the necessary
levels of trust could ever have been compatible with our selfish
genes. Because I believe this to be the key theoretical issue, it will
not surprise Corballis that I am critical of his thought-provoking
but non-adaptive account, preferring my own more explicitly Darwinian
alternative (Knight 1998; 1999; 2000; 2002).
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