Preschoolers infer contrast from adjectives if they can access lexical alternatives

Preschoolers infer contrast from adjectives if they can access lexical alternatives Alexandra C. Horowitz Michael C. Frank ahorowit@stanford.edu Department of Psychology Stanford University mcfrank@stanford.edu Department of Psychology Stanford University Abstract a novel term with respect to a set of possible objects (e.g. Clark, 1990; Diesendruck & Markson, 2001; Akhtar, Car- penter, & Tomasello, 1996). Although both reference disam- biguation and implicature are inferences about speakers’ lex- ical choices, a critical difference between them is the space of possible alternative interpretations. In reference disambigua- tion tasks, the possible alternatives are typically objects that are physically present and hence easy to reason about; in im- plicature tasks, the possible alternatives are typically unsaid lexical choices that may be hard to summon to mind. We refer to this idea (that implicatures are challenging because of the difficulty bringing to mind the relevant alternative possible utterances) as the linguistic alternatives hypothesis (Barner & Bachrach, 2010). In support of this hypothesis, Barner, Brooks, and Bale (2011) found that preschoolers could make implicatures from familiar scales such as numbers and from explicit descrip- tions (“the cat and the cow are sleeping” when three animals were pictured sleeping), but not from quantifiers (“some of the animals are sleeping”). In addition, even when the quan- tifiers were strengthened by “only” (“only some of the ani- mals are sleeping”), they still failed to make the implicature— indicating that the implicature per se was not the problem (be- cause if it were, adding “only” would have helped children restrict their interpretation of “some”), but rather that chil- dren’s difficulty in considering the alternative “all” may be responsible. In our current work, we further investigate the linguistic alternatives hypothesis as a potential explanation of children’s performance in other types of pragmatic tasks. In our previous work, we investigated preschoolers’ infer- ences about implicit dimensions of contrast from adjective use (Horowitz & Frank, 2012). The intuition driving this paradigm was that if a novel item is described as “tall,” it is likely that others of that kind may vary by height; if it’s described as “red,” others may vary by color. Older 4-year- olds were able to make this kind of contrast inference from both color and size terms, but younger 4-year-olds exhibited a bias to match by color regardless of the adjective used. This result may also be related to children’s ability to access the appropriate linguistic alternatives. Although children are fa- miliar with color names, they may not recognize color use as contrastive because there is not a particular implied contrast item per se (“red” implies that others may be “not red,” but not that another item will necessarily be a specific color). So our task may have been difficult for younger children because they could not bring to mind the appropriate color alternative. In our current work, we modify our task to use scalar properties with familiar implicit alternatives to children (e.g. When speakers use modified noun phrases (e.g. “the long book”), they provide information not only about a salient fea- ture of a single item (that this book is long), but also about implicit contrasts with possible alternatives (books can vary by length: some may be short). We investigate the development of preschoolers’ ability to detect implicit contrasts from speakers’ use of adjectives and make inferences about category struc- ture. In Experiment 1, we found that adults and preschoolers can make contrast inferences from adjective use in a supportive frame, and this ability improves over the preschool years. In Experiment 2, we reduced the cues to contrast and found that adults still inferred implied contrast from adjective use alone, but preschoolers did not. Perhaps the issue for preschoolers was an inability to consider alternatives from explicit descrip- tions (e.g. bringing to mind “short” from hearing “long”). Ex- periment 3 tested this hypothesis by reading preschoolers a book containing relevant opposite pairs immediately prior to the task. After reading the book, older 4-year-olds were able to make contrast inferences reliably, suggesting that increasing children’s access to lexical alternatives may boost their ability to make contrast inferences. Keywords: Pragmatics; adjectives; language development. Introduction A challenge for children learning language is not only to learn the explicit meanings conveyed by semantic content, but also to pick up on available, but implicit, information. For exam- ple, if I ask “where’s my left shoe?” a listener can learn not only that I am missing my left shoe (explicit), but also that I’m likely not missing its pair (implicit). Thus, speakers can provide cues about unstated information through their word choices. The goal of the current work is to investigate chil- dren’s sensitivity to this kind of implicit information. Although children have accumulated a substantial vocab- ulary by age 5, they still show surprising difficulties in mak- ing pragmatic inferences. Consider the scalar implicature that “some of the horses jumped over the fence.” For adults this utterance typically implicates that SOME BUT NOT ALL of the horses jumped, or else the speaker would have used the word “all” (Grice, 1975). In contrast, 5- to 6-year-olds are happy to accept the interpretation that “some” means SOME AND POSSIBLY ALL (e.g. Papafragou & Musolino, 2003; Noveck, 2000). Adults infer implicatures y across a number of lexical scales (e.g. , ), while children find these inferences challenging despite knowing the mean- ings of the individual lexical items. Why do children fail to make scalar implicatures despite their familiarity with the component words? This failure is especially puzzling given children’s proficiency in making other forms of pragmatic inference, such as in simple word learning tasks where they can disambiguate the referent of