LINGUISTICS 330
Lecture #1
INTRODUCTION TO THE PHYSIOLOGY OF SPEECH
Physiology is the science that deals with the function of biological systems.
Anatomy is concerned with defining, observing and classifying the structural properties of
bones, muscles, cells etc.
The physiological method of describing the anatomy of speech production indicates
which elements have a functional value with regard to speech production and which
anatomical elements are irrelevant.
PHYSIOLOGICAL PHONETICS: The discipline that includes both anatomical
and physiological concepts.
“ORGANS OF SPEECH”???
None of the sounds of human speech is produced by an organ biologically designed for a speech
function.
Is speech an overlaid function?
↓
We have no unique speech organs -- speech is overlaid on the
organs that have primary (= biological) functions (a simplistic
view).
Speech is not overlaid: The organs relevant to speech have the kind of shape, position etc.
because of adaptive evolution -- evolution that favoured speech over basic biological functions.
ARGUMENTS:
1.
Downward slant of the ribs
•
The regulation of subglottal air pressure (essential for speech!) is possible because
our ribs are slanted downward from our spine.
•
The geometry of the downward slant and the insertion of the intercostal muscles
(see later) makes it possible to
a.
expand the chest
b.
oppose the elastic recoil force → STEADY SUBGLOTTAL PRESSURE!!
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Because of the anatomy of our ribs and
our ability to schedule a complex pattern of inspiratory and
expiratory muscle activity acting in coordination with the
elastic recoil force of the lungs
WE CAN GENERATE STEADY SUBGLOTTAL AIR PRESSURE
THROUGHOUT MOST OF THE EXPIRATION
•
•
2.
Newborn humans: The ribs are almost perpendicular to the spine → it is
impossible to use the muscles to maintain steady subglottal air pressure.
(Only after the third month will the ribs restructure toward the adult configuration).
The ribs of adult chimpanzees and gorillas also slant downwards, so they too have the
anatomy necessary to regulate subglottal air pressure.
Placement of the larynx
•
Newborn infants: They can move the larynx upward into the nasopharynx.
The high position of the larynx allows the newborn to do this.
The tongue and larynx of the baby elevate, the tongue to press against the nipple and
the larynx to connect with the nasal passage -- the baby can continue to breathe while
feeding.
The larynx forms an airway through the nose to the lungs; this airway is sealed from the
mouth (by the epiglottis!) → food and drink can go on either side of the elevated
larynx.
•
mammals also have the elevated larynx -- thus the respiratory and digestive tracts are
separated.
Consequence: greater apes and human babies are incapable of the vocal tract
adjustments necessary for sounds such as [i], [u] and [a] (see explanation
later).
3.
Laryngeal modifications for phonation
Deficiencies of the human larynx with respect to respiration:
↓
short length of the arytenoid cartilages -- the airway is restricted to 50%
of the tracheal cross section.
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FUNCTIONAL ADVANTAGE FOR PHONATION!!
Horses: long arytenoid cartilages (114% cross section): the larynx does not impede
the airflow from the horse’s lungs during respiration.
Functional trade-off between more efficient respiration and phonation.
CONCLUSION
The anatomy of the human respiratory system and larynx is quite similar to that of some
animals which also produce vocalizations on the expiratory phase of respiration.
But: Adaptive evolution (see the three arguments above!) has contributed towards the
development of refined phonations necessary for speech (at the expense of reducing the
efficiency of some of our basic biological functions).
CURRENT DEBATES ON THE RELATIONSHIP BETWEEN THE
SUPRALARYNGEAL VOCAL TRACT (SVT) AND SPEECH
P. Lieberman (1992):
• One of the biological mechanisms that is necessary for human speech is the
SVT.
The human SVT which consists of the nasal, oral and pharyngeal cavities is unique.
•
placement of the larynx
(respiratory and digestive tracts are not separated)
Charles Darwin was perhaps the first, who noted:
“… the strange fact that every particle of food and drink which we swallow has to pass
over the orifice of the trachea, with some risk of falling into the lungs”.
•
the tongue forms the anterior margin of the pharynx as well as the
lower margin of the oral cavity: capable of three-dimensional
movement.
(Animals: flat, more massive tongue; it is positioned entirely
within the oral cavity).
•
the long pharynx in the adult human, along with the oral cavity,
produces the two-chamber resonator distinctive in human adults:
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e.g. If the tongue is moved upward and toward the lips to produce the
vowel [i], the cross-sectional area of the oral cavity will be constricted;
pharyngeal cavity: large.
For the vowel [å], the pharyngeal cavity is constricted. Oral cavity:
large.
The motion of the human tongue allows us to produce abrupt changes in
the cross-sectional area of the SVT.
Another important fact regarding the SVT:
•
the nasal cavity can be sealed completely by the velum: non-nasal
speech!
The anatomical condition of the SVT (the relatively low position of the larynx; tongue shape
and position; velic closure) allows a high transmission rate of human speech.
The human SVT allows the tongue to play a more extensive role in modifying the
oropharyngeal cavity during phonation than it does in any other species, thus a
wider range of vocalic speech sounds becomes available.
Increased range of vowel sounds; decreased nasality
Increase in the perception of speech sound differences!
Recent research suggests that languages were evolving for more than a million and a
half years prior to the first appearance of a truly modern vocal tract.
Evidence indicates that the vocal tract about 2 million years ago exhibited an
intermediate vocal tract configuration that is neither modern nor ape like.
•
it was probably capable of producing the entire range of non-vocalic articulatory
movements (except those involving the soft palate; also, all sounds would be less
distinctive due to nasality).
•
restricted range of vocalic sounds
HOMO ERECTUS WOULD HAVE BEEN CAPABLE OF A SOMEWHAT
INTERMEDIATE RANGE OF VOCALIC SOUNDS AND PROBABLY THE FULL
SET OF NON-VOCALIC SOUNDS.
Differences between the roles of vowels and consonants support this possibility:
•
•
major vowel substitutions are more flexible and frequent than consonant
substitutions: accents, dialect evolutions etc.
the greater importance of consonants is also evidenced by languages with few
vowel distinctions and with written scripts that do not specify vowels at all.
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•
different perceptual and production predispositions also distinguish vocalic
and non-vocalic sounds:
non-vocalic sounds are distinguished by discrete phonemic oppositions.
in production: optimization of place and VOT differences
in perception: discontinuous categorical perceptual biases (see later)
Vocalic sounds:
•
•
less quantified
more variable
Non-vocalic distinctions are determined by discrete invariant category boundaries,
vocalic distinctions are determined with respect to a variable category centre without
clear boundaries.
Phonetically modern languages may only extend back to the appearance of the modern
SVT; but there have been many stages of archaic languages → influencing and being
influenced by SVT evolution.
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