Taylor (1980) claims to show that the similarity in IQ between monozygotic twins reared apart found in prior studies is due to similarity in their environments. A reanalysis using Taylor's classification of environments but an alternative IQ measure shows that his findings do not constructively replicate. (Author/RD)

"The Bell Curve" declares that studies of separated identical twins--the "purest" of "direct" methods for estimating IQ heritability--indicate a value of +.75-+.80. But, the main study cited suggests a heritability of "two-thirds" for the middle class, and Herrnstein and Murray neglect to mention numerous…

The Ramey and Haskins intervention experiment is examined. Narrow transfer of training from cognitive intervention techniques to IQ test performance in early childhood, rather than enhancement of the g factor itself, is hypothesized as a cause of the typical fadeout of early IQ gains in later childhood. (Author/RD)

Wechsler Preschool and Primary Scale of Intelligence (WPPSI) and McCarthy Scales subtests were ranked according to relative reliance on left-cerebral-hemisphere function. Results suggest that black-white IQ discrepancies may be partially explained by differences in hemisphericity. (Author/RD)

Results from the Colorado Adoption Project, a longitudinal study initiated in 1975, are reported. The cognitive ability of parents and measures of one-year olds' mental development were significantly correlated for all three parent/child comparisons. Caldwell's HOME Responsibility measure was correlated with infant intelligence in adoptive and…

Extensive data on twins, nontwin siblings, siblings separated by adoption, and parent-child similarity indicate that the heritability of intelligence is closer to .50 than to .70. Differences could be due to environmental or genetic changes in the population, or to methodology. (Author/CP)

Separate dimensions of infant cognition were compared with parental general- and specific-cognitive abilities for 182 adoptive and 164 nonadoptive families. More parent-offspring resemblance was present when 24- rather than 12-month Bayley factors were used. Bayley factors were more related to parental g than to specific abilities. (Author/RD)