Schonemann P. H.
New questions about old heritability estimates
Bulletin of the Psychonomic Society, 1989, 27, 175-178.
This note summarizes the main results of three recent studies on the heritability of mental traits:
(1)The inferences Jinks and Fulker (1970) derived from Shields' (1962) twin data are invalid since the assumptions of the genetic model are consistently violated by these data. A purely environmental model fits them better by a factor of 2.
(2) Holzinger's heritability coefficient (h2) is invalid since his derivations imply that dizygotic twins share no genes.
(3) In contrast, Nichols' (1965) heritability coefficient (HR) follows from a strictly additive genetic model.
(4) However, the needed assumptions are consistently violated by Osborne's (1980) personality data, which produce an excessive number of inadmisible HRs. A purely environmental model fits these data better by a factor of 14.
Jointly, these results suggest that heritability estimates of mental traits in the literature should be view with caution.
A summary of basic results on heritability of IQ. For details consult:
Schonemann, P. H. (1990) Environmental versus genetic variance component models for identical twins: A critique of Jinks and Fulker's reanalysis of the Shields data. Cahiers de Psychologie Cognitive / European Bulletin of Cognitive psychology, 10, 451-473.
Schonemann, P. H. (1993) A note on Holzinger's heritability coefficient h**2 .
Schonemann, P. H. and Schonemann, R. D (1994) Environmental versus genetic models for Osborne's personality data on identical and fraternal twins. Cahiers de Psychologie Cognitive / Current Psychology of Cognition, 13, 141-167.
Schonemann, P. H. (1994) Heritability. In R. Sternberg (ed) Encyclopedia of Human Intelligence. New York; McMillan, p. 528-536.
Schonemann, P. H. (1997) Models and muddles of heritability