One frog, two frog, red frog, blue frog: factors affecting children's syntactic choices in production and comprehension.

Two experiments are reported which examine children's ability to use referential context when making syntactic choices in language production and comprehension. In a recent on-line study of auditory comprehension, Trueswell, Sekerina, Hill, and Logrip (1999) examined children's and adults' abilities to resolve temporary syntactic ambiguities involving prepositional phrases (e.g., "Put the frog on the napkin into..."). Although adults and older children used the referential context to guide their initial analysis (pursuing a destination interpretation in a one-frog context and a modifier interpretation in a two-frog context), 4 to 5-year olds' initial and ultimate analysis was one of destination, regardless of context. The present studies examined whether these differences were attributable to the comprehension process itself or to other sources, such as possible differences in how children perceive the scene and referential situation. In both experiments, children were given a language generation task designed to elicit and test children's ability to refer to a member of a set through restrictive modification. This task was immediately followed by the "put" comprehension task. The findings showed that, in response to a question about a member of a set (e.g., "Which frog went to Mrs. Squid's house?"), 4- to 5-year-olds frequently produced a definite NP with a restrictive prepositional modifier (e.g., "The one on the napkin"). These same children, however, continued to misanalyze put instructions, showing a strong avoidance of restrictive modification during comprehension. Experiment 2 showed that an increase in the salience of the platforms that distinguished the two referents increased overall performance, but still showed the strong asymmetry between production and comprehension. Eye movements were also recorded in Experiment 2, revealing on-line parsing patterns similar to Trueswell et al.: an initial preference for a destination analysis and a failure to revise early referential commitments. These experiments indicate that child-adult differences in parsing preferences arise, in part, from developmental changes in the comprehension process itself and not from a general insensitivity to referential properties of the scene. The findings are consistent with a probabilistic model for uncovering the structure of the input during comprehension, in which more reliable linguistic and discourse-related cues are learned first, followed by a gradually developing ability to take into account other more uncertain (or more difficult to learn) cues to structure.

Human simulations of vocabulary learning.

The work reported here experimentally investigates a striking generalization about vocabulary acquisition: Noun learning is superior to verb learning in the earliest moments of child language development. The dominant explanation of this phenomenon in the literature invokes differing conceptual requirements for items in these lexical categories: Verbs are cognitively more complex than nouns and so their acquisition must await certain mental developments in the infant. In the present work, we investigate an alternative hypothesis; namely, that it is the information requirements of verb learning, not the conceptual requirements, that crucially determine the acquisition order. Efficient verb learning requires access to structural features of the exposure language and thus cannot take place until a scaffolding of noun knowledge enables the acquisition of clause-level syntax. More generally, we experimentally investigate the hypothesis that vocabulary acquisition takes place via an incremental constraint-satisfaction procedure that bootstraps itself into successively more sophisticated linguistic representations which, in turn, enable new kinds of vocabulary learning. If the experimental subjects were young children, it would be difficult to distinguish between this information-centered hypothesis and the conceptual change hypothesis. Therefore the experimental "learners" are adults. The items to be "acquired" in the experiments were the 24 most frequent nouns and 24 most frequent verbs from a sample of maternal speech to 18-24-month-old infants. The various experiments ask about the kinds of information that will support identification of these words as they occur in mother-to-child discourse. Both the proportion correctly identified and the type of word that is identifiable changes significantly as a function of information type. We discuss these results as consistent with the incremental construction of a highly lexicalized grammar by cognitively and pragmatically sophisticated human infants, but inconsistent with a procedure in which lexical acquisition is independent of and antecedent to syntax acquisition.

Similar, and similar concepts.

This paper analyzes English symmetrical predicates such as collide and match. Its point of departure is an analysis of the concept 'similar' from Tversky (1977) that appears to show that similarity is psychologically asymmetrical. One basis for this claim from Tversky is that the sentences North Korea is similar to Red China and Red China is similar to North Korea are assessed as differing in meaning by experimental subjects; this seems to imply that the symmetrical entailment (R x, y <--> R y, x) fails for this concept. Five experiments are presented that show: (1) the apparent asymmetry of similar is reproduced for 20 predicates that are intuitively thought to be symmetrical, including equal and identical; (2) unique linguistic-interpretative properties hold for these symmetrical words, such as reciprocal interpretation when they appear intransitively, for example, North Korea and Red China are similar; (3) the asymmetrical interpretation of subject-complement constructions containing the symmetrical words is a consequence of general linguistic-interpretive principles. On the basis of the experimental findings, we offer an analysis of symmetrical predication. One major claim of the analysis is that symmetry is a property of lexical items and has no special syntax, that is, that John meets is semantically but not syntactically anomalous. A second claim is that the structural positioning of noun phrases in sentences containing symmetricals--rather than inherent semantic properties of the noun phrases themselves--sets their status as Figure and Ground (as described by Talmy, 1985) or Variant and Referent (as described by Tversky, 1977) in the comparison, even if the nouns are nonsense items. Finally, the behavior of symmetrical predicates is shown to vary as a function of their differing lexical class assignments and collateral semantic designations, such as activity versus state. Most generally, it is claimed that a deeper understanding of symmetrical terms comes from analyzing the semantics of syntactic structures in which they appear.

Words, words, words....

Traditional accounts of vocabulary acquisition assume that children succeed by aligning the utterance of words with their environmental contingencies, a word-to-world pairing. Experimental results suggest that such a procedure accounts for the acquisition of nouns but is insufficient for the acquisition of verbs. It is demonstrated that infants under two years of age systematically recruit the structural properties of sentences in which novel verbs occur to find their meanings: a sentence-to-world pairing procedure.

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 verb's 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.