Aside from a partial replication conducted by Scarr
(1981) and a report from Sweden by Fischbein (1980), the
hypothesis of group differences in heritability lay mostly
fallow for a 20-year period encompassing the time when
the Neisser et al. (1996) article was written. Interest in the
phenomenon was rekindled in 1999 when Rowe, Jacobson,
and Van den Oord (1999) analyzed data from the National
Longitudinal Study of Adolescent Health, a large, representative
sample of American youth, then in early adolescence,
who were administered a version of the Peabody
Picture Vocabulary Test. Rowe et al.’s analysis showed
that most of the variance in families with poorly educated
mothers was explained by the shared environment. (Shared
environment constitutes the environment that is shared by
siblings in the same family and that differs from one family
to another, as opposed to aspects of the environment that
can differ among siblings, such as being a firstborn versus
a later-born child.) Most of the variance for children from
well-educated families was explained by genes.