ABSTRACT
The Frame/Content theory of the evolution of speech production (MacNeilage,
1998) predicts that only modern humans superimpose a continual rhythmic
alternation between an open and a closed mouth-defined as a Frame-on the
sound production process. MacNeilage emphasizes that the question of skill
development in speech production requires some background. An important
issue to note in this perspective is that most work on sound preferences in
babbling and in early words has been done on consonants. But the question of
the emergence and control of these sounds has not been developed as explicitly
as for vowels. Since Lindblom (1986), principles explaining the emergence of
vowels in sound systems of human languages are better understood. Lindblom
and Maddieson (1988) suggested a consonant classification in three levels of
difficulty in terms of the number of separate active subcomponents required.
