Cynthia Fisher

When it is better to receive than to give: Syntactic and conceptual constraints on vocabulary growth

Abstract We ask how children solve the mapping problem for verb acquisition: how they pair concepts with their phonological realizations in their language. There is evidence that nouns but not verbs can be acquired by pairing each sound (e.g., ‘elephant’) with a concept inferred from the world circumstances in which that sound occurs. Verb meanings pose problems for this word-world mapping procedure, motivating a model of verb mapping mediated by attention to the syntactic structures in which verbs occur (Landau and Gleitman 1985, Gleitman 1990). We present an experiment examining the interaction between a conceptual influence (the bias to interpret observed situations as involving a casual agent) and syntactic influences, as these jointly contribute to childrens conjectures about new verb meanings. Children were shown scenes ambiguous as to two interpretations (e.g., giving and getting or chasing and fleeing ) and were asked to guess the meaning of novel verbs used to described the scenes, presented in varying syntactic contexts. Both conceptual and syntactic constraints influenced childrens responses, but syntactic information largely overwhelmed the conceptual bias. This finding, with collatoral evidence, supports a syntax-mediated procedure for verb acquisition.

On the semantic content of subcategorization frames

This paper investigates relations between the meanings of verbs and the syntactic structures in which they appear. This investigation is motivated by the enigmas as to how children discover verb meanings. Well-known problems with unconstrained induction of word meanings from observation of world circumstances suggest that additional constraints or sources of information are required. If there exist strong and reliable parallels between the structural and semantic properties of verbs, then an additional source of information about verb meanings is reliably present in each verbs linguistic context. Five experiments are presented which investigate the following hypothesis regarding the scope of these relations: The closer any two verbs in their semantic structure, the greater the overlap should be in their licensed syntactic structures. To investigate this hypothesis, data of two kinds were collected from different groups of subjects: (a) One group of subjects was asked to judge the semantic relatedness of verbs by selecting the semantic outlier in triads presented to them. (b) A second group of subjects was asked to judge the grammaticality of these same verbs in a large range of syntactic environments. These two types of data were then compared to assess the degree of correspondence in the two partitionings (syntactic and semantic) of the verb set. The findings, overall, support the view that the syntax of verbs is a quite regular, although complex, projection from their semantics. In conclusion, we discuss the kinds of features that are formally marked in syntactic structure and relate these to the problem of verb-vocabulary acquisition in young children.

Learning words and rules: Abstract knowledge of word order in early sentence comprehension

Children quickly acquire basic grammatical facts about their native language. Does this early syntactic knowledge involve knowledge of words or rules? According to lexical accounts of acquisition, abstract syntactic and semantic categories are not primitive to the language-acquisition system; thus, early language comprehension and production are based on verb-specific knowledge. The present experiments challenge this account: We probed the abstractness of young childrens knowledge of syntax by testing whether 25- and 21-month-olds extend their knowledge of English word order to new verbs. In four experiments, children used word order appropriately to interpret transitive sentences containing novel verbs. These findings demonstrate that although toddlers have much to learn about their native languages, they represent language experience in terms of an abstract mental vocabulary. These abstract representations allow children to rapidly detect general patterns in their native language, and thus to learn rules as well as words from the start.

Infants learn phonotactic regularities from brief auditory experience

Two experiments investigated whether novel phonotactic regularities, not present in English, could be acquired by 16.5-month-old infants from brief auditory experience. Subjects listened to consonant-vowel-consonant syllables in which particular consonants were artificially restricted to either initial or final position (e.g. /baep/ not /paeb/). In a later head-turn preference test, infants listened longer to new syllables that violated the experimental phonotactic constraints than to new syllables that honored them. Thus, infants rapidly learned phonotactic regularities from brief auditory experience and extended them to unstudied syllables, documenting the sensitivity of the infants language processing system to abstractions over linguistic experience.

Learning phonotactic constraints from brief auditory experience

Three experiments asked whether phonotactic regularities not present in English could be acquired by adult English speakers from brief listening experience. Subjects listened to consonant-vowel-consonant (CVC) syllables displaying restrictions on consonant position. Responses in a later speeded repetition task revealed rapid learning of (a) first-order regularities in which consonants were restricted to particular positions (e.g. [baep] not *[paeb]), and (b) second-order regularities in which consonant position depended on the adjacent vowel (e.g. [baep] or [pIb], not *[paeb] or *[bIp]). No evidence of learning was found for second-order regularities in which consonant position depended on speakers voice. These results demonstrated that phonotactic constraints are rapidly learned from listening experience and that some types of contingencies (consonant-vowel) are more easily learned than others (consonant-voice).

“Really? She Blicked the Baby?” Two-Year-Olds Learn Combinatorial Facts About Verbs by Listening

Children use syntax to guide verb learning. We asked whether the syntactic structure in which a novel verb occurs is meaningful to children even without a concurrent scene from which to infer the verbs semantic content. In two experiments, 2-year-olds observed dialogues in which interlocutors used a new verb in transitive (“Jane blicked the baby!”) or intransitive (“Jane blicked!”) sentences. The children later heard the verb in isolation (“Find blicking!”) while watching a one-participant event and a two-participant event presented side by side. Children who had heard transitive dialogues looked reliably longer at the two-participant event than did those who had heard intransitive dialogues. This effect persisted even when children were tested on a different day, but disappeared when no novel verb accompanied the test events (Experiment 2). Thus, 2-year-olds gather useful combinatorial information about a novel verb simply from hearing it in sentences, and later retrieve that information to guide interpretation of the verb.

Structural limits on verb mapping: The role of abstract structure in 2.5-year-olds' interpretations of novel verbs

Two experiments showed that 2.5-year-olds, as well as older children, interpret new verbs in accord with their number of arguments. When interpreting new verbs describing the same motion events, children who heard transitive sentences were more likely than were children who heard intransitive sentences to assume that the verb referred to the actions of the causal agent. The sentences were designed so that only the number of noun-phrase arguments differed across conditions (e.g. She’s pilking her over there versus She’s pilking over there). These experiments isolate number of noun-phrase arguments (or number of nouns) as an early constraint on sentence interpretation and verb learning, and provide strong evidence that children as young as 2.5 years of age attend to a sentence’s overall structure in interpreting it.

“Really? She Blicked the Baby?”

Children use syntax to guide verb learning. We asked whether the syntactic structure in which a novel verb occurs is meaningful to children even without a concurrent scene from which to infer the verbs semantic content. In two experiments, 2-year-olds observed dialogues in which interlocutors used a new verb in transitive (“Jane blicked the baby!”) or intransitive (“Jane blicked!”) sentences. The children later heard the verb in isolation (“Find blicking!”) while watching a one-participant event and a two-participant event presented side by side. Children who had heard transitive dialogues looked reliably longer at the two-participant event than did those who had heard intransitive dialogues. This effect persisted even when children were tested on a different day, but disappeared when no novel verb accompanied the test events (Experiment 2). Thus, 2-year-olds gather useful combinatorial information about a novel verb simply from hearing it in sentences, and later retrieve that information to guide interpretation of the verb.

Two-Year-Olds Use Distributional Cues to Interpret Transitivity-Alternating Verbs.

Two-year-olds assign appropriate interpretations to verbs presented in two English transitivity alternations, the causal and unspecified-object alternations (Naigles, 1996). Here we explored how they might do so. Causal and unspecified-object verbs are syntactically similar. They can be either transitive or intransitive, but differ in the semantic roles they assign to the subjects of intransitive sentences (undergoer and agent, respectively). To distinguish verbs presented in these two alternations, children must detect this difference in role assignments. We examined distributional features of the input as one possible source of information about this role difference. Experiment 1 showed that in a corpus of child-directed speech, causal and unspecified-object verbs differed in their patterns of intransitive-subject animacy and lexical overlap between nouns in subject and object positions. Experiment 2 tested childrens ability to use these two distributional cues to infer the meaning of a novel causal or unspecified-object verb, by separating the presentation of a novel verbs distributional properties from its potential event referents. Children acquired useful combinatorial information about the novel verb simply by listening to its use in sentences, and later retrieved this information to map the verb to an appropriate event.

A vowel is a vowel: Generalizing newly-learned phonotactic constraints to new contexts

Adults can learn novel phonotactic constraints from brief listening experience. We investigated the representations underlying phonotactic learning by testing generalization to syllables containing new vowels. Adults heard consonant-vowel-consonant study syllables in which particular consonants were artificially restricted to the onset or coda position (e.g., /f/ is an onset, /s/ is a coda). Subjects were quicker to repeat novel constraint-following (legal) than constraint-violating (illegal) test syllables whether they contained a vowel used in the study syllables (training vowel) or a new (transfer) vowel. This effect emerged regardless of the acoustic similarity between training and transfer vowels. Listeners thus learned and generalized phonotactic constraints that can be characterized as simple first-order constraints on consonant position. Rapid generalization independent of vowel context provides evidence that vowels and consonants are represented independently by processes underlying phonotactic learning.