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In his broad criticism of the biolinguistic approach to the theory of grammar, Everett (2005, 2006) discusses, among other things, the classical instance of the Poverty of the Stimulus Argument drawn from auxiliary fronting in English, originally made by Chomsky. Everett claims that: (i) the rule responsible for the attested pattern would not be structure-dependent, as it could be defined without making reference to hierarchical notions like “matrix clause” or “subordinate clause”; (ii) such rule requires no domain-specific innate bias in order to be learned, given that the stimulus in the primary linguistic data would be “rich” enough for the child to figure out the relevant grammatical mechanism at work; and (iii) such “richness” would lie in prosodic information present in the data, which, according to him, has been largely neglected by generativists. The aim of this article is to show that all three parts of Everett’s alternative analysis are conceptually problematic and empirically unsupported. As a matter of logic, the very idea that children rely on prosodic cues to learn the lexicon and the syntax presupposes UG. Moreover, I offer new experimental evidence that a significant portion of the facts is incompatible with Everett’s account. Therefore, his attempt to refute linguistic nativism misses the target.

The issue of how people acquire knowledge in the course of individual development has fascinated researchers for thousands of years. Perhaps the earliest recorded effort to put forth a theoretical account belongs to Plato, who famously advocated the idea that knowledge of many abstract categories (e.g., ‘‘equivalence’’) is innate. Although Plato argued with his contemporaries who advocated the empirical basis of knowledge, it was the British empiricists who most forcefully put forth the idea of the empirical basis of knowledge, with John Locke offering the famous ‘‘tabula rasa’’ argument. The first comprehensive psychological treatment of the problem of knowledge acquisition was offered by Piaget (1954), who suggested that knowledge emerges as a result of interactions between individuals and their environments. This was a radical departure from both extreme nativism and extreme empiricism. However, these ideas, as well those of empiricist-minded behaviorists, fell short of providing a viable account of many human abilities, most notably, language acquisition. This inability prompted Chomsky to propose an argument that language cannot be acquired from the available linguistic input because it does not contain enough information to enable the learner to recover a particular grammar, while ruling out alternatives (Chomsky, 1980). Therefore, some knowledge of language must be innate to enable fast, efficient, and invariable language learning under the conditions of the impoverished linguistic input. This argument (i.e., known as the Poverty of the Stimulus argument) has been subsequently generalized to perceptual, lexical, and conceptual development. The 1990 Special Issue of Cognitive Science is an example of such generalization. The current Special Issue on the mechanisms of cognitive development has arrived exactly 20 years after the first Special Issue. In the introduction to the 1990 Special Issue of Cognitive Science, Rochel Gelman stated

Natural language is full of patterns that appear to fit with general linguistic rules but are ungrammatical. There has been much debate over how children acquire these “linguistic restrictions,” and whether innate language knowledge is needed. Recently, it has been shown that restrictions in language can be learned asymptotically via probabilistic inference using the minimum description length (MDL) principle. Here, we extend the MDL approach to give a simple and practical methodology for estimating how much linguistic data are required to learn a particular linguistic restriction. Our method provides a new research tool, allowing arguments about natural language learnability to be made explicit and quantified for the first time. We apply this method to a range of classic puzzles in language acquisition. We find some linguistic rules appear easily statistically learnable from language experience only, whereas others appear to require additional learning mechanisms (e.g., additional cues or innate constraints).

Imitation requires the imitator to solve the correspondence problem--to translate visual information from modelled action into matching motor output. It has been widely accepted for some 30 years that the correspondence problem is solved by a specialized, innate cognitive mechanism. This is the conclusion of a poverty of the stimulus argument, realized in the active intermodal matching model of imitation, which assumes that human neonates can imitate a range of body movements. An alternative, wealth of the stimulus argument, embodied in the associative sequence learning model of imitation, proposes that the correspondence problem is solved by sensorimotor learning, and that the experience necessary for this kind of learning is provided by the sociocultural environment during human development. In a detailed and wide-ranging review of research on imitation and imitation-relevant behaviour in infancy and beyond, we find substantially more evidence in favour of the wealth argument than of the poverty argument.

In the last few years, nativist, modular views of moral cognition have been influential. This paper shares the view that normative cognition develops robustly, and is probably an adaptation. But it develops an alternative view of the developmental basis of moral cognition, based on the idea that adults scaffold moral development by organising the learning environment of the next generation. In addition, I argue that the modular nativist picture has no plausible account of the role of explicit moral judgement, and that no persuasive version of the ‘poverty of the stimulus' applies to moral cognition.