It all begins when a child comes into the world. There is nothing deliberate in the baby’s cry! The baby’s muscles, all of them, are under tension, and the air flowing out of the lungs triggers this baby’s cry.
« The acoustic structure of the human voice relies on the synergetic actions of various muscles. A toddler’s cry results from the concomitant contraction of the chest, abdomen, limbs and cervico-facial region. Human beings progressively learn how to control the body and expression language, how to discriminate the motor units required for sound emission – as opposed to those that are useless for this function – and what tension should be applied to what muscle and at what particular moment, in order to emit the intended sound »(1).
When babies are hungry, they contract one specific set of muscles and this produces a specific sound. When babies are cold, they contract another specific set of muscles and this produces another, different sound. The mother, based on her experience, will know how to interpret these sounds.
« Undoubtedly, a baby’s cry, this primary signal, is nothing but a reflex: there is no deliberate laryngeal function involved but a whole set of muscles triggering a global respiratory movement: when the toddler gets in exhalation phase, for air ejection, a contraction of the larynx will occur concomitantly and result in a squeal. A baby’s cry is thus the side-event of a global muscular phenomenon which is the primitive phase of a child’s body language. A baby’s cry is a random event related to an anatomical layout, but, over time, various shapes of cries appear and provide the mother with information about the muscular contraction state of her child. Let me explain this: when toddlers endure pain, their muscular tension is different from when they are hungry in respect to the muscular tension itself, as well as the starting point and the intensity of this tension. These various muscular tensions produce various types of cries for pain, hunger, happiness… but these are only side-events, with no direct relation to the expression of a baby’s condition. At this stage, a baby’s behaviour is purely of a muscular nature. The resulting side-events, though, are informative to the mother, as the various cries help her identify the various movements of her toddler and what caused them. Every scream has a definite shape because it results from various types of muscular tensions, and from their behaviour over time. Hence the variety of screams. It is important not to consider a baby’s cry as the first vocal element produced by children, as their first attempt to communicate: this is purely irrational on a physiological point of view. It is, though, the first acoustic expression of a toddler – an incidental expression» (2).
At some point, the child will understand, start to conceptualise and realise the interest of producing one particular sound related to a particular set of muscles contraction, as it triggers in return a reward from the mother or the parents. Systematically getting a reward following the systematic contraction of a specific set of muscles… this does sound like a Pavlovian reflex!
Over time, in their cots, babies learn how to use the contraction of various sets of muscles in order to produce different sounds.
It is very important that parents read stories to their toddlers and sing them lullabies: this helps children to gain the notions of pace and tunes. It allows them to develop the concept of sentence structuration over time. The acquisition of the language itself relies on the notion of time.
(1) Professor J.C. LAFON « message and phonetics » page 101.
(2) Professor J.C. LAFON « talk on language writings, Délémont 1977 » page 5.