From Andy Papanicolaou [920603 15:31]
It seems that most of the basic psychological phenomena have not
been dealt with - not systematically at any rate - in the context
of CT. Yet it is obvious that if CT is to be accepted as a
general psychological theory, it must deal with all (or most) of
these phenomena at least as effectively as the alternative open
loop approaches.
From a certain point of view, the task of providing a more
satisfactory explanation of psychological phenomena than open loop
approaches do, does not appear to be very challenging. yet when
one sits down to construct any reasonable and consistent
explanation for some of these phenomena, the task proves anything
but easy.
Take for example, the phenomenon of skill acquisition or habit
formation whereby a sensori-motor event sequence, originally
produced haltingly, awkwardly with great effort and requiring
conscious attention comes to be performed effortlessly
automatically and reliably following a number of trials or
repetitions.
An instance of that phenomenon could be the gradual acquisition of
the skill to pronounce reliably and correctly a speech syllable
consisting of phenonemes, some of which do not exist in the
learner's native language, like the monosyllabic French word, tu.
This word consists of an initial consonant common to both English
and French and a vowel sound which is a phoneme in French, but not
in English.
To produce that syllable a specific sequence of partially
overlapping articulatory gestures is required constituting a
pattern with some invariant features. The English-speaking learner
cannot at first produce the sound tu, ostensibly because of the
novelty of the required pattern of articulatory gestures. Instead,
the learner produces sounds closer to the familiar too or tee,
realizing meanwhile that he is off his intended target. After
several repetitions and with considerable concentration, he begins
to approximate the sound tu until, finally, he can produce it
effortlessly and reliably. The fact that he can do so by virtue of
having acquired the skill or habit of moving different components
(muscles) of his articulatory apparatus in the same specific way
suggests (without requiring) that a neuromotor plan has been
perfected which, once triggered by the intention to produce the
sound tu unfolds effortlessly into the appropriate muscle
movements.
Needless to say, the notion of a plan or a set of commands from the
brain to the muscles is not a control-theoretic notion at all.
This way of producing output is generally inefficient because any
unforeseen disturbances will make it impossible for the intended
perception to materialize.
On the other hand, some disturbances do indeed prevent the
production of the articulatory pattern that results in the intended
perception of the sound tu - those that prevent the execution of
any of the constituent movements at their appropriate time. The
lips, for example, must be rounded or else the entire set of
articulatory movements will not result in the intended perception
of tu. The range of variations in the shape and temporal unfolding
of the pattern is rather limited. The perception tu cannot be
achieved unless the same muscles are always used to always do
almost the same thing - to produce the same pattern of articulatory
gestures.
Again, this fact does not compel us to adopt the notion of the
"plan", but it does show why the notion has some appeal, and it
does urge one to come up with a CT model for the same phenomenon
that would have even greater appeal.
In an attempt to come up with such a model, one encounters several
difficulties. Here are a couple: Should one consider as the
reference signal the auditory percept tu that the learner heard
repeatedly from the teacher? It would seem, at first, to be the
sensible thing to do. Yet there are all kinds of empirical
findings suggesting that no phoneme can be perceived as such unless
some "motor plans" for its production have already been formed even
though the learner may not be able as yet to bring his articulation
to implement the plant (and produce the phoneme): The native
speaker of Japanese cannot hear, cannot experience the difference
between r and l when first exposed to these sounds. Slowly, she
may come to experience them (once a motor plan for their production
is presumably formed) but, instead, she would utter either one of
them in the place of the one she is supposed to utter. Finally,
she may come to articulate them reliably (once her articulators
have been presumably trained to implement the neuromotor commands).
We may forego the explanation involving neuromotor plans, but we
can hardly forego the indications that before acquiring a skill to
pronounce new speech sounds we cannot take it for granted that the
learner possesses auditory images of the new sounds to use as
reference signals.
Another difficulty: It is a fact that the process of acquisition
of the skill of pronouncing unfamiliar speech sounds is greatly
enhanced if the learner is given the opportunity to see how the
speaker's (the teacher's) mouth forms these sounds. Then the
learner imitates the part of the gesture pattern that is visible,
and this invariably helps. Now, this fact suggests that,
initially at least, it may not be the auditory image of the sound
but the visual image of the speaker's articulators that serves as
a reference signal. Or that these aspects of both images that are
available to the learner serve as reference signals. Moreover,
once the imitation of the speaker's (teacher's) visible gestures
help the learner to approximate the sound, the afferent signals
from the learner's articulators become also available as
references.
We can go on and on with difficulties, but at some point, we must
begin drawing the outlines of a CT model that simulates the process
of this sort of habit formation. If you have any suggestions, Tom
and I would surely appreciate them.