Heritability of Factor V: Verbal Comprehension

Abstract

33 pairs of M Z twins and 12 pairs of like-sexed DZ wins, 32 boys and 58 girls, 40 of whom were Negro and 50 white, whose ages ranged from 13 to 18, were given a battery of verbal comprehension tests which included the Heim Self-judging Vocabulary Test, the Wide-Range Vocabulary Tesr, the Heim Vocabulary Tesr, and the Spelling Achievement Test. Using three different heritability ratios, ( 1 ) the Holzlnger heritability coefficient, ( 2 ) the heritability ratio proposed by Nichols, and ( 3 ) the F ratio (Block), the relative incrapair similarity of MZ and I~ke-sexed DZ twins on the verbal comprehension tests was determined. All the MZ correlations were greater than the corresponding 7s for the DZ twin-pairs. Two of the six differences were significant ( p 4 .05). The range of heritability coefficient ratios (Holzinger) was from .35 to .78, with MZ intraclass rs ranging from .45 to ,815, with DZ rs from -3 4 to .40. The agreemenr among rests suggests that verbal comprehension as tested by the various performance tests is heritable with as much as .78 of the within-family variance attributable to hereditary factors.

The Heritability of Language: A Review and Metaanalysis of Twin, Adoption, and Linkage Studies

“…Bouchard & McGue 1981). To the extent that IQ tests directly or indirectly tap verbal abilities (see Osborne et al 1968), the MZ-DZ IQ difference is consistent with genetic factors affecting language. However, it is possible that nonverbal portions of IQ tests account for all or most of the heritability of fullscale IQ.…”

“…For the seven year olds in their study, Hohnen and Stevenson's literacy measure also included tests of children's ability to read irregularly spelled words-pint, answer-and nonsense words-kule, tocken-and to detect the correct spelling of a word in a word-pseudohomophone pair-room/rume. As shown in Table 8, the MZ correlations were greater than the DZ correlation coefficients for all five studies and for all reading tests, with Falconer's h 2 's ranging from .18 for the Neale Reading Accuracy test in Stevenson et al 1987 to 1.53 for the Heim Self-judging Vocabulary test (Vandenberg 1965) in Osborne et al 1968. In a metaanalysis that used the mean correlation coefficients for Osborne et al (1968) and Stevenson et al (1987), the unweighted r was .82 for MZ twins and .55 for DZ twins (t(5) ‫ס‬ 5.23, p ‫ס‬ .003), with heritable factors accounting for 53% of the variance in reading ability, and shared environment accounting for 28% of the variance.…”

“…As shown in Table 8, the MZ correlations were greater than the DZ correlation coefficients for all five studies and for all reading tests, with Falconer's h 2 's ranging from .18 for the Neale Reading Accuracy test in Stevenson et al 1987 to 1.53 for the Heim Self-judging Vocabulary test (Vandenberg 1965) in Osborne et al 1968. In a metaanalysis that used the mean correlation coefficients for Osborne et al (1968) and Stevenson et al (1987), the unweighted r was .82 for MZ twins and .55 for DZ twins (t(5) ‫ס‬ 5.23, p ‫ס‬ .003), with heritable factors accounting for 53% of the variance in reading ability, and shared environment accounting for 28% of the variance. The heritability estimate based on weighted mean correlations was slightly less (the r w was .86 for MZ twin pairs and .66 for DZ twin pairs, Z ‫ס‬ 2.84, p ‫ס‬ .002), with 41% of the variance in reading ability attributable to heritable factors, 45% attributable to shared environment factors, and 14% due to nonshared environment.…”

“…DF heritability estimates were .29 for the twins in Thompson et al 1991, .60 for the 6-year-old twins and .59 for the 7-year-old twins in Hohnen and Stevenson's 1999 study. As part of the Colorado Twin 22 When the MZ and DZ correlations that correspond to the median values of h 2 for Osborne et al 1968 andStevenson et al 1987 Significance levels are for one-tailed tests: * p Ͻ .05; ** p Ͻ .01; *** p Ͻ .001, **** p Ͻ .0001 † includes Osborne et al 1968 andStevenson et al 1987 Light and colleagues (1998) studied the reading abilities of 132 MZ and 91 DZ normal twin pairs. For phonologically based reading, genetic factors accounted for 68% of normal twins' performance (versus 52% for dyslexic twins).…”

“…Five studies of normally developing twins contained the information necessary to calculate Falconer's estimates of heritability (Foch & Plomin 1980, Hohnen & Stevenson 1999, Osborne et al 1968, Stevenson et al 1987, Thompson et al 1991. Osborne et al 1968 andFoch &Plomin 1980 used tests that primarily assess children's ability to read words in isolation. Stevenson et al 1987 used tests that assess ability to read words in isolation (Schonell reading test, Schonell & Schonell 1960) and to read prose (Neale reading tests, Neale 1967).…”