even more potent source of the rich-get-richer
and poor-get-poorer achievement patterns.
Therefore, we have sought to examine the
unique contribution that independent or out-ofschool
reading makes toward reading ability,
aspects of verbal intelligence, and general
knowledge about the world. As part of this
research program, our research group has pioneered
the use of a measure of reading volume
that has some unique advantages in investigations
of this kind (Cunningham and Stanovich,
1990; Stanovich and West, 1989).