Four experiments which involved 160 children aged 2 to 19 investigate the mutual exclusivity bias in children's word learning. Results indicate that the bias develops after the second birthday but does not gain full strength or become accessible to consciousness until after the third birthday. (RJC)

Considers the bases of criticism of parent report as an index of their children's behavioral development and ways in which problems associated with parent report were addressed in the construction of the MacArthur Communicative Development Inventories (CDIs). Examines the nature of responses elicited from parents as they complete the CDIs. (BC)

Examined overregularization of irregular verb forms in children's language learning. Found that overregularization errors are relatively rare; occur at a constant rate; and are not correlated with the proportion of regular verbs in parents' or children's speech. Also found that a period of correct performance precedes the child's first error. (BC)

In reply to the commentary on the research by Anglin reported in this monograph, considers two issues: (1) implications for research on children's vocabulary knowledge that follow from adopting various definitions of what a word is; and (2) the distinction between learning words and constructing word meaning through a knowledge of morphological…

Tested children in grades one, three, and five on their knowledge of a large sample of words. Found that comprehension of derived words improved dramatically from grade one to grade five and that words consisting of more than two morphemes were not well known by first graders but were relatively better known by fifth graders. (BC)

Comments on the research by Anglin reported in this monograph by considering two points. First, discusses possible problems in defining what a word is. Second, examines some problems with the methodology in vocabulary development research that involves testing individuals' knowledge of words by sampling words from dictionaries. (BC)

The MacArthur Communicative Development Inventories (CDIs) represent a breakthrough in measuring early language production. Nevertheless, the CDIs' word comprehension component may not be a valid measure, because parents report too high a word comprehension ability for their children. Suggests that administering the CDIs to parents in an interview…

Data from parent reports on 1,803 children, derived from the MacArthur Communicative Development Inventories, are used to describe the course of communicative development between 8 and 30 months of age. Found wide variability in children's rate of lexical, gestural, and grammatical development; correlations between several components of language…