Research consistently documents that girls outperform boys in literacy achievement, yet, when considering the starting point--early literacy--we do not have consensus on the origin, meaningful nature, or persistence of such differences. In this two-part study analyzing 5,816 Norwegian students (48.1% girls, average age of 6.1 years), we first…

Modern behavior-genetic studies of twins in the United States, Australia, Scandinavia, and the United Kingdom show that genes account for most of the variance in children's reading ability by the end of the 1st year of formal reading instruction. Strong genetic influence continues across the grades, though the relevant genes vary for reading words…

Two ways of measuring change are presented and compared: A conventional "change score", defined as the difference between scores before and after an interim period, and a process-oriented approach focusing on detailed analysis of conceptually defined response patterns. The validity of the two approaches was investigated. Vocabulary…

In this study, the relationship between latent constructs of phonological awareness (PA) and rapid automatized naming (RAN) was investigated and related to later measures of reading and spelling in children learning to read in different alphabetic writing systems (i.e., Norwegian/Swedish vs. English). 750 U.S./Australian children and 230…

Genetic and environmental relations between vocabulary and reading skills were explored longitudinally from preschool through Grades 2 and 4. At preschool there were strong shared-environment and weak genetic influences on both vocabulary and print knowledge but substantial differences in their source. Separation of etiology for vocabulary and…

The genetic factor structure of a range of learning measures was explored in twin children, recruited in preschool and followed to Grade 2 ("N"?=?2,084). Measures of orthographic learning and word reading were included in the analyses to determine how these patterned with the learning processes. An exploratory factor analysis of the…