Person:

Snedeker, Jesse

Recent imaging studies have found activation in areas associated with motion processing and motor planning during a range of cognitive tasks involving tools. This has led some researchers to conclude that motor information is central to the conceptual representation of tools. To explore this hypothesis, we used a two-alternative forced-choice task to examine whether children and adults use motor information to determine the extension of new tool categories. Adults, 5-year-olds and 3-year-olds were introduced to a novel tool (“a dax”) and shown its function and how to manipulate it. Then two unlabelled tools were presented, one with the same function and one with the same motor manipulation. All three groups systematically extended the novel label to the tool with the same function rather than the one with same motor manipulation. Both 3- and 5-year-old children continued to extend by function when the function was imaginary and not perceptually accessible. We conclude that function is central to conceptual content of tool terms while motor information is not.

Recent work in adult psycholinguistics has demonstrated that activation of semantic representations begins long before phonological processing is complete. This incremental propagation of information across multiple levels of analysis is a hallmark of adult language processing but how does this ability develop? In two experiments, we elicit measures of incremental activation of semantic representations during word recognition in children. Five-year-olds were instructed to select a target (logs) while their eye-movements were measured to a competitor (key) that was semantically related to an absent phonological associate (lock). We found that like adults, children made increased looks to competitors relative to unrelated control items. However unlike adults, children continued to look at the competitor even after the target word was uniquely identified and were more likely to incorrectly select this item. Altogether, these results suggest that early lexical processing involves cascading activation but less efficient resolution of competing entries.

The interpretation of scalar terms (like, e.g., some vs. all; the numerals) has been at the center of much theoretical debate. Recently, this debate has focused on whether Scalar Implicature (SI) computation is grammatically or post grammatically driven (cf., e.g., Russell, 2006 vs. Chierchia, Fox and Spector, 2008 and references therein). In the present work, we address these issues through experimental means arguing, specifically, for two theses: Thesis 1: The interpretation of both numerals and determiners like some/all are systematically affected by the polarity (Downward monotone or DE vs. Upward monotone or UE) of the local context in which they are embedded. Thesis 2: Numerals and Determiners differ in how the ‘exact’ interpretation comes about: for numerals such interpretation is much faster. Thesis 1, if true, provides evidence against the thesis that scalar items are lexically ambiguous (for no lexical ambiguity is polarity sensitive in such a way) and in favor of the view that the ‘exact’ vs. the ‘at least’ interpretation of both types of scalar items is an implicature. Thesis 2, if true, shows that the way in which the ‘exact’ interpretation comes about for numerals vs. determiners is partly similar and partly different. This can be construed as an argument against the thesis that these elements are ‘underspecified’ in similar ways (cf., e.g., Musolino, 2003).

Parents provide children with both genes (nature) and linguistic input (nurture). A growing body of research demonstrates that individual differences in children's language are correlated with differences in parental speech. Although this suggests a causal link between parental input and the pace of language development, these correlations could reflect effects of shared genes on language, rather than a causal link between input and outcome. We explored effects of maternal input on English vocabulary development in internationally-adopted (IA) children - a population with no genetic confound. IA preschoolers demonstrated some of the same correlations with input as in previous studies; specifically, measures of input quality were significantly correlated with vocabulary. However, IA infants did not demonstrate this pattern. Differences between the age groups may be related to the pace of acquisition; more rapid vocabulary development in the preschoolers suggests that access to, and children's ability to make use of input, may be a limiting factor for the infants.

Recent research on children's inferencing has found that although adults typically adopt the pragmatic interpretation of some (implying not all), 5- to 9-year-olds often prefer the semantic interpretation of the quantifier (meaning possibly all). Do these failures reflect a breakdown of pragmatic competence or the metalinguistic demands of prior tasks? In 3 experiments, the authors used the visual-world eye-tracking paradigm to elicit an implicit measure of adults' and children's abilities to generate scalar implicatures. Although adults' eye-movements indicated that adults had interpreted some with the pragmatic inference, children's looks suggested that children persistently interpreted some as compatible with all (Experiment 1). Nevertheless, both adults and children were able to quickly reject competitors that were inconsistent with the semantics of some; this confirmed the sensitivity of the paradigm (Experiment 2). Finally, adults, but not children, successfully distinguished between situations that violated the scalar implicature and those that did not (Experiment 3). These data demonstrate that children interpret quantifiers on the basis of their semantic content and fail to generate scalar implicatures during online language comprehension.

While there is ample evidence that prosody and syntax mutually constrain each other, there is considerable uncertainty about the nature of this interface. Here, we explore this issue with prepositional phrase attachment ambiguities (You can (feel_A) the (cat_B) with the feather). Prior research has been motivated by two hypotheses: (1) the absolute boundary hypothesis (ABH) posits that attachment preferences depend on the size of the prosodic boundary before the ambiguous phrase (boundary B) and (2) the relative boundary hypothesis (RBH) links attachment to the relative size of boundary B and any boundary between the high and low attachment site (boundary A). However, few experiments test the unique predictions of either theory. Study 1 examines how syntax influences prosodic production. The results provide modest support for RBH and stronger support for ABH. In Study 2, we systematically vary the size of both boundaries in an offline comprehension task. We find that absolute boundary strength influences interpretation when relative boundary strength is held constant, and relative boundary strength influences interpretation when absolute boundary strength is held constant. Thus, our theory of the prosody syntax interface must account for effects of both kinds.

To use natural language, speakers must map the participants in events or states in the world onto grammatical roles. There remains considerable disagreement about the nature of these so-called linking rules (Levin & Rappaport Hovav, 2005). In order to probe the nature of linking rules, we investigate verbs of psychological state, which demonstrate complex linking patterns both within and between languages. We find that the typical duration of the psychological state guides the application of linking rules to novel verbs in both English and Japanese, consistent with a universal constraint. Nonetheless, there are marked differences in the baseline preferences for the individual linking rules across the two languages. We discuss these findings both in terms of theories of exceptionless linking rules and accounts on which linking rules are governed by probabilistic biases as well as cross-linguistic variation.

While there is ample evidence that children treat words as mutually exclusive, the cognitive basis of this bias is widely debated. We focus on the distinction between pragmatic and lexical constraints accounts. High-functioning children with autism spectrum disorders (ASD) offer a unique perspective on this debate, as they acquire substantial vocabularies despite impoverished social-pragmatic skills. We tested children and adolescents with ASD in a paradigm examining mutual exclusivity for words and facts. Words were interpreted contrastively more often than facts. Word performance was associated with vocabulary size; fact performance was associated with social-communication skills. Thus mutual exclusivity does not appear to be driven by pragmatics, suggesting that it is either a lexical constraint or a reflection of domain-general learning processes.

Number words are generally used to refer to sets of an exact cardinal value, but cognitive scientists disagree about their meanings. Although most psychological analyses presuppose that numbers have exact semantics (two means EXACTLY TWO), many linguistic accounts propose that numbers have lower-bounded semantics (AT LEAST TWO), and that speakers restrict their reference through a pragmatic inference (scalar implicature). We address this debate through studies of children. First, we examine toddlers' offline comprehension of number words and find they interpret numbers exactly even in contexts where implicatures are cancelled. Next we consider arguments that patterns of numerical acquisition support lower-bounded semantics and find that these acquisition patterns are better explained by an exact account. Finally, we revisit data from online comprehension and demonstrate that five-year-old children access numerical upper bounds as rapidly as lower bounds, contrary to the hypothesis of lower-bounded semantics. We conclude that number words have exact meanings.

Early language development is characterized by predictable changes in the words children produce and the complexity of their utterances. In infants these changes could reflect increasing linguistic expertise or cognitive maturation and development. To disentangle these factors, we compared the acquisition of English in internationally-adopted preschoolers and internationally adopted infants. Parental reports and speech samples were collected for one year. Both groups showed the qualitative shifts that characterize first-language acquisition. Initially, they produced single-word utterances consisting mostly of nouns and social words. The appearance of verbs, adjectives and multiword utterances was predicted by vocabulary size in both groups. Preschoolers did learn some words at an earlier stage than infants, specifically words referring to the past or future and adjectives describing behavior and internal states. These findings suggest that cognitive development plays little role in the shift from referential terms to predicates but may constrain children’s ability to learn some abstract words.