How are words combined, is a sentence grammatical?

Child-directed Speech

Motherese/infant-directed speech (IDS)/child-directed speech (CDS), when talking to babies, adults use a higher-pitched voice, a wider range of pitches, longer pauses, and shorter phrases. Vowels are not only longer in duration, but also are more prototypical examples of the particular vowel being produced

  • Generally more straightforward - focused on here and now, directs joint attention, and connects to real world referents
  • Lots of repetition for new lexical items
  • Helps with language acquisition

Learning Syntax

Syntactic bootstrapping hypothesis: knowledge of language structure is generally useful for learning new verbs. If we know what the syntactic structure of the language is, it is easier to figure out the meaning of a new word

Negative evidence: correcting overgeneralizations. There is no negative evidence in the speech stream without explicit feedback

Cross-situational learning: computing correlations between hearing a word and experiencing its referent (see Smith & Yu 2008 for related study on whether cross-situational learning is a possible explanation for how children learn words)


  • Longest utterance
  • Average utterance (mean length of utterance or MLU)
  • Kinds of sentences the child can produce

Stages of development

  • Stage I (MLU 1.01 to 1.99): earliest word combinations
  • Stage II (MLU 2.00 to 2.49): grammatical morphemes start showing up
  • Stage III (MLU 2.50 to 2.99): varied simple sentences
  • Stage IV (MLU 3.00 and up): varied complex sentences
  • Stage V: new complex sentences

Types of Grammars

  • Prescriptive grammar: dictates how people should speak, gives rules and grammar based around a “standard” or “correct” way of speaking, ignoring variation between dialects or between different demographics of people
  • Descriptive grammar: we want to describe how people actually speak, not how we think they should speak
  • Open-class words: nouns, verbs, adjectives (can be added to)
  • Closed-class words: auxiliaries, prepositions, complementizers, determiners (usually fixed in language)
  • Sentence types
    • Declarative (statement): “that’s a doggie”
    • Imperative (command): “look at the doggie”
    • Interrogative (question): yes/no questions
    • Negative sentences: contain negation
    • Complex sentences: contain more than one main verb
  • Hirsch-Pasek and Golinkoff (1996): word order comprehension study. Do children know about subjects vs. objects and word order?

Two theories of syntax

  • Innate/generative: children do not “learn” anything specific for a given language, they already have a universal grammar (UG), they learn language-specific parameters to the UG
  • Experience-based/constructivist: grammatical knowledge comes completely from experience