Semantic Development

• Acquisition of words and their meanings• First words at about 12 months• Initially this is a slow, gradual process

– Maybe learn a couple of words a week– Object words, commands, some social words (bye-bye)

• Then, several months after it begins, word learning speeds up dramatically– Usually begins when child’s vocabulary is around 50-

100 words– The “Vocabulary Burst” or “Naming Explosion

The Vocabulary Burst

• Rapid increase in the rate of word learning in very early childhood. Estimated that the average 5-year-old knows about 6000 words– If child knows 100 words at 18-months, this means they learn

5900 words over the next 3 ½ years. – Almost 5 words/day– “Fast-Mapping”

• How do they do it?– Naming insight: Everything has a name and there’s a name

for everything– Application of word-learning strategies or principles specific

to this task:

Word Learning Principles

• Why do we need them?– Quine’s (1960) “gavagai” example

• Taxonomic assumption – Words are labels for categories of things

• Whole-object assumption – Words label whole objects, not parts or attributes

• Mutual Exclusivity– Avoid attaching two labels to the same object– The disambiguation effect (Merriman & Bowman,

1989)

Word-learning errors

• Undergeneralization– Using a word to narrowly, e.g. only using “cat” for your

own pet– More common in early word learning, prior to naming

explosion

• Overgeneralization– Using a word too broadly, e.g. using “cat” to label cats,

dogs, cows, etc…– More common after the naming explosion– Do they really think a cow is a cat? More likely it is

“lexical gap filling”

Syntactic development

• Shortly after the vocabulary burst, kids begin to combine words. – “mommy sock”

• Early word combinations typically express a common set of meanings– Recurrence “More bottle”

– Negation “No bottle”

– Possession “My bottle”

– Actor-action “Baby eat”

The 14 Morphemes (Brown, 1970)

• 14 early-learned morphemes that are essential to learning English syntax– plural –s, posessive –s, progressive –ing, past –ed, irregular past,

third person -s

– in, on

– the, a

– copula be, auxiliary be (contracted and uncontracted)

• Vastly increase the complexity of language

• Use Mean Length of Utterance in Morphemes as a measure of children’s syntactic development.

What are children learning?

• Are they simply remembering and imitating what they hear or are they learning syntactic rules?

• Good evidence that they are learning rules– How do children treat words they’ve never

heard before: The “Wug” Test– Overregularization of syntactic patterns

The “Wug” Test (Berko, 1958)

This is a wug. Now there are two of them. There are two

--------.

Can do this for possessive, progressive, past morphemes

How do kids do?

• Children as young as 3 productively use all of these morphemes on novel words

• -ing is acquired the earliest (consistency of form)• Plural, possessive, and past allomorphs next

– /wugz/ /wuks/ /wucIz/

– /wugd/ /wukd/ /wudId/

– Those adding the extra vowel are acquired a little later, but even children as young as 4 regularly apply the correct allomorph to the stem.

Overregularization

• Application of morphological and syntactic rules• Typically see this with irregular forms

– Goed, eated, hurted– Mouses, mooses, childs

• Children as old as 7 overregularize as will adults learning a new language

• Syntactic rules are represented as such, the exceptions are stored explicitly.– Double markings: “wented” or “mices”