Perceptual

• make sense of meaningless sensory input
• separate speech sounds from environmental sounds
• recognized words as the same across different speakers
• intermodal factors are involved (like vision)

4 month-old infants will look longer at a face making the correct articulation for the sound they are hearing than one that is not

high pitch, exaggerated intonation contour (sing-song), short sentences, longer pauses between phrases, prosodic repetition

• maintaining attention
• contributes to positive affect
• signals linguistic units of native language

• IDS emphasizes the parts of speech that are important 
• IDS helps infants to parse out separate sentences

• As adults we segment speech into meaningful units! 
•     Phrases within sentences
•     Words within phrases (e.g. pretty baby)
•     Syllables within words
•     Phonemes within syllables

sound production in the newborn is constrained by the oral cavity and respiratory patterns

vocal tracts of infants differ from adults

• Articulation: 
•     Infants can produce labial and dental consonants before velar consonants.
•     They can produce back vowels before front vowels