Prosody, generally defined as any perceivable modulation of duration, pitch or
loudness in the voice that conveys meaning, has been identified as part of the
linguistic system, or compared with the sound system of Western classical music.
This thesis proposes a different conception, namely that prosody is a phenomenon of
human expression that precedes, and to a certain extent determines the form and
function of utterances in any particular language or music system. Findings from
studies of phylogenesis and ontogenesis are presented in favour of this definition.
Consequently, prosody of infant vocal expressions, which are made by individuals
who have not yet developed either language or musical skills, is investigated as a
phenomenon in itself, with its own rules.
Recognising theoretical and methodological deficiencies in the linguistic and
the Piagetian approaches to the development of infant prosodic expressions, this
thesis supports the view that the origins of language are to be sought in the
expressive dialogues between the mother and her prelinguistic child that are
generated by intuitive motives for communication. Furthermore, infant vocalisations
are considered as part of a system of communication constituted by all expressive
modalities. Thus, the aim is to investigate the role of infant prosodic expressions in
conveying emotions and communicative functions in relation to the accompanying
non vocal-behaviours.
A crossectional Pilot Study involving 16 infants aged 26 to 56 weeks and their
mothers was undertaken to help in the design of the Main Study. The Main Study
became a case description of two first born infants and their mothers; a boy (Robin)
and a girl (Julie) both aged 30 weeks at the beginning of the study. The infants were
filmed in their home every fortnight for five months in a structured naturalistic
setting which included the following conditions: mother-infant free-play with their
own toys, mother-infant play without using objects, the infant playing alone, motherinfant
play with objects provided by the researcher, a 'car task' for eliciting
cooperative play, and the mother staying unresponsive. Each filming session lasted
approximately thirty minutes. In order to get an insight into the infants' 'meaning
potential' expressed in their vocalisations, the mothers were asked to visit the
department sometime in the interval between two filming sessions and, while
watching the most recent video, to report what they felt their infant was conveyingif
anything- in each vocalisation.
Three types of analysis were carried out:
a) An Analysis of Prosody - An attempt was made to obtain an objective, and not
linguistically based account of infant prosodic features. First measurements were
obtained of the duration and the fundamental frequency curve of each vocalisation
by means of a computer programme for sound analysis. The values of fundamental
frequency were then logarithmically transformed into a semitone scale in order to
obtain measurements more sensitive to the mother's perception.
b) A Functional Micro-Analysis of Non-Vocal Behaviours from Videos - The non
vocal behaviours of mother and infant related with each vocalisation were codified
without sound to examine to what extent the mothers relied for their interpretations
on non-vocal behaviours accompanying vocalisations.
c) An Analysis of the Mothers' Interpretations - The infants' messages were defined
as perceived by their mother.
The corpus comprised 713 vocalisations (322 for the boy and 391 for the girl)
selected from a corpus of 864, and 143 minutes of video recording (64 for the boy
and 79 for the girl). Correlations between the above three assessments were
specified through statistical analysis.
The findings from both infants indicate that between seven and eleven months
prosodic patterns are not related one to one with particular messages. Rather,
prosody distinguishes between groups of messages conveying features of
psychological motivation, such as 'emotional', 'interpersonal', 'referential', 'assertive'
or 'receptive'. Individual messages belonging to the same message group according
to the analysis of prosody, are distinguished on the basis of the accompanying nonvocal
behaviours. Before nine months, 'interpersonal' vocalisations display more
'alerting' prosodic patterns than 'referential' vocalisations. After nine months
prosodic patterns in Robin's vocalisations differentiate between 'assertive' and
'receptive' messages, the former being expressed by more 'alerting' prosodic patterns
than the latter. This distinction reflects a better Self-Other awareness. On the other
hand, Julie's vocalisations occurring in situations of 'Joint Interest' display different
prosodic patterns from her vocalisations uttered in situations of 'Converging Interest'.
These changes in the role infant prosody reflect developments in the infants'
motivational organisation which will lead to a more efficient control of
intersubjective orientation and shared attention to the environment. Moreover, it
was demonstrated that new forms of prosodic expression occur in psychologically
mature situations, while the psychologically novel situations are expressed by
mature prosodic forms. The above results suggest that at the threshold to language, prosody does not
primarily serve identifiable linguistic functions. Rather, in spite of individual
differences in form of their vocalisations, both infants use prosody in combination
with other modalities as part of an expressive system, that conveys information
about their motives. In this way prosody facilitates intersubjective and later
cooperative communication, on which language development is built. To what
extent such prelinguistic prosodic patterns are similar in form to those of the target
language is a crucial issue for further investigation