Language development

Infant speech perception

Infants show more interest in the human voice than other sounds

◦ Auditory system becomes functional around 25 weeks gestation

◦ maternal speech is audible in utero during the third trimester (DeCasper & Spence,

1986)

1 month

Babies can discriminate speech sound

6.5 months

Babies can discriminate strings of syllable

8 - 10 months

Babies lose their ability to discriminate universal sounds

(Werker & Tees, 1984)

◦ Form category boundaries to facilitate acquisition of their own language

Stages of Early Vocal Development: Infancy

Jargon (12 month)

Canonical

Expansion

Cooing

Phonation (birth)

vocal play

◦ production of non-speech and speech-like sounds (mostly vowels

babbling 6-12 mos

strings of simple consonant-vowel combinations

◦ First speech sounds

◦ include frequent phonemes, but not restricted to those in the language

◦ reduplicative: repeated syllables, e.g. ba-ba-ba (also canonical babbling)

◦ variegated: non-repeated syllables, e.g. ba-ga-dee-boo

reduplicative

repeated syllables, e.g. ba-ba-ba (also canonical babbling)

variegated

non-repeated syllables, e.g. ba-ga-dee-boo

Babbling - Independent of language being

acquired?

◦ Almost all infants babble (even deaf

infants)

◦ Developmental sequence very

similar across languages

◦ Early: p, t, k, b, d, g, m, n, s, h, w, j

◦ Later: f, v, θ, ð, ʃ, ʒ, ʧ, ʤ, ŋ, ɹ, l

◦ Sounds common cross-linguistically

are produced first; sounds rare

cross-linguistically produced later

Protowords

word-like structures; emerge during later babbling stage

◦ intermediate between variegated babbling and one-word utterances

One-word stage (~12-18 mos.)

◦ Single form functioning the same way as an entire phrase/sentence in adult

speech

◦ Usually monosyllabic/CV syllables

◦ May reflect combinations of words, but these words cannot be broken down and used

separately

= Holophrastic stage

◦ single form functioning the same way as an entire phrase/sentence in adult

speech

Early vocabulary development:

Infancy into Toddler years

Comprehension precedes production

5 months

Child's name is first word understood

8 months

children understand phrases; reliably discriminate between

"words" and nonwords!

10 months

children understand individual words

16 months

children understand between 100 and 300 words

The vocabulary "explosion"

• slow learning at first, but tends to

accelerate at ~ 18 months

(although this is variable across

individual children)

• may actually be several waves or

spurts...

mapping problem

Hypothesized lexical principles/constraints/biases

(often violated before vocabulary spurt):

▪ whole-object bias: attend to whole objects vs parts of objects

▪ mutual exclusivity: each object has only one label

▪ N3C (novel name-nameless category):

unknown label must refer to novel objec

Social mechanisms of word learning

ostensive learning

object, event, perceptual characteristic, etc.

exaggerated prosodic

structure; canonical word order

ostensive learning

◦ learning by pointing out examples

joint attention

◦ talking about the here-and-now; matching

words to specific discourse settings

◦ using eye gaze, pointing, or other means to draw attention to the same

object, event, perceptual characteristic, etc.

◦ using common ground (shared knowledge); focus on child's interests

child-directed speech

◦ slow, phonologically simplified, clearly segmented,

structure; canonical word order

◦ adapted to child's level of comprehension

Errors of word learning

over-extension

◦ words are used too generally, because set of

features is incomplete

under-extension

◦ words are used too specifically, because features are

misinterpreted as contrastive (distinguishing

between categories

The "gavagai" problem

translation is far more arbitrary than it seems. Based purely on observable behavior and stimulus conditions (seeing a rabbit), "Gavagai" could logically mean several different things

Word learning by type of word

nouns tend to predominate in early stages of word learning, but there may be cultural/linguistic differences

second wave involves emphasis on predication (at ~100 words)

◦ 1-word → 2-word combinations, using verbs and adjectives

third wave involves shift toward grammatical usage (at ~400 words)

◦ increase in use of function words

Two-word stage

◦ combinations of single known words

◦ Functional/inflectional morphemes are still missing

◦ Tend to follow word order of the target languag

Telegraphic stage

Multi-word utterances with functional/inflectional morphemes missing

Later syntactic development

◦ follows a U-shaped curve (correct→incorrect→correct)

Acquisition of inflections

• particularly with irregular forms, which occur on many highly

frequent verbs (e.g. past tense: ran → runned → ran)

• Stage 1: A few irregular past tense forms used correctly

• Stage 2: Acquire regular past tense suffix, and overgeneralize it to

irregular verbs (including those previously used correctly!)

• Stage 3: Recover from overregularization; adult-like performance

basic principles of typical language

development

1) Development is predictable

2) Developmental milestones are attained at

about the same age in most children

3) Developmental opportunity is needed

4) Children go through developmental

phases or periods

5) Individuals differ greatly