PSY 369: Psycholinguistics Language Acquisition: Morphology

Typically things inflections and prepositions start around MLU of 2.5 (usually in 2 yr olds) Wug experiment (Berko-Gleason, 1958) Language explosion continues Here is a wug. Now there are two of them. There are two _______.

Acquiring Morphology This is ungrammatical in the adult language its existence in child language shows that children are not simply imitating what they have heard. In this case, what they produce is not in their input. Children sometimes make mistakes. I holded the baby rabbits.

Why do they make errors like these? In the case at hand, we have what is called overregularization The verb hold has an irregular past tense form, held Because this form is used, the regular past tense-- that with -ed-- is not found (*hold-ed) I holded the baby rabbits. Acquiring Morphology

Where Examples: Horton heared a Who I finded Renée The alligator goed kerplunk Remember that regular forms require no stored knowledge (wug test) Whereas something must be memorized with irregulars

Stages in the acquisition of irregular inflections Acquiring Morphology With regular verbs, the default form -ed is used With irregulars, lists associating the verb with a particular form of the past tense have to be memorized: Past tense is -t when attached to leave, keep, etc. Also patterns of stem-changing

Stages in the acquisition of irregular inflections Acquiring Morphology

Stages in the acquisition of irregular inflections Acquiring Morphology On the face of it, learning these morphological quirks follows a peculiar pattern: Early: correct irregular forms are used Middle: incorrect regular forms are used Late: correct forms are used again Why do we find this type of pattern? Memory and rules

Frequency It is possible to predict which verbs will be subject to overregularization We find here a frequency effect The more often an irregular form occurs in the input, the less likely the child is to use it as an overregularization This is evidence that some part of overregularization occurs because of memory failures Something about irregulars is unpredictable, hence has to be memorized

Rules The use of overregularized forms starts at around the same that that the child is beginning to apply the default -ed rule successfully Early: All forms-- whether regular or irregular-- are memorized Middle: The regular rule is learned, and in some cases overapplied Late: Irregulars are used based on memory, regulars use the rule (the idea is that if the word can provide its own past tense from memory, then the past tense rule is blocked)

An interesting pattern Overregularization doesn’t replace correct forms Instead it replaces errors Early stages 74% correct (e.g. he held it) 26% bare form (e.g. he hold it) Middle stages: Overregularization is not very frequent (typically less than 5%) 89% correct 9% bare form 2% overregularized

Summary Overregularization looks at first like children are moving backwards On closer examination, the child’s overall performance is improving The pattern of overregularization provides a window on the process in which the child (over)generalizes a rule So how is the rule learned (learnt?)

What kind of “teaching” do kids get? What kind of feedback is available for learning? Are the kids even aware of mistakes? The children are apparently aware of the fact that their forms are strange: Parent: Where’s Mommy? Child: Mommy goed to the store Parent: Mommy goed to the store? Child: NO! Daddy, I say it that way, not you

Positive and negative evidence Kinds of feedback Positive evidence: Kids hear grammatical sentences Negative evidence: information that a given sentence is ungrammatical Kids are not told which sentences are ungrammatical (no negative evidence) Let’s consider no negative evidence further…

Negative evidence Negative evidence could come in various conceivable forms. “The sentence Bill a cookie ate is not a sentence in English, Timmy. No sentence with SOV word order is.” Upon hearing Bill a cookie ate, an adult might Offer negative reinforcement Not understand Look pained Rephrase the ungrammatical sentence grammatically

Kids resist instruction… McNeill (1966) Child: Nobody don’t like me. Adult: No, say ‘nobody likes me.’ Child: Nobody don’t like me. [repeats eight times] Adult: No, now listen carefully; say ‘nobody likes me.’ Child: Oh! Nobody don’t likes me.

Kids resist instruction… Cazden (1972) (observation attributed to Jean Berko Gleason) Child: My teacher holded the baby rabbits and we patted them. Adult: Did you say your teacher held the baby rabbits? Child: Yes. Adult: What did you say she did? Child: She holded the baby rabbits and we patted them. Adult: Did you say she held them tightly? Child: No, she holded them loosely.

Negative evidence via feedback? Do kids get “implicit” negative evidence? Do adults understand grammatical sentences and not understand ungrammatical ones? Do adults respond positively to grammatical sentences and negatively to ungrammatical ones?

Brown & Hanlon (1970): Adults understood 42% of the grammatical sentences. Adults understood 47% of the ungrammatical ones. Adults expressed approval after 45% of the grammatical sentences. Adults expressed approval after 45% of the ungrammatical sentences. This doesn’t bode well for comprehension or approval as a source of negative evidence for kids. Negative evidence via feedback?

Complete: consistent response, indicates unambiguously “grammatical” or “ungrammatical.” Partial: if there is a response, it indicates “grammatical” or “ungrammatical” Noisy: response given to both grammatical and ungrammatical sentences, but with different/detectible frequency. Negative evidence via feedback?

Marcus (1993) Kid gets response R to utterance U, there’s a 63% chance (20/32) that U is ungrammatical. Guess: ungrammatical, but 38% chance of being wrong. Ok, but nowhere near good enough to build a grammar. Negative evidence via feedback? Suppose response R occurs 20% of the time for ungrammatical sentences, 12% of the time for grammatical sentences.

Lacking confidence Based on R (20%-12% differential) they’d have to repeat U 446 times (and compile feedback results) to reach a 99% confidence level. This sounds rather unlike what actually happens. This is a serious task, a kid’s going to want to be sure. Suppose kid is aiming for 99% confidence (adults make at most 1% speech errors of the relevant kind—pretend this reflects 99% confidence).

In a way, it’s moot anyway… One of the striking things about child language is how few errors they actually make. For negative feedback to work, the kids have to make the errors (so that it can get the negative response). But they don’t make enough relevant kinds of errors to determine the complex grammar. Pinker, Marcus and others, conclude that much of this stuff must be innate. But this isn’t the only view. There is a raging debate about whether there are rules, or whether these patterns of behavior can be learned based on the language evidence that is available to the kids