Transcript No Slide Title

EUROPEAN SOCIETY FOR THE
STUDY OF COGNITIVE SYSTEMS
20-22 August 2007, Groningen,
The Netherlands
ABSTRACT
ASCENT OF INTELLIGENCE
Gesture and Language : Mind and
Body
Robin Allott
The acquisition of language was the turning-point
for the evolutionary separation of humans from
apes. From this flowed the ascent of human
intelligence with the ratcheting up of human mental
and cultural advance
as a result of interaction between individual
variations in brain structure and development and
continually advancing complexity of the social,
technological and cultural environment (a
manifestation of the Baldwin effect).
Both body and brain were involved in the acquisition and
advance of language, phylogenetically and ontogenetically.
The relation between mind-state and body-state was
manifested not only in the patterning of emotion (the
James/Lange theory) but also in the selection of words
(articulatory programs) to match patterns of perception,
both of external objects and also innate attitudinal patterns,
"mental" structures, which went to form both language
syntax and motor syntax (cf. Karl Lashley, Kant).
The key aspect of the motor theory of language
is that words, speech and language are the
outcome of an exaptation of the motor control
system, that is, a direct relation between
aspects of the motor cortical system and the
characteristic features of lexicon and syntax.
Progress in neuroscience, and
particularly recent experimental
research using fmri and other
techniques, has provided
material support for the motor
basis of language.
RECENT RESEARCH
(1) “A larynx area in the human motor cortex” Brown Ngan Liotti Cerebral Cortex
July 25 2007 A human evolutionary novelty perhaps related to emergence of
voluntary control of vocalisation
(2) “The organisation of behavioral repertoires in the motor cortex” 2006.
Graziano M. Annu. Rev of Neurosci. 29.
(2) "When Language Meets Action: The Neural Integration of Gesture and
Speech.” 2006 Willems Ozyurek Hagoort Cereb. Cortex 2006 Dec 11 (Epub)
fMRI evidence that speech and gesture share a high-level neural integration
system.
(3) "Speech and Gesture share the same communication system" 2006
Bernardis Gentilucci Neuropsychologia 44 178-190. Experiment suggests that
word and gesture are related at the levels of execution and processing with
implications for the evolution of language.
(4) “Comparison of the neural systems underlying speech and non-speech vocal
utterances” 2000 Jurgens. Existence in humans (and not in other primates) of a
direct connection between the motor cortex and the laryngeal motoneurons.
OTHER RELEVANT MATERIAL
(6) “Functional links between motor and language systems” 2005
Pulvermuller Hauk Nikulin Ilmoniemi Eur J Neurosci 3 1793-7. TMS
experiment showing specific links between action and language systems
during lexical processing.
(8) “Complex movements evoked by microstimulation of precentral cortex.”
2002 Graziano Taylor Moore Neuron 34, 841-851.
(9) “The cortical control of movement revisited.” Graziano Taylor Moore
Cooke Neuron 36, 349-362. "One possibility is that the mechanisms for
speech were built on a preexisting mechanism for motor control”.
(7) “Origin of speech: The motor route” Holden 2004 Science 303:13161319. Abundant behavioral evidence for an intimate connection between
language and motor abilities.
MORE SPECULATIVE
(5) “Hypoglossal canal and the origin of human vocal behavior” 1998 Kay
Cartmill Balow PNAS 95 5417-5419. The much larger canal in humans than in
apes or australopithecus makes possible richer motor innervation of the
tongue and so made possible language as a uniquely human ability.
(10) FoxP2 gene 2001 Varga-Khadem et al. Nature 413 519-523. Motor
control and language implications.
(11) “Language within our grasp”. 1998. Rizzolatti, G. and M. Arbib. Trends in
Neuroscience 21 188-194. Mirror neurons make possible empathy and
imitation and so provide a basis for the evolution of language.
(12) EvoDevo
(13) Baldwin effect
THE ORIGIN OF WORDS
FROM THE IMITATION OF SOUNDS SHAPES
AND ACTIONS
THEN TRANSDUCED INTO ARTICULATORY
PROGRAMS
BY MOTOR EQUIVALENCE
Motor equivalence has been the central
process in the origin and functioning of
language and the acquisition of words.
EVIDENCE ?
EXAMPLES ?
EXPERIMENT ?
THOUGHT EXPERIMENTS ?
Or
MATERIAL EXPERIMENTS ?
OR
MIND EXPERIMENTS ?
The sound [the word] is not “a directly imitative sign
but indicates a quality which the sign and the object
have in common. . . . sounds which partly
independently and partly in comparison with others
produce an impression which to the ear is similar to
that which the object makes upon the mind.”
Humboldt
Parallelisms of word and gesture (dual expressions of
meaning) can be made overt by specific controlled
mind/brain operations
LANGUAGE AND THE ASCENT OF
INTELLIGENCE
INTELLIGENCE ?
Brain size and structure ?
Baldwin effect ?
EvoDevo ?
BRAIN SIZE
The inescapable fact is that brains, and
particularly human brains, have much increased
in size in the course of evolution. The increase
in size must have brought survival benefits and
for humans it surely means that however
intelligence is measured greater size has moved
in step with greater intelligence - though at the
individual level the correlation is not exact.
BUT … all the day-to-day routines of bodily
existence require very little neural mass.
Ants, bees, mice, birds, dinosaurs, manage,
or managed, very well, with small, or
extremely small, brains (the ratio of brain to
body may be more significant, for example,
for mice or other small rodents).]
So why and how did humans come to acquire a
brain-mass much greater than is needed for
routine bodily functions ? From home habilis to
modern homo sapiens the brain grew from an
average 750 cc. to 1350-400 cc.
[No known comparable rate of increase in brain
size in any other species at any time in the
history of life on earth. Plotkin 1996]
HYPOTHESES
1. Social complexity
2. Foraging strategies
3. Language development
There has been intense and long-enduring discussion
of these issues and many unresolved arguments with
much speculation and little useful evidence. Here it is
only possible to make a few comments:
SOCIAL COMPLEXITY
Whether, for humans, social complexity
favouring larger brains could have
developed without some form of language
is unclear. On the other hand, there are
animals, ants, bees, termites, which
manage complex societies with minuscule
brains. The case is made mainly in terms
of ape behaviour - the orangutan, one of
the more intelligent animals is solitary.
FORAGING
This account has been developed mainly by
specialists in primate behaviour. It may go
some way to account for the relatively large
brains of chimpanzees and gorillas but has
little explanatory value for the remarkable
near-double increase in the human brain,
even when associated with the somewhat
implausible development of the idea of
Machiavellian intelligence - that deceiving
group members was one of the necessary
aspects of increased intelligence.
LANGUAGE
That the remarkable increase in human brain size (unmatched by
any similar rate of increase in other animals) should have some
relation to the equally remarkable (unmatched by other animals)
evolutionary human acquisition : language, seems an obvious and
plausible hypothesis.
But the debate, confusion and uncertainty about the process
by which humans invented, acquired or developed language,
or languages, still rages, after 2500 years. The question
about the evolutionary relation of human brain-size and
language goes with the unsettled question about the brain or
social processes making possible another remarkable
achievement, the untutored, extensive and rapid acquisition
of language, complex syntaxes and massive lexicons, by
children
EVO-DEVO
Evolutionary developmental biology
BALDWIN EFFECT
Behaviour evolution interaction
A NEW EVO-DEVO BALDWIN EFFECT
The accepted evolutionary account of the Baldwin effect
was that humans, and other animals, by changing their
behaviour changed their environment and so created
novel potentialities for natural selection which could
operate in succeeding generations, making it possible for
culture to modify evolution.
With the recent growth of the new discipline Evo-Devo
concerned with the relation between developmental and
evolutionary processes, a new application or
understanding of the Baldwin effect in relation to
development of the brain becomes possible.
CELL DEATH
In the development of the brain, many more neurons are produced than
are ultimately needed to create the mature brain. The neurons are
thinned out by programmed cell death; the initial supply of neurons (twice
as many as eventually survive) are in competition to establish appropriate
connections. Those which do not get the necessary access to a source of
NGF (nerve growth factor) die, this Neural Darwinism (in a sense
completely different from Gerald Edelman’s term) is natural selection at
work.
THE DYING CELL
3 cells compete for Nerve Growth Factor.
2 win and the 3rd dies
(repeating loop)
Through cell death each individual brain is sculpted to match
the environment in which the brain develops (both fetally and for
an extended period after birth). Cell death continues shaping the
brain long after birth. For all types of cells, from 8-14 the
average child loses approx. 20-39 billion cells a day. The
average adult loses approx.50-70 billion a day.
CELL DEATH AND EVOLUTION
Cell death can now be recognised as an important link between
brain and environment, operating through life to permit experience
to shape the brain. It is via cell death that the relation between
brain-size and culture including language can be understood. A
key point in the operation of this process in he developing brain is
individual brain variation. Each brain is unique in many ways,
including its size and the number of neurons which have to find
appropriate connections to survive.
BRAIN INDIVIDUAL DIFFERENCE
Natural selection can come into play on differences in brain structure
derived from the culture. Increased brain size means the availability
of more neurons (and more neuronal inter-connections) available to
match the extending experience of the individual- and so increase
the selective advantage of the individual in a changing culture. A
virtuous circle is established with the better adapted and no doubt
larger- brained individuals playing a larger part in manipulating the
environment in which the next generation will have to face natural
selection and in their turn have their brains shaped by experience.
Language in the group will account for an ever-larger
segment of total cultural input to the brain and will also act
as a powerful instrument in shaping the social system. A
ratchet effect is established which goes to promote a
persisting increase in brain-size (and skull-size coordinated by allometry with brain-size) until the skull-size
hits the anatomical constraint of birth-canal size..
SKULL AND BRAIN SIZE
The brain no doubt keeps on growing in
complexity to accommodate continuing language
and other cultural changes but the growth must
take the form of internal re-arrangement to
produce the elaborate infolding seen in the
modern human brain.
LEXICON INPUT
But how does language drive this? The major new language input
to the brain is through a rapidly expanding lexicon. The growing
lexicon, on the motor theory of language, requires that each word
creates a articulatory motor program (linked to and derived from
the visual or action percept) The influx of novel words involves an
increasing demand for neurons and neuronal connections.
Baldwin Evo-devo is the form in which language drives growth in
the size of the human brain in response to the acquisition of
words.
SYNTAX ?
Additional demand for neurons and
connections to accommodate syntax is
less significant. Language syntax can rely
substantially on pre-existing organisation
of the motor and visual systems, motor
syntax and vision syntax, and the
neurons and connections serving these.
SPEECH
But of course this only goes so far in explaining the evolutionary
role of language. Before the Baldwin Evo-Devo process can begin
to operate to increase brain-size, there must already be language
and language-related culture. There must already be words.
The central question remains: WHY and HOW could speech and
language have got going for humans at all? Why humans and not
dogs or apes? The most plausible possibility is, as Jan Wind
suggested long ago, not that there was some massive mutation
but a continuing process of cerebral reorganisation. Relatively
minor changes, well within the scope of inherent brain plasticity,
could have made speech possible.
WHAT FORM COULD THESE CHANGES HAVE TAKEN?
Research papers listed earlier offer some possibilities:
MOTOR CORTEX FOR SPEECH
Jurgens: Neuroanatomically, the step from
genetically determined controlled vocal patterns is
associated with the emergence of a direct connection
between the motor cortex and the laryngeal
motoneurons, a connection lacking in subhuman
primates.
INCREASED NERVE SUPPLY
Kay Cartmill Balow: “Hypoglossal canal and the
origin of human vocal behavior” The hypoglossal
canal (which carries nerves controlling tongue
movements) is much larger in humans than in
other primates or in australopithecus. The larger
canal is adapted to carry a much richer motor
innervation of the tongue and so to make possible
language as a uniquely human ability.
CONTROL OF THE LARYNX
Brown Ngan Liotti “A larynx area in the human motor cortex”
“A human evolutionary novelty perhaps related to emergence of
voluntary control of vocalisation.”
MOTOR CONTROL
Pulvermuller Hauk Nikulin Ilmoniemi “Functional links between motor
and language systems”. TMS experiment showing specific links
between action and language systems during lexical processing.
Graziano Taylor Moore Cooke “The cortical control of movement
revisited.” One possibility is that the mechanisms for speech were
built on a preexisting mechanism for motor control.
BUT WHERE DID THE WORDS COME FROM ?
Some, or all, of the listed cortical changes could have made
speech possible for humans (but not for other primates). But
for the Baldwin Evo-Devo effect to operate there had to be
words. Where did they come from? Where does any
individual word come from? Herder said that it was totally
impossible that words should be arbitrary, that someone
should invent say the word GREEN out of the top of his head
for the distinctive colour Green. If he picked a set of speech
sounds at random, say POGGLE, to mean Green, why should
others accept and understand him Even more impossible,
how could anyone arbitrarily invent the words IF, MIND, SAD,
THINK - there is nothing to point to for these words; there is
no sound or shape to imitate.
LANGUAGE WITHIN OUR GRASP
Rizzolatti and Arbib argued that the discovery of mirror neurons
linking responsive motor programming in the brain of an observer
with observed motor patterning of action of another individual, could
have been the basis for the evolution of language. The mirror
neurons could have made, and still make, imitation possible,
including imitation of gesture. Arbib argues that “the ability to imitate
is a key innovation”, “a neurobiological ‘missing link’ for the
hypothesis that primitive forms of communication based on manual
gesture preceded speech in the evolution of language”. “A possible
evolutionary path from manual skills to language”. Gallese says “the
discovery of mirror neurons may provide a new, though still sketchy,
neurobiological basis to account for the emergence of language”.
SO WHAT CAN IMITATION DO IN THE EMERGENCE OF
LANGUAGE ?
Some things can be indicated by gestures, a
tree, the sky, a direction, up or down, come and go,
high and low. Gesture can be used to point to things,
to indicate hearing, eating or drinking, etc. But for
many things manual gesture is inadequate: colours white black red, sounds, different animals - what
would be a manual gesture for a horse, a fish, a rose,
a cabbage? Imitation must extend much wider than
manual gesture, for example to animal cries, the
noise of the wind or rain, thunder, lightning, the sea.
IMITATION IN THE BRAIN
Imitation v mimicry - What matters is stored imitation
(requiring commitment of neurons and interconnecting fibres)
in the form of a link between word and imitated act, sound or
shape so that there can be ready access to the word and what
it refers to. Words are anchored in the motor patterning and
are expressible as bodily and articulatory gesture. Deacon
quoted by Gerhard: the “everyday miracle of word meaning
and reference”. So each individual word was an arbitrary
invention with an equally arbitrary linking to what it related to!
With Herder and Humboldt, surely not.
HOW DOES THE WORD GET LINKED TO WHAT IT
REFERS TO ?
How was each gesture invented? Was each gesture as
arbitrary as traditional linguistics says that each word is?
Clearly not. A gesture is patterned by the action seen, the
shape of what is seen, the sound hear, for a vocal
gesture. Mirror neurons may allow transfer of the pattern
of an action and the ability to reproduce the action as a
gesture (not in any way arbitrary) - but imitation has to be
possible for much beyond perceived action.
HOW WORDS WERE FORMED
The process by which words were formed was the inverse
of the process by which gestures and sounds can be
generated from existing word-forms - a reverse application
of motor equivalence. On seeing some one hitting
something, the action patterning was by motor
equivalence converted into articulatory patterning to
produce a speech-sound structure, a word, directly related
to the action patterning seen. Similarly on hearing an
animal sound, the typical sound of a cat or a lion, the
sound-patterning is transduced by motor equivalence to
form a word whose structure is derived from the sound
heard.
IN BRIEF
Gestures of all kinds were generated by imitation
of actions, shapes and sound. These were stored
as motor programs before humans acquired
speech
When cerebral reorganisation provided new direct
connections between the motor cortex, the
tongue and the larynx, there was a great increase
in the innervation of the articulatory apparatus
generally. The motor programs from gestural
origins were transduced automatically into words
structured by the gestural programs. The
meanings of words were automatically linked to
the action, sound and shape percepts to which