Language Development in Toddlerhood

All 6 Terms & Definitions

Vocabulary Explosion

The rapid acceleration in word learning that typically occurs between 18 and 24 months, during which children may add 10 or more new words per week. Associated with the emergence of the "naming insight" — the understanding that words are not context-specific signals but stable, conventional labels for categories of things.

Fast Mapping

The ability to acquire the approximate meaning of a new word after only one or two exposures, without the repeated pairings required by associative learning models. Susan Carey demonstrated that preschoolers fast-map novel colour terms in a single brief exposure. Underlies the speed of vocabulary growth from toddlerhood onward.

Mutual Exclusivity Constraint

The assumption that each object has only one name, so a novel label is most likely to refer to an object not yet named. Helps children map novel words to novel referents even in ambiguous referential environments. One of several lexical constraints proposed to explain how children narrow down the logically vast space of possible word meanings.

Telegraphic Speech

Two- to three-word utterances that omit grammatical function words and morphological inflections while retaining content words that carry the core semantic content. Characteristic of children between approximately 18 and 30 months. Named by analogy to the economical style of telegrams. Despite surface simplicity, telegraphic speech typically preserves the canonical word order of the ambient language.

Overextension and Underextension

Common word-use errors in toddlerhood. Overextension: applying a word too broadly, using "dog" for all four-legged animals. Underextension: applying a word too narrowly, using "cup" only for one particular cup. Reflect the child's active but imperfect hypothesis-testing about the scope of word meanings.

Child-Directed Speech Expansion

Adult caretakers spontaneously expand children's telegraphic utterances into grammatically complete forms — when the child says "daddy go," the parent replies "yes, daddy is going." Expansions provide corrective feedback in a conversational context and are associated with faster language development.