Diverse theories of infant speech production, i.e., e.g.:
 the universal theory (Jakobson 1941)
 the articulatory learning theory (cf. Ingram 1989)
 the maturational theory (Locke 1983)
 the refinement/attunement theory (Oller 1986) refer their diverse predictions to the commonly assumed stages of motor speech development.

• the earliest vocalizations
• reflexive (0-2 months)
• control of phonation (2-4 months)
• expansion/vocal play (5-6 months)
• canonical babble (7-9 months)
• variegated babble and first words (10-14 months) (the prelinguistic stage - up to the first word)
• and the period of the first 50 words

Early development of phonology: production, perception and self-organization
AGE
0-2m reflexive phonation
MOTOR
DEVELOPMENT
& PRODUCTION
PERCEPTION SELF-
ORGANIZATION
PREDISPOSITIONS
/REPRESENTATIONS cry cough grunts & sighs
[s] /other; sounds/voices; mother/others; intonation/mono
-tone;
(silence/sound) physiological restriction; discovering the vocal tract perceptual domains difficult to distinguish

2-4m control of phonation
( 1-4m cooing) cooing sounds;
V-like & C-like sounds; syllabic [n]; nasalized V;
C-like sounds at tongue-palate contact (  back
Cs); strings of vocalizations; vocal learning
3-5m – vocal imitation based on auditory exteroception
(hearing ambient language) & proprioception
(hearing own language) of Vs; articulatory movement & sound-related visual imitation
(of facial movements) at 4m - the vocal tract starts assuming more adult-like form; stored representations
(since infants able to improve their production); auditoryarticulatory map evidenced
(v. preliminary categorization)

5-6m expansion vocal play
( 3-6m expansion) increased coordination of articulation & phonation
(front C's  visual imitation); short/long sounds; marked sounds
& sequences possible (since the beginning); onomatopoea up to 5.5m - v.
few differences between NH
(normally hearing) & HI
(hearing impaired); phonological functions not served yet
(rather: vocal & perceptual gymnastics);
 extragrammatical phonology after 5.5m – auditory feedback influences production
(more) pre-phonology


7-9m canonical babble
(5-10) reduplicated babble, repetitive
CV's:
CV CV CV CV
(CV)...; mandibular oscillation cycles: close & open phases;
CV's – articulation place dependent; general propensity for rhythmical movement perception of close & open phases 
CV's perceived & imitated
(still universal perception) figure & ground principle; listener-friendly function; hand-waving
 leave-taking formula ease of articulation
(speakerfriendly function)

10-14m variegated babble & b d (preferred stops); m n j w h; left-quadrant V's; first words complex babble; trochee; segmental & prosodic features of babble preserved in early words;
( 10-18m meaningful speech) variability in word production; b (preferred among stops) words: CVCV, CVC,
(CVC+CVC  )
CVCCV(C),(CV)CCV(C)
7-11m – infants perceive SC
(silent centre)
/dVt/'s (German) ca.1 year – languagespecific perception starts
 onset of protophonology
 segmentation of input into groups
(feet, words); vowel harmony
[centr];
C-harmony [labial]; trochaic rhythm
[stress]; extraction of features/gestures of
CV's, later - also for
VC's: fortitions (language specificphonotactics

14m  first 50 words lenitions – make articulation of the above easier, e.g.
ke  kje; language-specific development of rhythm
(segments  writing,
"knowing" about phonetic segments)
(phonemic perception & production start (?))
(4-and 6-year olds still have problems with phonemic categorization) overproductivity of lenitions; fluctuations
(unsystematic application of processes); variability (intra&inter)

onset of phonology proper : language-specific phonology starts dissociating from extragrammatical phonology & morphology; regularization ("order")
(function-dependent hierarchies of processes)

Smith et al. (1995), Bohn & Polka (1995),
Clement & Koopmans-van Beinum (1995),
Kuhl & Meltzoff (1995), Kuijpers (1995),
Davis (1995), Studdert-Kennedy (1981),
Kent (1992), Werker & Pegg (1992),
Jusczyk (1992), Wode (1994)