hierarchical multiple regression to solve the interpretive
problem that avid readers excel in most
domains of verbal learning and that, therefore,
our measures of reading volume might be spuriously
correlated to a host of abilities
(Cunningham & Stanovich, 1990, 1991;
Stanovich & Cunningham, 1992, 1993;
Stanovich & West, 1989). We have found that
even when performance is statistically equated
for reading comprehension and general ability,
reading volume is still a very powerful predictor
of vocabulary and knowledge differences. Thus,
we believe that reading volume is not simply an
indirect indicator of ability; it is actually a
potentially separable, independent source of
cognitive differences.