Word Learning

Language learning raises unique problems of learning and memory. This is widely recognized with respect to syntax learning, but it is also true of word learning. Word learning is the process of developing generalized (i.e., abstracted) mental representations to associate a word form (e.g., sequence of speech sounds or hand shapes/movements) with a meaning (e.g., category of events or objects that the word refers to) and conditions of use (e.g., Where in a sentence does this word typically belong? In what social contexts does one use the word?). The remainder of this section describes some unique features and questions about word learning in comparison to other kinds of learning. The next section describes research findings on children's word learning, including the typical course of vocabulary development, individual differences, typical errors, and ecological and cognitive factors that facilitate word learning. Subsequent sections briefly describe the neurological changes associated with word learning, the relation of word learning to reading, the nature of word learning in multilingual individuals, and word learning in adulthood.

Word learning entails special questions because the corpus of words we learn, our lexicon, is a unique set of information. It is dynamic and additive: Consider how the compound word electronic [Page 779]mail, coined in the 1980s, was quickly reduced to e-mail, which has since spawned analogous terms such as e-commerce. Adults can rapidly understand such words despite their novelty. This illustrates how we can, throughout life, add new elements (words) to our lexicon. In so doing we establish new, systematic connections (of sound, meaning, syntax, and usage) to other words and other linguistic and conceptual knowledge. Although words are arbitrary in form (e.g., nothing about the sound dog is inherently doglike), the lexicon is nonetheless somewhat principled. For example, words are hierarchical in meaning (e.g., animal refers to a category that includes all referents of dog) and in structure (e.g., an -ed verb ending denotes the real or hypothetical completion of an act or state). Also, words are combined in particular ways to express more precise meanings (e.g., fire truck and truck fire have different meanings). The lexicon is both social and normative (e.g., only our cultural knowledge makes e-commerce understandable) and internalized (e.g., we use words to facilitate cognitive processes such as explicit memory).

Word learning can be called symbol learning because it encompasses not only spoken words but signed words and even pictorial symbols (e.g., brand logos). Several nonhuman species (i.e., apes, parrots, dolphins) can learn small numbers of abstract names and symbols for objects, properties, or actions. There is no evidence that nonhuman animals use the full human range of word meanings (e.g., not, think, silly, maybe), word variants (go, gone, went, had gone), or word functions (e.g., puns, metaphors, novel compounds such as “climbing wall”). Yet children as young as 2 to 4 years old flexibly adopt such a wide range of forms, meanings, and uses: They can learn words defined by tone variations (e.g., Mandarin; Yoruba), percussive “click” or ingestive noises (Sindhi, Xhosa, Zulu), or gestures (American Sign Language). They learn words that take complex inflections (i.e., changes to the forms of a word, such as run, ran, running). Such variations are extensive and complex in languages like Turkish and Hungarian. Children also can integrate word meanings with cultural and conceptual knowledge (e.g., American children know that Pokémon refers to fictional characters, toys, playing cards, a game, a TV program, DVDs, and a video game, but Pokémon Diamond only refers to the last of these). How do children learn all of this?

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