Ellen M. Markman Stanford University
Word learning is an inductive feat accomplished by the 2-year-olds of our species. To explain how such young children with limited informationprocessing abilities can so readily figure out what words mean, investigators have hypothesized that children are predisposed to elevate some hypotheses about word meanings over others. By greatly reducing the hypothesis space, these constraints on hypotheses help render the inductive problem soluble. Although the focus of this chapter is on three specific word-learning constraints: the whole-object, taxonomic, and mutual exclusivity assumptions, my goal is to consider broader fundamental questions about the nature of constraints on learning.
To begin, I briefly review the evidence for the three word-learning constraints. I then address misconceptions about the nature of biological constraints that pervade recent discussions of constraints on word learning where word-learning biases are interpreted as implying rigid, hard-wired, innate mechanisms that are immune from input. I argue that such constraints should be thought of as default assumptions, as probabilistic biases that provide good first guesses but not final solutions. Another misconception is to interpret these biases as necessarily being language specific. Analyses of other domains reveal, however, that all three assumptions appear in contexts other than word learning. This is not to say that they are completely general because, although some domains are governed by very similar principles, clear, important exceptions can readily be found. Domain specificity bears on questions about the origins of these constraints in that if comparable principles are found in other domains they may well be recruited for word learning. As