The Physical Foundation of Language (1973) set out a system of equivalence between speech sounds and gestures (positions and movements of the hand and arm). Speech sounds were formed into five groups, Vowel, Projective, Main Consonantal, Lateral and Circular. The number of speech sounds in each group ranged from 4 for the Circular Group to 5 for the Vowel and Lateral Groups and 7 for the Projective and Main consonantal groups.

Though the book assembled a good deal of circumstantial or supporting evidence for the equivalence scheme, the primary source of the scheme was through an introspective or mental-operation approach. This consisted essentially in clearing the mind from other distracting contents, mentally focusing on each speech sound, for example, the sound 'B', and then transferring attention and thus the motor pattern for articulation of the speech sound to the arm and hand (in a way similar to that in which one might transfer a pattern of action, for example writing one's signature, from the right hand and arm to the left hand and arm). The systematic relation of the hand and arm positions and movements with the speech sounds was derived directly from this 'transfer of attention' process.

The aspect of the equivalence scheme in the Physical Foundation of Language which requires more examination and explanation is the way in which the combination of two (or more) speech sounds is reflected in a combined pattern of position and movement in the hand and arm. For example, if 'B' is combined successively with each of the elements in the Vowel group, giving BA BE BI BO BU, how is the succession of combined positions, found by the 'mental' process, produced. Similarly when the order of combination is reversed, giving AB EB IB OB UB, how is the different sequence of arm and hand positions produced? By the 'transfer of attention' process, the sequence BA .. etc. leads to a regular array of arm positions progressively further out to the side from the starting position for B. The same is the case when other elements from the Main Consonantal group are combined with Vowels e.g. CA CE CI CO CU, the only difference being that the starting position is the higher one associated with C rather than with B. The reverse combinations, AB ... AC ... , have starting positions of the arm bent outwards rather than inwards but otherwise alter in an orderly way as the vowel is changed from A to E to I to O to U.

The process of combination also has to be examined when consonantal sounds from other groups are combined with vowels, for example, the Projective consonants (forming combinations such as JA JE JI JO JU, TA TE TI TO TU, and reverse combinations, AJ ... etc., AT ... etc.) and the Lateral consonants (SA SHA WA, AS ASH AX). There are also the combinations of two or more consonantal sounds (with or without a vowel) to be dealt with, eg. BL CL FL GL SP ST PL PR TR SPL SPR.

As an aid to understanding the ways in which the movement elements in the different groups are produced, Figure 1 shows the bony and muscular structures which govern the position and movement of the arm:

Insofar as combining speech sounds is equivalent to combining motor patterns, the problem can be seen as an anatomical one, how action of muscles and joints specified by neural programs can be combined within the limits set by the anatomical relations of the muscles, joints and bones (on the general problem see a recent (1997) paper by Buneo and others). If the initial speech sound in a combination is 'B', then this specifies a particular alignment of the bones of the upper arm and forearm, and particular tensions and relation of the muscles controlling the flexion of the arm. If to the speech sound 'B' must now be added, as far as is possible, the motor pattern associated with the vowel 'A' (to form BA), then instructions for 'A' have to be superimposed and melded with those already executed for the speech sound B. As the combined vowel is varied from A to E to I to O to U, there is a regularly changing value inherent in the instructions for the vowels which is reflected in the regular change in the positions of the arm and hand for the sequence of combinations BA BE BI BO BU. But in addition there is a general difference between the pattern for any vowel and the pattern for any consonant in the Main group, which determines the nature of the line of positions for BA .. etc, as this line differs from that for positions of the arm associated with the vowels A E I O U in isolation.

The most direct way of examining combinations such as BA BE etc. is to identify the muscle changes involved for the gesture equivalents of A E and B separately and then for the combination BA BE etc. For A, one can directly feel, with the left hand, the tightening of the biceps muscle of the upper right arm; what seems to be involved is a simple shortening of the muscle which lifts the forearm into the position of the arm-equivalent for A. Other vowels, E I O U, represent a progressively greater degree of shortening of the biceps muscle. Assume then that the neural instruction for a vowel is simply 'Contract the biceps'. Examining in a similar way, changes in muscle length and tension for the equivalent of B (with the arm brought in across the body and the elbow bent), one finds that a different system of muscles is activated, the thoracic muscles which draw the arm inward as well as well as a shortening of the biceps. The combination of the muscle changes for B and A to form BA thus involves the addition of a further shortening of the biceps to the muscular pattern already executed for B, and this produces the characteristic position of the arm for BA. The combinations following BA, BE BI BO BU, simply reflect the further progressive shortening of the biceps superimposed on the B muscular pattern.

One has to examine how, anatomically, the range of movements of the arm is produced by differential contraction and relaxation of the shoulder and arm muscles. The standard terms for arm and hand movements are adduction and abduction, supination and pronation, circumduction or rotation, flexion and extension.

For two of the groups listed above, the Circular Group and the Lateral Group, the position is fairly straightforward: the hand and arm movements in the Circular Group are categorised as circumduction or rotation; the movement elements in the Lateral Group involve abduction (moving out from the side of the body) or adduction (moving in and across the body) to systematically varying extents. The following are brief accounts of the anatomical basis of these movements:

CIRCULAR GROUP: L M N R ROTATION OF THE FOREARM

The inward rotation of the hand and forearm is termed pronation. The prime muscles involved are the pronator teres and pronator quadratus. The outward rotation of the hand and forearm is termed supination. The prime muscles involved are the supinator and the biceps; the biceps gives the power to the movement of rotation. The total range of rotation of the hand and forearm is 180 degrees, pronation extending from 0 degrees to 90 degrees(palm down), supination from 0 degrees to 90 degrees (palm up). The zero point is the mid-position (the elbow at the side, the hand or palm facing medially in the sagittal plane of the body). In supination the radius and ulna are parallel and the thumb is pointed laterally; pronation swings the lower end of the radius across the relatively stable ulna, carrying the hand with it, and points the thumb medially. These movements are made possible by rotation at the distal and proximal radioulnar joints. The wrist may be flexed, extended, abducted and adducted but true rotation is not possible. The radius with the hand attached rotates as a unit about the ulna. With the radius and ulna crossed there is pronation; with the two bones parallel there is supination.

LATERAL GROUP: S SH W X Z ABDUCTION AND ADDUCTION OF THE ARM

Abduction is movement away from the midsagittal (median) plane of the body and adduction is movement towards that plane. For the elements as initials in the Lateral group, movement is out from the side; for the elements as finals the movements are in from the side (medial). Abduction, movement of the arm out from the side of the body, is primarily produced by contraction of the deltoid muscle. Adduction is chiefly produced by the pectoralis major and the teres major.

The anatomical and neural basis for the movement elements in the remaining three groups, Vowel, Main Consonantal and Projective, is much more complicated:

VOWEL LINE: A E I O U ADDUCTION AND ROTATION OF THE ARM

The vowel line consists of a succession of positions of the arm from a start at the side of the body to a position vertically above the head, a total movement of approximately 180 degrees to a final position parallel to the body above the head. The first part of this movement, up to the point where the arm is level with the shoulder, is produced by rotation of the arm round the horizontal axis of the shoulder joint; this is produced by the concerted action of a considerable number of muscles including the deltoid, the teres major, the pectoralis major and muscles of the back. The second part of the movement, from the position of the arm level with the shoulder up to the highest point above the head, requires outward rotation of the humerus around its long axis and calls into play a range of other muscles.

MAIN CONSONANTAL LINE: B C D F G H

The movement is a combination of adduction of the arm across the body with progressive flexion of the forearm and inward rotation of the arm. The main muscles involved are the pectoralis major, the deltoid and the triceps brachii (with ancillary involvement of a number of other muscles).

PROJECTIVE GROUP: CH J P T Y

These elements are produced by a ballistic forward movement of the arm coupled with extension of the forearm.

NOTE: For consideration of muscular interaction in arm movement see:

Abbs, J.H. 1982. Open Peer Commentary on:
Stein, R.B. 1982. What muscle variable(s) does the nervous system control in limb movements? Behavioral and Brain Sciences 5: 535-5

pp. 541-2 "it seems plausible that in nature the controlled variable of many motor behaviors is a functional combination of several interlaced actions ... it may be that the precise combination of motor schemata defines skilled movement and is achieved through a coordinated control program, the purpose of which is to control the timing of activation of a number of subsystems ... coordinated control programs 'orchestrate' motor schemata to perform movements ...

Bizzi, E. 1983. Central processes involved in arm movement control. In The production of speech. ed. P, Macneilage, pp. 3-10. New York: Springer- Verlag.

p. 8 "Arm and head movements depend on neural patterns that are programmed prior to movement initiation. What is being preprogrammed is a process that is capable of controlling final head and arm position as an equilibrium point resulting from the interaction of agonist and antagonist muscles..

Buneo, Christopher A., John F. Soechting and Martha Flanders 1997. Postural Dependence of Muscle Actions: Implications for Neural Control. Journal of Neuroscience 1997 17(6): 2128-2142.

"The neural control of reaching entails the specification of a precise pattern of muscle activation distributed across the many muscles of the arm. Musculoskeletal geometry limits the possible solutions to this problem. Insight into the nature of this constraint was obtained by quantifying the postural variation in the mechanical actions of six human shoulder muscles. Estimates of muscle mechanical actions were obtained by electrically stimulating muscles to the point of contraction and recording the resulting forces and torques with a six-degree-of-freedom force/torque transducer. In a given experiment, data were obtained for up to 29 different arm postures. The mechanical actions of each muscle varied systematically with arm posture, regardless of the frame of reference used to define these actions. The nature of this dependence suggests that a relatively simple strategy can be used by the nervous system to account for the changing mechanical actions of arm muscles...."

"The following shoulder muscles of the right arm were examined in this study: anterior deltoid (AD), middle deltoid (MD), posterior deltoid (PD), latissimus dorsi (LaD), clavicular head of pectoralis major (CPec), and the upper portion of the sternocostal head of pectoralis major (SPec). "