A new paper-and-pencil test of spatial visualization was constructed from the figures used in the chronometric study of Shepard and Metzler (1971). In large samples, the new test displayed substantial internal consistency (Kuder-Richardson 20 = .88), a test-retest reliability (.83), and consistent sex differences over the entire range of ages investigated. Correlations with other measures indicated strong association with tests of spatial visualization and virtually no association with tests of verbal ability.

A very similar pattern of homogamy was found in samples of American and Swedish couples for physical, social, and behavioral variables. In the Swedish sample, there were only minor differences in assortment, i.e., in similarity to spouses, between MZ and DZ twins. Although our data are not conclusive on this point, there was an indication that the observed similarity of spouses for most variables is due to initial assortment rather than to convergence of phenotypes after initial contact. Exceptions are that spouses do appear to converge for highly plastic variables such as alcohol consumption and amount of social activity.

Four cognitive factors were extracted from test data obtained on 997 families (3,268 individuals) in Hawaii. Factor loading profiles for the two largest ethnic groups (Caucasians and Japanese) are nearly identical, as are profiles for three different age groups. Age curves are presented for factor scores and for four specific cognitive tests. The younger respondents on the age curves are biological offspring of older respondents represented on the same curves, facilitating an unusual control for between-family variance. When the data were stratified by ethnicity, differential rates of cognitive development were indicated.