259 research outputs found
Relativistic quantum mechanical methods in molecular calculations
Abstract In the present paper the theory for different relativistic methods is presented. Despite a lot of progress has been made for the inclusion of relativistic effects in electronic structure calculations, good methods are still resource-demanding. A rapid development of the fourcomponent method is, however, taking place. Also, "pseudo-relativistic" approaches are becoming more popular in the treatment of large systems. The importance of the interplay between the relativistic core and valence effects is also revisited.
Learning locative verbs : how universal linking rules constrain productivity
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 1989.Includes bibliographical references (leaves 250-253).by Jess Harry Gropen.Ph.D
Acquiring and processing verb argument structure : distributional learning in a miniature language
Adult knowledge of a language involves correctly balancing lexically-based and more language-general patterns. For example, verb argument structures may sometimes readily generalize to new verbs, yet with particular verbs may resist generalization. From the perspective of acquisition, this creates significant learnability problems, with some researchers claiming a crucial role for verb semantics in the determination of when generalization may and may not occur. Similarly, there has been debate regarding how verb-specific and more generalized constraints interact in sentence processing and on the role of semantics in this process. The current work explores these issues using artificial language learning. In three experiments using languages without semantic cues to verb distribution, we demonstrate that learners can acquire both verb-specific and verb-general patterns, based on distributional information in the linguistic input regarding each of the verbs as well as across the language as a whole. As with natural languages, these factors are shown to affect production, judgments and real-time processing. We demonstrate that learners apply a rational procedure in determining their usage of these different input statistics and conclude by suggesting that a Bayesian perspective on statistical learning may be an appropriate framework for capturing our findings
Balancing generalization and lexical conservatism : an artificial language study with child learners
Successful language acquisition involves generalization, but learners must balance this against the acquisition of lexical constraints. Such learning has been considered problematic for theories of acquisition: if learners generalize abstract patterns to new words, how do they learn lexically-based exceptions? One approach claims that learners use distributional statistics to make inferences about when generalization is appropriate, a hypothesis which has recently received support from Artificial Language Learning experiments with adult learners (Wonnacott, Newport, & Tanenhaus, 2008). Since adult and child language learning may be different (Hudson Kam & Newport, 2005), it is essential to extend these results to child learners. In the current work, four groups of children (6 years) were each exposed to one of four semi-artificial languages. The results demonstrate that children are sensitive to linguistic distributions at and above the level of particular lexical items, and that these statistics influence the balance between generalization and lexical conservatism. The data are in line with an approach which models generalization as rational inference and in particular with the predictions of the domain general hierarchical Bayesian model developed in Kemp, Perfors & Tenenbaum, 2006. This suggests that such models have relevance for theories of language acquisition
The retreat from locative overgeneralisation errors : a novel verb grammaticality judgment study
Whilst some locative verbs alternate between the ground- and figure-locative constructions (e.g. Lisa sprayed the flowers with water/Lisa sprayed water onto the flowers), others are restricted to one construction or the other (e.g. *Lisa filled water into the cup/*Lisa poured the cup with water). The present study investigated two proposals for how learners (aged 5–6, 9–10 and adults) acquire this restriction, using a novel-verb-learning grammaticality-judgment paradigm. In support of the semantic verb class hypothesis, participants in all age groups used the semantic properties of novel verbs to determine the locative constructions (ground/figure/both) in which they could and could not appear. In support of the frequency hypothesis, participants’ tolerance of overgeneralisation errors decreased with each increasing level of verb frequency (novel/low/high). These results underline the need to develop an integrated account of the roles of semantics and frequency in the retreat from argument structure overgeneralisation
Avoiding dative overgeneralisation errors: semantics, statistics or both?
Item does not contain fulltextHow do children eventually come to avoid the production of overgeneralisation errors, in particular, those involving the dative (e.g., *I said her "no")? The present study addressed this question by obtaining from adults and children (5-6, 9-10 years) judgements of well-formed and over-general datives with 301 different verbs (44 for children). A significant effect of pre-emption - whereby the use of a verb in the prepositional-object (PO)-dative construction constitutes evidence that double-object (DO)-dative uses are not permitted - was observed for every age group. A significant effect of entrenchment - whereby the use of a verb in any construction constitutes evidence that unattested dative uses are not permitted - was also observed for every age group, with both predictors also accounting for developmental change between ages 5-6 and 9-10 years. Adults demonstrated knowledge of a morphophonological constraint that prohibits Latinate verbs from appearing in the DO-dative construction (e.g., *I suggested her the trip). Verbs' semantic properties (supplied by independent adult raters) explained additional variance for all groups and developmentally, with the relative influence of narrow- vs broad-range semantic properties increasing with age. We conclude by outlining an account of the formation and restriction of argument-structure generalisations designed to accommodate these findings.26 p
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