Language DevelopmentLecture Notes: 9/25/14Constraints on Word Learning = Lexical Principles● Assumptions that children come pre-equipped with and use when mapping words to referents○ Whole-object assumption = words refer to the whole object, not to its parts○ Mutual-exclusivity principle = each object has only one nameFast Mapping● 18-month olds can learn meanings of words from just a few exposures and without explicit instruction● “Bring me the fode, not the duck, the fode”● Repeated, distributed exposure improves retention● Children retain the labels for at least two weeksAssociative Learning● Same words co-occur within the same situations● E.g., word “dog” appears in the presence of Bucky● Association forms between sound sequence (d-o-g) and Bucky● But “dog” also shows up in presence of dogs other than Bucky● Association between (d-o-g) and concept of dog● Must be infinitely flexible Task #3: Extending the word to other objects● Is “cup” the name for just this one particular cup, like “Bucky” is the name for one particular dog?Solving the extension problem● Taxonomic principle = a word can be extended to members of the same category (i.e. “dog” can apply to all dog-like creatures, but not to other things like collars, leashes, etc)● Preschoolers differ from 7 yr olds on categorization task (preschoolers sort thematically, but 7 yr olds sort taxonomically● But, if you give preschoolers words to go with objects, they start sorting categorically● Assumption: Same words label things that are of the same kind● Example○ Shape bias: Children tend to generalize on the basis of shape, rather than material, color, or texture.How do children know which things are of the same kind?● Theory 1: children have pre-existing concepts, and just map words onto them○ Ex. movement● Theory 2: children learn concepts and conceptual categories, just like they learn words○ Ex. by learning distinguishing features of each category (birds are things that have feathers, beaks, and talons)○ Ex. by learning prototypes for category members (robins are more “bird-like” thanpenguins).Early Vocabulary● Understanding comes in before production○ By 5 months: babies respond to their name○ By 8 months: children begin to understand common phrases○ By 16 months: children’s receptive vocabulary ranges between 90-320 words● Compare that to productive vocabulary○ Zero at 10 months, and under 50 at 16 monthsProtowords● Fake, invented words that mean something to the child● Transitional words expressing broad meanings● Often tightly bound to particular contexts or specific functions● Suggest that children have linked sounds to meaningsEarly Words● First word occurs sometime between 10 and 15 months● Early words differ from protowords in that these are true approximations of adult words● Often context-bound, part of routines, and not true symbols○ Often reflect parental input○ Eventually, decontextualizeThe first 50 Words● Acquired over the course of the 2nd year (15-24 months)● Usually, these are words that are most meaningful to the child, and relational words (blankie, uh-oh, no)● Include basic-level words (tree vs. plant or oak)● Typically, are the ones that are easy to pronounce● Of these, about 10 are used on the daily basis = core group● Variety of grammatical classes, but ~40% are nouns Why nouns?● Input- caregivers tend to use more nouns than any other grammatical class● Conceptual differences- nouns are easier to identify in the environment than verbs○ Nouns are more concrete and refer to things in the environment; easiest to learn through observation○ Verbs are relational (give entails someone performing the action of giving to someone), less obvious in the environment, and are difficult to learn through simple observation Early Words Gone Awry● Overextension = a child applies a word to things other than the correct ones (i.e., extends its usage)○ Usually, inconsistent but related to the original meaning of the word○ E.g. the word “puppy” is applied to puppies, kittens, and baby-hamsters; “daddy” is applied to all adult males● Underextention= a child applies a word to a limited subset of things that the word can refer to (limits its usage)○ E.g., the word bird is applied only to robins and swallows, but not to ducks or chickensWhy do early words go away?● Different/incomplete categories?○ But...children seem to comprehend differences between different concepts even when they use the same label for them○ Also, very strange categories (e.g., “moon” refers to moon, half-moon shaped slice of lemon, chrome dial on the dishwasher, wall-hanging with circles on it, half-a-Cheerio, etc.)● Retrieval difficulties?○ I.e., “puppy” may be easier to come up with than “kitten”● Conscious strategy?○ I.e., know that different category, but do not have the word for it yet, and use the closest