Premium
THE HERITABILITY OF FLUID, g f , AND CRYSTALLISED, g c , INTELLIGENCE, ESTIMATED BY A LEAST SQUARES USE OF THE MAVA METHOD
Author(s) -
CATTELL R. B.
Publication year - 1980
Publication title -
british journal of educational psychology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.557
H-Index - 95
eISSN - 2044-8279
pISSN - 0007-0998
DOI - 10.1111/j.2044-8279.1980.tb00809.x
Subject(s) - heritability , statistics , statistic , population , variance (accounting) , twin study , psychology , mathematics , demography , biology , sociology , genetics , accounting , business
S ummary . The heritability of the two second order general intelligence factors g c and g f , was studied by the MAVA design, employing 470 brothers reared together, 94 identical twins reared together, 124 fraternal twins reared together, and 1,543 boys (fluid intelligence) and 2,579 (crystallised intelligence) unrelated. All were in the 12–18 age range. The model and the empirical data on four constellations give seven simultaneous equations for predicting expected values of the concrete, empirical variances from seven abstract, unknown variances and correlations. The best fit was obtained, using a least squares solution by computer program, CAMALS, and evaluated by a Q statistic analogous to chi‐square. Two models offering reduced, parsimonious modifications of the full MAVA, were also tried but MAVA gave the highest index of good fit. Substantial differences exist between the heritability of g f and g c , alike in the present and in earlier MAVA studies, using differing methods of solution. H for crystallised intelligence is highest for within family variance and the mean value stands at only 0–45 for the general population—lower still by the present method. Fluid intelligence, on the other hand, has the highest heritability between families, reaching a mean of 0·92. Its general population value is 0·58 closely approaching the 0·60 which has tended to be the lower end of the range by the twin method. (The reason for the usual higher twin method values is exposed by the finding of higher sib than twin within family threptic variance.) Some support is found for a negative genothreptic correlation between families, fitting the socio‐psychological law of environmental coercion toward the mean.