The structure of working memory and its development across the childhood years were investigated in children 4 -15 years of age. The children were given multiple assessments of each component of the A. D. Baddeley and G. Hitch (1974) working memory model. Broadly similar linear functions characterized performance on all measures as a function of age. From 6 years onward, a model consisting of 3 distinct but correlated factors corresponding to the working memory model provided a good fit to the data. The results indicate that the basic modular structure of working memory is present from 6 years of age and possibly earlier, with each component undergoing sizable expansion in functional capacity throughout the early and middle school years to adolescence.

This review article presents evidence for the claim that frequency effects are pervasive in children's first language acquisition, and hence constitute a phenomenon that any successful account must explain. The article is organized around four key domains of research: children's acquisition of single words, inflectional morphology, simple syntactic constructions, and more advanced constructions. In presenting this evidence, we develop five theses. (i) There exist different types of frequency effect, from effects at the level of concrete lexical strings to effects at the level of abstract cues to thematic-role assignment, as well as effects of both token and type, and absolute and relative, frequency. High-frequency forms are (ii) early acquired and (iii) prevent errors in contexts where they are the target, but also (iv) cause errors in contexts in which a competing lower-frequency form is the target. (v) Frequency effects interact with other factors (e.g. serial position, utterance length), and the patterning of these interactions is generally informative with regard to the nature of the learning mechanism. We conclude by arguing that any successful account of language acquisition, from whatever theoretical standpoint, must be frequency sensitive to the extent that it can explain the effects documented in this review, and outline some types of account that do and do not meet this criterion.

Structural priming paradigms have been influential in shaping theories of adult sentence processing and theories of syntactic development. However, until recently there have been few attempts to provide an integrated account that explains both adult and developmental data. The aim of the present paper was to begin the process of integration by taking a developmental approach to structural priming. Using a dialog comprehension-to-production paradigm, we primed participants (3-4year olds, 5-6year olds and adults) with double object datives (Wendy gave Bob a dog) and prepositional datives (Wendy gave a dog to Bob). Half the participants heard the same verb in prime and target (e.g. gave-gave) and half heard a different verb (e.g. sent-gave). The results revealed substantial differences in the magnitude of priming across development. First, there was a small but significant abstract structural priming effect across all age groups, but this effect was larger in younger children than in older children and adults. Second, adding verb overlap between prime and target prompted a large, significant increase in the priming effect in adults (a lexical boost), a small, marginally significant increase in the older children and no increase in the youngest children. The results support the idea that abstract syntactic knowledge can develop independently of verb-specific frames. They also support the idea that different mechanisms may be needed to explain abstract structural priming and lexical priming, as predicted by the implicit learning account (Bock, K., & Griffin, Z. M. (2000). The persistence of structural priming: Transient activation or implicit learning? Journal of Experimental Psychology - General, 129(2), 177-192). Finally, the results illustrate the value of an integrative developmental approach to both theories of adult sentence processing and theories of syntax acquisition.

Participants (aged 5-6 yrs, 9-10 yrs and adults) rated (using a five-point scale) grammatical (intransitive) and overgeneralized (transitive causative) 1 uses of a high frequency, low frequency and novel intransitive verb from each of three semantic classes [Pinker, S. (1989a). Learnability and cognition: The acquisition of argument structure. Cambridge, MA: MIT Press]: ''directed motion'' (fall, tumble), ''going out of existence'' (disappear, vanish) and ''semivoluntary expression of emotion'' (laugh, giggle). In support of Pinker's semantic verb class hypothesis, participants' preference for grammatical over overgeneralized uses of novel (and English) E-mail address: Ben.Ambridge@Liverpool.ac.uk (B. Ambridge). 1 Throughout this paper, the term ''intransitive'' (whether referring to a verb or construction) refers only to non-causative intransitives -sometimes termed ''inchoative intransitives'' -(e.g., The man laughed) and not to intransitives with unspecified or unexpressed objects (e.g., The man ate). The term ''transitive causative'' (e.g., The sun melted the snow) is used to contrast sentences of this type with both transitive noncausatives (e.g., John saw Bill) and periphrastic causatives (e.g., The sun made the snow melt).www.elsevier.com/locate/COGNIT Available online at www.sciencedirect.com Cognition 106 (2008) 87-129 verbs increased between 5-6 yrs and 9-10 yrs, and was greatest for the latter class, which is associated with the lowest degree of direct external causation (the prototypical meaning of the transitive causative construction). In support of Braine and Brooks's [Braine, M.D.S., & Brooks, P.J. (1995). Verb argument strucure and the problem of avoiding an overgeneral grammar. In M. Tomasello & W. E. Merriman (Eds.), Beyond names for things: Young children's acquisition of verbs (pp. 352-376). Hillsdale, NJ: Erlbaum] entrenchment hypothesis, all participants showed the greatest preference for grammatical over ungrammatical uses of high frequency verbs, with this preference smaller for low frequency verbs, and smaller again for novel verbs. We conclude that both the formation of semantic verb classes and entrenchment play a role in children's retreat from argument-structure overgeneralization errors.

A paradox at the heart of language acquisition research is that, to achieve adult-like competence, children must acquire the ability to generalize verbs into non-attested structures, while avoiding utterances that are deemed ungrammatical by native speakers. For example, children must learn that, to denote the reversal of an action, un- can be added to many verbs, but not all (e.g., roll/unroll; close/*unclose). This study compared theoretical accounts of how this is done. Children aged 5–6 (N = 18), 9–10 (N = 18), and adults (N = 18) rated the acceptability of un- prefixed forms of 48 verbs (and, as a control, bare forms). Across verbs, a negative correlation was observed between the acceptability of ungrammatical un- prefixed forms (e.g., *unclose) and the frequency of (a) the bare form and (b) alternative forms (e.g., open), supporting the entrenchment and pre-emption hypotheses, respectively. Independent ratings of the extent to which verbs instantiate the semantic properties characteristic of a hypothesized semantic cryptotype for un- prefixation were a significant positive predictor of acceptability, for all age groups. The relative importance of each factor differed for attested and unattested un- forms and also varied with age. The findings are interpreted in the context of a new hybrid account designed to incorporate the three factors of entrenchment, pre-emption, and verb semantics.