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”